Meet the First Flightless Pterosaur: SoS 2428

Everyone knows about the various flightless birds: the penguin, the dodo, the ostrich… the list goes on. There are no flightless bats. And no one has ever discovered a flightless pterosaur… until now. Flightless pterosaurs have been the subject of speculation and science fiction. Henderson (2010) considered Quetzalcoatlus and its giant kin to be too large to fly. Not many workers agree with him. You’ll see why later.

Now we know what a flightless pterosaur really looks like. And it wasn’t all that big.

SoS 2428 (Figure 1) is a roadkill fossil that only Wellnhofer (1970) published on in the modern era. He described it as a “variation” of Pterodactlylus longicollum and gave it the number 57 in his catalog of “pterodactyloid” pterosaurs from Late Jurassic
Solnhofen strata. Others who viewed the fossil agreed. It was considered nothing special and the distal wings were considered missing. SoS 2428 has never been included in prior cladistic analyses. It wasn’t worth the effort. That became the traditional view. Then I tested it.

Figure 1. Click to enlarge. The first flightless pterosaur in situ. SOS 2428 is preserved crushed but articulated. The mandible appears on the plate, but the skull is visible beneath the plate. Other parts represent counterplates.

While similar to Pterodactylus longicollum in overall proportions, SoS 2428 had a flat rostrum, ultra-wide gastralia, ultra-long ribs, a hyper-elongated pelvis and distinct manual phalanx proportions (the feet are missing unfortunately). In cladistic analysis, SoS 2428 nested far from the holotype of Pterodactylus and its sister, P. longicollum.  A reduced pectoral girdle and vestigial distal wing phalanges indicate this pterosaur could not fly. Further hampering its volant abilities, SoS 2428 had a huge belly supported by enormously elongated hips and a sacral region that expanded to over 60 percent of the torso, crowding up the dorsal ribs.

Note the similarities in position, shape and size between m4.3 and rib #9. Also note the similarities between the coracoid and rib #10, and the scapula and rib #11. Did you see the joint between m4.1 and m4.2? Find it difficult to locate the humerus, radius and ulna? Join the crowd. I had trouble too, but I kept at it knowing there were unidentified elements in the fossil. This paper was rejected because several reviewers reported they looked at the fossil without seeing what I describe here.

All these differences had gone unnoticed because no one had ever attempted to produce an accurate tracing of this difficult specimen. Wellnhofer (1970) only traced the easy to see elements: some teeth and a femur among them. Interpretation is difficult, but the DGS (digital graphic segregation) method using Adobe Photoshop came through, segregating the ribs from the gastralia from the rib-like wing and shrunken pectoral elements (Figure 2).

he torso of the flightless pterosaur, SOS 2428,

Figure 2. Click to enlarge. The torso of the flightless pterosaur, SOS 2428, along with three digital tracings segregating the ribs, gastralia, spine, pectoral and wing elements.

SoS 2428 clearly represents a new and so far unnamed genus and species. Closest sister taxa include Huanhepterus, BSPG 1911 I 31, Wellnhofer’s No. 42 and SoS 2179 all of which have been considered close to ctenochasmatids or pterodactylids, but actually represent a clade close to azhdarchids, like Quetzalcoatlus.

No. 42 is the best known of this clade and it had proportions that caused Wellnhofer (1970) to nest it with Pterodactylus. Clearly it was able to fly. SoS 2428 had a longer rostrum, a longer neck, a longer sacrum, longer dorsal ribs, longer gastralia, a smaller pectoral girdle and wings (especially the distal elements) and a longer femur. With such small wings and such a large belly, SoS 2428 could not fly, but it could still flap.

Quetzalcoatlus had a vestigial distal wing phalanx, but it retained a large pectoral girdle, long wings and a small torso, thus it did not follow the pattern of SoS 2428, the flightless pterosaur. Quetzalcoatlus retained the traits of a volant pterosaur.

Lateral, ventral and dorsal views of SoS 2428

Fig. 3. Lateral, ventral and dorsal views of SoS 2428 alongside No. 42, a volant sister taxon. Note the reduced wings and pectoral girdle of no. 57, which also had an expanded gastralia basket and elongated dorsal ribs and a hyperelongated pelvis. With such small wings and such a large belly, it could not fly, but it could still flap.

Animals with a larger belly are often plant eaters that require a larger gut to digest their diet. SoS 2428 retained a large sternum, which means the pectoral muscles remained large for adducting the humeri perhaps for quadrupedal locomotion, but certainly for flapping. The elongated femur extended slightly anterior to the pelvis, but still was unable to place the hypothetical feet beneath the shoulder glenoid, the center of balance, as in all other pterosaurs, without lifting the hands off the substrate. Thus a quadrupedal pose was likely during beachcombing and feeding, while a bipedal pose supported by the anterior extension of the sacrum and ilium, was employed at other times.

Sos 2428. The flightless pterosaur.

Figure 4. Sos 2428. The flightless pterosaur.

A larger pterosaur with a longer rostrum, SoS 2179 was derived from SoS 2428. Only the skull is known. See it here. We can only imagine that the wings were smaller and the belly was bigger.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Henderson DM 2010.
Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology 30(3):768-785.

Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

Seven problems with the pterosaur wing launch hypothesis

How did pterosaurs take off?
Unlike bats and birds, pterosaurs, the first flying vertebrates, are all extinct. We can only imagine what it was like to see them fly, land and take off. It used to be thought that pterosaurs hung by their toes from cliff faces, like bats, before becoming airborne. Illustrations have shown pterosaurs clinging inverted to tree branches ready to drop off. The idea of bipedal pterosaur running downhill into a headwind was floated by Chatterjee and Templin (2004), but had few takers. Bennett (1997) imagined the first pterosaurs leaped with their hind limbs into flight. Padian (1981) imagined they ran first.

Vaulting pterosaur

Figure 1. Click to see video of the Habib/Molnar quadrupedal pterosaur launch sequence.

Recent studies by PhD candidate, Mike Habib (2008 pdf), on the dynamics of the pterosaur launch proposed a novel launch method (Figures 1 and 2.) based on the technique of Desmodus rotundus, the vampire bat (Schutt et al. 1999). The vampire launches itself quadrupedally, principally with its muscular forelimbs, opening its wings at the peak of its launch. Habib documented the great disparity in the comparative sizes and strengths of pterosaur forelimbs vs. the hindlimb and how these compared to bird limbs. Vampire bats are similar. In birds, Habib reported, the hind limbs provide the primary source of propulsion for launch, either by running or leaping, immediately before the wings take over. Habib reported that pterosaurs have stronger forelimbs than hindlimbs, just the opposite of birds. Thus, Habib reasoned, since all pterosaurs were quadrupeds (this is questionable, see below), they must have employed their strongest limbs, their wings  (this is also questionable, see below), to take off. Habib reported, “…expected flapping forces alone seem insufficient, at present, to explain the structural strength ratios of pterosaurs; it is simply implausible that pterosaurian lift coefficients would be several times higher than in birds…”

Dr. David Hone agreed with this hypothesis, “If pterosaurs actually launched like birds, with the hindlimbs producing most of the force, then the ratio of their bone strength values should be about the same as birds, and big pterosaurs should have slender wing bone elements (especially the proximal elements, like the humerus) and big, robust hindlimb bones.  Well, it turns out that the opposite is actually the case: pterosaurs have whopping huge forelimb bones and very slender hindlimb bones, and this gets more exaggerated in big pterosaurs.” Dr. Mark Witton is in agreement here. Julia Molnar created a video to demonstrate the Habib hypothesis here. Other images can be seen here and here. The forelimb launch seems to have become the widely accepted view.

Of course, evidence for either the Habib (2008) hypothesis or the heretical bird-style take-off would have to come in the form of take-off tracks. Unfortunately we don’t know of any such tracks. We only know of one landing trace (Mazin et al. 2009, Figure 3), which came in feet first. So let’s examine each of the precepts of Habib’s hypothesis and see if any problems arise.

Animation of a landing pterosaur matched to tracks.

Figure 3. Click to animate. Animation of a landing pterosaur matched to tracks based on Mazin et al. (2009).

Problem 1. Did all pterosaurs have stronger forelimbs than hindlimbs? While most pterosaurs had a larger diameter humerus than femur, not all did. Basal pterosaurs up to, but not including, Carniadactylus and Eudimorphodon had a humerus no thicker than the femur. The same held true for a few Rhamphorhynchus specimens, Sordes, some Pterodactylus specimens and at least one germanodactylid. The flightless pterosaur had a tiny humerus. Some pterosaurs, such as Zhejiangopterus and Fenghuangopterus had a much shorter humerus than femur. Thus the femur in these taxa would have had much more leverage, travel and associated muscles to launch the pterosaur further and higher. Why did some pterosaurs have a large diameter or longer humerus? I don’t know. I can’t see a clear phylogenetic pattern yet.

Kangaroo skeleton compared to a leaping pterosaur skeleton

Figure 4. Click to enlarge. Here a kangaroo skeleton is compared to that of a quadrupedally leaping pterosaur. The red arrows on the kangaroo indicate the major muscle pulls employed during each leap. Even with all those muscles, tensioned tendons and bone levers, kangaroo leaps only lift the toes to the height of the ankles. The pterosaur is less well-equipped with only a single major lever, the elbow as it straightens a very short distance, bound by the propatagium in front _preventing_ overextension of the elbow.

Problem 2. Were the proximal forelimb elements long enough and strong enough to produce the required height and airspeed during a forelimb launch to deploy the very long folded wings and initiate the first flap?
Habib (2008) reports the forelimb bones were more than strong enough. Were they long enough? The answer seems doubtful if one compares the skeleton of our greatest living leaper, the kangaroo with that of a pterosaur (Figure 4). Despite having five muscle groups from pelvis to toe contracting in a coordinated series, kangaroo initial leaps raise the toes only to the heights of the ankles. By contrast, pterosaurs had only their elbows and wrists to extend and they could extend their elbows a relatively shorter distance, not counting the effect of the propatagium, which in birds and bats prevents exactly this sort of overextension of the elbow. Even the vampire bat leaves 15-20 degrees of flex at the elbow during takeoff.

Problem 3. The evolutionary pathway to forelimb launching.
Pterosaur predecessors were bipeds that ran and/or launched themselves with their hind limbs. Basalmost pterosaurs were also bipeds, unable to touch the substrate with their hands. Nevertheless, the vast majority of pterosaurs had forelimbs long enough to touch the substrate without bending over. Thus quadrupedal locomotion was secondarily derived. That’s why pterosaur finger tracks point laterally and posteriorly instead of anteriorly, as in other tetrapods. At this point the forelimb launch pattern could have evolved. Meanwhile, the forelimbs/wings of pterosaurs were used for flapping, flying, clinging to tree trunks and, in beachcombing genera forelimbs supported the anterior torso while walking quadrupedally. However, in beachcombers, the forelimbs produced no forward propulsion vectors. The planted hands were never behind the elbows and shoulders. Pterosaur forelimbs acted more like crutches than traditional walking forelimbs (see walking pterosaur movie here).

So were does the impetus for a forelimb launch come from? There doesn’t appear to be an evolutionary sequence demonstrating the gradual acquisition of a rapid extension of the forearm at the magnitude needed to launch a pterosaur high enough to extend the wings and initiate flapping. Nor does there appear to be any change in pterosaur shoulder and elbow morphology that would signal such a change in behaviour. Moreover, flexion of the elbow would be constrained by the long pteroid in a few taxa and extension would be constrained by the propatagium in all taxa. The question of why most pterosaurs have a thicker, stronger humerus than femur remains unanswered. No skeletal correlates have been documented yet to gauge a large humerus or a large antebrachium with large claws, a large head or any other skeletal character. Such characters change one way or the other within genera such as Pteranodon and Rhamphorhynchus.

Problem 4. The margin of error.
Avoiding the narrow margin of error and calamity a pterosaur experiences every time it would have to snap open its (sometimes huge) wings during a forelimb launch (thousands of times during a lifetime) without ever striking the ground seems to tempt the odds. Moreover, the power and coordination needed to complete the vault and extend the wings in this fly-or-crash scenario gives little room for a learning curve in younger weaker pterosaurs or in the evolution of such a maneuver from predecessors that were already adept at performing the standard hind limb leap.

Here are three animations of Pteranodon (Figures 5-7) in the process of taking off. Two portray the widely accepted wing launch model (one successful and one not successful) and one portrays the heretical bird-style launch from a standing pose. Click each one to see the animation.

Successful Pteranodon wing launch based on work by Habib (2008).

Figure 5. Click to animate. Successful Pteranodon wing launch based on work by Habib (2008). Here the initial propulsion is strong enough to provide sufficient thrust and height for Pteranodon to unfold its wings and get off one downstroke. The timing of this launch has been slowed down from its hypothetical speed to help show what happens.

Unsuccessful Pteranodon wing launch based on Habib (2008).

Figure 6. Click to animate. Unsuccessful Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Successful heretical bird-style Pteranodon wing launch

Figure 7. Click to animate. Successful heretical bird-style Pteranodon wing launch from a standing start into a headwind  in which the hind limbs produce the initial thrust and the first downstroke takes over immediately in the manner of birds. Without a headwind a running start, like an albatross, would probably be required (see below). Note three wing beats take place in the same space that only one wing beat takes place in the Habib/Molnar model.

Problem 5. Opening time for the big wing finger.The vampire bat is able to snap open its wings in an instant at the acme of its leap because the finger bones are mere splints with little mass and therefore little momentum and drag. Moreover they can curl like human fingers and extend at least as quickly. Not so pterosaur wing fingers. They are long, stiff and massive by comparison. In many pterosaurs, the wing phalanges are the largest bones in the specimen, and some can exceed the skull in length. That means, relative to the vampire bat, the largest pterosaur wings would have to take longer to accelerate to opening speed, and then promptly decelerate to a stop at the acme of the leap. The individual phalanges didn’t bend much at all, so the entire wing finger acted like a very long rod or pipe. Imagine swinging a 1-2 meter length of PVC pipe through 180 degrees and stopping it precisely. That’s what a big pterosaur wing would have to do if it snapped open in the moments after lift off in the Habib/Molnar model. By contrast, in the bird-style model, a less snappy pterosaur can take as much time as a bird does to open its wings.

Nyctosaurus in lateral view

Figure 8. With such a short humerus it appears unlikely that this Nyctosaurus could achieve a forelimb launch of sufficient height and length to deploy those long wing fingers before crashing.

Problem 6. Incorrect reconstruction.
The Habib/Molnar reconstruction of the Anhanguera manus (Figure 9) had a few inaccuracies. The three free fingers were way to short. All pterosaurs have subequal metacarpals 3 and 4. Thus finger three (and usuallly two and one) always extended beyond the big wing metacarpolphalangeal joint. Ichnites confirm this. Only digits 1-3 ever appear in fossil handprints. The folded knuckle of finger 4 never made an impression. If knuckle 4 never touched the substrate then it could not be used to pinch the extensor tendon during the vault/preload phase of the quadrupedal launch, which was supposed to store energy prior to a sudden release of impulse power. Also, the metacarpals of all pterosaurs actually lined up anteriorly, as in all tetrapods, including lizards and fenestrasaurs. The Habib/Molnar reconstruction incorrectly placed metacarpals 1-3 on the dorsal (in flight) surface of metacarpal 4.

Errors in the Habib/Molnar reconstruction of the pterosaur manus

Figure 9a. Click to enlarge. Errors in the Habib/Molnar reconstruction of the pterosaur manus. The fingers were too small and incorrectly placed. The extensor tendon should not run over the extensor tendon process. It should split and run on either side of the knuckle.

The so-called catapult mechanism in pterosaurs

Figure 9b. Left: The so-called catapult mechanism in pterosaurs. Right. The actual design of pterosaur (in this case Anhanguera/Santandactylus) fingers.

The Habib/Molnar model illustrated the extensor tendon running over the extensor tendon process (which would have enabled it to be pinched during launch. However, if pterosaurs followed lizards and other tetrapods (as they probably did), the extensor tendon would have split at the knuckle, inserting on both sides of the first phalanx a short distance away from the knuckle. Such a split would have prevented the sort of tendon pinching called for in the Habib/Molnar model. Flexors were similar and a more distal insertion point permitted complete wing folding (shown in gray below, and more on that subject later) than would have been impossible with the Habib/Molnar model with insertion at the flexor process tip. That sort of engineering would only have permitted folding the wing at right angles before running out of pull.

Problem 7. Did pterosaurs really have weak hind limbs?
On pterosaur.net Habib reported, “For all of the large pterosaurs, insufficient strength was present in the hindlimbs to initiative a bird-like launch. In addition, for most species, a bipedal launch position would have placed the wings at an inappropriately high angle of attack.” Of course, modern stilts, flamingoes and storks do very well in their bird-style launches, even with their “stilt”-like leg bones. Bending forward at the hip would have positioned the wings at the appropriate angle of attack (see below).

Bipedal lizard video marker

Figure x. Click to play video. Just how fast can quadrupedal/bipedal lizards run? This video documents 11 meters/second in a Callisaurus at the Bruce Jayne lab.

As descendants of bipedal lizards with sprawling femora (see below), pterosaurs would have run like highly improved lizards (see video), likely during take-off without a headwind. The Bruce Jayne lab in Cincinnati, Ohio, documented a zebra-tailed lizard, Callisaurus draconoides, running quadrupedally and later in the video, bipedally (Irschick and Jayne 1999). Note, the heels of the lizard never touch the ground. Speeds reach 5 m/sec or 11 mph for a 10 cm (snout/vent) length. Note that footfalls occur every three body lengths. That’s fast! What could a better-equipped pterosaur do? We’ll have to wait for running/takeoff footprints to find out, but here is an animation of a running Quetzalcoatlus to fire-up your imagination (Figure 10). Successive footfalls occur at a snout to vent length, which is quite a distance!

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 10. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate.

Albatross video showing take-off

Figure 11. Click for video. Albatross take-off in a no headwind situation. Running and flapping provides sufficient airspeed to provide lift.

It is important to note that bird legs and pterosaur legs had one fundamental difference: bird femora are not only tucked close to the body they are constrained by torso skin from moving much. So bird strides really begin at the knee. Birds elongate their metatarsals to produce yet another flexible leg section (the so-called “backwards knee”). By contrast, pterosaur femora swing from the hip and they all had relatively short metatarsals. Thus any mathematical comparisons, like those performed by Habib (2008) between the two types of flyers are going to be affected by this basic difference.

We end with a video (Figure 11) of several albatross taking off in a no headwind situation. With headwind an albatross need only unfold and lift its wings to become airborne.

I respect Mike Habib’s mathematical studies on pterosaurs, but I remain his loyal opposition for the reasons listed above. We have corresponded on this problem without swaying each other. Look for more studies from him in the near future. We’re both looking for those elusive pterosaur take-off tracks that will prove our hypotheses!

ADDENDUM: 
Every week since it was originally posted, this report on pterosaur wing launching has been a very popular post. There’s more to this story in a more recent blog here.

References:
Bennett SC 1997.
The arboreal leaping theory of the origin of pterosaur flight. Historical Biology 123(4): 265-290.
Chatterjee S and Templin RJ 2004.
Posture, locomotion, and paleoecologyof pterosaurs. The Geological Society of America Special Paper, 376:1–63.
Habib MB 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana B28:159-166.
Mazin J-M, Billon-Bruyat J-P and Padian K 2009. First record of a pterosaur landing trackway. Proceedings of the Royal Society B doi: 10.1098/rspb.2009.1161 online paper
Padian K 1984. The origin of pterosaurs. In: Reif W-E. & F.Westphal, Eds. Proceedings of the Third Symposium on Mesozoic Terrestrial Ecosystems, Short Papers.  Tübingen, Attempto Verlag: 163-168.
Schutt WA Jr, Altenbach JS, Chang YH, Cullinane DM, Hermanson JW, Muradali F and Bertram JEA 1997.
The dynamics of flight-initiating jumps in the common vampire bat Desmodus rotundus. The Journal of Experimental Biology 200: 3003-3012.

Darwinopterus, NOT the Transitional Pterosaur

Google Darwinopterus and you’ll get entries like: “the remarkable transitional pterosaur,” “one hell of an intermediate,” “fills evolution gap.” The news has been out for awhile now. Darwinopterus (Figure 1) has been hailed as the long lost transitional taxon bridging the basal long-tailed pterosaurs and the later short-tailed pterosaurs.

Or was it?

Pterosaurs, the flying reptiles of the Mesozoic, have been known for over 200 years, but until recently no taxon has been put forth as the transitional “link” between the primitive short-handed, long-tailed forms and the more derived long-handed, short-tailed ones. Lü et al. (2009) claimed to fill that gap with an unusual pterosaur, Darwinopterus modularis, which appeared to combine traits from both groups.

The skull and neck were described as “typically pterodactyloid,” while the remainder of the skeleton was considered “identical to that of basal pterosaurs.” This specimen was used to support the hypothesis of “modular evolution” in which the transition from basal to derived pterosaurs was posited to proceed in two phases: (1) skull and neck followed by  (2) post-cervical axial column, limb girdles and limbs.

Darwinopterids

Figure 1. Click to enlarge. Some of the several Darwinopterus specimens now known.

Four big problems arose from the Lü et al. (2009) study: 
1.The cladistic results were not robust. There were no distinct sister taxa and there was a great loss of resolution at the Darwinopterus node. No sequence of basal taxa in the Lü et al. (2009) analysis documented a gradual accumulation of Darwinopterus characters. Instead, four proximal sister taxa nested in an unresolved clade and one of those included four sister taxa in an unresolved clade. Similarly, three derived clades without resolution nested as sisters. A fine mess! And not the way evolution works!

2. The gamut of included taxa was not sufficiently broad ( = inclusive) to recover a single tree result matching evolution’s own single tree. Instead 500,000+ trees were recovered! Such loss of resolution provides little to no recoverable data. Missing from the inclusion set were all the tiny pterosaurs (skulls smaller than 2 cm in length, Figure 3) because they were traditionally considered juveniles and thus unworthy of inclusion. Also missing were several specimens considered congeneric with others but were distinct in several regards.

3. Evolution does not otherwise proceed in modules. Most fossil vertebrates can be identified by just a skull, tooth, pes or pelvis, but “modular evolution” would play havoc with this, creating chimaeras with the head of one taxon on the torso of another, as imagined in Darwinopterus by Lü et al. (2009). There is another, more parsimonious, explanation (see below).

4. Lü et al. (2009) used more than one specimen to score Darwinopterus, Scaphognathus and other pterosaurs. In Darwinopterus, the YH skull was a third longer with a larger antorbital fenestra, smaller orbit and deeper skull. Such characters change scores. Lü et al. (2009) also incorrectly scored several taxa (details on request).

Here’s how to solve all four problems at once:
Increase the size of the cladistic study inclusion set (Figure 4).

I added Darwinopterus to a cladistic analysis of 170 taxa (152 pterosaurs + 18 outgroup taxa, Figure 4)). These were tested against 185 characters. That analysis employed three times the number of taxa employed by Lü et al. (2009) against fifty percent more characters. While the Lü et al. (2009) resulted in 500,000+ trees, my analysis recovered a single tree in which there was not one, but four “pterodactyloid”-grade clades (not including the darwinopterids/wukongopterids). Completely unexpected, but it makes sense when you look at the details in each of the lineages. This new family tree goes a long way to explaining many of the mysteries surrounding pterosaurs.

Darwinopterus and kin nesting between Sordes and Scaphognathus

Figure 2. Nesting between Sordes and Scaphognathus were Pterorhynchus, Kunpengopterus, Darwinopterus and Wukongopterus (not shown), taxa with a longer skull, a longer neck and a reduced to absent naris..

Darwinopterus nested as the sister to Wukongopterus (Wang et al. 2009). Both nested as sisters to Kunpengopterus (Wang et al. 2010) and Pterorhynchus (Czerkas and Ji 2002). This clade nested between Sordes and Scaphognathus (Figure 2.), far from any of the actual transitional pterosaurs (see below). Lü et al. (2009) included Pterorhynchus in their analysis, but they did not score 27 percent of the characters. Of the remaining 80 characters 19 were scored differently in Darwinopterus and Pterorhynchus. Of these 19, I found 10 scores to be valid. Two of these described the longer rostrum in Darwinopterus. Three described the absence of a distinct naris in Darwinopterus. Of the remaining 9 characters all were incorrectly scored. (Details on available on request.)

The Actual Transitional Taxa
There were four transitional lineages (see below and Figure 4) that produced four convergent clades of “pterodactyloid”-grade pterosaurs, none of which came close to including Darwinopterus. At the bases of the four pterodactyloid-grade clades were four separate series of tiny pterosaurs, smaller than their predecessors and smaller than their successors. Each sequence documented a gradual transition from basal to derived.  Two arose from distinct Dorygnathus specimens. Two arose from the small Scaphognathus specimens (Figure 3).

The descendants of Scaphognathus.

Figure 3. Click to enlarge. The descendants of Scaphognathus. Note the size reduction followed by a size increase.

The widely-held hypothesis that small, short-rostrum pterosaurs were juveniles of larger forms is falsified by this study. Those tiny pterosaurs had a short rostrum because their ancestors within Scaphognathus also had a short rostrum. Other tiny pterosaurs did not have a short rostrum. They were basal to other clades leading to the azhdarchids and to the ctenochasmatids. If the tiny pterosaurs were juveniles, they should have nested with their parents, as in Pterodaustro.

Remember: pterosaurs were derived from a clade of lizards that grew isometrically, not allometrically. Juveniles were close matches to adults. This is never more clear than when looking at pterosaur embryos here, here and here. Even the Darwinopterus embryo was the spitting image of its mom, with a long rostrum and tiny eyes.

Pterosaur family tree

Figure 4. Click to enlarge. The family tree of the Pterosauria.

Other pterosaurs also had tiny transitional taxa. Between Campylognathoides and Rhamphorhynchussize reduction is documented. Preceding Nyctosaurus and Pteranodon a small taxon appears.

The fact that pterosaurs reduced their size during morphological transitions indicates that size reduction was a survival technique producing new morphologies (and sizes!) to keep genetic lineages from going extinct. Eudimorphodontids, dimorphododontids, dorygnathids, campylognathids and rhamphorhynchids did not survive into the Cretaceous, but their reduced descendants did. Thereafter size increases created some of the most spectacular forms now known. The tiny scaphognathids and dorygnathids were their common ancestors. This new heretical hypothesis of pterosaur relations plays havoc with traditional hypotheses, including the one invoking Cope’s rule by Hone and Benton (2007).

So what was Darwinopterus, if not a transitional pterosaur?
Sadly, Darwinopterus and Wukongopterus produced no known descendants. They were derived pterorhynchids about the same size as others. In the context of their phylogenetic nesting, both Darwinopterus and Wukongopterus inherited their so-called “basal” traits from a sister to Pterorhynchus, which also had a rather short metacarpus, long tail, long pedal digit 5 and long tail. The elongation of the skull and reduction of the naris were well underway in Pterorhynchus. The elongation of the neck was relatively slight. These traits were convergent with those in “pterodactyloid”-grade pterosaurs. A sister taxon, Wukongopterus, did not have an elongated neck. Kunpengopterus had a longer neck, but not an elongated skull (see above).

As always, I encourage readers to see the specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Czerkas SA and Ji Q 2002. A new rhamphorhynchoid with a headcrest and complex integumentary structures. In: Czerkas SJ ed. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum:Blanding, Utah, 15-41. ISBN 1-93207-501-1. 
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011a. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
Wang X, Kellner AWA, Jiang S and Meng X 2009. An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. Anais da Academia Brasileira de Ciências 81 (4): 793–812.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi & Rodrigues T 2010. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062.
Zhou C 2009. New material of Elanodactylus prolatus Andres & Ji, 2008 (Pterosauria: Pterodactyloidea) from the Early Cretaceous Yixian Formation of western Liaoning, China.Neues Jahr. Geo. Paläo. Abh. (DOI: 10.1127/0077-7749/2009/0022.)

The Myth of the Pterosaur Uropatagium

Two things helped pterosaurs fly: bones and the various soft tissues the bones supported. Unfortunately, soft tissues were not so well preserved. While pterosaur wings have warranted the lion’s share of attention, relatively little has been said about the membranes pterosaurs carried behind their knees. See Figure 1. And what little that has been reported, unfortunately, is, well, um… based on a single misidentification that has wormed its way into most pterosaur books, reports and artwork. Most pterosaur experts have accepted this misidentification as fact, and have drawn erroneous inferences from this misstep.

Take, for instance, Dr. David Hone’s contribution to Pterosaur.net, “On the ground the ‘rhamphorhynchoids’ were probably pretty poor. Their large rear membrane would have shackled their hindlegs together making walking difficult, and the shape of their hips and upper legs meant that [they] could only really sprawl and not walk upright.”

The “large rear membrane” Hone referred to is the hypothetical “uropatagium,” purportedly a single sheet of skin, etc., spanning the hind legs of basal pterosaurs from the groin to the tips of the bent back lateral toes, but not involving the tail. See Figure 2.

Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

Figure 1. Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

Never mind that Sharovipteryx clearly had paired uropatagia (one membrane trailing each hind limb). Nevermind that pterodactyloid-grade pterosaurs (Figure 1) also had paired uropatagia. Nevermind that no other animal ever had such a membrane. Nevermind the evolutionary and embryological implications and consequences. Don’t even ask if the cloaca (common egg and waste exit) was located above or below the apex of this membrane. According to most pterosaur experts, one basal pterosaur “clearly” had a uropatagium… so they all did.

Bats have analogous structures, left and right uropatagia (plural of uropatagium), but their membranes stretch between the ankle and the tail.

In pterosaurs Unwin and Bakhurina (1994) reported the “uropatagium” stretched from lateral toe to lateral toe and these “controlled” the trailing edge of this aerodynamic surface. Not sure how exactly. Not sure what pivoted or extended. That was never detailed. Look down at your own feet and imagine a membrane spanning the gap between your legs, but not from knee to knee — from outer toe to outer toe. That’s what we’re dealing with. The long stiff pterosaur tail had to be free of such a membrane. Otherwise, if embedded, it would have pointed directly into the ground between the ankles.

Uropatagium of Sordes according to Sharov 1971 and Unwin/Bakhurina 1994.

Figure 2. Uropatagium of Sordes according to Sharov 1971 and Unwin/Bakhurina 1994.

The short history of the uropatagium.
The “uropatagium problem” goes back to 1971 when Aleksandr G. Sharov described a well-preserved, small Jurassic pterosaur, which he named Sordes pilosus. It was complete, articulated and only slightly damaged (only the skull appeared to be much the worse for wear). Best of all, the holotype of Sordes preserved soft tissue: wing membranes, hair and an additional, completely unexpected membrane between the hind legs.  See figures 2 and 3.

Fast forward to 1994 and we find Dr. David Unwin and Dr. Natasha Bakhurina reporting on the same specimen in Nature, agreeing with Sharov (1971) that the soft tissue between the legs was a genuine uropatagium and reporting “well preserved wing membranes show that the hind limbs of pterosaurs were intimately involved in the flight apparatus; connected externally to the main wing membrane and internally by a uropatagium, controlled by the fifth toe.”

This false paradigm continues unchecked today.

Currently on Pterosaur.net, contributor Dr. Dave Hone writes: “The key issue here is the uropatagium – with the hindlimbs shackled together in rhamphorhyncoids, they are left with all of their limbs effectively joined together, a wing membrane from finger to ankle, the uropatagium linking the two legs, and then the other wing on the other side.”

On closer examination (using the DGS method), the “uropatagium” turns out to be something else entirely. Turns out Sordes was no different than Sharovipteryx and dozens of other pterosaurs in having two small uropatagia, each one filling the angle behind each thigh, knee and shin. See Figure 3. The other, darker material between the ankles drifted there during taphonomy. Its the proximal part of the left wing.

The myth of the pterosaur uropatagium

Figure 3. Click to enlarge. The Sordes uropatagium is actually displaced wing material carried between the ankles by the displaced radius and ulna.

The famous Sordes holotype specimen is preserved crushed upon its belly. The right wing was virtually pristine, naturally articulated and nicely preserving a narrow wing membrane. The well-defined trailing edge extended from the wing tip up to an acute curve behind the metacarpals then back toward the body, paralleling the ulna to a point aft of the elbow and finally inserting near the middle of the front of the femur (Peters 2002 and Fig. 3).

The proximal left wing of Sordes did not fare so well. The three distal phalanges of the left wing were in their correct place, but the first (proximal) wing phalanx was bent in toward the body, just a short distance from the distal humerus. Sharov (1971) tentatively identified this phalanx as the radius + ulna, probably because it was in the mirror-image position of the right radius + ulna. The left humerus was parallel to the right one, but less well preserved. A complete hand with articulated short fingers was in the area of the supposed skull. Nevermind the skull.  The left radius and ulna were missing! No one ever noticed this before.

I found the radius and ulna. They had drifted back between the left ankle and left wing, along with a certain amount of proximal wing tissue. Some of this folded, spindled and mutilated wing membrane came to rest between the ankles, creating the illusion of the rear margin of a symmetrical “uropatagium. It is easy to see there is no preservation of membrane material in the center of the gap between the legs. Also note that the actual uropatagia have arcing shapes matching those of sister pterosaurs. So, the purported uropatagium, the soft tissue around and between the ankles, turns out to be nothing more than displaced material from the left wing..The sharp lines preserved between the left wing and left ankle drawn by prior workers turn out to be either the radius or the ulna (they are very much alike) with the other forearm bone intersecting it at a slight angle.

I have never seen the fossil itself, only an image on my monitor. Those who viewed the fossil first hand overlooked this data. I also overlooked this data in Peters (2002) when I noted that lines marking “trailing edges” were continued beyond the outline of the specimen, suggesting that they represented geological faults created during the splitting of the plate and counterplate. That still holds true for the right wing. I didn’t realize the left radius and ulna were missing until I undertook a detailed tracing of the area.

So, just like all other pterosaurs and their fenestrasaur sisters, Sordes had twin uropatagia behind its knees. No membrane stretched from ankle to ankle and toe to toe. Rhamphorhynchoids did not have shackled hindlimbs. Nor did the hind leg affect or restrict the movements of the wing because there was no attachment of the wing to the ankle (Peters 2002). Hope this clears things up.

Read more about the evolution of fenestrasaur/pterosaur uropatagia here.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Peters D 2002.
A New Model for the Evolution of the Pterosaur Wing—with a twist. Historical Biology 15:277-301.
Sharov AG 1971. New flying reptiles fro the Mesozoic of Kazakhstan and Kirghizia. – Trudy of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.

The Myth of the Bat Wing Pterosaur

Toy Pteranodon, ca. 1962, from the Marx Company.

Toy Pteranodon, ca. 1962, from the Marx Company.

To paraphrase Dr. Robert T. Bakker in The Dinosaur Heresies: I remember the first time the thought struck me! There’s something very wrong with that toy Pteranodon. It was a Marx toy (Fig. 1) with big, floppy wings that could NOT have been folded away. The wings extended, like bat wings, to the hind limbs, and so had a very deep chord, a shape still in favor by most pterosaur workers. Even as a kid I knew birds and bats could fold their wings close to their bodies, as compact as possible. The Marx Pteranodon looked to be incapable of that. The pterosaurs in the Jurassic Park series suffered from the same deep-chord malady (Fig. 2).

Saggy blanket Pteranodon wing membrane from Jurassic Park 2

Figure 2. The deep chord wing model produces a "sagging blanket" wing membrane whenever the wing is folded. That is NOT reflected in known fossils.

Comparing pterosaurs, bats and birds.

Figure 3. Comparing pterosaurs, bats and birds.

Wings made pterosaurs the first vertebrates to achieve powered flight, but the shape of those wings has been argued about for decades. Most experts (Unwin and Bakhurina 1994; Elgin, Hone and Frey 2011, for instance) follow the traditional bat-wing model (Figure 3), with a deep trailing edge curving back to attach at the ankle. Such a wing is incapable of being folded away without sagging.

Another wing model emerged when Bennett (1987) reported on bicondylar and fused tail bones in Pteranodon that could move only up and down. He proposed a wing model in which trailing edge attached to the tail tip and so could be lifted and depressed like an airplane elevator (Figure 4).

At about the same time, Padian (1987) and Padian and Rayner (1993) argued against the bat-wing model in favor of a more bird-style model by attaching the trailing edge to the middle or posterior of the pelvis (Figure 4) with hind legs tucked in. Ironically, while arguing against the bat-wing paradigm, Padian and Rayner (1993) fell sway to its influence and invented more wing tissue aft of the elbow in their reconstruction than they showed in various fossils (see below).

Padian and Bennett wing models

Figure 4. Various "narrow chord" wing membrane proposals, but note that all, except Peters (2002) include a large amount of material aft of the elbows, as in the bat-wing model.

Here’s the evidence for the traditional bat-wing model.
Elgin, Hone and Frey (2011) documented the latest evidence for pterosaur wing shape. Unfortunately, rather than firmly documenting their conclusions, they could only report, “A review of relevant pterosaur specimens … strongly suggests that the trailing edge of the wing extended down to the lower leg or ankle in all specimens where the brachiopatagium is completely preserved.” Strongly suggests???!!!  I was hoping for something a little more fim. Here’s their evidence:

Darkwing Rhamphorhynchus

Figure 5. Darkwing Rhamphorhynchus traced by Elgin, Hone and Frey (2011). The displaced humerus is highlighted in yellow. Note the trailing edge of the wing is directed toward the elbow.

1. The “darkwing” Rhamphorhynchus was traced “as is” with a continuous tone deemed to represent a wing membrane that attached at mid thigh (Figure 5). Note that the left humerus was disarticulated and displaced posteriorly. Even so, the wing membrane trailing edge was directed precisely at the elbow, as in the Peters (2002) model. The strip of soft tissue extending down the thigh was on a level below the wing membrane, not continuous with it. The Zittel wing specimen of Rhamphorhynchus was not used by Elgin, Hone and Frey (2011) despite preserving a exquisite wing membrane that was extremely short at the elbow, supporting the Peters (2002) model.

Jeholopterus wing and soft tissue traced

Figure 6. This Elgin, Hone and Frey (2011) tracing did not distinguish between hairs and wing membranes. It also did not include data from the counterplate.

2. The holotype Jeholopterus specimen (Figure 6) was traced only from the plate with no distinction made between the long pycnofibers (hairs) and wing membrane. An alternative reconstruction is offered here in which the counterplate is also employed and a more precise tracing of the soft tissues are documented separating the narrow wings from the long pycnofibers.

Vienna specimen of Pterodactylus.

Figure 7. Elgin, Hone and Frey excused this narrow-at-the-elbow preservation as the result of "membrane shrinkage."

3. The Vienna specimen of Pterodactylus (Figure 7) was traced accurately, without much membrane posterior to the elbow. Rather than taking this example at face value (and it compares well with the Zittel wing, among others), Elgin, Hone and Frey (2011) invented the taphonomic malady “membrane shrinkage” to explain away the absence of wing membrane needed to fulfill their bat-wing paradigm. Nevermind that there was no “membrane shrinkage” elsewhere on the specimen. The Vienna specimen is animated below. It shows that if one adopts the “what you see is what you get” approach to evidence, the wing membrane extends and folds away very nicely indeed– as is!

Figure 8. Bennett (2007) Anurognathus? with yellow added to show extent of wing membrane when only three wing phalanges are employed.

4. The private specimen of Anurognathus (Bennett 2007a, Figure 8 ) was employed by Elgin, Hone and Frey (2011), but they did not use gray tones to delineate what they considered wing membranes. Rather three lines indicated it. They noted that no membrane attached to the ankle, but failed to note that the trailing edge they drew extended straight to the elbow, as in the Peters (2002) model. The DGS method revealed fourth wing phalanges largely buried in the matrix beneath the left foot and right tibia, revealed here.

Eosipteruswing

Figure 9. Elgin, Hone and Frey (2011) traced the wing membranes of Eosipterus, noting that no membranes were present lateral to the tibiae. Here a yellow tone completes the membrane patches and produces a complete shape that follows the Zittel wing/Peters (2002) model.

5. Elgin, Hone and Frey (2011) employed Eosipterus (Figure 9) in which they traced patches of wing membrane not realizing that when one completes the puzzle, the results support the Peters (2002) wing shape model. Again, no material was found lateral to the ankles or shins.

6. The best example of the bat-wing model has always been Sordes pilosus (Sharov 1971, Figure 10). This is the only specimen in which wing material was preserved lateral to the ankles–but there’s more to this story! Elgin, Hone and Frey (2011) traced few details and overlooked the displaced radius (or ulna) that formed the trailing edge of their interpretation of the left wing (details here). It was indeed the left wing, but torn, displaced and preserved in such a way that the membrane continued between the ankles where it created the illusion of a uropatagium. Elgin, Hone and Frey also failed to note the continuation of the right wing trailing edge as it headed toward the metacarpophalangeal joint before turning back to the elbow and anterior femur, again as in the Peters (2002) model.

Sordes as traced by Elgin, Hone and Frey 2011

Figure 10. Click to enlarge. Sordes as traced by Elgin, Hone and Frey 2011 on the left. On the right wing they failed to note the continuing trailing edge of the wing membrane that curved toward the elbow. On the left wing they failed to note the displaced radius (or ulna) that produced the illusion of a trailing edge membrane that extended to the ankle and created a false uropatagium between the ankles. These errors are highlighted in yellow, orange and pink on the right hand image.

Elgin, Hone and Frey (2011) made several more mistakes when they created their reconstruction of the pterosaur wing, detailed in Figure 11. These workers, like many others before them, ignored and made excuses for clear “what you see is what you get” evidence supporting the Peters (2002) model in favor of the unsupportable, centuries-old bat-wing paradigm.

Figure 8. Click to enlarge. Problems with the Elgin, Hone and Frey (2011) pterosaur wing model with corrections proposed by Peters (2002).

Figure 11. Click to enlarge. Problems with the Elgin, Hone and Frey (2011) pterosaur wing model with corrections proposed by Peters (2002).

Elgin, Hone and Frey (2011) say these specimens suffer from "membrane shrinkage."

Figure 12. Click to enlarge. Elgin, Hone and Frey (2011) say these specimens suffered from "membrane shrinkage." Actually, as you can see, the wing fingers are twisted on the Rhamphorhynchus such that the membrane was preserved in front of the bones. Overlooked were the proximal membranes which are visible even in this black and white photo. The Jeholopterus? specimen has torn wing membranes. They also did not "shrink."

Now for the heretical view.
Peters (2002) argued for a “what you see is what you get”model and reconstructed a narrow trailing edge essentially stretched between the elbow and wing tip with a short fuselage fillet filling the gap between the elbow and mid thigh (Figures 13, 14). This wing shape is duplicated in every pterosaur in which wing material is known. Note how well it folds up to prevent damage. A deep-chord wing (at the elbow) cannot do that. Note that phalanx four either curves or is bent posteriorly, matching the curvature of the trailing edge of the tip caused by aktinofibrils separating like strips on a bamboo fan, stretching membrane between them. Note that the wing is aerodynamically taut only at full extension and that tension runs between the elbow and wing tip. The hind limb is independent.

Pterosaurs originated as flapping leapers, not as gliders. Those wings developed distally first, not as gliding membranes close to the body (contra Bennett 2008).

Figure 13. Click to animate. The Vienna specimen of Pterodactylus (wings folded). Animation opens the wings and legs to reveal the true shape of pterosaur wings, stretched between the elbow and wingtip with a short fuselage fillet extending from elbow to mid femur.

Arthurdactylus

Figure 14. Click to enlarge. The left wing of the pterosaur Arthurdactylus in dorsal view based on the Peters (2002) bird-wing model.

The bird-wing model for pterosaur wings reaches its acme in ornithocheirids like Arthurdactylus (Figure 14.) Not only does this wing shape create a nice airfoil like that of a sailplane, but it folds away to virtual invisibility!

There never has been evidence for any membrane lateral to the tibia. Please send any, if found. All available evidence supports the bird-wing model.

(There were also earlier rumblings about the correct orientation of the pteroid: forward and variable (Frey) vs. medial and fixed (Bennett 2007b, Peters 2009). Medial and fixed is correct, but we’ll take a look at that issue later.)

As always, I encourage readers to see the specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Bennett SC 1987. New evidence on the tail of the pterosaur Pteranodon (Archosauria: Pterosauria). Pp. 18-23 Currie, PJ and Koster EH, eds. Fourth Symposium on Mesozoic Terrestrial Ecosystems, Short Papers. Occasional Papers of the Tyrrell Museum of Paleontology, #3.
Bennett SC 2007a. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Bennett SC 2007b. Articulation and Function of the Pteroid Bone of Pterosaurs. Journal of Vertebrate Paleontology 27(4):881–891.
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E. Buffetaut & D.W.E. Hone (eds.), Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
Elgin RA, Hone DWE, and Frey E. 2011.The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111 doi:10.4202/app.2009.0145 online pdf
Padian K 1987. The case of the bat-winged pterosaur. In: Czerkas, S.J. and Olson, E.C., eds, Dinosaurs Past and Present (Natural History Museum of Los Angeles County/ University of Washington Press, California/Seattle) Vol. II, pp. 65–81.
Padian K and RaynerJV 1993. The wings of pterosaurs. American Journal of Science 239-A, 91–166.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing—with a twist. Historical Biology 15:277-301.
Sharov AG 1971.New flying reptiles fro the Mesozoic of Kazakhstan and Kirghizia. Trudy of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.

What exactly IS a pterosaur? – part 3 of 3

In part 1 we looked at two competing hypotheses of pterosaur origins: the more popular and traditional archosaur hypothesis and the typically avoided and heretical fenestrasaur hypothesis.

In part 2 we took a closer look at the character traits used by Senter (2003) and Nesbitt (2011) to connect pterosaurs to archosaurs.

Here, in part 3, you’ll meet a series of taxa that document a gradual increase in pterosaurian traits: Lacertulus, Meyasaurus, Huehuecuetzpalli and the fenestrasaurs. An asterisk (*) marks the pterosaurian characters. Links will take you to reptileevolution.com for additional imagery and data. References follow the descriptions.

Click to enlarge. Squamates, tritosaurs and fenestrasaurs in the phylogenetic lineage preceding the origin of the Pterosauria.

Click to enlarge. Squamates, tritosaurs and fenestrasaurs in the phylogenetic lineage preceding the origin of the Pterosauria.

Lacertulus bipes (Carroll and Thompson 1982) Late Permian, ~5 cm snout/vent length. Lacertulus was originally described as a facultatively bipedal* primitive lizard or eosuchian representing a distinct lineage of one or the other. Here Lacertulus was derived from a sister to Homoeosaurus and Gephyrosaurus and was a phylogenetic predecessor to a new clade of lizards, the Tritosauria (“third lizards”) that includes Meyasaurus and its descendants, including pterosaurs. The Lacertulus fossil is complete and articulated, but poorly preserved, especially anteriorly.

Overall, Lacertulus was about half the size of Homoeosaurus. The nasal was notched* above the naris slightly expanding the size of the opening. The maxilla formed the majority of the ventral margin of the naris.* The pterygoid extended anteriorly as far as the palatine.* The lateral process of the palatine was set further posteriorly.* Distinct from most lizards, the teeth were subthecodont in implantation.*

There were 24 presacral vertebrae, perhaps one fewer than in Gephyrosaurus. The neural arches were low and not fused to the centra. The neural spines were low to absent.

The forelimbs were much shorter than the hind limbs. The radius and ulna had little to no end expansion, so they were aligned closer to one another*. The olecranon was ossified in a pattern distinct from living lizards. The carpals were tiny but ossified and rounded, rather than locked in a tight mosaic as in many living lizards.

The pelvis was taller than long with a distinct anterior process on the ilium.* Such a process in living lizards capable of bipedal locomotion helps raise the front of the body off the ground (Snyder 1954). The pubis was narrower, producing a larger thyroid fenestra. The femur was longer than half the glenoid-acetabulum length.* The tibia was more robust than the fibula.* The astragalus, calcaneum and centrale remained unfused,* unlike most lizards.* The pes was twice the length of the manus. Metacarpals 1-4 were bound together. The foot was large with a tendril-like digit 4 ideal for arboreal (tree branch) locomotion. The phalanges of pedal digit 5 were likewise elongated.*

Meyasaurus faurai (Vidal 1915, Evans and Barbadillo 1996) Early Cretaceous, ~10 cm skull length. Despite being a large Late Cretaceous relic, Meyasaurus was derived from a sister to the Late Permian Lacertulus and phylogenetically preceded Huehuecuetzpalli.

Distinct from Lacertulus the skull of Meyasaurus had a more sharply angled rostrum* and a longer temporal area. The postorbital did not descend as far. The premaxillary dorsal process extended beyond the naris.* The parietal was larger. The pineal opening was a mere pinprick and located further forward*. The frontal-parietal suture was straight and much wider than the frontal-nasal suture.* The frontal was narrower between the orbits.* The teeth were tiny and the posterior teeth had twin cusps (bicuspid), a character sometimes retained in Gekko. Multiple cusps are seen in Sharovipteryx and Longisquama as well as basal pterosaurs.

The cervicals of Meyasaurus were more robust* with large paddle-shaped ribs. The scapulocoracoid was fenestrated anteriorly,* as in other lizards. The clavicle was more robust. The humerus was expanded distally. Metacarpal 4 was shorter than 3. The pelvis, tail and hind limbs are unknown in the adult, only in a referred juvenile.

Huehuecuetzpalli mixtecus (Reynoso 1998) Middle to Late Albian, Early Cretaceous ~110 mya, ~9.5 cm snout to vent length. Huehuecuetzpalli nested at the base of all lizards in the original analysis of Reynoso (1998). Here Huehuecuetzpalli was derived from a sister to Meyasaurus and was a phylogenetic predecessor to Cosesaurus, and Macrocnemus

Distinct from Meyasaurus, the skull of Huehuecuetzpalli was narrower* (in dorsal view) with a posteriorly displaced and enlarged naris*. The premaxilla was extended anteriorly*. The premaxillary ascending process extended nearly to the orbit*. The nasal was further split by the posterodorsal expansion of the naris*. The pineal foramen was on the frontal/parietal suture*. The postfrontal was reduced*. It lost contact with the upper temporal fenestra, replaced with a lateral extension of the parietal and a medial extension of the postorbital*. Rather than a broad and solid palate (as in Lacertulus), the pterygoid was shorter, narrower and reduced to just the transverse processes and the quadrate processes*. The vomers and palatines were also reduced to struts*.

Transverse processes and chevrons were smaller.* Three sacrals were present.* The caudals were attenuate.* The chevrons paralleled the centra.*

An ossified sternum* covered the posterior tip of the T-shaped interclavicle. The scapula and coracoid were further fenestrated anteriorly,* as in most living lizards. The scapula was very short, but likely was made taller by a cartilage extension, as in many living lizards. The radius and ulna were expanded at their ends.* Metacarpals 3 and 4 were subequal.* The carpus was unossified, even in the adult. This had important ramifications in the lineage of a successor, Cosesaurus with regard to the appearance of the pteroid.

The ilium developed a long posterior process.* The fibula was less than half the width of the tibia.* The calcaneum was half the size of the astragalus. Metatarsal 5 was shorter and torsioned.* Metatarsals 3 and 4 were subequal. Pedal digit V was further elongated with p5.1 more than half the length of mt 4.*

The robust hind limb and three sacral vertebrae might suggest a facultative bipedal capability in the manner of similar living lizards and Lacertulus, despite the lack of an anterior ilial process.

Mammals, crocs, birds, turtles and other lizards all practice allometric growth in which changes occur with maturity. In contrast, a juvenile Huehuecuetzpalli is known and it is virtually identical in proportion to the adult (Reynoso 1998). More data is needed, but from what little is known, this clade experienced isometric growth.* Juveniles and hatchlings were virtually identical to adults. They lacked a short snout and large eyes.

Macrocnemus bassanii
(Nopcsa 1931) Ladinian, Middle Triassic ~220mya

The smallest specimen of Macrocnemus, BES SC 111 (Renesto and Avanzini 2002), was originally considered a juvenile, but it was morphologically distinct from the other larger specimens. Here it is the most primitive Macrocnemus now known. BES SC 111 was derived from a sister to Huehuecuetzpalli and it documents a further elongation and narrowing of the naris,* a shorter temporal region,* a longer neck of eight vertebrae,* an incipient strap-like scapula,* a broader ventral pelvis* and a more pterosaur-like palate,* but pedal phalanx 5.1 is reduced, which is an autapomorphy (a unique trait within this clade). None of the tail vertebrae show any sign of caudal autotomy,* which in several living lizards permits the tail to breakoff during an attack only to regrow later.

Langobardisaurus tonneloi was a sister to Macrocnemus that retained an elongated pedal 5.1 phalanx.

 

Cosesaurus aviceps (Ellenberger and DeVillalta 1974) Middle Triassic ~225 mya, ~16cm long was derived from a sister to Macrocnemus. Cosesaurus phylogenetically preceded Sharovipteryx and Longisquama.

Distinct from Macrocnemus, the rostrum of Cosesaurus had a more deeply concave dorsal profile, which further reduced the naris to a long slit. The rostrum was shorter. By contrast, the postorbital region was expanded to include a larger cranium.* The maxilla had three openings, together representing the origin of the single antorbital fenestra without a fossa.* The palatine had no lateral process.* The parasphenoid was relatively enlarged. The occiput was steeply angled as if the cervicals were typically held further beneath the skull.*

The cervicals were midway in length between those of Macronemus and Huehuecuetzpalli.* Four sacrals were present.*

The scapula was reduced to a slender strap-like shape oriented posterodorsally.* The coracoid was reduced to a stem,* resulting from further coracoid fenestration expanded posteriorly until only the posterior quadrant-shaped rim remained. The coracoid stem inserted into a socket* created by the anterior migration of the sternum* to the transverse processes of the interclavicle.

The sternum was broader* and anteriorly displaced* such that the anterior rim was coincident with the transverse processes of the interclavicle and clavicles. The clavicles were shorter and only transverse in orientation.* They did not extend along the anterior rims of the coracoids and scapula, as in most tetrapods including Macrocnemus. Instead the clavicles wrapped around the coincident interclavicle and sternum anterior rims creating the sternal complex* otherwise found in Longisquama and pterosaurs (Wild 1993). The interclavicle developed an anterior process making it cruciform.* The two centralia, best seen in Sphenodon, had migrated to the medial edge of the wrist where they assumed new identities as the pteroid* and preaxial carpal* (Peters 2009). The manus was much larger and longer than the forearm,* with metacarpals and digits less disparate in size* except digit V, which was reduced to a vestige.*

The pelvis was considerably smaller overall, but with a longer anterior process of the ilium* and a much smaller pubis and ischium. A new bone, the prepubis,* extended beyond the pubis increasing its effective length. The proximal tarsals were the same width*. Metatarsals I-IV were less disparate in length.* Pedal 5.1 was longer than the rest of the digit.*

Soft tissue impressions of a sagittal crest and plumes, plus extradermal membranes trailing the limbs (primitive patagium and uropatagium)* were preserved. “Hairs” emanated from the caudal vertebrae.*

In Cosesaurus the coracoids were socketed, as in birds and pterosaurs. If similar in function, Cosesaurus was flapping its forelimbs long before the advent of a wing-like morphology. This was likely a secondary sexual characteristic enabled by facultative bipedal locomotion.

Digitigrade, occasionally bipedal footprints attributed to the ichnogenus Rotodactylus (Peabody 1948) were matched to the pes of Cosesaurus (Peters 2000a). Digit 5 made a small circular impression far behind the other four toes*, of which digit 1 only impressed the ungual. The proximal phalanges were all held elevated,* because the metatarsophalangeal joint was a simple butt joint*, incapable of much movement. A flexed digit V* impressed its dorsal surface far behind the other four toes, a configuration unknown outside of the Fenestrasauria.

Sharovipteryx miribilis (Sharov 1971) Norian, Late Triassic, ~210 mya was originally considered a pseudosuchian, then a prolacertiform (Peters 2000). Here Sharovipteryx nests as a tritosaurid lizard derived from a sister to Cosesaurus. Sharovipteryx is a sister to Longisquama and pterosaurs.

Distinct from Cosesaurus, the skull of Sharovipteryx had an upturned premaxilla with procumbent teeth.* The naris was enlarged* and a smaller antorbital fenestra was present. The postorbital was higher relative to the orbit.* The rostrum was straighter.* The ventral mandible was more convex. The teeth were more varied in shape, with rear teeth having several cusps.* Long hyoids emerged from the base of the throat. These were moved laterally to create aerodynamic strakes from the extended neck skin.

The cervicals were elongated. The dorsals were shortened.* 24 presacrals were present, but three of them were located between the ilia.* Several more caudal vertebrae joined the sacral series.* This was probably in response to the increase in stress at the fulcrum of the obligate bipedal configuration. The caudals were lengthened.* The dorsal ribs extended horizontally creating a wide but shallow torso, yet another aerodynamic surface.

The coracoid was straighter. The entire forelimb was reduced. The humerus was short but robust with a large deltopectoral crest.* The ulna and radius were also robust, but shorter than the metacarpus. Digit IV was discovered by Sharov (1971) extending back to the pelvis*. The other shorter digits, long considered missing, follow the pattern of sister taxa.

The ilium was hyper-elongated, both anteriorly and posteriorly.* The puboischium was deeper than in Cosesaurus.* The prepubis was straighter. The hind limbs were extremely long* with a femur longer than the torso. The distal femur had a short anterior extension to prevent overextension of the tibia. The tibia was longer than the femur.* The metatarsals spread apart, unlike other fenestrasaurs. Digit V was further elongated such that pedal 5.1 was longer than metatarsal 4.

Various extradermal membranes surrounded Sharovipteryx. The neck skin was six times wider than the cervicals and able to be spread even wider by lateral extension of the hyoids. Fiber-supported uropatagia extended from the hind limbs,* from digit 5 to the base of the tail. Smaller membranes extended anterior to the femur and at the base of the tibia. Webbing was present between the toes.* Elongated fibers tipped the tail*, a likely precursor to the vane in pterosaurs. Fiber-embedded membranes were also preserved in the damaged areas around the forelimbs.

With its diminutive forelimbs, Sharovipteryx would seem to be dissimilar to pterosaurs, but the rest of its traits find no better match. With such long hind limbs, Sharovipteryx was unable to walk quadrupedally, but leaping was greatly improved. It is widely held that pterosaurs were ALL quadrupedal, but Cosesaurus and Sharovipteryx were facultative and obligate bipeds respectively. Hone and Benton (2007) objected when Peters (2000) presented fenestrasaurs as bipeds despite the fact that matching footprints confirm that configuration and less well-endowed living lizards are able to stand and run bipedally (Snyder 1954). They offered no competing reconstructions.

The origin of the Pterosauria from basal Fenestrasauria

The origin of the Pterosauria from basal Fenestrasauria

Longisquama insignis (Sharov 1970) Norian, Late Triassic, ~210 mya was derived from a sister to Cosesaurus and Sharovipteryx and was a phylogenetic predecessor to the basal pterosaur, MPUM6009.

Distinct from Cosesaurus, the skull of Longsiquama had a more constricted (in dorsal view) snout, which enhanced binocular vision. The orbits were larger. The posterior teeth had larger cusps*. The quadrate leaned posteriorly.*

The cervicals were shorter* and the dorsal series was longer, especially so near the hips and between the ilia. Even so the presacral count was reduced to 21.* The sacrum curved dorsally 90 degrees,* which elevated the attenuated tail.* These vertebral modifications made Longsiquama somewhat similar to a lemur, which also leaps from tree to tree. Such a long torso provided more room for plumes, gave the backbone great flexibility, and provided more room for egg production.

The pectoral girdle was little changed from Cosesaurus, but the clavicles curved around the sternal complex* and the sternal keel was deeper.* Now fused together the interclavicle, clavicles and sternum formed a sternal complex.*

It is difficult to determine if metacarpal IV was torsioned* or not and difficult to ascertain the ability and degree of finger 4 to fold. The fingers were all greatly enlarged, especially finger 4.* The loss of continuity in the PILs (parallel interphalangeal lines) indicates that finger 4 no longer worked in consort with digits 1-3.*

The posterior ilium was angled dorsally* matching the dorsally curved sacrum. The pubis and ischium were much deeper,* which provided a much larger pelvic aperture to pass a much larger egg. The hind limb was more robust. The foot was relatively large with digits of increasing length laterally.* The metatarsals were compressed,* as in Cosesaurus. Pedal digit V had a curved proximal phalanx.

Longisquama was named for its extradermal dorsal plumes. Another set of plumes arose from its skull and neck. Former caudal hairs (in Cosesaurus) formed a tail vane*. Pterosaur-like patagia trailed the forelimbs*. Longisquama was overloaded with secondary sexual characteristics. From plumes to flapping arms, Longisquama was all about creating an exciting presentation unrivaled in the Triassic. Longisquama had everything Cosesaurus had, only wildly exaggerated. With increased bipedalism and active flapping, Longiquama probably experienced the genesis of aerobic metabolism.*

Pterosaurs did not develop from Longisquama. They shared a common ancestor. The pterosaurs, once they developed larger wings, did not continue to elaborate the plumes as those would have hampered flight. Pterosaurs did not have more robust hind limbs or a long dorsal vertebral series.

Eudimorphodon? Carniadactylus? MPUM 6009 (Wild 1978) Norian, Late Triassic, ~210 mya was originally considered a juvenile Eudimorphodon ranzii. Later Dalla Vecchia (2009) considered this specimen congeneric with Carniadactylus, but the morphological differences are too great. Often called “the Milan specimen” MPUM 6009 is a distinct taxon and the most primitive known pterosaur following the analysis of (Peters 2007) with the resulting tree seen here.

Distinct from Longisquama, the skull of the Milan specimen was proportionately larger. The antorbital fenestra was larger, reaching the top of the skull. The mandible was more gracile.

Atypical for most pterosaurs, but similar to Longisquama and anurognathid pterosaurs, the cervicals were relatively short, but much more robust. The dorsal series was shorter. The caudals were more slender.

The sternal complex had posterior indentions marking the contributions of the now fused clavicles and sternum. The coracoid retained its quadrant curve, but was more robust. The hand was relatively smaller, but manual digit IV was hyper-elongated to form the spar for a wing membrane. Complete folding of digit IV against the ulna was possible due to the torsion of metacarpal IV. Manual digit V became an even smaller vestige, but still retained three phalanges including a sharp ungual.

The ilium was slightly shorter. The pubis and ischium were ventrally separated. The femoral head was inturned but no distinct neck was visible. The prepubis extended halfway to the knee. The hind limb was relatively the longest among pterosaurs, similar to that of Longisquama. The digitigrade pes was relatively smaller. Pedal 5.2 and p5.3 were fused and preserved folded against p5.1, which was straight. The pedal digit V ungual was retained.

Cranial and dorsal plumes were similar to those in Cosesaurus, but smaller than in Longisquama. The wing membranes extended behind the elongated wing finger. A better flyer than Longisquama, MPUM 6009 had wing proportions more like those of other pterosaurs. It is doubtful that MPUM 6009 was ever a quadruped owing to the relative limb lengths.

Many of the evolutionary changes from Longisquama to MPUM 6009 (i.e. larger skull, shorter torso) could have been the result of paedomorphosis or they could have been the result of natural selection in a flyer, rather than a leaper, with certain traits (long legs, elevated tail, short neck) retained. As in Longisquama, the pelvic aperture and wide posterior sacrals indicate a relatively larger egg could have been delivered.

This series of taxa documents the origin of the pterosaur wing without having to imagine wing pronation, loss of digit V, loss of ungual 4 and migration of metacarpals I-III to the anterior face of metacarpal IV, as Bennett (2008) postulated.

Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoolological Journal of the Linnean Society 118: 261–308.
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E. Buffetaut & D.W.E. Hone (eds.), Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
Carroll and Thompson 1982. A bipedal lizardlike reptile fro the Karroo. Journal of Palaeontology 56:1-10.
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.) rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465-469. PDF online
Hone DWE and Benton MJ 2008. Contrasting supertree and total-evidence methods: the origin of the pterosaurs. In: Hone DWE, Buffetaut E, editors. Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Vol. 28. Munich: Zittel B. p. 35-60.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Nopcsa F 1931. Macrocnemus nicht Macrochemus. Centralblatt fur Mineralogie. Geologic und Palaeontologie; Stuttgart. 1931 Abt B 655–656.
Peabody FE 1948. Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah. University of California Publications, Bulletin of the Department of Geological Sciences 27: 295-468.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7:11-41.
Peters D 2000b. A reexamination of four prolacertiforms with implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Renesto S and Avanzini M 2002. Skin remains in a juvenile Macrocnemus bassanii Nopsca (Reptilia, Prolacertiformes) from the Middle Triassic of Northern Italy. Jahrbuch Geologie und Paläontologie, Abhandlung 224(1):31-48.
Sharov AG 1971. New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. – Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113.
Snyder RC 1954. The anatomy and function of the pelvic girdle and hind limb in lizard locomotion. American Journal of Anatomy 95:1-46
Vidal LM 1915. Nota geologica y paleontologica sobre el Jurásico superior de la provincia de Lérida. Bolletino del Instituto de Geologica Minerales España, 36: 1-43.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.
Wild R 1993. A juvenile specimen of Eudimorphodon ranzii Zambelli (Reptilia, Pterosauria) from the upper Triassic (Norian) of Bergamo. Rivisita Museo Civico di Scienze Naturali “E. Caffi” Bergamo 16: 95-120.

We’ll look at soft tissue in pterosaurs in the next two posts.

 

What exactly IS a pterosaur? – part 2 of 3

In part 1 we looked at two competing hypotheses of pterosaur origins: the more popular and traditional archosaur hypothesis and the typically avoided and heretical fenestrasaur hypothesis.

In part 2 we take a closer look at the character traits used by Senter (2003) and Nesbitt (2011) to connect pterosaurs to archosaurs. Reconstructions of the featured taxa can be seen by clicking on these links: Scleromochlus, Eudimorphdon, Austriadactylus, Cosesaurus, Sharovipteryx and Longisquama.

In part 3 we will review a series of taxa that actually document a gradual increase in pterosaurian traits: the basal squamates, MeyasaurusLacertulus, Huehuecuetzpalli and the fenestrasaurs, Cosesaurus, Sharovipteryx and Longisquama.

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Senter (2003) employed the Triassic pterosaurs Eudimorphodon and Austriadactylus and found the following 21 synapomorphies for the Pterosauromorpha (Scleromochlus + pterosaurs):

1. Angle between scapular blade and acromion process > 160 degrees.
True for Scleromochlus.
True for Pterosaurs.
True for Cosesaurus through Longisquama. BTW, these taxa all have a strap-like scapula.

2. Sharp tapering of snout to an anterior point in lateral view.
True for Sclermomochlus, but only in dorsal view.
True for pterosaurs.
True for Cosesaurus through Longisquama.

3. Maxilla contacts external naris.
False for Scleromochlus, as in sister taxa Gracilisuchus and Terrestrisuchus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

4. Anterior extremity of maxilla anterior to external naris.
False for Scleromochlus as in sister taxa Gracilisuchus and Terrestrisuchus.
True for pterosaurs.
True for Cosesaurus through Sharovipteryx (unknown in Longisquama).

5. Antorbital fossa absent anterior to internal antorbital fenestra.
False for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

6. Jugal extends anterior to contact with lacrimal.
True for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

7. Ventral margin of squamosal (anteriorly) below mid-height of orbit.
False for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

8. Interdental plates absent.
This has not yet been determined for these crushed taxa.

9. Number of sacral vertebrae increased to four.
True for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

10. Anterior hemal arches < 1.5x length of associated vertebrae.
True for Scleromochlus for first arch, but subsequent arches are > 2x. Hemal arches are oriented ventrally.
True for Austriadactylus. Unknown in Eudimorphodon.
True for Cosesaurus through Longisquama. In fenestrasaurs, including pterosaurs, hemal arches are oriented posteriorly.

11. Anteriormost T-shaped hemal arch proximal to ninth caudal vertebra.
No hemal arches are T-shaped in these taxa.

12. Sternum > 2x length of sternal end of coracoid.
False for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

13. Metacarpal 1 > 0.6x length of metacarpal 2.
True for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

14. Metacarpal IV subequal in length to or longer than metacarpal III.
False for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

15. Manual phalanx 2.2 > 1.3x length of phalanx 2.1.
False for Scleromochlus.
True for pterosaurs, but only for Eudimorphodon and Austriadactylus among basal pterosaurs.
False for Cosesaurus through Longisquama.

16. Manual digit V demonstrably absent, including metacarpal.
Probably false for Scleromochlus. Digits 4 and 5 are not visible, but they would be extremely tiny. In the sister taxon, Terrestrisuchus digit 5 is present.
False for pterosaurs. Widely considered absent in pterosaurs, manual digit 5 is actually present as a vestige on all pterosaurs.
False for Cosesaurus through Longisquama.

17. Dorsoventrally shallow extension of iliac blade anterior to pubic peduncle.
False for Scleromochlus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

18. Fibular midshaft diameter < 0.5x tibial midshaft diameter.
True for Scleromochlus. But also true for sister taxa, Gracilisuchus and Terrestrisuchus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

19. Pedal phalanx p5.1 elongated.
False for Scleromochlus. Also absent in sister taxa, Gracilisuchus and Terrestrisuchus.
True for pterosaurs.
True for Cosesaurus through Longisquama.

20. Height of maxilla ventral to internal antorbital fenestra, < 1/3 total maxillary height.
True for Scleromochlus.
False for Eudimorphodon. True for Austriadactylus.
False for Cosesaurus and Longisquama.

21. Mandibular fenestra absent.
False for Scleromochlus and sister taxa including Terrestrisuchus and Gracilisuchus.
True for pterosaurs. Nesbitt (2011) reported a mandibular fenestra in a specimen of Dimorphodon, but that is a misidentification detailed here.
True for Cosesaurus and Longisquama.

In summary, according to these characters, pterosaurs were closer to Cosesaurus, Sharovipteryx and Longisquama when traits are properly scored.

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Nesbitt (2011) listed the following characters to support a relationship of pterosaurs with dinosaurs. My comments follow in blue.

Archosauria/Avesuchia – crocodilians, pterosaurs and dinosaurs – SUPPORT:

(1) Palatal processes of the maxilla meet at the midline. Not in basal pterosaurs.

(2) Lagenar/cochlea recess present and elongated and tubular. Not in pterosaurs.

(3) External foramen for abducens nerves within prootic only. I can’t comment on this.

(4) Antorbital fossa present on the lacrimal, dorsal process of the maxilla and the dorsolateral margin of the posterior process of the maxilla (the ventral border of the antorbital fenestra). Not in pterosaurs.

(5) Posteroventral portion of the coracoid possesses a ‘‘swollen’’ tuber. Not in pterosaurs. The stem of the coracoid is the remainder after expanded fenestration.

(6) Lateral tuber (= radius tuber) on the proximal portion of the ulna present. Not in pterosaurs.

(7) Longest metacarpal: Longest metatarsal < 0.5. Not in pterosaurs.

(8) Anteromedial tuber of the proximal portion of the femur present. Not in pterosaurs.

(9) Tibial facet of the astragalus divided into posteromedial and anterolateral basins. Not in pterosaurs.

(10) Calcaneal tuber orientation, relative to the transverse plane, between 50 and 90 degrees posteriorly. Not in pterosaurs.

Ornithodira/Avemetatarsalia – pterosaurs and dinosaurs – SUPPORT:

(1) Distal end of neural spines of the cervical vertebrae unexpanded. Also in Huehuecuetzpalli and fenestrasaurs.

(2) Distal expansion neural spines of the dorsal vertebrae absent. Also in Huehuecuetzpalli and fenestrasaurs.

(3) Second phalanx (2.2) of manual digit II longer than first phalanx. Also in Huehuecuetzpalli, but not in Cosesaurus through Longisquama.

(4) Trenchant unguals on manual digits I–III. Also in Huehuecuetzpalli, Sharovipteryx and Longisquama.

(5) Tibia longer than the femur. Also in Sharovipteryx and Longisquama, but not in Herrerasaurus or Saturnalia.

(6) Distal tarsal 4 transverse width subequal to distal tarsal 3. In pterosaurs the distal tarsal that is subequal to distal tarsal 4 is the centrale, a trait shared with fenestrasaurs. Whenever present in pterosaurs, distal tarsal 3 is tiny.

(7) Size of articular facet for metatarsal V less than half of lateral surface of distal tarsal 4. In pterosaurs and fenestrasaurs the articulation is always more than half.

(8) Anterior hollow of the astragalus reduced to a foramen or absent. Also in Huehuecuetzpalli and fenestrasaurs.

(9) Anteromedial corner of the astragalus acute. Also in Huehuecuetzpalli and fenestrasaurs.

(10) Compact metatarsus, metatarsals II–IV tightly bunched (at least half of the length). Also in Huehuecuetzpalli and fenestrasaurs except Sharovipteryx.

(11) Osteoderms absent. Also in Huehuecuetzpalli and fenestrasaurs.

(12) Gastralia well separated. Also in Huehuecuetzpalli and fenestrasaurs.

Pterosauromorpha – closer to pterosaurs than to dinosaurs – SUPPORT:

(1) Anterodorsal process (= nasal process) of the premaxilla greater than the anteroposterior length of the premaxilla. Also in Huehuecuetzpalli and fenestrasaurs.

(2) Anterodorsal margin of the maxilla borders the external naris. Also in Huehuecuetzpalli and fenestrasaurs.

(3) Concave anterodorsal margin at the base of the dorsal process of the maxilla. Also in Huehuecuetzpalli and fenestrasaurs.

(4) Skull length more than 50% of length of the presacral vertebral column. Also in Huehuecuetzpalli, but not fenestrasaurs.

(5) Dentition markedly heterodont. Also in Sharovipteryx and Longisquama.

(6) Cervical centra 3–5 longer than a middorsal vertebra. Also in fenestrasaurs, except Longisquama.

(7) Distal caudal vertebrae prezygapophyses elongated more than a quarter of the adjacent centrum. Not true in the basalmost pterosaur MPUM 6009, but certainly true in many other pterosaurs.

(8) Postglenoid process of the coracoid elongate and expanded posteriorly. Also in fenestrasaurs.

(9) Pteroid bone present. Also in fenestrasaurs.

(10) Manual digit IV length more than or equal to 50% of total forelimb length. Also in Sharovipteryx and Longisquama.

(11) Anterior (= preacetabular, = cranial) process of the ilium long and extends anterior to the acetabulum but shorter than the posterior process of the ilium. Not present in any pterosaur. The anterior process is always longer.

(12) Metatarsal I length 85% or more [typo: of metarsal IV?]. Also in fenestrasaurs.

(13) Metatarsal V dorsal prominence separated from the proximal surface by a concave gap. Also in fenestrasaurs.

The big problem with Nesbitt (2011) was the refusal to test fenestrasaurs with pterosaurs after acknowledging the literature (Peters 2000). A more comprehensive analysis of the Reptilia recovers fenestrasaurs, including pterosaurs, in a new third clade of lizards, the Tritosauria, now all extinct. When pterosaurs are recognized as lizards and the new reptile tree is widely accepted, definitions for the Ornithodira, Pterosauromorpha, Avesuchia, Panaves and Avemetatarsalia will become redundant with the Reptilia.

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Overlooked by all prior workers, the lizard Huehuecuetzpalli and related fenestrasaurs had an unfused mesotarsal tarsus without a calcaneal heel, convergent with dinosaurs and homologous with pterosaurs. Fenestrasaurs had an antorbital fenestra. These are the two basic characters that have traditionally nested pterosaurs with archosaurs. All archosaurs have a reduced manual digit 4 and pedal digit 5, but Huehuecuetzpalli and fenestrasaurs did not. The origin of the pterosaur wing is documented here and will be discussed in future blogs.

References:
Nesbitt SJ 2011. 
The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. unpublished Ph. D. dissertation. Northern Illinois University, 1-279.

 

So, what exactly IS a pterosaur? Part 1 of 3

Pterosaurs are widely considered to be so different from all other reptiles that (according to the traditional hypothesis) no other taxa come close to them. But is this just the product of taxonomic exclusion? Have we even considered other candidates?

Virtually all workers say pterosaurs are archosaurs close to dinosaurs. Only one heretic (yours truly) has shown that pterosaurs are fenestrasaurs close to lizards. Let’s look at both sides of “the argument.”

The traditional archosaur hypothesis. Representing the traditional “archosaur” view, Hone and Benton (2007) put it best when they reported, “The Pterosauria has been a notoriously difficult clade to place in the diapsid tree: pterosaurs appear suddenly in the fossil record and in full possession of all their highly derived characters. Pterosaurs have been allied to virtually every basal and crown-group archosaur clade as well as to the dinosaurs, but few characters can be found that unite them with any other clade among the archosaurs (Bennett 1996). The appearance of pterosaurs in the Late Triassic without obvious antecedents, their complex flight-adapted anatomy and the fact that the basal pterosaurs have already acquired all those adaptations, gives few opportunities to compare structures to those of other archosaurs or diapsids.”

There’s no improvement in current thinking as Dr. David Hone reports in Pterosaur.net, “Pterosaurs are really, really strange… there is little to tie pterosaurs to other groups through shared characters. This means that it is actually quite hard to see how pterosaurs fit in the great tree of life… Pterosaurs share some characters in common with each of the two groups, primarily features of the legs with the dinosauromorphs, and a few scattered ones, mostly in the neck, with the archosauromorphs. There is not much to chose between them, and even many pterosaur experts disagree, but right now the weight of evidence falls (just) on the side of the dinosauromorphs.”

Given this professional shrug of the shoulders as a starting point, our goal will be to find three or four taxa that document an increasing number of pterosaurian traits. These traits might include wings, but they don’t have to.

But first, here is another looks at the traditional model after cladistic analysis:

Recently Dr. Sterling Nesbitt (2011) recovered a family tree in which pterosaurs nested at the base of a branch that included Lagerpeton and Dinosauriformes as sisters. Together these taxa comprised a clade named the Ornithodira (Gauthier 1986; = Avemetatarsalia, Benton 1999), which nested as a sister to the Ornithosuchidae and both were derived from the more basal Phytosauria, Euparkeria and the Proterochampsidae in order of greater distance (Fig. 1).

In essence, Nesbitt (2011) recovered the traditional archosaur tree. He elected to exclude Scleromochlus from his analysis despite the fact that several earlier studies (Sereno 1991, Bennett 1996) nested the little reptile as the closest sister to pterosaurs. Scleromochlus had a wide flat skull with a deep antorbital fossa, extremely small hands and no fifth toe, traits that should disqualify it from a close relationship with pterosaurs. A larger study nests Scleromochlus as a sister to the basal crocodyloform, Gracilisuchus. Nesbitt (2011) also ignored the fenestrasaurs of Peters (2000, see below), which represent the opposing candidate lineage.

Fig. 1. These are the taxa that Nesbitt (2011) reports are sisters to the pterosaur Dimorphodon.

Fig. 1. These are the taxa that Nesbitt (2011) reports are sisters to the pterosaur Dimorphodon.

When you put reconstructions of Nesbitt’s taxa together into an evolutionary sequence (Fig. 1), there appears to be something very wrong  in the sequence. It doesn’t provide what we are looking for, “an increasing number of pterosaurian traits.” Nor does it appear to work the way evolution typically does, in small steps. There really isn’t much to tie these taxa together and plenty of absent and vestigial digits to immediately remove all of them from any consideration as pterosaur sister candidates. Characters used by Nesbitt 2011 to link pterosaurs to these taxa are discussed in the upcoming part 2 of this report.

There are further problems in Nesbitt (2011). Proterochampsa and Paleorhinus are obvious sisters, so what is Euparkeria doing between them? Ornithosuchus and Euparkeria are obvious sisters, so what is Paleorhinus doing between them? Having the bipedal Scleromochlus and Lagerpeton as pterosaur sisters is also problematic because, according to the traditional archosaur view, no pterosaurs were bipeds. (More on that problem in weeks to come.)

By the way, Bakker (1986) considered pterosaurs to be dinosaurs…not dinosaur cousins, but dinosaurs themselves. That’s an hypothesis that is even tougher to support.

Figure 2. A new series of taxa documenting a gradual accumulation of pterosaur traits. These are lepidosauriforms then tritosaurs then fenestrasaurs, then pterosaurs.

Figure 2. A new series of taxa documenting a gradual accumulation of pterosaur traits. These are lepidosauriforms then tritosaurs then fenestrasaurs, then pterosaurs.

The ‘heretical’ fenestrasaur hypothesis. Over ten years ago Peters (2000) presented four taxa, Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama that documented an increasing number of pterosaurian traits. In cladistic analysis, the three fenestrasaurs (plus Langobardisaurus) consistently nested closer to pterosaurs than any other included taxon. Reconstructions of these taxa, along with the basal lizard, Huehuecuetzpalli, Macrocnemus and Jesairosaurus, are provided to demonstrate the evolutionary continuity of this sequence and to make the lizard connection more apparent. Not only are these taxa the right size (each one could sit on your hand), as they get closer and closer to pterosaurs they document “an increasing number of pterosaurian traits.” Some of these characters are found elsewhere within the Reptilia (like cusped teeth), but other traits cannot be found anywhere else except in pterosaurs (full list upcoming in part 3). The fenestrasaurs, true to their name, had an antorbital fenestra, but without a fossa, convergent with that seen in archosauriforms. Cosesaurus had a pteroid (Peters 2009), a pterosaur-style sternal complex and prepubes, all documented here.

I invite you to learn more about the lineage preceding pterosaurs by starting here with Huehuecuetzpalli. If you want to go all the way back to the beginning of reptiles to see a more complete lineage, click here.

Why are fenestrasaurs not included in other cladistic analyses seeking to determine the origin of the pterosaurs or in those that happen to include pterosaurs? Well twice they were…sort of. Otherwise in the last eleven years these taxa have been mocked, suppressed and ignored. The reasons why filter through the following.

Fig. 3. Red arrow points to the antorbital fenestra without a fossa in Cosesaurus.

Fig. 3. Red arrow points to the antorbital fenestra without a fossa in Cosesaurus.

1. In his PhD dissertation, Dr. Phil Senter (2003) was able to nest pterosaurs with Scleromochlus and dinosaurs by misrepresenting the fenestrasaurs and pterosaurs (details upcoming in Part 2). For instance, Senter illustrated an antorbital fenestra on Cosesaurus, (Fig. 3.), but reported and scored it missing. Likewise he reported the antorbital fenestra missing in Longisquama (Fig. 4), not realizing it was filled in with rotated palatal elements. And once again, Senter illustrated the fenestra. He also mistook a rotated and fused set of parietals for twin bumps on the posterior rim of the skull and likened these to similar traits on Coelurosauravus. Unfortunately Senter mixed up the supratemporal and parietal on Coelurosauravus, 
among a dozen other errors. Read more about these problems here and in the upcoming part 2 of this report.

The skull of Longisquama has portrayed by other workers and as documented here.

Fig. 4. A short history of Longisquama skull tracings. All workers have traced an antorbital fenestra, but Senter (2003) reported it was not present. Note the level of detail provided by the DGS method in the lower tracing.

2. Arguing against Peters (2000), Hone et al. (2009) reported, “Moreover, the suggestion of a close relationship between pterosaurs and prolacertiforms such as Cosesaurus is contradicted by a considerable weight of opposing evidence.” Oddly, their so-called ‘evidence’ consisted of six pre-2000 cladistic analyses in which Cosesaurus was not included as a tested taxon and only one supertree analysis (Hone and Benton 2008) in which only a quarter of its characters were scored—and that data were lifted from Evans (1988) who borrowed from Sanz and Lopez-Martinez (1984) who obviously gave Cosesaurus only a cursory glance as demonstrated by their cartoonish reconstruction (Fig. 5.) Supertree testing means you don’t have to look at the specimens themselves, only at the data of others.

Cosesaurus illustrated as a juvenile Macrocnemus by Sanz and Lopez-Martinez

Figure 5. Cosesaurus illustrated as a juvenile Macrocnemus by Sanz and Lopez-Martinez (1984).

Hone et al. (2009) reminded readers that Hone and Benton (2007) criticized Peters (2000b) on methodological grounds, which, ad hominem, conveniently permitted them to sidestep three quarters of the traits of Cosesaurus and completely avoid consideration of the other pterosaur sister taxa proposed by Peters (2000b), Sharovipteryx and Longisquama. In essence, Hone and Benton (2007, 2008) decided to test whether pterosaurs nested closer to a series of prolacertiforms [fenestrasaurs] or to archosauriforms by eliminating and excluding the fenestrasaurs! That’s no test. That’s a rigged experiment. A one-party election. Why would they undo their own test? And then why would they trumpet their vague and, by their own admission (see above), inconclusive results? Further damning their results, Hone and Benton (2008) nested members of the Choristodera outside of the Choristoderes (separated by lepidosaurs). They also recovered lepidosaurs outside of the Lepidosauromorpha. Beyond all logic, Hone and Benton (2008) nested Cosesaurus as a sister to Proterosuchus (Fig. 6).

Fig. 6. Hone and Benton recovered Cosesaurus as a sister to Proterosuchus, which, on the face of it, appears unlikely.

Fig. 6. Hone and Benton recovered Cosesaurus as a sister to Proterosuchus, which, on the face of it, appears unlikely.

Hone and Benton (2007, 2008) arrived at their supertree conclusions because the one matrix that included pterosaurs (Bennett 1996), was the only one they employed. By eliminating the fenestrasaur candidates, there was no test! It was all smoke and mirrors. Finally, for reasons only they know, Hone and Benton (2008) did not reference Peters (2000). Rather the Peters prolacertiform/fenestrasaur hypothesis that they had spent two consecutive papers (2007, 2008) “testing,” was falsely credited to Bennett (1996) after it was correctly credited in their 2007 paper.

This is just a snapshot of the efforts paleontologists have been going through to avoid detailed examination of the basal fenestrasaurs and avoid including them in analyses that also include pterosaurs.

Part two of this report will examine character lists from Senter (2003) and Nesbitt (2011) that include pterosaurs.

Part three will examine the series of taxa in figure two that lead to pterosaurs while documenting the gradually increasing number of pterosaurian traits found there.

As always, I encourage readers to see the specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data. More info and references can be reviewed here.

Confusion regarding the term “prolacertiform” with regard to pterosaurs stems from the fact that much larger, more inclusive recent studies after Peters (2000) recovered trees in which Prolacerta nested with the Archosauriformes while pterosaurs nested elsewhere on the tree, with the Fenestrasauria among the Squamates in a third clade, called the Tritosauria, or “third lizards,” documented here and here.

References:
Bakker RT 1986. The Dinosaur Heresies. New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction. Zebra Books, 481 pp.
Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoolological Journal of the Linnean Society 118: 261–308.
Benton MJ 1999. Scleromochlus taylori and the origin of dinosaurs and pterosaurs. Philosophical Transactions of the Royal Society of London Series B Biological Sciences 354: 1423–1446.
Evans SE 1988. The early history and relationships of the Diapsida. Pp. 221–260 in: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Syst Assoc Sp Vol No. 35A. Clarendon Press, Oxford.
Gauthier JA 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Science 8: 1–55.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total-evidence methods: the origin of the pterosaurs. In: Hone DWE, Buffetaut E, editors. Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Vol. 28. Munich: Zittel B. p. 35–60.
Hone DWE, Sullivan C and Bennett SC 2009. Interpreting the autopodia of tetrapods: interphalangeal lines hinge on too many assumptions. Hist Biol, iFirst article, 2009, 1–11, doi: 10.1080/08912960903154503.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Peters D 2000. A reexamination of four prolacertiforms with implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293–336.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29(4):1327–1330.
Sanz, JL and López-Martinez N 1984. The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Geobios 17:747–753.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. Journal of Vertebrate Paleontology 10 (supplement to 3): 1–53.

Welcome to The Pterosaur Heresies

In ‘The Dinosaur Heresies, New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction’ (1986) Dr. Robert T. Bakker opened chapter one with this remark: “I remember the first time the thought struck me! ‘There’s something very wrong with our dinosaurs.’” What followed was a radical new view of dinosaurs, much of which has come to be widely accepted.

The Dinosaur Heresies book by Dr. Robert Bakker.

The Dinosaur Heresies book by Dr. Robert Bakker.

There is also something very wrong with our pterosaurs. Examining and correcting those errors is the reason for this blog.

The living pterosaur experts, for all their learning, skill and experience, have too often held to their traditions and paradigms, rather than testing them. I trust everyone already knows that science is all about testing. Here several problematic paradigms will be examined, tested and the results will be presented. Many prior traditions will have their faults exposed and new, more parsimonious solutions will be recovered.

The results presented here have been, and will be, criticized as being “unscientific.” The dictionary defines “scientific” as: “systematic, methodical, organized, well-organized, ordered, orderly, meticulous, rigorous; exact, precise, accurate, mathematical; analytical, rational.” To counter than critical claim, in every test you will be able to clearly see which candidate hypothesis is the more precise and meticulous. Evidence will always trump tradition. Ultimately readers will decide for themselves which side of each argument appears valid.

Often evidence will be presented in digital photographs. It’s still the best way to share data. Detractors claim that my research is unsound because I rely on photographs scanned into a computer where I use my flatscreen as a wide-view microscope and tracing instrument. They would prefer that I use a traditional binocular microscope, prism (camera lucida) and pencil to trace fossil elements. Here, several examples will be presented to demonstrate the magnitude gain in recovered data when using the DGS (Digital Graphic Segregation, aka Photoshop) method. Now, admittedly, this gain in recovered data may be due to persistence alone, not the instrument. However, in crushed and scattered fossils, the ability to color-code individual ribs and gastralia to clarify the chaos of a “road-kill” fossil has really helped in several cases. The ability to take those digital tracings and reconstruct the animal has proven to be a boon. The ability to change image contrast to reveal subtle impressions is another strategy that a microscope and pencil cannot duplicate. Here, evidence will be presented in photographs using animation, overlays and any other digital device available. Here you’ll see also several examples of pencil tracings produced from firsthand observations that do not compare well with data recovered using DGS.

Let me be clear: Three-dimensional fossils need to be seen first-hand. The DGS method only works with two-dimensional fossils, crushed into a single plane.

Evidence will also be presented in reconstructions. Pterosaur workers have been very shy about creating and presenting skeletal reconstructions from the crushed specimens they study and present. However, putting the bones back together turns out to be a very good test to see if left elements match right elements and that all the elements fit together properly and similarly to those of purported sister taxa. They’re also easier to understand.

Pterosaur relations (family trees), like those of all other prehistoric and living animals and plants, are recovered using cladistic analysis employing computers to run through huge amounts of data to recover ‘most parsimonious’ results. Unfortunately, pterosaur workers have been very shy about expanding their inclusion list to accept various lizard taxa reported to be pterosaur ancestors, preferring instead to consider and include only those traditional archosaurs that share so few traits. Furthermore tiny pteros have never been included in prior analyses. Here they are.

So, why don’t I publish on all these findings? I have. My bibliography is here. Unfortunately, I’ve been blackballed in the last few years. The problem is this: if my hypotheses are right, the present hypotheses (written and supported by living professors) are wrong. The referees for my peer-reviewed submissions are the very people whose hypotheses I dispute. You can see for yourself, it’s not in their best interest to let these papers get published. Beyond mere politics and self-preservation, these professors firmly believe in their hypotheses. Here I’ll show several examples of the twisted logic I have seen as they attempt to support their hypotheses with trumped up evidence, instead of letting the real evidence help create the hypotheses.

For your own peace of mind, and to even the academic playing field, remember this: there is no class called Pterosaur 101. This is a subject everyone learns on their own, in the library, online, in the field and in the back halls of great museums. I’m not saying that everything published on pterosaurs is wrong. Far from it. I rely on the literature for my data. I’m not saying that everything I say is right. I’m constantly correcting my own errors. What I am saying is that several current problems in pterosaur studies remain unsolved because alternate, heretical solutions have remained ignored, mocked, untested and suppressed.

Until now.

Enjoy the view — the heretical view (with a tip of the field hat to Dr. Robert Bakker).

Final thought: All presented solutions should be tested and tested again. After all, this IS science.