A Closer Look at the Sordes “Uropatagium”

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

Figure 1. Uropatagium of Sordes according to Sharov 1971 and Unwin/Bakhurina 1994.

Sharov 1971
In 1971 Alexander Sharov described and illustrated the holotype of Sordes pilosus, a Jurassic pterosaur with extensive soft tissue preservation (Fig. 1). Sharov (1971) illustrated a uropatagium spanning the hind limbs and not attached to the tail which was angled off to the left.

Unwin and Bakhurina 1994
Twenty-three years later, Drs. David Unwin and Natasha Bakurina (1994) reported on the fibers embedded in the uropatagium of Sordes, which they described as attached to and controlled by the medially-directed fifth toe. Unfortunately since then another pterosaur with the same sort of uropatagium has not been found. The cartoonish drawing presented by Unwin and Bakhurina (1994) was a disappointment in view of the Sagan Standard, “Extraordinary claims require extraordinary evidence.”

Peters 2002
Peters (2002) noticed stratification beyond and in line with the proposed trailing edge membranes of earlier workers, and also noted that the right wing preserved a narrow-aft-of the elbow configuration, contra earlier reports. Noting the medial overlapping of membranes between the ankles, Peters (2000) suggested that twin uropatagia may have slightly overlapped one another. This turned out to be a mistake (see below).

Problems
For several decades paleontologists have been perplexed by the concept of a membrane spanning and binding the hind limbs, wondering if the cloaca opened above it or below it, wondering how such a morphology could have evolved, wondering how the hind limbs could have extended laterally with the tension of the membrane constantly pulling them medially. They wondered if the the tail had become detached form the midline of the uropatagium, which had an apparent V-shaped notch midway between the ankles.

Acceptance
Despite these questions and misgivings, the concept of the “single uropatagium” has remained firmly in place and widely accepted to the present day. This has become the traditional hypothesis. You can see recent illustrations of just such a uropatagium  hereherehere and a description by Dr. David Hone, “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 could only really sprawl and not walk upright.”

Elsewhere? No.
The big problem is, no other pterosaur has a uropatagium. All other specimens that preserve anything like it preserve paired uropatagia, shallower membranes extending behind each hind limb to the tail, with little to no membrane aft of the ankle and no direct connection to pedal digit 5. The pterosaur precursor, Sharovipteryx also had distinct paired uropatagia.

So what’s going on back there in Sordes?

The paired uropatagia and displaced wing membrane in the holotype of Sordes pilosus.

Figure 2. Click to enlarge and see the rollover image. The paired uropatagia and displaced wing membrane in the holotype of Sordes pilosus.

More Detail
Earlier we looked at the myth of the Sordes uropatagium. Here more detail is offered. The apparent membrane lateral to the left tibia, (directed a little above the ankle actually) is bordered by the displaced and otherwise missing ulna. The ulna is attached to the similarly displaced proximal portion of the left wing membrane, complete with aktinofibrils. Note: the membrane is quite narrow. The wing membrane extends beneath the left ankle, folds between the ankles and the torn tip continues toward the right fifth toe. A small portion of the torn wing membrane appears above the right foot. You can see the in situ specimen in closeup here. Earlier workers assumed that only the margin of the uropatagium was preserved because nothing is found more proximal to the body. Here, what you see is what you get.

Note the continuity of the membrane beneath the left tibia and tail. Note the doubling of the membrane, like a folded, crushed ribbon, creating the illusion of a medial angle between the ankles. Note the presence of aktinofibrils, which otherwise are found only on the wing. Note the pale borders of the actual paired uropatagia behind each knee — as in other pterosaurs and basal fenestrasaurs. Note pedal digit 5 was beneath the metatarsus.

Jumbles of hair lateral to the left ankle have no “core” and no certain origin, but may have come from the left anterior femur along with the drifting of the left ulna and radius and other hairs lateral to the left knee (which has a patella).

A Taphonomic Coincidence
By coincidence the ulna was oriented toward the ankle. By coincidence the membrane folded like a ribbon between the ankles.

The Value of DGS (Digital Graphic Segregation) in Testing Observations
It has often been said that the DGS (aka: Photoshop) method is intrinsically inferior to seeing the specimen first-hand. Well, apparently not in Sordes, nor in Jeholopterus, the IVPP embryo and several other pterosaurs and other reptiles, like Vancleavea in which either more detail was uncovered without seeing the actual fossil and subsequent testing failed to confirm original findings.

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 from the Mesozoic of Kazakhstan and Kirghizia. – Transactions 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.

wiki/Sordes

Rhamphorhynchus. Growth Series? Or Speciation?

One of the biggest mistakes I found in paleontology was the unwarranted lumping of all Rhamphorhynchus specimens under one species based on long bone measurements and statistics. Forsaking phylogenetic analysis, Dr. S. Chris Bennett introduced this hypothesis in 1995 and it has been followed and referenced ever since (Unwin 2005) without confirmation (more below). Phylogenetic analysis was not attempted then (or since).

Figure 1 shows the Rhamphorhynchus clade to scale and in roughly phylogenetic order (left to right) based on the large pterosaur study here. A long list of Rhamphs have never been included in a phylogenetic analysis before, so this is a first. One look (at Figure 1) is all it takes to see the morphological variety present here to say nothing of the phylogenetic size variation. The annotated Nexus file is available on request.

The family tree of the Rhamphorhynchus.

Figure 1. Click to enlarge. The family tree of Rhamphorhynchus to scale. That’s Campylognathoides batting first. The largest of the bunch, no. 81, phylogenetically followed the smallest, No. 10. This clade is ripe for a great dissertation. 

From Large to Small to Giant to Medium-Sized
The genus Rhamphorhynchus is led off by the C3 (Pittsburgh) specimen of Campylognathoides, the phylogenetic ancestor. The basal taxon, R. intermedius (No. 28) was the one closest to Campylognathoides in trait similarity. Continuing the size trend, a smaller series of Rhamphs follow, including R. longicaudus (see below). The giant of the bunch, R. longiceps was followed by a series of medium-sized Rhamphs with longer first wing phalanges and nares set further back on the skull.

One of the Littlest 
Rhamphorhynchus longicaudus (Smith-Woodward 1902, B St 1959 I 400, no. 10 of Wellnhofer 1975, Fig. 2), Late Jurassic ~155 mya, was considered a juvenile by Bennett (1995). Actually it is just another tiny species with a distinct morphology nesting close to other tiny species. Similar in size to and derived from a sister to the BMM specimenno. 10 phylogenetically preceded the giant Rhamphorhynchus longiceps no. 81. Another R. longicaudus specimen, No. 11, actually had proportions more typical of R. longiceps and R. muensteri. It has not been included yet in phylogenetic analysis.

rhamphorhynchus_longicaudus-no10

Figure 2. Rhamphorhynchus longicaudus no. 10. Click for more info.

Distinct from the BMM specimen, the skull of R. longicaudus had a longer, thinner rostrum and a relatively larger skull with a narrower lateral temporal fenestra. No. 10 had a hooked lower jaw longer than its upper, the opposite of most other Rhamphs. It had a low hard crest and a high soft crest on its skull. The anterior teeth were longer and sharper. The cervicals were longer relative to the dorsals. The caudals were more gracile and longer. The sternal complex was somewhat cardiod in shape and reduced in size. The forelimb elements were all more gracile. The posterior is unknown in no. 10, but reconstructed here based on similar specimens. The pubis and ischium were close if not joined. The hind limb elements were all more gracile, including the metatarsals and toes.

Rhamphorhynchus longiceps

Figure 3. Rhamphorhynchus longiceps (Smith-Woodward 1902) BMNH 37002, no. 81 in Wellnhofer 1975. Click for more info.

The Giant of the Bunch
Rhamphorhynchus longiceps (Smith-Woodward 1902, BMNH 37002, no. 81 in Wellnhofer 1975, Fig. 3), was the largest known Rhamphorhynchus. Derived from one of the smallest known species, R. longicaudusR. longiceps phylogenetically preceded R. muensteri.

Distinct from R. longicaudus, the skull of R. longiceps was more robust and longer than the torso. The rostrum was pointed and probably sharpened with a keratinous extension. The orbit was only twenty percent of the skull length. The premaxillary teeth were reduced and bunched together. The anterior dentary was concave dorsally. The cervicals decreased in length anteriorly. Seven sacrals were present. The tail was robust but unknown in length. The dorsal ribs were more robust. The sternal complex was rectangular but gently rounded both anteriorly and posteriorly. The humerus was robust. The posterior ilium was as long as the anterior. The pubis and ischium were separate. The prepubic perforation was filled in. The The pedal digits were longer than the metatarsus.


Growth Series? Or Speciation?
Dr. Peter Wellnhofer (1975) continued the traditional labeling of various Rhamphorhynchus  morphotypes as distinct species. Twenty years later, using statistics measured from long bones, Bennett (1995) envisioned a growth series in Rhamphorhynchus with dramatic morphological changes during maturation. This is a blunder. These specimens are morphologically distinct down to the phalangeal proportions (Peters 2011, Fig. 4) and so represent a phylogenetic sequence. The largest specimen is followed phylogenetically by smaller specimens. We also know from pterosaur embryos that hatchlings greatly resembled their parents and therefore did not go through great morphological changes during maturation. The “juvenilization” during size reduction goes back to accelerated developments at the embryonic stage. Read more about the speciation of Rhamphorhynchus here.

 

Figure 4. Click to enlarge. Rhamphorhynchus pedes.Figure 4. Click to enlarge. Rhamphorhynchus pedes.

Figure 4. Click to enlarge. Note the variety in Rhamphorhynchus pedes. These are not conspecific.

Just Like Pteranodon
A similar phylogenetic blunder without phylogenetic analysis occurred when Bennett (1991, 2001) considered all specimens of Pteranodon restricted to just two species. That hypothesis was challenged here.

An Encouraging Note to Any Future Pterosaur Workers
I hope someone takes this lead and runs with it. A darn good dissertation could be written using two to three dozen Rhamphorhynchus specimens, lumping and separating them.

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 1995. A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: Year-classes of a single large species. Journal of Paleontology 69: 569–580.
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
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
Smith-Woodward A 1902. On two skulls of the Ornithosaurian  Rhamphorhynchus. Annals and Magazine of Natural History, London, (7) 9: 1-5.
Unwin DM 2005. The Pterosaurs: From Deep Time. New York, Pi Press, 1-352.
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

wiki/Rhamphorhynchus

What the Dark Wing Rhamphorhynchus Tells Us

When the “Darkwing” Specimen of Rhamphorhynchus (Goldfuss 1831, von Meyer 1846, Frey and Tischlinger 2002, JME SOS 4785) appeared, it looked like all of our arguments about wing shape in pterosaurs were finally over. And that’s how it was promoted. In this specimen (Fig. 1) the wing membrane is clearly delineated, layered and undoctored.

Figure 1. The darkwing specimen of Rhamphorhynchus. Top: in situ. Middle: Soft tissues highlighted. Bottom: Neck and forelimb reconnected to their natural positions.

First Take – The Traditional Hypothesis
Tischlinger and Frey (2002) made no attempt at restoring the broken, folded and mutilated pieces of the specimen, as shown above. Rather they interpreted the soft tissue behind the elbow (in orange above) as a continuation of the wing membrane despite the obvious differences in texture and the separate layers each appears on, while ignoring what would happen if the wing were extended into the flying position  (Fig. 1). Moreover there is a sharp right angle between the wing membrane and the schmootz lateral to the tibia, not the smooth curve predicted by the deep chord/attached to the ankle wing hypothesis.

Second Take – The Heretical Hypothesis
If you put this “Humpty”  back together again (which is ridiculously easy to do) and extend the wing into the flying position it becomes more than clear that the key portions of the wing membrane behind the elbow and wrist were not preserved/exposed. So it doesn’t tell us what the Zittel wing has told us for several decades. Posterior to the elbow the pterosaur wing had a narrow chord and was stretched between the elbow and wingtip with a small fuselage fillet extending back to the femur.


References
Elgin RA, Hone DWE and Frey E 2010. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica in press. doi: 10.4202/app.2009.0145
Goldfuss A 1831. Beiträge zur Kenntnis vershiedener Reptilien der Vorwelt. Nova Acta Academiae Leopoldinae Carolinae, Breslau and Bonn, 15: 61-128.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Tischlinger H and Frey E 2002. Ein Rhamphorhynchus (Pterosauria, Reptilia) mit ungewöhnlicher Flughauterhaltung aus dem Solnhofener Plattenkalk. Archaeopteryx, 20, 1-20.
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

wiki/Rhamphorhynchus

Dendrorhynchoides – The Real Tail Found

Dendrorhynchoides (Ji and Ji 1988, Fig. 1) was originally described as a rhamphorhynchid pterosaur with a long tail. However, it was immediately apparent that this assignment was an error and that Dendrorhynchoides was an anurognathid due to the round skull. But what about that long tail?

Dendrorhynchoides in situ

Figure 1. Dendrorhynchoides in situ. Click for more info. Note the long, robust tail. It is an implant that has been doctored in.

Unwin et al. (2000) reported that the tail was actually doctored in and belonged to some other sort of creature, likely a tiny dromaeosaurid dinosaur close to birds. On the other hand, I thought the tail could be genuine because Dendrorhynchoides nested close to the MCSNB 3359 specimen of Peteinosaurus and  MCSNB 8950, both of which had a substantial tail of similar shape.

Adding More Taxa Cleared Up the Matter
The embryo anurognathid (IVPP V13758) was found to have a vestigial tail and nested between Peteinosaurus and Dendrorhynchoides. That provided the impetus for a second look. By employing the phylogenetic bracketing concept, you can make predictions about missing parts in transitional taxa. The predictions are not guaranteed, but they do make great guides.

Dendrorhynchoides after DGS (digital graphic segregation).

Figure 2. Dendrorhynchoides after DGS (digital graphic segregation). Click to enlarge. Here the doctored tail is outlined in brown. The real tail is identified with an arrow. Contra published reports and Wikipedia, the sternal complex and m4.4 are both present and all the parts of the skull can be identified.

There It Is. The Real Tail. 
On closer examination the overlooked (by everyone) real tail of Dendrorhynchoides  appeared (Fig. 2). It was tiny and bead-like, as in the IVPP embryo. Stretched out the real tail was actually longer than the chimaera, but much more gracile (Fig. 3).

But Wait, There’s More
Contra earlier reports, the entire skull can be identified using DGS (digital graphic segregation). Manual 4.4 for both wings can be seen hidden among the ribs. Edges of the sternal complex are also visible. It is relatively the widest among all pterosaurs producing a much wider than deep torso, more so than in the flat-head anurognathid. Soft tissue wing membranes and uropatagia can also be delineated. As in other pterosaurs, the wing membrane stretched between the wing tip and the elbow with a fuselage fillet extending back to the femur.

Dendrorhynchoides reconstructed.

Figure 3. Dendrorhynchoides reconstructed. The chimaera tail likely belonged to a tiny dinosaur. Click for more info.

A Second Dendrorhynchoides?
The specimen GLGMV 0002, was attributed to Dendrorhynchoides (Hone and Lü 2010), but it is not related.

Science Is a Process
Several mistakes were made with Dendrorhynchoides over the years, but the process of science finds the errors and rectifies the nestings. First appearances can be deceiving even with phylogenetic bracketing. Sometimes you just have approach a specimen with an open mind and know what you’re looking for before you see it.

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
Hone DWE and Lü J-C 2010. A New Specimen of Dendrorhynchoides (Pterosauria: Anurognathidae) with a Long Tail and the Evolution of the Pterosaurian Tail. Acta Geoscientica Sinica 31 (Supp. 1): 29-30.
Ji S-A and Ji Q 1998. A New Fossil Pterosaur (Rhamphorhynchoidea) from Liaoning. Jiangsu Geology 4: 199-206.
Unwin DM, Lü J and Bakhurina NN 2000. On the systematic and stratigraphic significance of pterosaurs from the Lower Cretaceous Yixian Formation (Jehol Group) of Liaoning, China. Mitteilngen der Museum für Naturkunde in Berlin, Geowissenschftlichen Reihe 3: 181-206.

wiki/Dendrorhynchoides 

The Flat-Head Pterosaur

Part of a Private Collection Made Public
There is a tiny little anurognathid pterosaur in a private collection that Dr. S. Chris Bennett (2007) described as a small Anurognathus ammoni (Döderlain 1923). Here that specimen was found to nest next to Anurognathus, but it was neither conspecific nor congeneric with Anurognathus. It was distinct in morphology from flat head to tiny toe. It actually shares more characters with it phylogenetic predecessor,  Dendrorhynchoides (Ji and Ji 1998 ), including a very wide sternal complex and torso. While most pterosaurs had long pointed jaws and most anurognathid pterosaurs had a round, bubble-like skull, this particular anurognathid had the flattest, widest, most pancake-like skull of all. The eyeballs would have popped up above the skull outline, like a frog’s eyeballs. Figure 1 portrays both anurognathids to scale. The many differences are easy to see. Let’s run through them.

Figure 1. The flat-head pterosaur, a private specimen (on the left) attributed by Bennett (2007) to Anurognathus ammoni (on the right).

Figure 1. The flat-head pterosaur, a private specimen (on the left) attributed by Bennett (2007) to Anurognathus ammoni (on the right).

The Skull
The skull was described by Bennett (2007) as having an enormous orbit in the anterior half of the skull, little to no antorbital fenestra, and a broad set of parietals with widely spaced upper temporal fenestra among several other autapomorphies. (You can view those illusory interpretations here). No sister taxa have these traits. Nevertheless, this false and frankly, goofy to monstrous reconstruction has become widely accepted. Such a reconstruction replaces the large air-filled antorbital fenestra of all other pterosaurs with gel-filled eyeballs. Such a reconstruction moves the eyeballs into the anterior half of the skull, the opposite of all other pterosaurs. Bennett (2007) mistook the curved and dentally subdivided maxilla for a giant sclerotic ring preserved on edge, which no other crushed specimen of any tetrapod ever does. Bennett (2007) was unable to segregate the layers of bones so reconstructed a wide, flat parietal, the opposite of all other pterosaurs. Here DGS (digital graphic segregation) was able to delineate all the skull bones recovering identical left and right elements that resemble those of sister taxa and produce a reconstruction in line with sisters, rather than completely different as in the Bennett (2007) reconstruction (see both here).

At left the traditional Bennett (2007) interpretation. On the right, interpretation based on finding and tracing paired bones.

Figure 2. At left the traditional Bennett (2007) interpretation. On the right, interpretation based on finding and tracing paired bones.

The Post-Crania
The rest of the skeleton was much more typical of anurognathid pterosaurs. The cervical series was relatively longer than in Anurognathus. The torso was not as wide as in Dendrorhynchoides and the dorsal ribs were more gracile. The caudals were greatly reduced. The sternal complex was not quite as wide. The pteroid was smaller. Bennett (2007) determined that manual phalanx 4.4 was missing, but it is largely buried. The distal portion reappears at the pelvis and all sister taxa have four long wing phalanges. Pedal digit 2 is not the longest. The proximal pedal phalanges had more typical proportions than the short ones in Dendrorhynchoides.

The Flathead Anurognathid

Figure 3. The SMNS anurognathus as reconstructed in various views. Black circle is hypothetical egg.

Why The Wide Face?
Obviously the wide flat skull gave the private specimen some sort of competitive advantage. Certainly the wider gape captured more tiny insects. The disc-like shape, like a flying saucer, may have been raised and lowered in the airstream to affect the flightpath and such a shape reduced aerodynamic drag while streamlined in the neutral position.

Think About the Size of the Egg!
With such a tiny pelvic opening, the egg of the private specimen would have been very tiny, on the order of 3-4 mm in diameter. The hatchling would have stood one-eighth as tall as the 6 cm adult or less than 8 mm in height (possibly taller if the egg was elongated).  Such a fly-sized pterosaur risked desiccation if it flew in dry air, so it may have scurried about in damp leaf litter snatching insects on the ground as a juvenile.

Click here for more information and images.

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 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Bennett SC 2008. Morphological evolution of the wing of pterosaurs: myology and function. Zitteliana B28: 127-141.
Döderlain L 1923Anurognathus ammoni, ein neuer Flugsaurier. Sitzungsberichte der Königlich Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-physikalischen Klasse: 117-164.
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica doi: 10.4202/app.2009.0145 online pdf
Ji S-A and Ji Q 1998. A New Fossil Pterosaur (Rhamphorhynchoidea) from Liaoning. Jiangsu Geology 4: 199-206.
Peters D 2001. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15:277–301.
wiki/Anurognathus

Another Use for Pterosaur Tale Vanes

Where are Pterosaur Tail Vanes Found?
Basal pterosaurs are often illustrated with tail vanes, but they are not found on many basal pterosaurs. Soft tissue preservation is rare. The Campylognathoides/Rhamphorhynchus clade had the most prominent tail vanes. Various Dorygnathus may have had something like a vane. It’s never clear. Sordes had some sort of tail expansion and Pterorhynchus did not have a single vane, per se, but several very short ones along the length. The tail vane seems to have coalesced from several smaller vanes, which, in turn, may have developed from specialized ptero-hairs seen on the tail of Cosesaurus.

Tail vane animation on the C5 specimen of Campylognathoides.

Figure 1. Click to animate. Tail vane animation on the C5 specimen of Campylognathoides zitteli.

Tail Vane Usage
The tail vane has typically been considered a steering mechanism, but airplanes don’t steer with their tail (vertical stabilizer). That just produces a skid and lots of drag. To initiate a turn airplanes, birds and bats roll into a bank.  Presumably pterosaurs did likewise. The tail vane would have worked like feathers on an arrow shaft, keeping the back of the tail in line with the line of least drag, in line with the body at all times, and all without effort.

Correlations
You might note that the most prominent tail vanes are also found in the clade with the longest wings in relation to their body size. In Campylognathoides and Rhamphorhynchus the wing tips extend far above their head. The tail itself was stiff, able to rise and fall tilting at its base. The same was true of the wings. They were stiff and able to fold and unfold at the metatarsophalangeal joint. Those are similar actions as seen from the side. That got me thinking.

The Metronome Hypothesis
What if the tail rose and fell like a metronome? The wings could open and fold in counterpoint. Together the three elements might have produced a secondary sexual behavior that attracted mates… or was just a way to relax.

Pure speculation.  Enjoy the animation.

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.

Where’s the Wing Membrane??

CM 11426 (no. 44 in the Wellnhofer 1970 catalog), Late Jurassic ~150 mya, was considered by Wellnhofer (1970) to be the largest specimen of Pterodactylus micronyx. Never previously tested in any prior analysis, a large phylogenetic analysis shown here actually nests no. 44 far from Pterodactylus. That means this specimen needs new nomenclature. Key to today’s discussion, no. 44 preserves a wing membrane and other soft goodies as in specimens shown here (don’t forget to rollover the image) and here (wait 5 seconds for the second frame).

No. 44 in situ and with wing membranes highlighted. Click to see rollover image and reconstruction.

A Rare Example of Wing Tissue Preservation
Wing membranes are preserved in no. 44 along with neck skin, a propatagium (in front of the elbow) and a uropatagium (behind the thigh). The specimen is nicely laid out in lateral view. The wing membrane is slightly twisted in this specimen as evidenced by the whisp of wing membrane in front of the distal wing finger. This is due to the axial rotation of the wing finger during burial. (Imagine the wing finger flipped over so the convex shape is anterior in life.) Even so, IF the proximal wing membrane did attach at the ankle, as some workers propose, where is it?

The Fact Is: It’s Not There
There is no wing membrane extending to the ankles. No, it extends to the elbow, then takes a slight detour back to the anterior femur. That’s a fact supported by evidence here and elsewhere. The small hole over the torso is either an artifact of preservation or preparation.

I have heard, “well, the wing membrane might not be the same in all pterosaurs.” The fact is: it IS the same in all pterosaurs. No one has shown an iota of evidence for anything different. All evidence supports the “stretched between the wing finger and elbow” hypothesis (Peters 2002). There is no other evidence. It’s not here. It’s not anywhere. That’s the myth of the bat wing pterosaur.

C’mon Guys. Let’s Follow the Evidence!
Note: In No. 44 the wing virtually disappears when folded. That doesn’t happen in Jurassic Park, David Attenborough’s Flying Monsters 3D or Walking With Dinosaurs because the animators added too much wing membrane between the elbow and ankle.

My Offer Still Stands
If anyone can produce evidence for a deep wing membrane, I’ll marry their sister and gladly eat my hat.

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 RA, Hone DWE and Frey E 201X (in press). The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica doi: 10.4202/app.2009.0145 online pdf
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

A New Wing Shape for Pterosaurs?

A recent paper by Palmer and Dyke (2011) revised the wing shape and orientation of pterosaurs based on mechanical and aerodynamic constraints. Unfortunately they got the anatomy wrong in several instances spelled out below. Those mistakes affected their results.

Once Again, the Deep Wing Paradigm Has Been Promoted as True
Palmer and Dyke (2011) reported, “We know that the margin of the pterosaur wing membrane was unconstrained posteriorly and attached distally to the ankle and body.” Without critical examination, they accepted and cited Elgin, Hone and Frey (2011) and Kellner et al. (2010) which were critically reexamined here and here.

How to fix the Palmer and Dyke (2011) pterosaur wing

Figure 1. The Palmer and Dyke model is on the right. The Stromer/Schaller/Peters model is on the left.

Palmer and Dyke (2011) Made Several Mistakes
In airplanes, birds and bats the CG (center of gravity) is at the wing spar root (between the shoulder joints). Presumably the same was true of pterosaurs. Move the elbow back to where it belongs and add flesh to the thighs based on pelvis length to add more mass aft of the CG. Permit the aktinofibrils to make a spoon-shaped wingtip, as they do in fossils. Split the uropatagium into uropatagia (as in Sharovipteryx and Sordes) and move the femur laterally to create an airplane-like horizontal stabilizer. No pterosaur is preserved with wing membranes attached to the ankles. Rather the membranes always are directed to the elbow with a small fuselage fillet attached to the femur.

The great majority of pterosaur workers, including the two anonymous referees who green-lighted this paper, follow the Palmer and Dyke (2011) model (on the right), despite its falsehoods and problems. The heretical view (on the left) follows the fossil evidence strictly. If anyone can produce and trace a specimen with a deep wing membrane attached at the ankle, I’ll marry their sister.

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 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
Kellner AWA, Wang X, Tischlinger H, Campos DA, Hone DWE and Meng X 2010. The soft tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane. Proc Royal Soc B 277: 321–329
Palmer C and Dyke G 2011.
 Constraints on the wing morphology of pterosaurs. Proceedings of the Royal Society B. published online 28 September 2011.
doi: 10.1098/rspb.2011.1529
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Schaller D 1985. Wing Evolution. In: Hecht M, Ostrom JH, Viohl G and Wellnhofer P, eds, The Beginning of Birds. Proceedings of the International Archaeopteryx Conference, Eichstätt 1984, (Freundes Jura Museum, Eichstätt), pp. 333–348.
Stromer E 1910. Bemerkungen zur Rekonstruktion eines Flugsaurier-Skelettes. Monatsberichte der deutschen Geologischen Gesellschaft 62, 85–91.
reptileevolution.com/pterosaur-wings.htm

The Tritosauria – An Overlooked Third Clade of Lizards

Traditionally there have been just two lizard clades in the Squamata. The Iguania included Iguana, Draco, Phrynosoma and other similar lizards. The Scleroglossa included Tupinambis, Chalcides, Varanus, Heloderma and all the snakes and amphisbaenids. Squamate outgroups within the Lepidosauria included members of the Rhynchocephalia (such as Sphenodon) and the basal lepidosaur, Homoeosaurus, which probably appeared in the Permian, but is only known from the Late Jurassic.

Traditional Nesting
Wikipedia reports the following about the Squamata, “Squamates are a monophyletic  group that is a sister group to the tuatara. The squamates and tuatara together are a sister group to crocodiles and birds, the extant archosaurs.” This is the traditional concept, but testing this in a larger study finds that lizards and archosaurs are not closely related. Not by a long shot.

The Tritosauria, a new lizard clade that was previously overlooked.

Figure 1. Click to enlarge. The Tritosauria, a new lizard clade that was previously overlooked.

The New Heretical Tritosauria
The large study (Peters 2007) recovered a third clade of squamates just outside of the Squamata (Iguania + Scleroglossa), but inside the Lepidosauria (which includes Sphenodon and the other Rhynchocephalia). At the base of this third clade, called the Tritosauria (“third lizards”), are three very lizardy forms, none of which had fused proximal ankle bones, a trait shared by most squamates (at least those that have legs!). Lacertulus, Meyasaurus and Huehuecuetzpalli are known from crushed but articulated fossils. Lacertulus was considered a possible biped (Carroll and Thompson 1982) based on its long hind legs. It is likely that Huehuecuetzpalli (Reynoso 1998) was also a biped. All three were considered close to the base of the lepidosauria, not closely related to any living lizards.

The Tritosauria
A Clade of Misplaced and Enigmatic “Weird-Ohs”

Phylogenetically following Huehuecuetzpalli three distinct clades emerge within the Tritosauria. Some of these were formerly considered “prolacertiforms” (Peters 2000), but now we know that none are related to ProlacertaAll three subclades have some pretty weird members.

The Tanystropheidae
This clade was named by Dilkes (1998) to include “the most recent common ancestor of MacrocnemusTanystropheus and Langobardisaurus and all of its descendants.” Clade members include several long-necked taxa, some of which, like Dinocephalosaurus, preferred swimming to walking. Tanystropheus was the largest, attaining 4.5 meters in length.

The Jesairosauridae
This clade includes Jesairosaurus (Jalil 1991) and the drepanosaurs, from Hypuronector to Drepanosaurus.  This clade included several arboreal, hook-tailed taxa with short-toed feet that were able to grasp slender branches in their slow-motion quest for insects. All were rather small.

The Fenestrasauria
This clade was named by Peters (2000) to include “Cosesaurus, Preondactylus, their common ancestor and all of its descendants.” This clade started off with bipeds that flapped their arms, probably for display during mating rituals because some members, like Longisquama were exotically decorated with extradermal membranes and plumes. Powered gliding (as in Sharovipteryx) was followed by flapping flight in pterosaurs, the first flying vertebrates. Several pterosaurs secondarily developed a quadrupedal pace. Quetzalcoatlus was the largest tritosaur, attaining a wingspan of 10 meters.

Summary
Due to the wide gamut and large inclusion list of the present phylogenetic analysis, many former enigmas, mismatches and leftovers came together in a new clade of lepidosaurs that was previously overlooked. Together, the Tritosauria include some of the strangest and, at times largest, of all lizards. Hyper-elongated necks and hyper-elongated fingers, together with experiments in both a sedentary marine lifestyle (Dinocephalosaurus) and a homeothermic aerial lifestyle (Dimorphodon, for example) make this a truly dynamic and diverse clade. Some of these out-of-the-ordinary morphologies seem to have been kick-started by early experiments with bipedalism. While the arboreal niches of drepanosaurs and pterosaurs are relatively easy to identify, the long-necked tanystropheids may also have used bipedalism and a long neck to reach into tree boughs to snatch prey, creating their own arboreal niche.

Unfortunately, only pterosaurs and Huehuecuetzpalli survived the end of the Triassic and they did not survive the end of the Cretaceous. So tritosaurs are the only major clade of lizards that is extinct 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
Carroll and Thompson 1982. A bipedal lizardlike reptile fro the Karroo. Journal of Palaeontology 56:1-10.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 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.
Reynoso V-H 1998. Huehuecuetzpalli mixtecus gen. et sp. nov: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodríguez, Central México. Philosophical Transactions of the Royal Society, London B 353:477-500.

Longisquama Wings

Longisquama: Almost Too Fascinating. And a Lot of Work!
The general morphology of Longisquama has been difficult to ascertain. Sharov (1970), Senter (2003) and Martin (2000) provided simple tracings without much resolution. Peters (2000) added details, but was unable to actually “see” many details due to inexperience. There I said it. Okay, I’m better now than I was 12 years ago. I’ve got more under my belt.

A dozen years ago I was also under the existing paradigm that the posterior half of Longisquama was missing, as Sharov (1970) reported. No one ever suspected that Longisquama had the long hind legs of a biped and the wings of a pterosaur. Even when they are traced out (Figure 1), they are still difficult to see and were mistaken for displaced plumes by Sharov (1970).

New tracings of Longsiquama

Figure 1. Click to enlarge. New tracings of Longsiquama (B) soft tissues and (C) bones.

Persistence Pays Off!
A new tracing of Longisquama (Figure 1) reveals long hidden details including the tail, pelves, two hind limbs and two folded wings framed by elongated wing fingers (Figure 2). Workers who have seen this fossil claim they did not see this level of detail. That’s because the human eye, even aided by a binocular microscope, cannot segregate and aggregate all the chaos and layers of detail in this fossil. It takes a computer and DGS (digital graphic segregation) to tease out each bone one at a time. By digitally tracing the elements the details emerge and form a complete picture with matching left and right elements that confirm identification. This technique has been widely criticized, but the results speak for themselves.

Despite the “weirdness” of Longisquama, there are very few autapomorphies present. Instead, nearly every trait bridges the morphological gap between Cosesaurus and pterosaurs. It took persistence and the recognition of past errors to make these tracings come together. Follow these methods and the results should be identical.

The wings of Longisquama

Figure 2. Click to enlarge. The wings of Longisquama digitally segregated, including soft tissue. A. In situ. B. Both forelimbs. C. The right forelimb. D. The left forelimb. All elements match left to right.

The “proto-wings” of Longsiquama were midway in size and shape between the nonvolant forelimb of Cosesaurus and the fully-fledged wings of basal pterosaurs (Figure 3). Fingers 1-3 were quite a bit larger than those of either sister taxa. Metatarsal 4 was axially rotated so the finger four flexed in the plane of the wing, as in pterosaurs, rather than toward the palm, as in all other tetrapods. The large claws on the hands suggest an arboreal habitat.

Figure 1. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

Cosesaurus and Longisquama are the Archaeopteryx and Microraptor of pterosaurs, demonstrating the first steps in the origin of flight for the first volant vertebrate clade, the Pterosauria.

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 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 doi: 10.4202/app.2009.0145 online pdf
Jones TD et al 2000. Nonavian Feathers in a Late Triassic Archosaur. Science 288 (5474): 2202–2205. doi:10.1126/science.288.5474.2202. PMID 10864867.
Martin LD 2004. A basal archosaurian origin for birds. Acta Zoologica Sinica 50(6): 978-990.
Peters D 2000. 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.
Senter P 2004. Phylogeny of Drepanosauridae (Reptilia: Diapsida) Journal of Systematic Palaeontology 2(3): 257-268.
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.

wiki/Longisquama