New Como Bluff (Latest Jurassic) pterosaurs

Bits and pieces
of new Latest Jurassic pterosaurs are coming out of aquatic deposits in western North America according to McLain and Bakker 2017. The material is 3D and not very mineralized, so it is extremely fragile.

Specimen(s) #1 – HMNS/BB 5027, 5028 and 5029
“One proximal and two distal femora match a complete femur (BYU 17214) referred to Mesadactylus. Unexpectedly, both of the BBF distal femora possess a large intercondylar pneumatopore. BYU 17214 also possesses an intercondylar pneumatopore, but it is smaller than in the BBF femora. Distal femoral pnuematicity is previously recognized only in Cretaceous azhdarchoids and pteranodontids.”

The Mesadactylus holotype and referred specimens reconstructed to match the flightless pterosaur, Sos2428.

Figure 1. The Mesadactylus holotype (Jensen and Padian 1989) nests with the North American anurognathids. Several referred specimens (Smith et al. 2004), when reconstructed nest at the base of the azhdarchidae, with Huanhepterus and the flightless pterosaur SOS 2428.  The new BYU 17214 femur is essentially identical to the femur shown here.

Earlier we looked at two specimens referred to Mesadactylus. One is an anurognathid (Fig. 1). The other is a basal azhadarchid close to Huanhepterus, not far removed from its Dorygnathus ancestors in the large pterosaur tree. Instead McLain and Bakker compare the femora with unrelated and Early Cretaceous Dsungaripterus, which convergently has a similar femur. The better match is to the basal azhdarchid, so distal femoral pneumaticity does not stray outside of this clade. By the way, it is possible that Mesadactylus was flightless.

Specimen(s) #2 – HMNS/BB 5032 (formerly JHU Paleon C Pt 5)
“A peculiar BBF jaw fragment shows strongly labiolingually compressed, incurved crowns with their upper half bent backwards; associated are anterior fangs. We suspect this specimen is a previously undiagnosed pterosaur.”

These toothy specimens were compared to two Early Cretaceous ornithocheirids, one Middle Jurassic dorygnathid, and one Latest Jurassic bird, Archaeopteryx. None are a good match. A better, but not perfect,match can be made to the Early Jurassic pre-ctenochasmatid, Angustinaripterus (Fig. 2) which has relatively larger posterior teeth than does any Dorygnathus specimen.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

As before,
we paleontologists don’t always have to go to our ‘go to’ taxon list of familiar fossils. Expand your horizons and take a fresh look at some of the less famous taxa to make your comparisons. You’ll find a good place to start at ReptileEvolution.com

References
McLain MA and RT Bakker 2017. Pterosaur material from the uppermost Jurassic of the uppermost Morrison Formation, Breakfast Bench Facies, Como Bluff,
Wyoming, including a pterosaur with pneumatized femora.

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Laquintasaura: verrrry basal ceratopsian from the Early Jurassic

Figure 2. Phytodinosauria with a focus on Stegosauria (yellow green).

Figure 1. Subset of the LRT focusing on the Phytodinosauria. Here Laqunitasaura nests at the base of the Ceratopsia.

I still hold to the hypothesis|
that a phylogenetic analysis that is able to lump and separate taxa is better than one that cannot do this. In the large reptile tree (LRT, 989 taxa), Laquintasaura venezuelae (Barrett et al. 2014; Early Jurassic, 200mya ~1m in overall length; Fig. 2) nests at the base of the ceratopsia (outside of Hexinlusaurus and Yinlong) and not far from the base of the Ornithopoda (outside of Changchunsaurus). It is very plesiomorphic and very early even for an ornithischian, let alone a ceratopsian.

Figure 1. Laquintasaura and tooth from Barrett et al. 2014. The early and plesiomorphic ornithischian has a naris shifted dorsally and other traits that nest it between the base of the onithopoda (Changchunsaurus) and the base of the ceratopidae (Hexinlusaurus).

Figure 2. Laquintasaura and tooth from Barrett et al. 2014. The early and plesiomorphic ornithischian has a naris shifted dorsally and other traits that nest it between the base of the onithopoda (Changchunsaurus) and the base of the ceratopidae (Hexinlusaurus). Compare to premaxillary teeth in figure 3.

Barrett et al. were not so sure where Laquintasaura nested
as they reported, “A strict consensus of these 2160 MPTs places Laquintasaura in an unresolved polytomy with the major ornithischian clades Heterodontosauridae, Neornithischia and Thyreophora along with other early ornithischian taxa, such as Lesothosaurus.”

The Barrett et al. diagnosis reports:
“Laquintasaura can be differentiated from other early ornithischians by the following autapomorphic combination  of dental characters: cheek tooth crowns have isosceles-shaped outlines, which are apicobasally elongate, taper apically, are mesiodistally widest immediately apical to the root/crown junction, possess coarse marginal denticles extending for the full lengths of the crown margins, and possess prominent apicobasally extending striations on their labial and lingual surfaces. Postcranial autapomorphies include: sharply inflected dorsal margin of ischium dorsal to the obturator process; femoral fibula epicondyle medially inset in posterior or ventral views; and astragalus with a deep, broad, ‘U’-shaped notch in anterior surface.”

I had no access to the fossil(s).
And I had to trust the drawing produced by Barrett et al. (Fig. 1) for my data. Contra the Barrett et all. analysis, there was no loss of resolution with Laquintasaura in the LRT.

Figure 2. The skull of Yinlong a basal certatopsian.

Figure 3 The skull of Yinlong a basal certatopsian. Those premaxillary teeth are quite similar to those figure in Barrett et al. for Laquintasaura. Note the dorsal naris, horizontal ventral premaxilla.

References
Barrett PM, Butler RJ, Mundil R, Scheyer TM, Irmis RB, Sánchez-Villagra MR. 2014. A palaeoequatorial ornithischian and new constraints on early dinosaur diversification. Proceedings of the Royal Society B 281:20141147. http://dx.doi.org/10.1098/rspb.2014.1147

Jurassic birds took off from the ground – SVP abstracts 2016

Everyone knows:
Ground up hypothesis – 

implies and includes flapping, always has. Birds flap, always have, at least since the elongation and locking down of the coracoid in ancestral troodontids.

Trees down hypothesis –
has always implied gliding. Gliders don’t flap, never have.

But
baby birds dropping out of trees always flap. It’s what they do. But that fact is often ignored in bird origin videos.

And, as everyone knows by now…
young birds with pre-violant wings flap them like crazy when climbing bipedally — even vertical tree trunks… also something several animated bird origin videos ignore, perhaps because of one glaring opposite extant example: the young wet hoatzin that struggles to climb with all four limbs.

With that preamble…Habib et al. 2016 provide us
a hypothesis on the origin of bird flight that appears to ignore trees and experimental work with pre-volant birds and goes straight to take-off from flat ground. Is that okay?

From the abstract:
“Many small non-avian theropods possessed well-developed feathered forelimbs, but questions remain of when powered flight evolved and whether it occured more than once within Maniraptora. Here, using a first principles modeling approach, we explore these questions and attempt to determine in which taxa takeoff and powered flight was possible. Takeoff is here defined as a combination of both the hindlimb driving the ballistic launch phase, and the wing-based propulsion (climb out). [1]

“Microraptor, Rahonavis, [2] and all avian specimens generated sufficient velocity during leaping or running for takeoff. We re-ran our analysis factoring in life history changes that can alter the flight capability in extant avians, such as egg retention and molting, to examine how these would influence take off capacity. Of the two, molting shows the most significant effects.

“When these results are coupled with work detailing the lack of arboreal features among non-avian maniraptorans and early birds, they support the hypothesis that birds achieved flight without a gliding intermediary step, something perhaps unique among volant tetrapod clades.” [3] [4] [5]

Figure 2. Cosesaurus running and flapping - slow.

Figure 1. Cosesaurus running and flapping – slow.

Notes

  1. Interesting that Habib et al. ignore the presence of trees, which are key to Dial’s hypothesis (updated in Heers et al. 2016)  and opts to go straight from ground to air. That kind of ignores key work, doesn’t it? You might recall that Dr. Habib became famous as the author of the infamous but popular forelimb quad launch hypothesis for pterosaurs.
  2.  Microraptor and Rahonavis are NOT in the lineage of birds in the LRT, but both show how widespread long feathered wings were in Theropoda. The former has elongate coracoids by convergence. The latter does not preserve coracoids, fingers or feathers, but does have the long forearm that might imply bird-like proportions for missing bones… or not.
  3. Apparently Habib et al. assume that pterosaurs and bats originated as gliders when present largely ignored evidence indicates exactly the opposite. Cosesaurus (Fig. 1) was a pterosaur precursor with elongate coracoids, unable to fly, but able to flap. Bats rarely glide, so it is unlikely that they did so primitively. Lacking coracoids, bats employ elongate clavicles to anchor flight muscles.
  4. Okay, so remember the preamble (above) about gliding and trees. When Habib et al. bring up ‘a gliding intermediary step‘, they are implying the presence of trees (high places) in competing and validated-by-experiment hypotheses for the origin of bird flight  — which they are ignoring. They also ignore the fact that baby birds don’t glide when they fall out of trees. They flap like their lives depend upon it. I find those omissions odd, but its not the first time pertinent work has been ignored in paleontology.
  5. In the LRT Xiaotingia (Fig. 2) is the most primitive bird-like troodontid to have elongate coracoids and so may have been the first flapper in the lineage.
Figure 1. Xiaotingia with new pectoral interpretation. See figure 3 for new tracing.

Figure 2. Xiaotingia with new pectoral interpretation.

References
Habib M, Dececchi A, Dufaault D and Larsson HC 2016. Up, up and away: terrestrial launching in theropods. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
Heers AM, Baier DB, Jackson BE & Dial  KP 2016. 
Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development. PLoS ONE 11(4): e0153446. doi:10.1371/journal.pone.0153446
http: // journals.plos.org/plosone/article?id=10.1371/journal.pone.0153446

YouTube video showing birds running up tree trunks while flapping with nonviolent wings

ScienceNews online promo.

The first Jurassic feather – SVP abstract 2016

Pittman et al. 2016
describe a new way of looking at fossils, with laser stimulated fluorescence. I can’t show you what attendees saw at SVP as it is awaiting publication, but other examples can be seen here online. This image from Tom Kaye (Fig. 1) was bumped by me with Photoshop to increase contrast and perhaps reveal a wee bit more detail.

Figure 1. Archaeopteryx feather from T. Kaye. Second image is Photoshop contrast bump created here.

Figure 1. Archaeopteryx feather from T. Kaye. Second image is Photoshop contrast bump created here. Pittman et al. laser stimulated fluorescence imagery was shown at SVP and is awaiting publication. 

From the Pittman et al. 2016 abstract
“The single feather initial holotype of Archaeopteryx lithographica is one of the world’s most iconic fossils, but contains a 150 year old mystery. The specimen’s 1862 description by Hermann von Meyer shows that the calamus is 15 mm long and 1 mm wide. However, the calamus is no longer visible on the fossil, and there is no record of when or how it disappeared. The specimen is a rare example of a lone Archaeopteryx feather, giving access to its entire morphology, as opposed to only parts of it in the overlapping feathers of articulated specimens. This makes it an important addition to the anatomical record of Archaeopteryx and basal birds more generally. After 150 years, laser stimulated fluorescence has recovered the calamus as a chemical signature in the matrix and reveals preparation marks where the original surface details have been obliterated. The feather has recently been imaged by others under UV light as well as with X-rays at the Stanford Linear Accelerator Center, with no reports of the existence of the calamus. This demonstrates the capability of laser stimulated fluorescence to visualize important data outside the range of current methodologies. The feather has at different times, been cited as a primary, secondary and covert, and has even been suggested to belong to another taxon. With the new calamus data in hand, the morphology of the feather was examined within the framework of modern feather anatomy. The percentage of calamus length to overall feather length, when plotted against a histogram of 30 phylogenetically and ecologically diverse modern birds, comes out in the middle of the range, placing it in the flight feather regime. The most recent identification of the feather as a primary dorsal covert can be discounted because the rachis is in line with the calamus rather than curving upwind of the calamus centre line. The curvature of the rachis is also too pronounced to function as a primary or tail feather. If the feather is scaled as a secondary in the wing of Archaeopteryx, only five feathers fit the reconstruction along the ulna, rather than the 9-13 that have been estimated for this taxon and the 7-14 that are found in modern birds. These inferences suggest that the isolated feather is fundamentally inconsistent with those of Archaeopteryx and is instead a secondary of another early bird taxon or potentially even a feather of a non-avialan pennaraptoran theropod.”

Kaye’s work with fossil imaging
has revealed many interesting and otherwise invisible traits. Let’s call this one more ‘feather in his cap.’

References
Pittman M, Kaye TG, Schwarz D, Pei R and Xu X 2016. 150 year old Archaeopteryx mystery solved. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125923

What is Orientognathus? Nesting via description, not observation

Orientognathus chaoyngensis (Lü et al. 2015) is a new Late Jurassic rhamphorhynchoid pterosaur known at present from a series of comparative descriptions. No illustration or photograph of the incomplete(?) material is yet known (at least to me at present).

Given these limitations, let’s see how close we can nest this new enigma.

Data provided:

  1. toothless tip of dentary, slightly pointed
  2. mc4/humerus ratio = 0.38
  3. ulna < each individual wing phalanx
  4. tibia subequal to femur
  5. deltopectoral crest more developed than in Qinlongopterus
  6. anterior teeth stouter and longer than in Pterorhynchus
  7. teeth are straight and longer than in Jianchangnathus
  8. pteroid/humerus ratio = 0.21; pteroid has expanded distal end
  9. larger than other rhamphorhynchine pterosaurs from Late Jurassic NE China (measurements not indicated).

Evidently there is not much known of this specimen:
jaw tips and teeth, a pteroid, a humerus, an ulna, a metacarpal 4, a complete (?) wing (doubtful because the phalanx ratios are not compared to one another) and a femur are all that are mentioned here.

Step one: tibia = femur:
In almost all pterosaurs the tibia is longer than the femur. Just a few specimens have this odd sub equal ratio, so that winnows down the long list of pterosaurs to a short list of possible candidates (left me know if I overlooked any other candidates). You can click the name to view the reconstruction.

  1. Rhamphorhynchus gemmingi? MYE 13 (von Meyer 1859, No. 75 in the Wellnhofer 1975 catalog)
  2. Scaphognathus ( 2 specimens)
  3. St/Ei I (JME 1)

Step two: ulna < each individual wing phalanx
That trait removes both specimens of Scaphognathus and the St/Ei (JME 1) specimen, leaving only one candidate.

Step three: A closer look at Rhamphorhynchus MYE 13 (Fig. 1).

  1. Toothless tip of dentary, slightly pointed: Yes.
  2. mc4/humerus ratio = 0.38  No. = 0.50, but then MYE 13 has a relatively shorter humerus than most Rhamphorhynchus specimens.
  3. ulna < each individual wing phalanx Yes
  4. tibia subequal to femur  Yes
  5. deltopectoral crest more developed than in Qinlongopterus Yes
  6. anterior teeth stouter and longer than in Pterorhynchus Yes
  7. teeth are straight and longer than in Jianchangnathus Yes
  8. pteroid/humerus ratio = 0.21 (but is the pteroid complete?); No. In MYE 13 the ratio is 0.66, but, as above, the humerus is atypically short  AND pteroid has expanded distal end  Yes
  9. Larger than other rhamphorhynchine pterosaurs from Late Jurassic NE China
    Maybe. Wing fingers in Rhamphorhynchus specimens are relatively larger than are those in other Late Jurassic pterosaurs, so if only a wing is known it could belong to a relatively smaller skull and torso. Otherwise the mid-sized specimens listed above (except tiny Qinlongopterus) are all about the same size. 
Figure 1. The MYE 13 specimen of Rhamphorhynchus (n75 in the Wellnhofer 1975 catalog is currently the closest match to the Orientognathus description.

Figure 1. The MYE 13 specimen of Rhamphorhynchus (n75 in the Wellnhofer 1975 catalog is currently the closest match to the Orientognathus description.

So, we’ll test these hypotheses
when the images become available, hopefully with scale bars. Then we’ll do a comparison.

References
Lü J-C, Pu H-Y, Xu L, Wei X-F, Chang H-L and Kundrát M 2015. A new rhamphorhynchoid pterosaur (Pterosauria) from Jurassic deposits of Liaoning Province, China. Zootaxa 3911 (1): 119–129.  http://dx.doi.org/10.11646/zootaxa.3911.1.7

 

Pulling Bavarisaurus out of the belly of Compsognathus

Figure 1. Click to enlarge. The little Jurassic lizard Bavariasaurus was found inside the belly of the little Jurassic dinosaur, Compsognathus. But it is not the same genus as the holotype.

Figure 1. The little Jurassic lizard Bavariasaurus was found inside the belly of the little Jurassic dinosaur, Compsognathus. Illustration by Franz Nopcsa 1903.

As everyone knows, one Jurassic lizard, Bavarisaurus macrodactylus (Figs. 1-4, = Homoesaurus macrodactylus Wagner 1852, Hoffstetter 1964; length: ~20cm, (Lower Tithonian), Solnhofen), was found inside the belly of a small Jurassic dinosaur, Compsognathus (BSPHM AS-1-563). All curled up like the good meal it was, Bavarisaurus has been added to various lepidosaur phylogenetic analyses, but, to my knowledge, it has not been reconstructed in the literature. However, Tracy Ford did a good job here.

Figure 2. Like Michelangelo removing the excess marble, I removed every trace of Compsognathus, leaving nothing but Bavarisaurus in step 1.

Figure 2. Like Michelangelo removing the excess marble, I removed every trace of Compsognathus, leaving nothing but Bavarisaurus in step 1.

Not sure how much good this will do, but I took all the bones I could see and segregated from the dinosaur bones (Fig. 2), then rearranged them as well as I could (Fig. 3). Seems like Bavarisaurus had quite a long tail when it is all stretched out! Looking at the maxilla and mandible you’ll notice the teeth don’t match. Small triangle-shaped teeth are on the dentary, but posteriorly-oriented narrow, sharp teeth appear on the maxilla. The presumes that I have the maxilla correctly oriented.

Figure 3. Click to enlarge. Moving the bones of Bavarisaurus into a reasonable reconstruction is step 2.

Figure 3. Click to enlarge. Moving the bones of Bavarisaurus into a reasonable reconstruction is step 2.

The next step was to tentatively nest the elements phylogenetically, then clean them up in a better presentation in dorsal and lateral views (Fig. 4). A final scoring of elements nests Bavarisaurus more securely.

Figure 2. Click to enlarge. Cleaned up reconstruction of the former Bavarisaurus (cololizard at present). Gray areas added based on sister taxa. This is a tritosaur.  Note the large naris bounded ventrally by the maxilla. The ventral pelvis is shallower. I don't understand the pterygoid morphology anteriorly. The upper and lower teeth don't match. That's a red flag, but it is the only data available.

Figure 2. Click to enlarge. Cleaned up reconstruction of the former Bavarisaurus (cololizard at present). Gray areas added based on sister taxa. This is a tritosaur.  Note the large naris bounded ventrally by the maxilla. The ventral pelvis is shallower. I don’t understand the pterygoid morphology anteriorly. The upper and lower teeth don’t match. That’s a red flag, but it is the only data available.

Bavarisaurus is another tritosaur. 
And that’s why it nests uncertainly at the base of the Squamata in prior analyses that did not include any or many other tritosaurs — because it doesn’t nest in the Squamata. In the large reptile tree Bavarisaurus nests between Meyasaurus and the Dahugou lizard + Lacertulus, not far removed from Dalinghosaurus, which it resembles by convergence.

So based on the presence of Lacertulus in the Late Permian, something very much like Bavarisaurus originated in the Permian and continued to the Late Jurassic where we find the first and last of this genus inside the ribcage of Compsognathus.

References
Evans SE, Raia P and Barbera C 2004. New lizards and rhynchocephalians from the Lower Cretaceous of southern. Italy. Acta Palaeontologica Polonica 49:393–408.
Hoffstetter R 1964. Les Sauria du Jurassique supérieur et specialement les Gekkota de Baviére et de Mandchourie. Senckenberger Biologische 45, 281–324.
Nopcsa F 1903. Neues ueber Compsognathus. Neues Jahrbuch fur Mineralogie, Geologie und Palaeontologie 16: 476-494.
Wagner A 1852. Neu-aufgefundene Saurier, Uberreste aus dem lithographischen Schiefern und dem obern Jurakalke: Abhandlungen der Bayerischen Akademieder Wissenschaften Mathematisch-naturwissenschafliche Kl, 3(6): 661-710.

Variation in Three Sordes Specimens

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

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

Despite it’s fame and antiquity
(some 40 years after discovery) very little has been published on the first hairy pterosaur, Sordes pilosus (Sharov 1971). We’ve seen photos of three (Figs. 2, 4, 6) of the eight or nine reported specimens and Sharov’s original illustration of the holotype (Fig. A). Then there’s my own published tracing (Peters 2002) based on photos of the holotype (PIN 2585/3, Fig. 2). Other workers (Elgin et al. 2011, Unwin and Bakhurina 1994, Wellnhofer 1991) have simply lifted or retraced Sharov’s tracing of the bones and membranes, which are a little cartoony at best.

Three years ago,
for the Sordes webpage of reptileevolution.com I took the easy road out and created a chimaera, adding the head of 2585/25 (Figs. 3, 4) to the headless holotype 2585/3 (Figs. 1, 2). That’s not a good practice. In doing so one assumes that each of the contributing specimens is conspecific. That’s almost never true in pterosaurs as work with Rhamphorhynchus, Dorygnathus, Germanodactylus, Pteranodon, and Pterodactylus has already demonstrated.

Today we’ll reconstruct the three specimens (PIN 2585/3, PIN 2585/25 and a third unidentified specimen) that have been published as photos to compare and contrast them.

Figure 1. Sordes holotype 2785/3. The skull is perhaps present, but so degraded it must be considered unknown.

Figure 1. Sordes holotype PIN 2585/3. The skull is perhaps present, but so degraded it must be considered unknown. Here it is grayed out to show it is poorly known and the skull reconstruction makes it a chimaera.

The holotype PIN 2585/3 (Figure 1). is complete, but lacking a skull.

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

Figure 2. Sordes holotype, PIN 2585/3. Soft tissue in abundance, but the skull is largely gone. Click to see where the displaced radius and ulna are.

The PIN 2585/3 holotype is the only Sordes specimen for which bones were identified, which is key to specimens that preserve so much camouflaging soft tissue. The displaced arm bones that dragged the wing membrane back to the hind limbs are shown here.

Figure 2. The PIN 2585/25 specimen of Sordes. This is the specimen that shows the skull in lateral view.

Figure 3. The PIN 2585/25 specimen of Sordes. This is the specimen that shows the skull in lateral view. Scale unknown.

The second specimen PIN 2585/25 also has a short torso, in this case subequal to the skull. No soft tissue here, but a great view of the skull in lateral view.

Figure 4. Sordes specimen PIN2585/25. No soft tissue here.

Figure 4. Sordes specimen PIN2585/25. No soft tissue here.

The third specimen (no number known so far) has lots of hair, but preserves the skull in ventral view. You can still see the buried side from the inside through the mandibles,  so you can still get close on skull reconstruction.

Figure 3. PIN specimen number unknown. Scale unknown. This is the specimen that shows the  mandible in ventral view with a fish alongside.

Figure 5. PIN specimen number unknown. Scale unknown. This is the specimen that shows the mandible in ventral view with a fish alongside.

The third specimen has a longer torso, longer than the skull. The shape of the humerus is different. The wing is relatively short. The teeth are smaller. So is the antorbital fenestra.

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

Figure 6. The third Sordes specimen PIN number unknown. That is a small fish in the middle. Lots of soft tissue here.

The third specimen (Fig. 6) includes a fish alongside and lots of hair. The radius and ulna are largely buried beneath the dorsal vertebrae with only the ends exposed.

Figure 8. The three Sordes specimens. Scale for right specimen only. Others scaled to matching skull lengths.

Figure 7. The three Sordes specimens. Scale for right specimen only. Others scaled to matching skull lengths. Missing tails here are missing in the fossils. The humerus is different in each specimen.

Putting all the Sordes specimens together (Fig. 7, sorry no scale here as scale bars are unknown for two of the specimens). This form of presentation makes it easier to see the differences and similarities.

Phylogenetic analysis nests all three Sordes specimens very close to the basalmost Dorygnathus, the Donau specimen (Fig. 9). Actually, for one of them, a little too close.

Figure 8. The Donau specimen of Dorygnathus is very close to Sordes.

Figure 8. The Donau specimen of Dorygnathus is very close to Sordes.

Like the tall third specimen of Sordes, Dorygnathus has a longer torso, but not a larger sternal complex, which remains a small triangle. So, the small sternal complex that characterizes Dorygnathus (easy to distinguish from broad-chested Rhamphorhynchus), originated with Sordes.

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 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