The best ‘Sordes’ uropatagium… is another overlooked wing

This much talked about, but rarely seen ‘Sordes’ specimen
(Fig. 1), has been known for decades. It made a brief appearance some 30 years ago at an SVP talk by David Unwin where it caused quite a stir. I haven’t seen it again since. A scale bar is not shown and the museum number is unknown, but may be one of these three: PIN 104/73, PIN 2585/36, PIN 2585/37.

Today this rare ‘tail-less’ specimen made another brief appearance
in an online Palaeontological Assocation talk “Resolving the pterosaur bauplan using a quantitative taphonomic approach” by Rachel Belben (2012, video link), one of Unwin’s students. We looked at Belben’s nearly identical 2020 abstract here.

Figure 1. Image from Belben’s December 2020 talk about the pterosaur bauplan. That’s Belben inset in red. Click to view video on YouTube.

Not one, but two similar Sordes specimens
were presented by Unwin at SVP decades ago. Both appeared to have a distinct uropatagium stretched bat-like between the sprawling hind limbs (Figs. 1, 2). Everyone wondered whether that membrane was 1) above or below the cloaca, 2) attached or not attached to the tail, and 3) what sort of precursor taxa would gradually develop such a membrane controlled by hyperflexed lateral toes. In bats, of course, the vaguely similar calcar arises from the ankle. The toes are not involved.

Sharov 1971
first described and figured the Sordes holotype (Fig. 2, upper right) with a small drawing that appeared to clearly show a uropatagium stretched between the hind limbs and controlled by those odd Tanystropheus-like elongated lateral toes.

Unwin and Bakhurina 1994
brought this odd bit of flight membrane to a wider audience with a short paper in Nature. Their drawing (Fig. 2 middle right) paid less attention to detail.

Peters 1995
disputed the uropatagium, considering it a displaced wing membrane. That critical hypothesis was presented again in Peters 2002 (Fig. 2, left and bottom).

Elgin, Hone and Frey 2012
sided with Sharov, Unwin and Bakhurina, also paying little attention to the specimen.

Figure 2. Sordes wing drift hypothesis from Peters (2002) which attempted to show that the wings and uropatagia of Sordes were more like those of other pterosaurs than the other way around. The very deep uropatagia are misinterpretations prior to the realization that the left brachiopatagium (main wing membrane) was displaced to the ankle area.

Back in 2011,
the uropatagium of the Sordes holotype showed up here with another tracing (Fig. 5) that showed the displaced radius + ulna and its displaced membrane.

Figure 3. The PIN 2585/3 specimen of Sordes showing displaced left radius and ulna dragging their membranes along with them. The right wing is articulated and shows a short chord wing membrane. Uropatagia are in red.

A new tracing of the rare specimen
(Fig. 4) shows the purported uropatagium extending far beyond the hind limb. That indicates a problem! This is not a uropatagium. Maybe that’s why we haven’t seen this rare specimen for 30 years. A closer examination reveals a series of pterosaur arm bones beneath the hind limb elements. Arm bones or not, this ‘uropatagium’ is a brachiopatagium, a wing membrane, complete with aktinofibrils (Fig. 5).

Figure 4. Color tracing applied to the rare ‘Sordes’ specimen reveals another displaced wing (deep blue) along with overlooked wing elements. See figure 5 for a reconstruction.

Adding what little is known
to the large pterosaur tree (LPT, 256 taxa) nests the rare specimen not with Sordes, but with the tiny flightless anurognathid PIN 2585/4 specimen that shares the plate with the holotype of Sordes, PIN 2585/3 (Fig. 2). We looked at that rarely seen specimen earlier here.

Figure 5. Reconstruction of the specimen in figure 4.

Distinct from the flightless PIN 2585/4 anurognathid specimen,
this one has large, robust wings.

In summary
this rarely seen specimen

1. is not Sordes
2. does not present a uropatagium
3. can now explain why a Sordes-like tail is absent here
4. evidently has never been carefully examined before
5. has fooled pterosaur experts for decades
6. is one source of pterosaur mythology that many pterosaur workers and their minions continue to believe in fifty years after its original description.

Someone please tell Rachel Belben
so she can wash her hands of this decades-old error and start fresh.

The Sordes uropatagium is a misinterpretation.
We need to bury this mistake and forget it. Stop promoting and believing this myth. It has been exposed.

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References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeonntologica Polonica 56(1): 99-111.
Peters D 1995. Wing shape in pterosaurs. Nature 374, 315-316.
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

https://pterosaurheresies.wordpress.com/2015/03/10/the-evolution-of-the-sordes-wing-and-uropatagia-1971-to-2011/

https://pterosaurheresies.wordpress.com/2015/03/09/how-one-sordes-evolved-into-dorygnathus-via-cacibupteryx/

https://pterosaurheresies.wordpress.com/2014/03/15/variation-in-three-sordes-specimens/

https://pterosaurheresies.wordpress.com/2012/07/17/what-is-happening-between-the-legs-of-sordes/

https://pterosaurheresies.wordpress.com/2020/10/21/svp-abstracts-3-belben-contributes-to-the-bat-wing-pterosaur-myth/

 

Pterosaurs NOT an enigmatic group, contra Belben and Unwin 2019

The following abstract
was presented during the most recent SVPCA meeting in 2019.

Belben and Unwin 2019
are both associated with the University of Leicester. Sadly, Dr. Unwin has been responsible for many of the inaccurate to totally wrong ideas many current pterosaur workers and artists now consider as canon. Think Sordes and the deep chord bat-wing membrane stretching to the ankles hypothesis and the incorporation of pedal digit 5 into the single uropatagium stretching between the two. Think pterosaur eggs laid deep under brush or under ground. Think the archosaurian genesis for pterosaurs. Think the Monofenestrata hypothesis of relationships.

I’ll break down today’s abstract for you
as yet another example of Dr. Unwin stuck in his own groove outside of science and reality, much of it due to inaccurate observation and taxon exclusion, both of which are curable maladies.

From the Belben and Unwin 2019 abstract:
“Quantitative taphonomy [see below for definition] has huge potential for furthering our understanding of vertebrate palaeobiology. So far, however, it has been a neglected field with little development. Here we show how quantitative taphonomy can be used to determine the ‘bauplan’ of pterosaurs.

With well over 250 good fossils, many complete skeletons, some of these with extensive soft tissue, we already know the ‘bauplan’ of pterosaurs very well (Fig. 1). Start here for an introduction and links.

“With no descendants and a unique morphology, pterosaurs remain an enigmatic group despite a high degree of research interest for over 200 years.”

Pterosaurs do not have a unique morphology, nor are they an enigmatic group. Peters 2000a b, 2002, 2007, 2009 showed the pterosaur ‘bauplan’ arose gradually from a clade of taxa Dr. Unwin refuses to recognize, the Fenestrasauria, nor does he cite the above references. Dr. Unwin prefers to keep his objects of study in the ‘enigmatic’ jar for reasons that should baffle any reputable scientist. If you wonder why I have to self-cite, welcome to the world of paleo politics where academics don’t argue against a hypothesis, they don’t cite it.

“One aspect still debated is the basic construction and extent of the wing membrane, fundamental to locomotory abilities and other key aspects of their biology.”

The wing membrane question was settled over a decade ago and need not be debated because every example of pterosaur wing membrane presents the same conservative pattern: stretched between elbow and wing tip with a fuselage fillet. (Peters 2002). Precursor membranes are known in Cosesaurus (Peters 2009) and are less obvious in Longisquama. The pteroid and preaxial carpal arise from a migration of two centralia (Peters 2009). Details summarized here.

“Did the wing membrane connect all four limbs, bat-like, forming a single flight surface and single anatomical module? Were they bird-like, with separation of limbs to create four anatomical modules? Or were they a unique two or three module construction?”

This has never been a question for Dr. Unwin before. He has always promoted the invalid bat-like wing design and the invalid single uropatagium design.

Figure 1. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees and a precise impression of the wing membranes as they were. The animation extends the limbs into the flight configuration.  

“Soft tissue evidence is patchy and found in only a tiny number of species, and the insights it provides is limited.”

False. Dr. Unwin knows better. There are many excellent examples of soft tissue only one of which (Fig. 1) would be necessary to answer the wing membrane and uropatagia issues. The rest confirm the first (Peters 2002).

“Quantitative taphonomy, through metrics of completeness, articulation, and joint geometry, can test limb association, and help identify anatomical modules.”

Dr. Unwin, why don’t you stop avoiding the number one issue and just once accurately trace your first pterosaur specimen with soft tissue. Study it. Play with it. Reconstruct it. Animate it. Score it for a wide range of traits against all the 240 best known pterosaur specimens, as shown here. I think you’ll find the process enlightening and you’ll finally be able to teach your students something about your favorite subject without cloaking pterosaurs in question marks. Don’t be seen as the bumbling professor who held back pterosaur research for several decades by sticking to your invalid postulates. When the word gets out, you may find it hard attracting students, which is your livelihood.

Examining the quantitative taphonomy (= depositional setting, = everything but the pterosaur itself) only delays the inevitable day of reckoning when you will have to finally, seriously and precisely trace a pterosaur specimen and present your findings for critical review.

“Over 100 pterosaurs have been analysed thus far, with an intended data set of 200+ individuals from more than 40 species representing all principal clades. This will allow different models to be mapped across the phylogeny.”

Are you examining the quantitative taphonomy of 200+ individuals or the 200+ individuals themselves? Sounds like the former is in play. Please don’t attempt to map the different taphonomic models across your incomplete cladogram to find out what a pterosaur ‘bauplan’ is. Instead, start with the Vienna specimen of Pterodactylus (Fig. 1). Get precise with it. Don’t pass the chore down to a grad student seeking approval and fearing for their grade. Use the large pterosaur tree (LPT, 240 taxa) for sister taxa. Trace and reconstruct your own specimens. You can pull yourself out of your self-inflicted academic muck!

“Fossil birds and bats will be similarly analysed in order to provide context and constrain the models, as their bauplan can be safely inferred from extant forms.”

Figure 1. Click to enlarge and animate. Cosesaurus flapping – fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

That’s nice. But birds and bats are not related to pterosaurs nor to each other. Why not stop wasting your time and go see Cosesaurus, Sharovipteryx and Longisquama. Don’t forget Langobardisaurus, Macrocnemus and Huehuecuetzpalli. Don’t stop until you can reconstruct and score them in your sleep. Dr. Unwin, you’re stuck in the tail-dragging dark ages. You’re supposed to be a pterosaur expert, so quit calling them enigmas. You need to turn your mind around. The following citations might help.

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References
Belben R and Unwin D 2019. Quantitative taphonomy – they key to understanding the pterosaur bauplan?
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
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.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.

Quantitative taphonomy = “This approach uses the hypothesis that taphonomic alteration varies in a predictable way with depositional setting. In other words, each specific environment (e.g., low-salinity muddy bay, storm-dominated clastic shelf) is characterized by a unique suite of physical, chemical and biological processes: these processes imprint a unique and predictable “taphonomic signature” on the death assemblage.” Davies et al.  2017

 

A Closer Look at the Sordes “Uropatagium”

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  here, here, here 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?

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