Pterosaurs Tarsals – More Evidence vs Padian 1983

Some pterosaurs (like Rhamphorhynchus and the new Painten pterosaur) had 4 or 5 tarsals. Others had only two (like Pteranodon, Figs. 1-3).

Figure 1. Pteranodon tarsals (in color). Blue = astragalus. Yellow + calcaneum. YPM = Yale Peabody

The question is: 
In those pterosaurs with two tarsals is it more parsimonious that the 1) distal tarsals disappeared? or 2) the distal tarsals fused to the proximal tarsals? or 3) converging with birds, did the proximal tarsals fuse seamlessly to the tibia/fibula?

What does the evidence indicate?

There are pterosaur workers (Padian 1983, Bennett 2001, Nesbitt 2011, Witton 2013) who consider the tibia + fibula of pterosaurs a “tibiotarsus” because they say the proximal tarsals (astragalus + calcaneum) fused seamlessly to the distal tibia/fibula (Fig. 1). (We looked at this earlier here.) Birds have this sort of tibiotarsus. Padian 1983 compared bird tibiotarsi to Dimorphodon (Fig. 2) and the case looked pretty good back then.

However,
It’s important to remember that birds had a long ancestry as dinosaurs with distinct ascending processes of the astragalus that ultimately fused seamlessly to the tibia after the miniaturization that preceded and succeeded Archaeopteryx. Pterosaurs don’t have that long history, nor do they have ancestors with an ascending processes, nor did they undergo phylogenetic miniaturization prior to getting their wings. Even Archaeopteryx has a distinct ascending process — not seamless.

Under the Padian 1983 hypothesis 
the two tarsals found with Dimorphodon are distal tarsals. Likewise, Bennett (2001) proposed a tibiotarsus for Pteranodon. Eaton (1913, Fig. 1) called them podials, a general name form carpals or tarsals. We don’t see the same long ancestry progress in pterosaur ankles. In fact, there’s no ancestry for this type of ankle at all.

Figure 2. Pterosaur distal tibia. Left: Dimorphodon. Right Pteranodon in anterior (above) and posterior (below) views. Padian (1983) and Bennett (2001) consider the bulbous parts to be the fused proximal tarsals. They are not. The proximal tarsals, astragalus (blue) and calcaneum (yellow) are distinct. Missing here are any distal tarsals. Padian identified this view of Dimorphodon as the anterior, because it looked so much like the anterior of the distal bird tibiotarsus (not shown here). But look again. It looks more like the posterior of the distal tibia of Pteranodon identified by Bennett.

Figure 3. Foot and tarsus of Pteranodon, FHSM-P-2062 and restored and relabeled on top, from original online mislabeled image found at OceansofKansas.com (below). Note, the distal tibia bulge is posterior in Pteranodon, but bulges both ways in Dimorphodon and other pterosaurs, like the Painten pterosaur.

Rather, when you look at basal pterosaurs like Peteinosaurus (Fig. 4), you find four distinct tarsals.

Figure 4. Peteinosaurus and Dimorphodon BMNH4212 pedes. Four tarsals are present on both. Yes the tarsals have moved in Dimorphodon with the distal tarsals rising to the level of the proximal tarsals. 

Same with the classic specimen of Dimorphodon. The engraving (Fig. 5) shows four tarsals.

Figure 5. Click to enlarge. The four tarsals identified on the the classic BMNH 41212 specimen of Dimorphodon. Non-foot bones are ghosted out. Calcaneum = yellow. Astragalus = blue. Distal tarsal 4 = pink. Centrale = magenta. Yes, they have moved during taphonomy, If you count four tarsals, that’s all I’m asking for now.

This is in contrast to Padian’s (1983) interpretation of BMNH 41212 (Fig. 6) where he adds a cylindrical joint to the distal tibia with a circumference smaller than in the other tibia at left.

Figure 6. Tarsals of Dimorphodon BMNH 41212 specimen according to Padian 1983. Figure 5 matches in most regards — except for the tarsals.

Padian 1983 removed tarsals from the matrix of two far less complete specimens attributed to Dimorphodon, YPM 350 and YPM 9182 (Figs. 7-9). Oddly, the smaller of the two specimens (YPM 9182) fused the two large tarsals to one another (the only such event I am aware of). The larger specimen (YPM 350) did not.

Figure 7. The YPM 9182 specimen attributed to Dimorphodon. Note the tarsals fuse to one another despite the smaller size. The femora do not match. The ventral maxilla is straighter. The jugal is deeper. M4.2 is shorter.  So there is some doubt that this is indeed congeneric with Dimorphodon. The question here is: did the calcaneum fuse to the fourth distal tarsal? And if so, did Padian get his tarsal backwards? With Padian’s orientation the tarsal has a posterior tuber. But no pterosaur ever developed a tuber, certainly not on any distal tarsals. And not on any calcaneum either. Let’s keep an eye out for further examples of this. 

Figure 8. About the size of the classic Dimorphodon, the YPM 350 specimen has unfused tarsals. Note the very few bones. The specimen is extremely disarticulated. The other two tarsals could have been easily scattered. This specimen appears to be closer to the classic Dimorphodon in all regards.

Figure 9. Location of the tarsals (red circles) on the YPM 350 and YPM 9182 specimens attributed to Dimorphodon by Padian 1983. Do you think some other tarsals could have escaped?

Padian 1983 noted the cylindrical shape of the distal tarsals and their convergence with the bird tibiotarsus. But there are pterosaurs, like the Painten pterosaur (Fig. 10), that have a cylindrical distal tibia AND four tarsals.

Figure 10. The Painten pterosaur with tarsals colorized. There are four of them. Note the cylindrical shape of the distal tibia/fibula.

So, the evidence for Dimorphodon having only two tarsals is fading. The evidence for cylindrical distal tarsals is strong. Pteranodon has only two tarsals. Whether they were created by fusion or reduction awaits further evidence. There is no evidence for a gradual evolution of fusion in the tarsals and tibia/fibula. Rather, there is plenty of evidence for the retention of paired distal and paired proximal tarsals. There is also evidence in YPM 9182 for the fusion of the proximal tarsals in certain pterosaurs.

Ramifications
Nesbitt 2011 fell prey to the idea of a fused tibiotarsus in pterosaurs when he wrote: “a few peculiar features in the hind limb of lagerpetids merit discussion and suggest that they may be more closely related to pterosaurs than to dinosaurs. Specifically, the ankle of lagerpetids is more similar to that of basal pterosaurs (in particular, Dimorphodon) than to basal dinosauriforms and early dinosaurs. The calcaneum and astragalus are coossified, the ventral surface of the calcaneum is rounded like that of the astragalus, there is no posterior groove of the astragalus, and the calcaneum lacks any sort of calcaneal tuber in both Dimorphodon and lagerpetids. These four character states shared between lagerpetids and Dimorphodon are absent in basal dinosauriforms (e.g., Marasuchus, Asilisaurus). Basal dinosauriforms have a separate calcaneum and astragalus, the ventral surface of the calcaneum, although rounded, is different from the ventral surface of the astragalus, they have a posterior groove of the astragalus, and the calcaneum bears a small calcaneal tuber. It is possible that pterosaurs and lagerpetids share additional ankle characters or differences; however, the ankle of Dimorphodon is heavily ossified, thus concealing the distal end of the tibia and the proximal surface of the astragalus.”

The large reptile tree demonstrates that pterosaurs have no relationship with Lagerpeton and neither do basal dinosaurs, which are distinct from both.

References
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.
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.
Padian K 1983. Osteology and Functional Morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidesa) Based on New Material in the Yale Peabody Museum. Postilla 189 44pp.

New AMNH Exhibit on Pterosaurs – Outdated before it opens

Figure 1. Click to play. AMNH pterosaur exhibit video featuring Mark Norell, Alex Kellner and Mike Habib. Please don’t tell me those pteroids and fingers are pointing forward! Gaak!

The American Museum of Natural History
(AMNH) is putting on a pterosaur exhibit: “Pterosaurs, Flight in the Age of Dinosaurs,” April 5 to January 4, 2015. Mark Norrell, curator and chair of the Paleontology Division and Alex Kellner of the Museu Nacional, Rio de Janiero (and a former AMNH staff member) oversee the exhibit. Here‘s the website.

Sadly the exhibit is behind the times.
Here (Fig. 1) is a sample of outdated art from their exhibit with corrections added.

Figure 1. Dawndraco kanzai (formerly Pteranodon) was redescribed by Kellner, hence its inclusion in the exhibit. Wing membranes to the ankles echoes the famous AMNH display, but no pterosaur has this morphology and configuration. Rather the wings were stretched between elbow and wing finger with a fuselage fillet to the thigh. And the hind limbs extended like horizontal stabilizers behind the wings.

When a museum opens a new exhibit
it should come with outstanding news. Unfortunately this is a celebration of the way pterosaurs have been misinterpreted with no happy ending.

Their Dimorphodon (Fig. 2) contains several errors. Pedal digit 5 never framed the uropatagium. Rather it enabled perching, acting like a universal wrench, as shown here.

Figure 2.Above: AMNH art for Dimorphodon. Below: from reptile evolution.com. Corrections noted.

The AMNH answers: What is a pterosaur?
From the AMNH website: “Neither birds nor bats, pterosaurs were reptiles, close cousins of dinosaurs who evolved on a separate branch of the reptile family tree. They were also the first animals after insects to evolve powered flight—not just leaping or gliding, but flapping their wings to generate lift and travel through the air. They evolved into dozens of species. Some were as large as an F-16 fighter jet, and others as small as a paper airplane.  Scientists have long debated where pterosaurs fit on the evolutionary tree. The leading theory today is that pterosaurs, dinosaurs, and crocodiles are closely related and belong to a group known as archosaurs.”

Sadly we know the “leading theory” cannot be supported. The actual ancestors have been known since 2001, but ignored.

Figure 3. Click to enlarge. According to the AMNH, Scleromochlus is “one of the closest early cousins of pterosaurs.” Oddly, they gave it the skull of Longisquama. Note the vestigial hands. These cannot elongate to become the hyper-elongate wings and the pedal digit 5 is a vestige that cannot elongate to match the hyper-elongate lateral pedal digit of basal pterosaurs.

Scleromochlus a closest cousin?
The AMNH reported Scleromochlus (Fig. 3) was “one of the closest early cousins of pterosaurs,” ignoring the readily observable fact that the hands were vestiges and so was pedal digit 5, which is actually absent in Scleromochlus and its kin. Oddly, they gave it the skull of Longisquama (Fig. 4), an actual pterosaur cousin. Actually pterosaurs descend from fenestrasaurs like Cosesaurus, Sharovipteryx and Longisquama (Fig. 4).

Figure 5. Click to enlarge. Lepidosaurs, tritosaurs and fenestrasaurs in the phylogenetic lineage preceding the origin of the Pterosauria. Note all these taxa have a long manual digit 4 and an long pedal digit 5, traits you won’t find in archosaurs. There’s also a sternum, a stem-like coracoid, a deltopectoral crest an attenuated tail and every other trait it takes to make a pterosaur. And, oh, yes, soft tissue for membrane formation!!!

The AMNH devotion to inaccuracy
also includes their version of Rhamphorhynchus (Fig. 6) with wings too short, feet too small and belly not deep enough.

Figure 6. The AMNH Rhamphorhynchus with errors noted alongside a more accurate rendition of the dark wing specimen

Hopefully,
someday museums will devote their displays to accurate renditions that actually teach the public something valid about pterosaurs. It’s embarrassing to see them hold on to such outmoded phylogenies and inaccurate representations.

If you think I’m wrong, please go see the specimens and repeat the analyses.That’s good Science. Repeatability.

 

 

 

 

 

 

Update on the Rossman 2002 “Brazilosaurus”

Figure 1. Click to enlarge. The nesting of Rossman’s “Brazilosaurus” (the PIMUZ AIII 0192 specimen) at the base of the Thalattosauria is confirmed with the addition of post-cranial and new cranial data.

Today: Some new data and a new reconstruction of the skull and postcrania of the intriguing and potentially important postcrania of PIMUZ A/III 0192. This mesosaur-ish reptile was attributed by Rossman 2002 to Brazilosaurus sanpauloensis. 

Earlier the only data I had on this specimen was a line drawing of a skull from Rossman 2002. This data resulted in a nesting outside of Brazilosaurus + Stererosternum + Mesosaurus, at the base of the Thalattosauria. Notably, with the additional data, the nesting did not change.

Crushed skulls are often the best Because all the parts are crushed into a single plane and you can rebuild that “house of cards” or “crushed eggshell” in many views. Some parts are visible through the orbit. The occiput often flips to the side.

Mesosaurs are key
Workers have attempted to nest mesosaurs based on its lack of temporal fenestration — and they (Modesto 2006) end up with pareiasaurs and millerettids and procolophonoids. But with it’s hyper-long teeth, Mesosaurus is clearly a derived form. What we’re looking for is a basal taxon that looks like Mesosaurus with small plesiomorphic teeth. Then perhaps we’ll see more evidence for the diapsid skull morphology. And that’s exactly what we find.

Figure 2. Click to enlarge. The Rossman “Brazilosaurus” PIMUZ AIII 0192. This turns out to be THE  basal thalattosaur as well as a basal mesosaur. Due to severe crushing elements from the other side of the skull made it appear that the skull lacked fenestration following the generally accepted but mistaken hypothesis that all mesosaurs lacked temporal fenestra. Note the tiny forelimbs and deep tail chevrons. Low dorsal spines and gracile ribs are also noteworthy.

Here (Fig. 1) the Rossman (2002) “Brazilosaurus” nests at the base of the Thalattosauria, whether using the Rossman data as is, or pulling slightly different traits out (Fig. 2).

Rossman (2002) presented photos of several interesting mesosaurs. Among them was the SMF-R-4710 specimen attributed to Stereosternum (Fig. 3). This one does nest with Stereosternum, but with more open temporal fenestrae, its nests at the base of the mesosaurs, close to the base of the ichthyosaurs and thalattosaurs.

Figure 3. Click to enlarge. The SMF-R-4710 specimen attributed to Stereosternum, but with larger temporal fenestrae, smaller teeth and other distinct traits. The high unfused dorsal processes are also seen on Hupehsuchus and Utatsusaurus.

If you think this Stereosternum specimen is starting to look a lot like Wumengosaurus, you’d be right. And Wumengosaurus now nests at the base of Hupesuchus + Ichthyosaurs, so we’re getting closer and closer to the common origin of both. One keeps its teeth, the other does not.

Figure 3. Stereosternum SMF-R-4710 reconstructed from traced image (in color below). Here temporal fenestration is clearly diapsid.

Lest you doubt
Running the large reptile tree with all temporal fenestration traits deleted recovers a single tree unchanged from the full character list tree. If anyone wants to come up with better data or a better tracing, please use specimen numbers.

There are so many specimens of mesosaurs
and so many variations and only three names for them (Mesosaurus, Brazilosaurus, Stereosternum). Someone needs to put it all together and catalog some of the important specimens (e.g. the holotypes). We’ll need new generic names for the specimens above.

If someone has a good photo of the Brazilosaurus holotype (Shikama and Ozaki 1966), please let me know.

References
Cope ED 1886. A contribution to the vertebrate paleontology of Brazil. Stereosternum tumidum, gen. et sp. nov. Proceedings of the American Philosophical Society 23(121):1-21.
Modesto S 2006. The cranial skeleton of the Early Permian aquatic reptile Mesosaurus tenuidens: implications for relationships and palaeobiology. Zoological Journal of the Linnean Society, 2006, 146, 345–368.
Shikama T and Ozaki T 1966. On a Reptilian Skeleton from the Palaeozoic Formation of San Paulo, Brazil” Transactions and Proceedings of the Palaeontological Society of Japan, New Series 64: 351–358.

 

DGS finds sutures in Trioceros (Jackson’s chameleon) skull

I wanted to add a chameleon to the large reptile tree because I had only three taxa in the Iguania, Draco, Phrynosoma and Iguana. The problem is, the skull of Trioceros jacksonii, (Jackson’s chameleon, Fig. 1) has very indistinct sutures. So I used DGS.

Figure 1. The chameleon Trioceros jacksonii colored using DGS. The sutures are difficult to see in the original skull, much easier in the colorized tracing.

Using the above data, gathered after determining skull sutures with DGS, Trioceros nested with Phyrnosoma (the horned lizard) which shares the following traits: 1) tiny premaxillary teeth; 2) vertical quadrate; 3) squared off (hyper-exaggerated in this case) rostral profile; and 4) several other traits. And, nicely, that’s exactly where others nest it.

I don’t know chameleon skulls so well (this is my first exposure). The dentary appears to extend a bit too far behind the coronoid, but then, maybe that’s what chameleons do. Comparisons to other species seem to bear this out.

Figure 2. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

Jackson’s chameleon gives birth to live offspring. Eight to thirty are born after a six-month gestation. Sexual maturity is at 5 months of age. Adutl size is 12 in. (30cm). The diet is insects caught by a hyper-extensible tongue. The tail is prehensile. Fingers 1-3 oppose fingers 4 and 5. Toes 1 and 2 oppose toes 3-5, as in other chameleons.

References
Boulenger GA 1896 Description of a new chameleon from Uganda. Annual Natural History 6(17):376.

wiki/Trioceros

 

How important are temporal fenestrae in reptile systematics?

Turns out temporal fenestrae are not so important in reptile systematics. Removing all characters that reference or compare temporal fenestrae from the large reptile tree results in exactly the same recovered tree.

Contra popular opinion, the large reptile tree demonstrates that temporal fenestra appear several times in the evolution of reptiles.

The synapsid configuration evolved at least five times:
Once in caseasaurs + bolosaurids (including Acleistorhinus and Eunotosaurus) and a second time in traditional synapsids (including protodiapsids), a third time in Lanthanosuchus + Macroleter, a fourth time in basal owenettids leading to lepidosauriformes (but without the lower temporal bar), and a fifth time in nodosaurs and pachycephlosaurs by sealing up the upper temporal fenestra with armor.

The complete diapsid configuration evolved at least thrice:
Once in Petrolacosaurus, its kin and descendants, a second time in sphenodontids + rhynchosaurs and a third time in macrocnemids (including drepanosaurs, tanystropheids, fenestrasaurs and pterosaurs).

The anapsid (basal reptile) configuration reappeared at least twice:
Once in Mesosaurus and again in ankylosaurs both by sealing up the original diapsid openings with expanding bone.

The complete euryapsid configuration appeared at least thrice: 
Once in Trilophosaurus and again in Araeoscelis and again in Placodus again by sealing up the original diapsid openings with bone in each case.

There may be others.

So when Benton 1982, echoing all standard textbooks up to that time wrote: “The reptiles are divided into subclasses according to the number of openings behind the eye sockets,” he reflected hypotheses that linger to this day. Like the problems that overemphasis on the ankle and calcaneal tuber produce, temporal fenestra should be considered as just another trait, not an overriding trait.

And I’m not even considering those taxa that completely lose the temporal bars that define temporal fenestra in other reptiles.

On another note…
Earlier I was happy to present a postcranial model for the rhynchocephalian/proto-rhynchosaur Priosphenodon. Further study indicated that the manus and pes were switched on the model based on sister taxa. I am told that the artist was not supervised. The posted image has been updated to demonstrate the evidence.

 

 

 

 

Updating a little Scaphognathus

When I find better data, I use it.
Case in point, the Maxberg specimen of Scaphognathus (n110 in the Wellnhofer 1975 catalog, no. 992 in the solnhofen-fossilienatlas.de catalog). My earlier data came from Wellnhofer (1991). The earlier image can still be seen by googling “maxberg specimen Scaphognathus“.

The Maxberg specimen is smaller than the holotype, but that doesn’t make it a juvenile, as Bennett (2004, 2014) proposes. Think of it as a sparrow compared to a blue jay in size relative to the larger holotype of Scaphognathus (n109, Fig. 1).

In phylogenetic analysis, the Maxberg specimen descends from the larger holotype (n109). It is similar in size, but not identical in morphology, to the SMNS 59395 specimen of Scaphognathus. The Maxberg specimen is larger than proximal descendant taxa seen here (Fig. 1). So, more than Darwinopterus, Rhamphodactylus or the Painten pterosaur, the Maxberg specimen is a transitional taxon, bridging part of the gap between the long-tails rhamphs and the short-tailed pterodacs.

Figure 1. Scaphognathians to scale. Click to enlarge.

I found the Maxberg specimen on the Solnhofen commercial fossil site – solnhofen-fossilienatlas.de catalog – which we looked at earlier here and here.

Figure 2. The Maxberg specimen of Scaphognathus as found at the Solnhofen commercial fossil website.

The photo (Fig. 1) is rather low in contrast, so the first step is to boost it (Fig. 3).

Figure 3. Same Scaphognathus specimen, image contrast boosted. Tip of the tail has a vane-like shape.

Next step: color tracing (Fig. 4).

Figure 3. Tracing of the Maxberg specimen of Scaphognathus. Two odd little ellipses are traced here, both able to pass through the reconstructed pelvis exit. These could be anything. They need to be looked at more closely. Note the ilia are back shifted relative to the sacral vertebrae. Long, tail stiffening zygopophyses are visible.

Reconstruction brings it all together (Fig. 4). So much easier to deal with when not looking like a roadkill. Not sure why more pterosaur workers don’t do this.

Figure 4. The Maxberg specimen of Scaphognathus reconstructed. Even with the updates, the nesting does not shift. There’s something interesting going on with the nares, splitting into a primary and secondary naris. Like all Scaphognathus, this specimen has tiny feet. This is the first or maybe second stage in the reduction of the tail as all descendant taxa (Fig. 1) have an even more gracile tail.

The new image updates the old one in several subtle ways, none of which are enough to shift the nesting. There are two oval structures in the matrix. And they happen to be just the right size to be pterosaur eggs. Someone will have to take a closer look at this to determine if the bumps are pterosaurian or not. There is a symmetrical disturbance in the matrix at the tail tip that appears to represent a vane, though distinct from the more distinct tail vanes of Campylognathoides and Rhamphorhynchus.

Phylogenetically the Maxberg specimen is basal to cycnorhamphids and ornithocheirids.

References
Bennett SC 2004. New information on the pterosaur Scaphognathus crassirostris and the pterosaurian cervical series. Journal of Vertebrate Paleontology, 24: 38A
Bennett SC 2014. A new specimen of the pterosaur Scaphognathus crassirostris, with comments on constraint of cervical vertebrae number in pterosaurs. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 271(3): 327-348.
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33. 1975b. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. 1975c. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.
Wellnhoffer P 1991. The Illustrated Encyclopedia of Pterosaurs. London: Salamander. 192 pp.

wiki/Scaphognathus

Finally, some Priosphenodon post crania!

Earlier we looked at the skull of Priosphenodon (aka Kaikaifilusaurus) No dorsal or occipital views, but plenty of data to nest it at the base of the rhynchosaurs, despite its identification as a rhynchocephalian (sphenodontian).

Now (Fig. 1), courtesy of Dr. Sebastián Apesteguía (Argentina), who wrote his thesis on Priosphenodon, an image of the skeleton as a museum model is available. I understand that the carpals are among the few imagined parts here.

Figure 1. Priosphenodon model. This is the first data I’ve seen on the dorsal skull and postcrania. Photo courtesy of Dr. Apesteguía. Inset shows that the foot and manus of the model were switched based on comparisons to Hyperodapedon, a related rhynchosaur. The artist was unsupervised.

You’ll note
the wide, bulging cheeks and extremely narrow parietal (skull roof), as in rhynchosaurs. The nares had not become confluent. That comes in more highly derived forms. But look at those twin anterior dentary tips, as in rhynchosaurs. No anterior process on the ilium though. Stance probably not as sprawling as this, and not as erect as in rhyncosaurs.

References
Photo courtesy of Dr. Sebastian Apesteguía Specimen model at the new museum of Cipolletti (Rio Negro Province, Argentina), currently under construction. The sculptor is Jorge Antonio Gonzalez.

The “lost” quadratojugal and supratemporal of Wumengosaurus

In basal enaliosaurs, the quadratojugal tends to be ignored or misidentified. Claudiosaurus is one such example. That’s because the qj generally shifts during taphonomy.  Wumengosaurus is another such taxon based on several specimens (Fig. 1). There is also a misidentified supratemporal here.

Figure 1. The unidentified supratemporal (in yellow/green) and quadratojugal (in lavender) in two Wumengosaurus specimens. Postorbital in violet. Squamosal in magenta. this is the ichthyosaur temporal region pattern, losing the lateral temporal fenestra, but gaining a secondary lateral temporal fenestra by the raising of the quadratojugal.

Why look for a bone that’s not identified?
Because sister taxa (Stereosternum, Mesosaurus, ichthyosaurs)  have a supratemporal and quadratojugal.

The fact that the lateral temporal fenestra disappears between the quadratojugal and squamosal in ichthyosaurs, yet both are arched posterior to the jugal means ichthyosaurs have a secondary lateral temporal fenestra, convergent with the typical lateral temporal fenestra of basal diapsids and protorosaurs + archosauriforms. And that’s how ichthyosaurs need to be scored in phylogenetic analysis.

References
Jiang D-Y, Rieppel O, Motani R, Hao W-C, Sun Y-I, Schmitz L and Sun Z-Y. 2008. A new middle Triassic eosauropterygian (Reptilia, Sauropterygia) from southwestern China. Journal of Vertebrate Paleontology 28:1055–1062.
Maisch MW 2010. Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art. Palaeodiversity 3: 151-214.
Wu X-C, Cheng Y-N, Li C, Zhao L-J and Sato T 2011. New Information onWumengosaurus delicatomandibularis Jiang et al., 2008, (Diapsida: Sauropterygia), with a Revision of the Osteology and Phylogeny of the Taxon. Journal of Vertebrate Paleontology 31(1):70–83.

wiki/Wumengosaurus

New Painten “Pro-Pterodactyloid”

A new, excellently preserved and unnamed private specimen has been published by Tischlinger and Frey (2013). It comes from the Latest Kimmeridgian of the Jurassic, just before the last age of the Jurassic, the Tithonian. The specimen is owned by a private research institute headed by Birgit Albersdörfer.

Figure 1. The Painten pterosaur (privately owned) from Frey and Tischlinger 2013. Excellent preservation and preparation here.

From their abstract: “The new specimen provides evidence of a late stage of a gradual evolution from the basal pterosaur construction (the so-called ‚rhamphorhynchoid‘ grade) to a pterodactyloid one. — The Painten pro-pterodactyloid demonstrates the evolutionary pathway towards a pterodactyloid flight configuration, which is characterized by the reduction of the fifth pedal ray (digit), shortening of the tail and the elongation of metacarpal IV with respect to the humerus to more than 70% of the length of the latter.”

Figure 2. Click to enlarge. Painten pterosaur compared to phylogenetic sister taxa. Ornithocephalus and SMNS 81775 are the basal taxa here. Note that while everything else grows on derived taxa, the metacarpus stays the same size. The large size of the Painten pterosaur, along with the greater length of pedal digit 3 and the brevity of the metacarpus sets it apart in its own clade, of which this the first known representative. Larger than its relatives, this is an unlikely juvenile (contra Hone, see below).

Tischlinger and Frey considered the Painten pterosaur “the last step on the long road from a basal pterosaur to the pterodactyloid.” (translated from the original German). They described it thoroughly.

Unfortunately, no phylogenetic analysis was provided.
So I provide one. Placing the Painten pterosaur into the large pterosaur tree nests it as a very basal Pterodactylus, between the very tiny SMNS 81775 specimen and Ningchengopterus, both basal to all valid Pterodactylus genera and all very much within this particular pterodactyloid-grade clade that began several nodes earlier. So the Painten pterosaur is a transitional specimen of sorts (aren’t they all? except for the terminal taxa) but only transitioning between the tiny Scaphognathus descendants and the genus Pterodactylus. Even so, several autapomorphies are present like the presence of a pedal digit 3 longer than pedal digit 2 and a very short prepubis.

The problem is
There are so many pterosaurs that converge on the morphology of Pterodactylus that aren’t really related to Pterodactylus that this genus has become a wastebasket taxon and is need of a big revision. All problems are solved with phylogenetic analysis, but no one, apparently, is interested in doing this.

The other problem is
Because they have not included multiple specimens from single genera and tiny pterosaurs most pterosaur paleontologists are still stuck in the old paradigm that all pterodactyloid-grade pterosaurs had a single common origin creating a monophyletic clade. Phylogenetic analysis shows this is not true. There were four convergent origins for the pterodactyloid grade. This is why the putative Painten transitional taxon looks so different from the putative Darwinopterus transitional taxon. They are not related to one another, but represent different clades. On the same subject from another point-of-view, Tischlinger and Frey hoped to nest their new pterosaur based on the old “rules” about which traits defined a basal pterosaur and which traits defined a pterodactyloid. You can’t do that. That’s putting the cart before the horse. You have to use a phylogenetic analysis and let the data and the analysis tell you how the traits are ordered. The order of longer and shorter traits may be more complex than the old “rules” indicate. They don’t always proceed in a step forward – step forward progress. You have to take what Nature gives you, and not try to pigeonhole new finds into old clades.

The third problem is
The belief in the mosaic pterosaur, one under modular evolution in which some body parts are advanced while others are not. Again, this is an illusion based on two few taxa in the analysis.

Let’s look at the Painten pterosaur in more detail.

Figure 4. The feet and tail of the Painten pterosaur with colors applied to bones. One loose proximal tail bone (red) is displaced at left. Left manual 4.4 is broken and re-healed in a jagged fashion. The wing tips are large, pulley-like joints. The wing unguals (dark blue) are displaced.

Pedal digit 5 is rarely so wonderfully preserved (Fig. 3). Note the distal tip of p5.2. It has a joint surface, but the next phalanx, the ungual, is not readily observable.

However, if we take a closer look the ungual is there on both feet (Fig. 4), on edge on the left foot and flattened on top of mt5 on the right foot. Along the same lines the wingtips (m4.4) appear to also have joint surfaces, but no unguals. The left ungual has been displaced and now appears at mid phalanx of m4.4. The right ungual is nowhere to be seen, perhaps as a result of the breakage of the phalanx, or simple taphonomy or burial.

Tischlinger and Frey note that pedal digit 5 could be used for “tensioning the tail wing membrane (uropatagium), but to a very limited extent.” Unfortunately only one specimen has been promoted to link pedal digit 5 to the uropatagium, the holotype of Sordes, and that is a misidentification. No pterosaurs link pedal digit 5 to the uropatagium, but Sharovipteryx does.

Figure 5. The wrist of the Painten pterosaur. Here the vestige of manual digit 5 (blue) is clearly visible on the palmar side of the left wrist.

Manual digit 5 is usually disturbed during taphonomy.
Here it is (in dark blue) undisturbed, but curled, on an axially rotated metacarpus. The undisturbed pteroid is articulated to the radiale. The extensor tendon process is not coosified to m4.1. The fingers are all rotated into the plane of the substrate. In vivo they would have pointed palmar side down, as in other tetrapods.

Transitional?
Tischlinger and Frey agree with the Darwinopterus transitional hypothesis, which is falsified when more taxa are included in analysis. They consider the Painten pterosaur, with it’s short tail and short pedal digit 5, to be the next step from Darwinopterus toward the pterodactyloid grade. These are traits that Darwinopterus had not acquired.

If you think the consensus is correct on this issue, remind yourself that Tischlinger and Frey merely accepted the findings of others, despite the red flags and oddities. I test issues using established methods, like phylogenetic analysis. I don’t have to make up excuses for data or imagine the evolution of body plans because all that comes from the order of the nodes in the recovered trees.

That’s good Science, right? Repeat the experiment if you don’t agree, then let me know if you come up with something different.

Tischlinger and Frey discuss various ways or paths by which the rhamph body plan evolved to become the pterodac body plan, but this is all simple dreaming without a large phylogenetic analysis of the Pterosauria. This the -only- method by which you can actually trace the appearance and subsequent modification of the various traits in much greater resolution, precision and verifiable validity.

Finally, if Rhamphodactylus, Darwinopterus and the Painten pterosaur were indeed phylogenetic sisters representing closely related steps in the evolution of the pterodactyloid grade, shouldn’t they look more alike (Fig. 5)? Phylogenetic analysis indicates they were not related, only convergent.

Figure 5. Three putative transitional pterosaurs. The Painten pterosaur, Darwinopterus and “Rhamphodactylus” to scale showing their variety and transitional status. These three are not related to one another, but acquired similar traits by convergence.

The Painten pterosaur is still very special
The Painten pterosaur is a transitional taxon leading to higher Pterodactylus specimens. It also represents a new clade in the pterosaur bush that had its own traits. Unlike other sister taxa pedal digit 5 is longer than the others. The middle dorsal vertebrae are compressed to be much shorter than the anterior and posterior verts, creating a shorter torso. The prepubis is remarkably tiny. The teeth are more needle-like than those of others.  Pedal digit 5 is more robust than in sister taxa.

Postscript
Dave Hone in his Archosaur Musings Blogpost described the Painten pterosaur as a “small, juvenile animal.” He did not say why, or to which adult it would be most closely associated. Hone may have followed the old paradigm that states a large orbit and unfused extensor tendon process are juvenile traits. He may not be aware that phylogenetic analysis (the large pterosaur tree) demonstrates that both are phylogenetic, rather than ontogenetic in nature.

Hone reported, “The fifth toe also seems to be something of an intermediate – it is not a small nub like the pterodactyloids, but nor is the second phalanx that long and it’s not curved either as in other basal forms.” Evidently he was not aware of the many pterodactyloids with longer lateral toes, often tucked beneath the other four. The relative shortness of metacarpal 4 was noted by both Tischlinger and Frey and Hone which they considered intermediate trait between shorter rhamphs and longer pterodacs. Unfortunately that assumes linear progression in evolution, which is not born out when phylogenetic analysis shows that more basal taxa had relatively longer metacarpals. We have to avoid wishful thinking and rigorously test all such “eyeball” assumptions.

References
Tischlinger H and Frey E 2013.  Ein neuer Pterosaurier mit Mosaikmerkmalen basaler und pterodactyloider Pterosauria aus dem Ober-Kimmeridgium von Painten (Oberpfalz, Deutschland) — A new pterosaur with mosaic characters of basal and pterodactyloid pterosauria from the Upper Kimmeridgian of Painten (Upper Palatinate, Germany) Archaeopteryx 31:1-13.

Private pre-ctenochasmatid also with soft tissue

www.solnhofen-fossilienatlas.de is a commercial website selling fossils over the Internet. Sometimes they have spectacular fossils for sale. Yesterday we looked at a new Pterodactylus with bold soft tissue preservation. Today we’ll look at their “juvenile Pterodactylus“ #2042 with subtle soft tissue preservation. As you probably know by now, it’s not a juvenile.

Figure 1. Click to enlarge. Tiny private pterosaur. These had been considered juveniles, but this one nests at the base of the ctenochasmatidae. Can you see the tail here? It is ephemeral, but present.

I don’t know the scale of this specimen, but phylogenetic bracketing gives it a skull length of about 2 cm (Fig. 3). The soft tissue does not have a distinct color here, but a distinct texture. Like Pterodactylus (the Vienna specimen), the wing membrane extends to the elbow with a hollow area just aft of the elbows and this blends into a fuselage fillet (Fig. 2). So, this is one more specimen that supports the elbow to wingtip model, contra the traditional ankle to wingtip model that is based completely on hope and excuse, not evidence.

Figure 2. Click to enlarge. Private tiny pterosaur #2042. Select areas colorized. Once again, those wing membranes do not connect to he tibia. The indigo business in the gut might be a prepubis, but that would mean there were three prepubes in there. Otherwise it might be an embryo.

Giant procumbent teeth characterize this taxon, and for good reason. It is nearly identical to a specimen (St/Ei 1= JME 1) that nests between the much larger Angustinaripterus and slightly larger proto-ctenochasmatids.

Figure 3. Click to enlarge. Private pterosaur #2042 together with St/Ei1, which nests at the base of the ctenochasmatidade, close to Angustinaripterus.

Possible embryo?
When all the ribs, prepubes and gastralia had been accounted for, there was a little shape, somewhat like the skull and vertebrae of #2042 in the lower abdomen, but 1/7 the size of the adult. This will take further examination to look for details.

Let me know if this specimen ever appears in a museum.

St/Ei = Stadt/Eichstätt (JME SoS) Jura Museum, Eichstätt, Germany