The Pterosaurs From Deep Time: Nits and Picks #2

Figure 1. The Pterosaurs From Deep Time by Dr. David Unwin

In 2005, Dr. David Unwin, one of the top experts on pterosaurs, authored a popular book on pterosaurs, The Pterosaurs from Deep Time. This is part 2 of the Nits and Picks. Here is part 1.

Unwin p. 230
“The exact point at which the pterosaurs branched off from other diapsid reptiles is not at all clear, and intermediate forms between pterosaurs and other reptiles have yet to poke their heads out from the fossil record (or if they have done so, they are keeping their identity well-hidden).”

This is Dr. Unwin creatively ignoring Peters (2000a, b, 2002) which introduced the fenestrasaurs, Cosesaurus, Sharovipteryx and Longisquama, plus the non-fenestrasaur Langobardisaurus, as pterosaur precursors/sisters. Why would he do this? Instead Unwin (2005, p. 231) promoted an imaginary creature, a lizard-like, tree-climbing sprawler without manual digit 5, with a hyperelongated manual digit 4, a large muscular tail and extradermal membranes between the extremities. Bizarre. Why was it lizard-like with sprawling hind limbs when Bennett (1996), Benton (1999) and Senter (2003) reported that upright, bipedal and digitigrade Scleromochlus was a pterosaur sister? Even highly criticized Cosesaurus was upright, bipedal and digitigrade. This imaginary creature seems to have been chosen only to provide a platform on which to add extensive dermal membranes (but then flying squirrels also have upright limbs!).

Unwin, p. 232
“It seems possible, then, that insects powered pterosaurs to a true flapping flight ability.” Then slightly later, “really big insects are quite common in the Carboniferous and Permian, but disappear in the Late Triassic, at just the time that pterosaurs are thought to have taken to the air. Coincidence? Perhapss, but at the moment, an insect-powered origin of flight for pterosaurs is the only reasonable theory on the table.”

Incredible! By eating giant flying insects to extinction Unwin (2005) thinks pterosaurs were “powered” to flapping flight. Gaaakk!! This doesn’t even attempt to address morphology but hangs the “important” question on diet. Unwin (2005) doesn’t mention that pre-flapping pterosaur precursors were also insect-eaters, or that the giant insects would have been larger and more agile in the air than basal pterosaurs. He also ignores the explanation for wing evolution provided by Peters (2002) based on fenestrasaur morphology and the gradual acquisition of pterosaurian traits.

Unwin p. 241
In trying to explain the extinction of long-tailed “rhamphorhynchoid” pterosaurs (after 75 million years of success), Unwin reported, “the problem lay…when rhamphorhynchoids were on the ground…with their arms and legs shackled together by the cheiropatagium and a large cruropatagium draped between the legs.”

Of course this ignores the fact that all Triassic and Early Jurassic “rhamphorhynchoids” were extinct by the Late Jurassic, so extinction was happening continually and proceeded to continue in “pterodactyloids” throughout the Cretaceous. This also hangs all the “rhamphorhynchoid” problems on the false interpretation of the Sordes uropatagium (aka cruropatagium) discussed earlier.

Unwin, p. 244
“Pterodactyloids’ appearance in the Late Jurassic is almost as dramatic as the debut of pterosaurs in the Triassic. Frustratingly, we still have no evidence for their ancestors…”

So imagine Unwin’s excitement when he was presented Darwinopterus! Lü, Unwin, Jin, Liu and Ji (2009) considered it the long-sought link. No wonder they invented “modular evolution” to explain away the “pterdactyloid” skull and neck attached to a “rhamphorhynchoid” post-cervical region. Unfortunately his cladogram recovered 500,000+ trees with no resolution surrounding Darwinopterus. That should have been a red flag.

No, “pterodactyloids” had four origins and darwinopterids represent a fifth departure from basal pterosaur patterns as demonstrated by the large study. Furthermore Unwin’s cladogram ignored the tiny pterosaurs, which are key to understanding the four origins of the “pterodactyloid”-grade pterosaurs.

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
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.)
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7(1): 11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, DeKalb, IL, 1-279.
Unwin DM 2005. The Pterosaurs: From Deep Time. Pi Press, New York.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London: Salamander. 192 pp.

The Pterosaurs From Deep Time: Nits and Picks #1

Figure 1. The Pterosaurs From Deep Time by Dr. David Unwin

In 2005, Dr. David Unwin, one of the top experts on pterosaurs, authored a popular book on pterosaurs, The Pterosaurs from Deep Time. Essentially it updated the pterosaur facts and hypotheses of its predecessor, The Encyclopedia of Pterosaurs (Wellnhofer 1991). Unwin wrote: “Much has changed since the Encyclopedia first appeared. The many critical ideas about pterosaur biology that were fought over in the 1990s… have been resolved into a convincing and (among pterosaurologists) widely agreed-upon picture.”

That is true. Most pterosaurologists do agree with the concepts, observations and hypotheses contained in Deep Time. However one pterosaurologist, the heretic among us, tends to disagree … often. That goes both ways, of course. Dr. Unwin completely ignored the pterosaur foot, origin and flight membrane hypotheses published by Peters (2000a, b, 2002) and they were not included in his otherwise complete and extensive bibliography. Rather than exploring opposing topics and throwing arguments against them, Dr. Unwin pretended that they never existed. That’s a shame, because that was a great opportunity for Dr. Unwin to really let me have it.

Today’s topic of juvenile and tiny pterosaurs will highlight several topics and ideas from Deep Time that do not agree with the evidence.

Unwin, p 142
“As a rule, this means that juveniles tend to be uncommon in the vertebrate fossil record, and individuals at very early stages of growth (newborn or even prenatal), are rare or unknown — except, oddly enough, in pterosaurs.”

Unfortunately Dr. Unwin considered all tiny pterosaurs to be newborns and juveniles when phylogenetic analysis (and other evidence, see below) indicates that they, too, are adults. In pterosaurs size reduction was a trait of transitional taxa in most clades. Most pterosaurologists do indeed consider a short snout and large orbit to be a juvenile character, but actually it is just a scaphognathine trait. As lizards, pterosaurs did not follow archosaur growth patterns but developed isometrically (embryos looked just like parents). The JZMP and Pterodaustro embryos falsify the traditional short-snout, large-orbit hypothesis. Many other tiny pterosaurs also had a long snout (see below). The third embryo, the IVPP specimen, came from parents with a short snout, but the eyes were still smaller than originally published.

Figure 2. Pterodaustro embryo. There certainly is no short snout/large eye here!

Dr. Unwin, p. 151
“The snout often grew faster than neighboring regions, so that large-eyed short-face flaplings finished up with long, low skulls and relatively small eyes.”

Some tiny pterosaurs, like B St 1936 I 50 (no. 30 in the Wellnhofer 1970 catalog) and Senckenberg-Museum Frankfurt a. M. No. 4072, (no. 12 of Wellnhofer 1970), do not have a short snout and large orbit. (Click the blue links to see them).

Dr. Unwin, p. 156
“…there doesn’t seem to have been any “small” species, which is even stranger than you may think. Consider that the vast majority of birds and bats are less than one-third of a meter in wingspan. By contrast, adutls of the smallest pterosaur species known at present, such as Anurognathus ammoni, are at least 40 cm in wingspan, and most of them are bigger. A biased fossil record? Hardly. Otherwise, we wouldn’t have found all those flaplings and juvenile…”

Once again, if something is apparently missing, but replaced by something identical to it, it’s not wise to prejudicially ignore what is present. Test the oddities and autapomorphies with a phylogenetic analysis and you too will discover that those “flaplings” were adults of several “small” species.

Dr. Unwin p. 156
“This suggests a rather surprising conclusion: Young pterosaurs were the small species, or at least occupied some of the living spaces (niches) in which one might have expected to encounter small adults.”

So close, yet so far… mmmm. If only Dr. Unwin had performed a phylogenetic analysis instead of taking a falsified tradition at face value. Phylogenetic analysis is key to understanding the pterosaurs. But it only works when they are all included, as demonstrated here.

More on Deep Time later.

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
Unwin DM 2005. The Pterosaurs: From Deep Time. Pi Press, New York.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London: Salamander. 192 pp.

More About Doswellia and Archeopelta

The phylogenetic position of Doswellia (Weems 1980) has been troublesome because it is so different from other Triassic reptiles. Recent cladistic analyses (Desojo, Ezcurra  and Schultz 2011) have shed light on the nesting of Doswellia and the large study has nailed it down.

Figure 1. Doswellia in several views from Weems (1980).

Doswellia Basics
As a diapsid, Doswellia lost its lateral temporal fenestrae. The orbits were on top of the flattened skull. The missing rostrum was narrow and elongated if it fit the narrow and elongated mandible. The posterior mandible was deeper than the skull. Different than its sisters, the Doswellia ilia have rotated laterally such that the lateral surface now faces ventrally. The posterior dorsal ribs extended only laterally matching the elongated transverse processes of the anterior caudals. The anterior dorsal ribs extended laterally then abruptly turned ventrally at mid-length. The femur was relatively short, indicating a low-slung configuration. The seven cervicals were elongated such that the elongated, but relatively small skull was shorter than the cervicals.

That Very Strange Ilium Compared
(Desojo, Ezcurra  and Schultz 2011) compared the ilium of Doswellia (updated from Weems 1980) to several other reptiles. Unfortunately they included several unrelated taxa (Mesosuchus, Vancleavea and Erythrosuchus) and excluded Champsosaurus and Youngoides RC91, two Doswellia sisters in the large study. Fortunately Proterochampsa was tested against Doswellia and it nests as a close sister, but unfortunately no ilium has been published for this taxon. In this case, there were no closely related taxa with a similar ilium. Thus Doswellia is alone with regards to its ilium.

Fortunately the large study relies on a large suite of characters. Until a closer sister taxon comes along, Doswellia will continue to nest between Youngoides and Champsosaurus, with Archeopelta closer (but not yet included in the large study).

Figure 2. Comparing various ilia to that of Doswellia (in pink). Desojo (2011) included an unrelated lepidosaur, Mesosuchus, an unrelated thalattosaur, Vancleavea, and an unrelated euarchosauriform, Erythrosuchus due to poor prior poorly assembled inclusion sets. Chanaresuchus is the closest sister in the top row and there was no resemblance. On the bottom row are Youngina and Champsosaurus, two closer sisters to Doswellia and even here there was no distinct synapomorphy. The ilium of Doswellia was oriented laterally, not vertically, like the others and that difference sets Doswellia apart from all known sister taxa. The ventral pelvis was medially oriented in Champsosaurus and Doswellia and the acetebulum was partly open ventrally.

Archeopelta
Archeopelta (Desojo, Ezcurra  and Schultz 2011) is known from less complete material (dorsals and a few other nearby parts), but appears to be the closest known sister with regard to a suite of characters not listed in the large study.

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
Desojo JB, Ezcurra MD and Schultz CL 2011. An unusual new archosauriform from the Middle–Late Triassic of southern Brazil and the monophyly of Doswelliidae. Zoological Journal of the Linnean Society, 2011, 161, 839–871. DOI: 10.1111/j.1096-3642.2010.00655.x
Dilkes D and Sues H-D 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29(1):58-79.
Weems RE 1980. An unusual newly discovered archosaur from the Upper Triassic of Virginia, U.S.A. Transactions of the American Philosophical Society, New Series 70(7):1-53

wiki/Doswellia

Quetzalcoatlus, in Flight

A note added November 12, 2020
Quetzalcoatlus was flightless due to clipped wings (vestigial distal wing phalanges). Here is the link on that data.

As a Guide to Artists and Modelmakers
Many artists add pterosaurs to their illustrations and many model makers have been assigned the task of reconstructing flying pterosaur skeletons for museums. This blog is here to provide some heretical suggestions that, doggone it, make more sense all the way around!

Figure 1. Quetzalcoatlus in dorsal view, flight configuration. Inset: a full-scale model at the Texas Memorial Museum.

Properly Configuring Quetzalcoatlus in Flight – The Knees
It is a common tradition to extend the hind limbs behind flying pterosaurs and, judging by the full-scale model at the Texas Memorial Museum (TMM, Fig. 1), this practice also extends to the largest of them all, Quetzalcoatlus. Imagine the mechanical strain at the ball joint of that extended femur!  Unfortunately that configuration also assumes a dinosaur-like right angle femur for Quetzalcoatlus, something only basal pterosaurs had. Q and its sisters had sprawling, lizard-like hind limbs, yet still able to place the feet beneath the torso as blogged earlier, and as shown here. Plus, extending the legs posteriorly gives the uropatagia (preserved not on Q but on other pterosaurs) nothing to do. Finally, the large thigh muscles originating from the anterior ilium would have been overextended if the leg was posteriorly oriented.

Much better to extend the sprawling femur in a sprawl: laterally with the knees not drooping too much. Then extend the tibia in the same plane. This gives Q a horizontal stabilizer (Fig. 1), like an airplane and echoes the hind limbs of Sharovipteryx, a pterosaur forebearer. In flight, the legs would have provided their own lift in this configuration, without additional strain on the hips to hold them up in the airstream.

Properly Configuring Quetzalcoatlus in Flight – The Feet
In the TMM model the soles of the feet are pointing to the sky. This give the feet nothing to do but dangle. However, with the knees and shins out, the soles point medially, back to the tail root between them. Spreading the toes allows the skin between them (preserved on other pterosaur specimens) to form aerodynamic surfaces to create lift. In this case the lift would be lateral, which pulls the feet out laterally, which helps the knees to stay extended with less effort, again, as in Sharovipteryx.

Properly Configuring Quetzalcoatlus in Flight – The Elbows
It’s traditional to extend the elbows straight out from the chest laterally, then extend the wrist straight out from the elbow. In birds and bats this would be considered over-extension. In Q let’s move the elbows back to where birds and bats put them and let’s raise the elbows slightly to provide the wing some curvature. Everyone knows a wing should be curved. Funny how few pterosaur artists add this subtle but vital element.

Properly Configuring Quetzalcoatlus in Flight – The Wing Finger
The model makers of Q. correctly included a substantial angle between metacarpal 4 and digit 4, following a natural stop in the specimen. This is different than in other pterosaurs, like Anurognathus and Nyctosaurus, in which the fully extended wing finger virtually lines up with the fourth metacarpal. This gives the Q wing a deeper chord at the base of the flight finger. This depth may be related to the brevity of phalanx 4 giving Q more of a duck wing, than an albatross wing.

Properly Configuring Quetzalcoatlus in Flight – The Neck
The TMM model makers extended the neck in their full-scale Q about as far as it could go. However, soft-tissue fossil evidence (Frey and Martill 1998) in Pterodactylus indicates that the longer necks were supported by a tall, narrow, muscle and tendon complex that spanned across the arc of a ventrally convex cervical series. So such a neck curve is integral.

Properly Configuring Quetzalcoatlus in Flight – The Head
No doubt Q could have moved its head anywhere it wanted to, but the standard flight position would have been “nose down” as reported (Witmer et al. 2003) in other long rostrum pterosaurs, like Anhanguera. It’s not that the back of the head drooped down. It was the front that did.

I Haven’t Yet Mentioned the Wing Membranes
But notice how nicely this configuration works with an independent hind limb not encumbered by the deep-chord wing membrane that is the modern paradigm. Read more about wing membranes here.

Footnote
The flying Q. model of Paul MacCready had the hind limbs tucked in, like a bird, following Kevin Padian’s reconstruction of the early ’80s. The model flew just fine. However with a sprawling femoral head, such a configuration would have been a strain on the animal and therefore highly unlikely. No one illustrates that configuration today.

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
Frey E and Martill DM 1998. Stissue preservation in a specimen of Pterodactylus kochi (Wagner) from the Upper Jurassic of Germany. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210: 421–441.
Witmer LM, Chatterjee S, Fransoza J and Rowe T 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behaviour. Nature 425:950-953. online pdf
Flying Pterosaur Model of Paul MacCready online pdf

Phytosaurs and their Sisters

The nesting of phytosaurs (parasuchians) has moved around quite a bit.
Gauthier (1984) nested Parasuchia between Proterochampsa and Aetosauria. Benton and Clark (1985) nested Parasuchia between Ornithosuchidae and Gracilisuchus.  Bennett (1996) found Parasuchia nested with Suchia between Euparkeria and Ornithosuchia + Pterosauria. Sereno (1991) nested Parasuchia between Proterochampsa, Ornithosuchia and Dinosauromorpha. Benton (1999) nested Phytosauridae between Proterochampsidae and Stagonolepidae and Scleromochlus. Benton (2004) nested Phytosauridae with Gracilisuchus. Norrell (2006) and Nesbitt (2007) nested Parasuchia between Stagonolepidae and Pterosauria. (These were all referenced and illustrated n Nesbitt 2011, see below.)

Figure 1. A selection of phytosaurs (parasuchians).

The Latest Nesting
Nesbitt (2011) provided the latest and largest published tree. He nested phytosaurs as derived from Euparkeria and basal to two clades within the Archosauria. Ornithosuchidae was at the base of one branch and pterosaurs were at the base of the other.

It’s puzzling how aetosaurs, pterosaurs and Scleromochlus made earlier lists. They bear little to no resemblance to phytosaurs. It’s also noteworthy that there has been little consensus in prior studies.

It’s a shame that so many earlier studies eschewed generic taxa for suprageneric taxa. The mysteries remained mysteries. Sister taxa did not share many traits. The large study sheds light on the relationships of phytosaurs and all of the members of the Reptilia.

Figure 2. The sisters of Phytosaurs, including Cerritosaurus, Proterochampsa and the RC91 specimen of Youngoides. Click to enlarge.

Given All These Choices Where Does the Large Study Nest Phytosaurs?
Unfortunately only skulls are known for the closest sisters of phytosaurs. Those who nested Proterochampsa with phytosaurs were correct, as confirmed by  the large study. However, nobody mentioned Cerritosaurus, the phytosaurs’ other sister taxon. At the base of all three nests Youngoides minor. It lacks an antorbital fenestra. The Choristodera are also sisters and Doswellia is at the base of that large and varied clade. Chanaresuchus and its sisters are related beyond Cerritosaurus.

Phytosaur Family Tree
I have not attempted a phytosaur family tree. Paleorhinus (Fig. 2) and Parasuchus are generally considered basal phytosaurs.

Shared Traits?
A pair of dorsal and displaced nares distinguish phytosaurs from all euarchosauriformes (Euparkeria, Ornithosuchidae, Gracilisuchus, Dinosauromorpha, etc.) and pterosaurs. Proterochampsa shares that trait. Cerritosaurus and the chanaresuchids do too, but to a lesser extent.

A skull that is wider than tall is also a shared trait. The rostrum is elongated. The top of the skull is narrower than the base at the jaw joint. The top of the skull is flat across the upper temporal fenestra. The orbits are elevated or on top of a flattened skull. The postfrontal and postorbital are fused. An antorbital fenestra developed independently in this clade. Phytosaurs share with chanaresuchids a skull longer than half the presacral length of cervicals. Certainly many of these traits find convergence elsewhere on a tree where convergence runs rampant. Even so, the rules of parsimony place phytosaurs with these pararchosauriformes and the clade is a sister to the euarchosauriformes.

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
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.

Build Your Own Paper Pteranodon!

Click to download pdf. Build Your Own Pteranodon Paper Model

Happy Thanksgiving (here in the USA)!

Download the pdf. Print out on 8.5×11″ “cover stock” paper.
Cut out the pieces. Fold them as instructed. Glue them together.
Run piano wire under the wings if you don’t want them to droop.
Hang on thread.

This model might fly, but the landing will bend the rostrum!

Enjoy!

From your friend at The Pterosaur Heresies.

Thanks for coming back.

Microtuban, a New Basal Azhdarchid

Microtuban altivolans (Elgin and Frey 2011) is a new basal azhdarchid pterosaur with the characteristic tiny fourth phalanx. Only the mid-section of this pterosaur is preserved, including smashed wing parts.

Figure 1. Sisters to Microtuban include No. 42 (more primitive) and Jidapterus (more derived).

Juvenile? No.
The scapula and coracoid are unfused and the extensor tendon process includes a large suture. Elgin and Frey (2011) considered these to be ontogenetic signals that inferred the specimen was a juvenile or sub-adult, as in archosauromorphs. Unfortunately this is false. Pterosaurs are lizards and they don’t follow archosauromorph growth patterns. The sister taxa (Fig. 1) all have similar fusion patterns and they are adults.

Africa? No.
Elgin and Frey (2011) considered Microtuban, from the of Early Cenomanian (Late Cretaceous) of Lebanon, “the most complete pterosaur fossil discovered from Africa.” Oops. Lebanon is actually in the Middle East. Minor faux pas.

Phylogenetic Nesting
Elgin and Frey (2011) reported, “The phylogenetic placement of M. altivolans within the Azhdarchoidea [the Tapejaridae, the Thalassodromidae, the Chaoyangopteridae, and the Azhdarchidae] therefore remains uncertain.” They considered it a “thalassodromid/ chaoyangopterid.

Here, in a larger study, Microtuban nests readily at the base of the Azhdarchidae [Jidapterus through Quetzalcoatlus] and was derived from a sister to No. 42. (By the way, in the larger study Chaoyangopterus was not at all related to Thalassodromeus.) The manual phalanx proportions in Microtuban were identical to those of its azhdarchid and protoazhdarchid sisters, none of whom, no matter their size, fused the scapula to the coracoid until Quetzalcoatlus.

A Reduced Phalanx 4
While more primitive than other azhdarchids, wing phalanx 4 was relatively shorter (less than 5% of the total wing finger) in Microtuban, probably because it represents a late-surviving clade member on its own branch. The reduction of phalanx 4 is also found in Sos 2428, the flightless pterosaur, which is another Microtuban sister. I suspect that another sister, Huanhepterus, also had such a short phalanx 4, but no one I know has actually seen the post-crania.

Loss of Phalanx 4 in Other Pterosaurs?
Elgin and Frey (2011) reported that Anurognathus, Beipiaopterus and Nyctosaurus all had only three wing phalanges. This is true only for derived Nyctosaurus. Check it out.

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
Elgin and Frey 2011. A new azhdarchoid pterosaur from the Cenomian (Late Cretaceous) of Lebanon. Swiss Journal of Geoscience. DOI 10.1007/s00015-011-0081-1

At Least Two Flat-Footed Pteranodon Specimens

Plantigrade Pteranodon Pes
Bennett (1991, 2001) determined that the pes of a specimen of Pteranodon, UNSM 2062, was plantigrade (Fig. 1). Note the interphalangeal lines are not continuous. That means the joints would not have worked in unison during the step cycle, a situation unknown in all other tetrapods.

Figure 1. A Pteranodon pes, UNSM 2062 as reconstructed plantigrade by Bennett (1991, 2001) and as reconstructed digitigrade. PILs added. Black elements are foreshortened during elevation into the digitigrade configuration.

Digitigrade Pteranodon Pes
In a discussion on PILs (parallel interphalangeal lines, Peters (2000) determined that a restored chimaera foot belonging to two specimens of Pteranodon, KUVP 27827 and FHSM VP 2183, was digitigrade because the PILs (parallel interphalangeal lines) in that specimen were complete and continuous when the metatarsus was raised. Using a chimaera as an example was not a good idea (chalk it up to naiveté as that was my first paper), but the concept was confirmed by complete specimens UNSM 2062 (Fig. 1) and UNSM 50036 (Fig. 3) with nearly identical pedal element proportions. (Whew!)

A Few Years Later
After finding pedal variation in specimens of Rhamphorhynchus, Dorygnathus, Pterodactylus and other pterosaur genera, Peters (2011) tested several other Pteranodon specimens and found digitigrade configurations (UNSM 2062 and UNSM 50036), except in three plantigrade pedal specimens (Fig. 3). One belonged to AMNH 5099. The other two (in yellow, Fig. 3) belonged to the chimaera specimen KUVP 2212. One or both pedes likely do not belong to the skull of KUVP 2212, but were added to make the specimen “complete.”

Figure 3. A selection of Pteranodon pedes. On the left is a specimen, UNSM 50036, considered digitigrade and phylogenetically, but not physically, associated with P. ingens skull material. In yellow are the chimaera feet questionably associated withy the skull ofof KUVP 2212. On the right are the other two plantigrade pedes associated with P. sternbergi clade specimens.

Plantigrady vs Digitigrady
A plantigrade pes has continuous PILs when the metatarsals are against the substrate. When the metatarsals are nearly all the same length (as in UALVP 24238), or all aligned (as in AMNH 5099), this is more likely to occur because the the elevated metatarsophalangeal hinges does not push or pull the phalanges. However, when there are distinct differences in metatarsal length (as in UNSM 50036), then elevation of the metatarsus (at least during the step cycle, but perhaps during the standing configuration) tends to push and pull the phalanges as the shorter metatarsals tend to become more vertical than the longer metatarsals. If the pes is digitigrade in configuration, then the PILs will line up in simpler, more continuous patterns when the proper elevation is reached (Fig. 3). Proximal phalanges tend to elevate as well, but not always.

The two plantigrade pedes associated with skulls are both in one clade, the clade associated with P. sternbergi (Fig. 4). The two digitigrade pedes are associated with postcranial skeletons that are not part of this clade, but have a phylogenetic association with the P. ingens (YPM 2594) clade.

It’s also key to note the pedal differences are phylogenetically associated with cranial (Fig. 4) and other postcranial differences confirming that Pteranodon includes many more that just two species (contra Bennett 1991, 2001) and should not be divided into several genera (contra Kellner 2010).

Figure 4. Pteranodon skulls in phylogenetic order. Those boxed in white are mentioned in this blog. P is KUVP 2212. Q. is YPM 2594, Pteranodon ingens. Z is UALVP 24238. Z2 is AMNH 5099.

The Value of Restoration and Reconstruction 
Some paleontologists consider restoration and reconstruction unimportant. Unfortunately, they’re missing important morphological relationship data. Puzzlingly, Hone, Sullivan and Bennett (2009) argued against the value of PILs, despite stating several times that PILs could be drawn through joints and their examples all supported the concept as noted by Peters (2010), who defended his hypothesis. Notably they never tested PILs on a four or five-toed specimen.

Summary and Consequences
Surprisingly I found plantigrady in a select Pteranodon clade after finding digitigrady in the other branch of the same genus. It’s important to let the facts and data determine the results and patterns. Others have flatly stated that all pterosaurs were plantigrade (Unwin 1997, 2006) based on just a few plantigrade footprint samples (Mazin et al. 1995, Lockley et al. 1995 and others). This is an error (Peters 2011).

Bennett (1991, 2001) would have been correct in his assessment of plantigrady in Pteranodon, if he had only chosen a plantigrade pes as his example! Fortunately, his error led to the discovery of PILs. Chris once told me, “They would be important if they were real.” Well, they are, and this blog demonstrates their importance.

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
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153.
Hone DWE, Sullivan C and Bennett SC 2009. Interpreting the autopodia of tetrapods: interphalangeal lines hinge on too many assumptions. Historical Biology iFirst article, 2009, 1–11 DOI: 10.1080/08912960903154503.
Kellner AWA 2010. Comments on the Pteranodontidae (Pterosauria, Pterodactyloidea)
with the description of two new species. Anais da Academia Brasileira de Ciências 82(4): 1063-1084.
Lockley MG, Logue TJ, Moratalla JJ, Hunt AP, Schultz RJ and Robinson JW 1995. The fossil trackway Pteraichnus is pterosaurian, not crocodilian; implications for the global distribution of pterosaur tracks. Ichnos 4:7-20.
Mazin J-M, Hantzpergue P, Lafaurie G and Vignaud P 1995. Des pistes de ptérosaures dans le Tithonien de Crayssac (Quercy, France). Comptes rendus de l’Academie des Sciences de Paris 321: 417-424.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500
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
Unwin DM 1997. Pterosaur tracks and the terrestrial ability of pterosaurs. Lethaia 29: 373-386.
Unwin DM 2006. The Pterosaurs From Deep Time. Pi Press, New York. 347 p.

wiki/Pteranodon

What Kind of Pterosaur Was Samrukia?

Reports of a Giant Bird
A recent paper by Naish et al. (2011) reported the discovery of a “gigantic bird” from the middle of the Late Cretaceous based on a posterior mandible (Fig. 1). They named the specimen Samrukia nessovi.

May Instead Represent a Large Pterosaur
Dr. Eric Buffetaut argued that Samrukia was a pterosaur, not a giant bird, but did not assign a specific genus to it. He criticized the Naish et al. (2011) analysis for not including pterosaurs, only birds and dinosaurs [ed. note: Nice to hear someone else also criticizing inclusion/exclusion problems.]

If Indeed a Pterosaur, What Kind?
Very few large Cretaceous pterosaurs have a mandible with a convex dorsal rim, a concave ventral rim, a transverse ridge anterior to the jaw joint and a very short retroarticular process (in addition to several other traits). Criorhynchus appears to be the best match for Samrukia. 

Figure 1. Various pterosaur mandibles compared to Samrukia. Very few pterosaurs have a convex dorsal rim, a concave ventral rim and virtually no retroarticular process, but Criorhynchus appears to be a good match.

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
Naish D, Dyke G, Cau A, Escuillié F and Godefroit P 2011. A gigantic bird from the Upper Cretaceous of Central Asia. Biology Letters in press. doi:10.1098/rsbl.2011.0683.
Naish D (August 9, 2011). Big birds in the Cretaceous of Central Asia: say hello to Samrukia. Tetrapod Zoology. online blog
Buffetaut E (in press). Samrukia nessovi, from the Late Cretaceous of Kazakhstan: A large pterosaur, not a giant bird. Annales de Paléontologie, published online before print 10-NOV-2011. doi:10.1016/j.annpal.2011.10.001

A Chronology of Basal Reptilia

The dual origin of the Reptilia (following Cephalerpeton) was blogged earlier. Here we’ll take a look at the chronology of basal reptiles during the Carboniferous and Permian.

Figure 1. Click to enlarge. A chronology of the basal Reptilia.

The Most Primitive Known Reptile Was Not the Oldest
Cephalerpeton nested as the most basal reptile, the one closest to the nearest outgroup taxon, Gephyrostegus. Unfortunately the fossil record of both succeed the earliest known reptiles, Westlothiana and Casineria, by some 40 million years. That means the first appearance of Cephalerpeton had to precede its first (and only) appearance in the fossil record by a similar time span. Thus Cephalerpeton was a long-lived taxon. Supporting this hypothesis, the appearance of the proximal sister to Gephyrostegus, Silvanerpeton, first appeared in the fossil record alongside Casineria.

The first appearance of Cephalerpeton during the Kasimovian, some 305 million years ago, also followed the first appearances of several other reptilian taxa, including Hylonomus, Paleothyris and Solenodonsaurus. The first appearance of Cephalerpeton also coincided with the first appearances of Haptodus and Archaeothyris. Such timing demonstrates long ghost lineages in which one can expect to find more Cephalerpeton specimens back to the basal Visean, 345 million years ago.

Protorothyris and Limnoscelis Ghost Lineages
Protorothyris, an outgroup taxon to the Synapsida and Protodiapsida, first appeared in the fossil record about 290 million years ago. That succeeded the first appearances of phylogenetic descendants by some 15 million years. So, Protorothyris was also a long-lived taxon with an earlier origin.

Limnoscelis, a basal diadectomorph, succeeded its phylogenetic successor, Solenodonsaurus.

Turtle Ancestry
The earliest know turtles, Odontochelys and Proganochelys, first appeared in the Late Triassic, 225 million years ago. Their phylogenetic predecessor, Stephanospondylus, appeared 290 million years ago. That gives turtles 65 million years (nearly the entire Permian and Triassic) to develop their unique morphologies from their closest known sister taxon at the base of the Permian.

Therapsid Ancestry
Basal therapsids, like Nikkasaurus and Biarmosuchus, first appeared some 250-255 million years ago. Their closest outgroup sisters, Ophiacodon and Archaeothyris, lived some 50 million years earlier.

Heleosaurus and Milleretta Ghost Lineage
Heleosaurus appears in the fossil record approximately 270 mya, but its phylogenetic successors appeared 305 mya, 35 million years earlier. Thus Heleosaurus was a long-lived taxon.

Milleretta appears in the fossil record approximately 255 mya, but its phylogenetic successors, including Bolosaurus, appeared 300 mya, 45 million years earlier. Thus Milleretta was also a long-lived taxon.

Most of the rest of the taxa are chronologically ordered with regard to their phylogenetic order. Sphenodon, the living Tuatara, is a living example of a long-lived taxon.

Morphological Stasis and Rapid Radiation
The chronological tree (Fig. 1) illustrates the twin topics of morphological stasis and rapid radiation. The Tournaisian (Early Carboniferous) was a time of rapid change in our reptilian predecessors. Most of the rest of the Early Carboniferous was a time of stasis with a rapid radiation in the Pennsylvanian, producing all of the major reptilian clades. The Permian is where we find most of the basal reptile fossils. Here we find some basal taxa (presumably earliest Permian) surviving to the end of the Permian, a case of stasis. The Triassic, as I need not remind anyone, was a time of rapid radiation following the Permian extinction event.

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.