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.

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 4. 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.

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 6. The PIN 2585/3 specimen of Sordes showing displaced left radius and ulna dragging their membranes along with them. The right wing is articulated.

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.

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.

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.


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/

 

Unwin and Martill 2019 find pterosaurs ‘naked’ and ‘ugly’

Unwin and Martill 2019 report:
“With key roles in flight, thermoregulation and protection of the body, the integument was of fundamental importance to pterosaurs. Determination of the basic anatomy of this structure could provide a range of new insights into the palaeobiology of these enigmatic volant reptiles. Presently, however, there are several conflicting hypotheses regarding the construction of the integument, all founded on limited numbers of specimens, and not one of which is fully consistent with the available fossil evidence.

As mentioned yesterday, pterosaurs are not enigmatic. Unwin and Martill have chosen to avoid the scaly lepidosaurian ancestors of pterosaurs cited by Peters (2000, 2007). The integument found on pterosaurs has similar precursor integument on sister fenestrasaurs like Sharovipteryx (Fig. 1) and Longisquama, adding two taxa to their short list of pterosaurs preserving scaly integument and pycnofibers exclusive of the extradermal membranes (wings and uropatagia).

Figure 1. Note the neck skin (integument) of Sharovipteryx, a pterosaur sister.

Figure 1. Note the neck skin (integument) of Sharovipteryx, a pterosaur sister.

Unwin and Martill continue:
“We have developed a new 
model based on investigations of more than 100 specimens all of which show some form of exceptional preservation. This data set spans the entire temporal and systematic ranges of pterosaurs and a wide variety of preservational modes.”

So… “a limited number of specimens” (see above) just turned into “more than 100 specimens.” Did they just want to see if anyone was paying attention?

“The model has three principal components:
(1) A thin epidermal layer. The external surface of the integument was glabrous [= free from hair or down, smooth] with a smooth, slightly granular, or polygonal texture.

Attenuate ‘bristles’ fringed the jaws in two anurognathids and small tracts of filaments may have adorned the posterior cranium in some pterosaurs.

Perhaps these jaw and skull filaments should have been separately numbered because they are different than glabrous tissue.

(2) A layer of reticular and filamentous collagen and of variable thickness and complexity, formed much of the dermis.

Helically wound bundles of collagen fibres (aktinofibrils), were present throughout all flight patagia. Variation of aktinofibrils in terms of their dimensions, packing, orientation and stiffness permitted localized variation in the mechanical properties and behaviour of the flight patagia whichvaried from relatively stiff distally to more extensible and flexible proximally.

‘Feather-like’ structures reported in Jeholopterus appear to be partially unraveled or decayed aktinofibrils.

Again, these are all distinct tissues worthy of their own numbers.

Unwin and Martill have no idea that Jeholopterus was a vampire bat analog (Peters 2008) covered like no other pterosaur with fluffy, silent, owl-like extradermal integument. Neither Unwin nor Martill seem to make reconstructions, so neither has any idea what Jeholopterus looked like, unless they looked here (Fig. 2).

Finally, Unwin and Martill are mixing in flight membranes here. Perhaps THAT is where they get so many examples because otherwise dermal material is exceedingly rare. Integument generally means ‘covering’, so their inclusion of wing membranes is a little misleading, especially considering the ‘naked and hairless’ portion of their abstract headline.

Figure 2. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer.

Figure 2. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer.

Collagen fibre bundles were also present in footwebs, and in the integument of the neck and body. These structures have often been mis-identified as ‘hair’ (pycnofibres).

Again, this variety of tissues should have been numbered separately because they are different than tissue forming much of the dermis.

(3) A deep dermal layer with muscles fibres, blood vessels and nerves.

This variety of demal tissues were already described for the flight membranes, but it could also apply to normal tetrapod skin, like our own.

The pterosaur integument was profoundly different from that of birds and bats, further emphasizing the sharp disparity between these volant tetrapods.”

Why didn’t Unwin and Martill compare pterosaur integument to lepidosaur integument, specifically that of Sphenodon and Iguana (Fig. 3)? These are the two closest living relatives of pterosaurs in the large reptile tree. According to the LRT, Unwin and Martill are looking in the wrong places.

The spines of Iguana.

Figure 3. The dorsal and gular spines of Iguana are homologous with those in Sphenodon.

Not sure where Unwin and Martill
are getting data for pterosaur skin exclusive of the extradermal membranes. They don’t say. The dark wing Rhamphorhychus (Fig. 4) has the most incredible preservation of extradermal membranes, but the skull, neck and torso were prepared down to the bone.

Figure 1. The darkwing specimen of Rhamphorhynchus. Top: in situ. Middle: Soft tissues highlighted. Bottom: Neck and forelimb restored.

Figure 4. The darkwing specimen of Rhamphorhynchus. Top: in situ. Middle: Soft tissues highlighted. Bottom: Neck and forelimb restored.

So, why do Unwin and Martill think the Mesozoic got ugly?
Their abstract does not seem to answer their click-bait headline, which describes naked, hairless and featherless pterosaurs without giving one example of same based on evidence. On the contrary, employing phylogenetic bracketing, between Sharovipteryx (Fig. 1), Scaphognathus and Sordes (the hairy devil, Fig. 5), basal pterosaurs were not naked. Their fibers were not the same as hair or feathers, but unique to fenestrasaurs.

The hind limbs and soft tissues of Sordes.

Figure 5. The hind limbs and soft tissues of Sordes. Above, color-coded areas. Below the insitu fossil.

Finally…
Why were pterosaurs considered naked by Unwin and Martill when hairy Sordes (Fig. 5) was studied by Unwin, known to Martill, and not mentioned in the abstract? Very strange, indeed coming from these two.


References
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.
Unwin D and Martill D 2019. When the Mesozoic got ugly – naked, hairless, (and featherless) pterosaurs. SVPCA abstracts.

Another flightless pterosaur: the anurognathid PIN 2585/4

This is one of those fossils
I had heard about a long time ago, but never saw until today. I read once, (not sure where, but perhaps in Bakhurina 1988?), that there was a second specimen of Batrachognathus on the holotype Sordes plate. Problem was, I could never see another pterosaur on the Sordes plate. That left a big question mark over my head. Now I know that the widely circulated images of Sordes deletes or separates the second pterosaur from Sordes on the original plate (Fig. 1).

Today,
I finally saw both pterosaurs on the same plate on an online image (Fig. 1). Apparently this is the only instance of two distinct genera of pterosaurs found on the same plate. Not sure how this image snuck out of Russia.

Figure 1. The holotype of Sordes, PIN 2585-3. includes a small anurognathid, PIN 2585-4.

Figure 1. The holotype of Sordes, PIN 2585-3. includes a small anurognathid, PIN 2585-4. 3 frames, 5 seconds each.

Not sure why this little anurognathid
has not gotten more attention. By the way, It does not nest with Batrachognathus in the large pterosaur tree. Perhaps it did back in 1988 when only a few anurognathids were known. But now we have many more anurognathids to compare it to. Sordes (Sharov 1971) has been known for over 45 years. That’s a long time to overlook/ignore/ a find like this. Apparently this is the specimen that was said to have bristles around the jaws (Bakhurina 1988) because it does and the holotype  (Rjabinin 1948) does not.

Figure 2. Tracing of the anurognathid PIN 2585-4 with soft tissue in gray. This, obviously, is a low-rez image. Even so, nearly all of the major bones preserved on the plate could be traced. The skull, in particular, matches sister taxa at reptileevolution.com, in contrast to the Bennett 2007 interpretation.

Figure 2. Tracing of the anurognathid PIN 2585-4 with soft tissue in gray. This, obviously, is a low-rez image. Even so, nearly all of the major bones preserved on the plate could be traced. The skull, in particular, matches sister taxa at reptileevolution.com, in contrast to the Bennett 2007 interpretation.

The PIN 2585-4 specimen has tiny wings
and large legs. Based on comparisons with other anurognathids, this specimen appears to be yet another flightless pterosaur. An unrelated flightless pre-azhdarchid, SOS 2428, was reported on here several years ago.

Figure 3. Click to enlarge. The PIN 2585/4 anurognathid reconstructed in two views. Note the small wings and large legs on this flightless pterosaur.

Figure 3. Click to enlarge. The PIN 2585/4 anurognathid reconstructed in two views. Note the small wings and large legs on this flightless pterosaur, the second one now known. Finger four retains 5 elements including a tiny ungual.

An obligate biped
with strong hind limbs and extremely long tibiae, the PIN 2585/4 specimen would have been a better bipedal runner and, based on comparisons to volant pterosaurs, probably could not fly with such gracile, small wings. It would also have a tough time walking as a quadruped, so was obligated to walk as a biped, like long-legged Bergamodactylus and Sharovipteryx. We have individual pedal traces for anurognathid pterosaurs. No trackways yet. And no forelimb marks either.

So, the anurognathid could not fly,
but PIN 2585/4 was still a strong flapper. There is nothing reduced about its sternal complex and pectoral girdle. We can image it running and flapping for added thrust, something like Cosesaurus did before the advent of wings in the Middle Triassic (Fig. 4).

Figure 2. Cosesaurus running and flapping - slow.

Figure 4. Cosesaurus running and flapping – slow.

The forelimbs are gracile
in PIN 2585/4 with shorter elements. unlike its more typical closest known sister, CAGS IG 02-81, which was clearly volant and had shorter hind limbs.  The fore claws of virtually all flying pterosaurs were capable of touching the ground (Fig. 5).

The CAGS IG 02-81specimen attributed to Jeholopterus

Figure 6. The CAGS IG 02-81 specimen attributed to Jeholopterus. Currently it nests  the sister to the flightless anurognathid. Note the proportional differences.

All of the skeletal elements
in PIN 2585/4 resemble those in sister taxa, except the proportions of the fore and hind limbs. Note that the orbits are in the back of the skull, as in CAGS IG 02-81 and ALL other pterosaurs — in contrast to the misinterpretation offered by Bennett (2007) for the flathead anurognathid that has been widely and erroneously accepted.

Figure 6. The flightless anurognathid, PIN 2585/4, is the same size as other typical anurognathids, but its long legs make it taller.

Figure 7. The flightless anurognathid, PIN 2585/4, is the same size as other typical anurognathids, but its long legs make it taller. Click to enlarge.

Here’s how it went down today:
When I first saw the image on Google, I wondered what that fossil was… and then I saw that familiar tail and foot of Sordes… and then I realized this is the long sought double pterosaur fossil! I wasn’t expecting the specimen to be flightless, but it soon dawned that the proportions indicated we had a second flightless pterosaur here. So, a very exciting day all around. If this has been published elsewhere, please let me know. I am not aware of it.

I would have published on this find, except…

  1. It’s not my fossil.
  2. I haven’t seen or studied the specimen first hand.
  3. And even if I had, as I’ve done on several specimens before,  past experience tells me that today’s pterosaur referees don’t want me publishing any more. Apparently they want to save the discoveries for themselves.
  4. Apologies if someone else is working on this specimen and/or is awaiting publication. I am not aware of anyone doing this.

The PIN 2885-4 specimen has been sitting around for 45 years.
They had their chance. This blog has made a habit of finding discoveries in overlooked and ignored specimens. And once again I demonstrate that you don’t have to see the specimen or have a PhD to make a contribution. Recognition is something else altogether.

References
Bakhurina NN 1988. [On the first rhamphorhynchoid from Asia: Batrachognathus volans Riabinin 1948, from Tatal, western Mongolia]. Abstract of paper in Bulletin of the Moscow Society for the Study of Natural History, Geological Section 59(3): 130 [In Russian].
Rjabinin AN 1948. Remarks on a Flying Reptile from the Jurassic of Kara-Tau. Akademia Nauk, Paleontological Institute, Trudy 15(1): 86-93.
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].

wiki/Sharovipteryx

wiki/Batrachognathus

 

The evolution of the Sordes wing and uropatagia: 1971 to 2011

When insect-specialist, A. Sharov (1971),
first traced the wings of the Sordes holotype (PIN 2585/3) he considered every soft tissue on the specimen some sort of wing membrane with little to no taphonomic displacement (Fig. 1c). Sharov added a skull where there should have been one. He attached the wings to the ankles and considered a V-shaped dark patch the trailing edge of a single uropatagium stretched between the hind limbs (detached from the tail, framed and controlled at least in part by pedal digit 5). Such a structure had never been seen before on any pterosaur.

Sharov also traced large puffs of soft tissue anterior to the right free fingers and lateral to the left ankle (Fig. 1c). These have been ignored ever since.

Unwin and Bakhurina (1994)
echoed Sharov’s observations in an international publication, Nature (Fig. 1d), focusing on the membrane attachment to the ankles and the uropatagium stretching between them and the lateral toes, already extremely bent as in most basal pterosaurs. Unfortunately, less data, rather than more, was presented. And pterosaur workers were left scratching their heads. How does an embryo develop a membrane between the two hind limbs and not attach to the tail (as in bats)? Was the cloaca above or below this membrane? How could a pterosaur walk bound like this? How could it fly bound like this?

Figure 4. 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.

Figure 1. 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. Unfortunately the very deep and hairy uropatagia are misinterpretations prior to the realization that the left brachiopatagium (main wing membrane) was displaced to the ankle area (Figure 3). Click to enlarge.

Peters (1995)
suggested that some elements of Sordes had taphonomically drifted. Moving the elements back to their purported in vivo positions created a morphology more like that of all other pterosaurs. Unfortunately some identification mistakes were made due to inexperience and working with low resolution second hand data, but further work demonstrates the basic idea of taphonomic shifting was sound.

Figure 1. Sordes interpreted by me in Nature 1995. At that time. remember, no one had ever heard of a uropatagium. And the purported "fact" that this flap of skin spanned the hind limbs without connecting to the tail seemed pretty hard to swallow for a majority of paleontologists. The only images available were small and indistinct. Even so, an attempt was made here to understand the taphonomy of the specimen and how it came to sport such a strange autapomorphy that has not been seen since on any pterosaur fossil. Despite the sincerity of this effort, it includes several mistakes rectified now in ReptileEvolution.com/sordes.htm after publication of the specimen in a larger format with higher resolution.

Figure 2. Sordes reinterpreted by Peters (1995). Since no other pterosaur had such a wing and uropatagium plan as Sharov had proposed and Unwin and Bakhurina echoed, I assumed the parts had taphonomically drifted from their in vivo positions. I was largely correct but some mistake were made. The V-shaped patch between the ankles actually is part of the left wing, not the right one, which is undisturbed in the fossil. And what everyone thought was the skull is actually the left hand and m4.1.

Peters (2002)
refigured the Sordes wing (Fig. 1a, b, e), this time attributing certain odd alignments to matrix planes and taphonomic shifting. This was part of a larger study examining a wide range of pterosaur wing plans. Unfortunately, the uropatagia were again incorrectly interpreted, this time as uropatagia that had overlapped medially during taphonomy. The purported skull was ignored.

ReptileEvolution.com (Peters 2011)
offered a new interpretation that identified bones thought to have been the skull roof as left manual 4.1 (Fig. 3). Bones thought had been considered facial bones were reidentified as the free fingers and metacarpus, somewhat busted up. In one of those wonders of taphonomic displacement, in this fossil it appears that manual 4.1 was joined to the distal left humerus,! This left the radius and ulna unaccounted for. And there’s our solution!

The myth of the pterosaur uropatagium

Figure 3. The Sordes uropatagium is actually displaced wing material towed to the ankles by the displaced radius and ulna.

Impressions of the ulna and radius (click here for rollover image) were identified near the left ankle. These formed the straight lines that were thought by previous authors to be the straight trailing edge of an undamaged wing membrane (Sharov 1971, Unwin and Bakhurina 1994). Unfortunately no prior workers raised the question: how could the trailing edge be taut straight when relaxed?

However, it is interesting to note in figure 1 that the tracings of this area made by Sharov (1971) and Unwin and Bakurina (1994) do not match. What were they each looking at?

In the Sordes holotype, along with the displaced ulna and radius came a large chunk of wing membrane, now detached, folded upon itself like a ribbon and spanning the ankles, giving the illusion of a uropatagium trailing edge. Note that no trace of this purported uropatagium exists close in to the femora. Instead faint impressions of the twin uropatagia, identical to those of other pterosaurs and Sharovipteryx, are faintly preserved behind each knee.

Figure 5. Sordes from Elgin, Hone and Frey 2011. While we were all hoping for more detail, we got less.

Figure 4. Sordes from Elgin, Hone and Frey 2011. While we were all hoping for more detail, we got less.

Elgin, Hone and Frey 2011
published a tracing of Sordes, repeating Sharov’s original interpretation, assuming that little to no taphonomic displacement took place (Fig. 4). Based on the left wing membrane trailing edge, this seems to have been traced from Unwin and Bakhurina 1994 (Fig. 1c, more details and links below) rather than Sharov (1971).

Very few pterosaurs are perfect specimens
Prior workers, even after noticing the back-turned cervicals of Sordes, the lack of a skull with identifiable features and the apparent loss of the left free fingers together with m4.1 (originally misidentified as an in-place radius and ulna, Fig. 1c), did not consider the possibility of taphonomic displacement. Nor did they attempt to more accurately trace the skeleton and soft tissue since 1971(!). Nor did they attempt to reconcile the soft tissues of Sordes with those of other pterosaurs, except when Elgin, Hone and Frey (2011) attempted the exact opposite (details and data here and here) with even less detail to their tracings (Fig. 4) than Unwin and Bakhurina (1994)! They explained away all the other wing differences to fit the Sordes model and NOT with greater precision.

Unfortunately
most pterosaur workers (e.g. Unwin 2005; Elgin, Hone and Frey 2011; Witton 2013) continue to reconstruct their pterosaurs with deep chord wing membranes in blind accord with Sharov (1971) rather than changing the Sordes wing to match that of all other pterosaurs (more here on that topic). They argued that the Zittel wing must have been trimmed or must have extended to the ankles. They argued that the Vienna specimen of Pterodactylus (Fig. 4) likewise must have had wings attached to the ankles, when they clearly do not, and explained away the difference with the term, “shrinkage.”

The Vienna Pterodactylus.

Figure 5. The Vienna Pterodactylus. Click to animate. Wing membranes in situ (when folded) then animated to extend them. Contra Elgin, Hone and Frey (2011) there is no shrinkage here or in ANY pterosaur wing membrane. There is only an “explanation” to maintain the Sordes deep chord wing hypothesis when it is the Sordes wing that needs to conform to this very clear data.

If you think this defies all logic,
I agree with you. And yet, it continues…

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, D. M. 2005. The Pterosaurs fromDeep Time. Pi Press, New York, 347 pp.
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.

wiki/Sordes

How one Sordes evolved into Dorygnathus via Cacibupteryx

I have seen images of three
more or less complete Sordes (Sharov 1971, Oxfordian/Kimmeridgian) specimens (Figs. 1-3). Unfortunately only the holotype PIN 2585/3 (Fig.1) was described (Sharov 1971). Later Unwin and Bakhurina (1994) echoed Sharov’s findings, that Sordes had wing membranes attached to the legs and another membrane (uropatagium) between the legs, but their tracings were, at best, outlines. No one else who has actually seen this taxon has further described the holotype in more detail with precise tracings.  And it’s been almost 45 years!

Figure 2. Sordes holotype, PIN 2585/3. Soft tissue in abundance, but the skull is largely gone.

Figure 1. Sordes holotype, PIN 2585/3. Soft tissue in abundance, but the skull is largely gone.

The Sordes paratype PIN 2470/1 (Fig. 2) includes a fish and lots of hair. (Unwin 2006 reports that nine specimens of Sordes were found in the 1960s), all undescribed at present.

Figure 4. The third Sordes specimen PIN number unknown. That is a small fish in the middle. Lots of soft tissue here.

Figure 2. The paratype of Sordes specimen PIN 2470/1). That is a small fish in the middle. Lots of soft tissue here.

A third specimen
of Sordes (PIN 2585-25) is also well known and shows the skull in lateral view. Soft tissue is present here, but much less extensive. Even less well known are the five or six other specimens (among them: PIN 104/73, PIN 2585/36, PIN 2585/37) Are they just bits and pieces? Does anyone know? Are they published anywhere? I have a note into the PIN for more info, but so far no reply.

Figure 2. The PIN 2585-25 specimen of Sordes.

Figure 3. A third specimen of Sordes, PIN 2585-25.

The three specimens have all been identified as Sordes, but they nest in three distinct nodes on the large pterosaur tree, phylogenetically closer to other taxa than to each other (Fig. 4).

Figure 4. The three Sordes specimens to scale. They are close, but not identical. Shown above each is a closer sister taxon.

Figure 4. The three Sordes specimens to scale. They are close, but not identical. Shown above each is a closer sister taxon. Click to enlarge.

The Cacibupteryx connection
Cacibupteryx caribensisi (Gasparini, Fernández, and de la Fuente, 2004) Oxfordian, Late Jurassic ~160 mya was considered a rhamphorhychid and a scaphognathid, but it nests as a very basal dorygnathid. Derived from a sister to SordesCacibupteryx phylogenetically preceded all specimens of Dorygnathus.

Figure 5. Cacibupteryx ( IGO-V 208) to scale with the 2470/1 specimen attributed to Sordes. These two nest together in the large pterosaur tree, not quite with Sordes. These two were contemporaries, both from the Tropic of Capricorn, not a world apart, as they are now, but part of the supercontinent Pangaea prior to the appearance of the North Atlantic.

Figure 5. Cacibupteryx ( IGO-V 208) to scale with the 2470/1 specimen attributed to Sordes. These two nest together in the large pterosaur tree, not quite with Sordes. These two were contemporaries, both from the Tropic of Capricorn, not a world apart, as they are now, but part of the supercontinent Pangaea prior to the appearance of the North Atlantic.

The Jianchangopterus connection
The holotype of Sordes (Fig. 4) nests with Jianchangopterus, at the the base of Pterorhynchus + the Wukongopteridae not far from the base of Scaphognathus and its many descendants. So with one Sordes at the base of all dorygnathids and one Sordes near the base of all scaphognathids, that means Sordes is the last common ancestor of all pterodactyloid-grade pterosaurs in the large pterosaur tree — still pretty far from any pterodactyloid-grade pterosaurs, which had four separate origins.

One wonders
why the other six specimens of Sordes have not been released. Are they just scraps? It’s been fifty years since their discovery. It’s time those specimens were presented and all three Sordes specimens were reintroduced in an academic publication. Since the three well-preserved specimens attributed to Sordes nest close to one another, but are not conspecific or even congeneric on the cladogram. doubt may be cast on the identity of the remaining specimens. We’ll have to see…

References
Cheng X, Wang X-L, Jiang S-X and Kellner AWA 2012. A new scaphognathid pterosaur from western Liaoning, China. Historical Biology iFirst article available online 29 Nov 2011, 1-11. doi:10.1080/08912963.2011.635423
Gasparini, Z, Fernández M and de la Fuente M 2004. A new pterosaur from the Jurassic of Cuba. Palaeontology 47(4): 919–927. doi:10.1111/j.0031-0239.2004.00399
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.
Zhou C-F 2014. Cranial morphology of a Scaphognathus-like pterosaur, Jianchangnathus robustus, based on a new fossil from the Tiaojishan Formation of western Liaoning, China. Journal of Vertebrate Paleontology 34(3):597-605.

wiki/Jianchangnathus
wiki/Cacibupteryx
wiki/Sordes