150 million years of pterosaur flight efficiency

Venditti et al. 2020
attempts to chronicle an increase in pterosaur flight efficiency over their 150 million year long clade span.

From the Venditti et al. abstract:
“The long-term accumulation of biodiversity has been punctuated by remarkable evolutionary transitions that allowed organisms to exploit new ecological opportunities. Mesozoic flying reptiles (the pterosaurs), which dominated the skies for more than 150 million years, were the product of one such transition. The ancestors of pterosaurs were small and probably bipedal early archosaurs (Andres et al. 2014), which were certainly well-adapted to terrestrial locomotion.”

Citation and taxon exclusion here. Andres et al. 2014 cherry-picked four euarchosauriform outgroups for the Pterosauria: Euparkeria, Ornithosuchus, Herrerasaurus and Scleromochlus. All of these taxa have a short to vestigial manual digit 4, the opposite of pterosaurs. This list followed the direction of co-author Mike Benton, well known for citation and taxon exclusion to promote his pet hypotheses, invalidated by Peters 2000, 2007, 2009. Readers have seen Benton omissions many times. The actual ancestors of pterosaurs were not archosaurs, but these lepidosaurs: Cosesaurus (Fig. 1), Sharovipteryx and Longisquama. So Venditti et al. 2020 starts off poorly, without a proper phylogenetic context.

By the way, Andres et al.  2014 did not find ‘the earliest pterodactyloid,’ but bits and pieces of a gracile dorygnathid, Sericipterus found in the same formation.

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.

Continuing from the Venditti et al. abstract:
“Pterosaurs diverged from dinosaur ancestors in the Early Triassic epoch (around 245 million years ago); however, the first fossils of pterosaurs are dated to 25 million years later, in the Late Triassic epoch.”

False: Pterosaurs diverged from fenestrasaur ancestors (Peters 2000).

“Therefore, in the absence of proto-pterosaur fossils, it is difficult to study how flight first evolved in this group.”

False. We have those proto-pterosaur fossils and pterosaur ancestors all the way back to Cambrian chordates. Adding taxa resolved this problem in Peters 2000, 2007, 2009 and that continues today.

“Here we describe the evolutionary dynamics of the adaptation of pterosaurs to a new method of locomotion. The earliest known pterosaurs took flight and subsequently appear to have become capable and efficient flyers. However, it seems clear that transitioning between forms of locomotion^2,3—from terrestrial to volant—challenged early pterosaurs by imposing a high energetic burden, thus requiring flight to provide some offsetting fitness benefits.”

Or the other way around, as documented by the four fenestrasaurs listed above.

“Using phylogenetic statistical methods and biophysical models combined with information from the fossil record, we detect an evolutionary signal of natural selection that acted to increase flight efficiency over millions of years.”

What is ‘flight efficiency’? Are hummingbirds more efficient? Or are albatrosses? Or ducks? Did the authors use the proper pterosaur wing shape (Fig. 2) ? Or the traditional invalid batwing-shape preferred by those in the Benton arc.

Figure 2. The Vienna Pterodactylus. Click to animate. Wing membranes in situ (when folded) then animated to extend them. There is no shrinkage here or in ANY pterosaur wing membrane. There is only an “explanation” to avoid dealing with the hard evidence here and elsewhere.

“Our results show that there was still considerable room for improvement in terms of efficiency after the appearance of flight.”

Without valid outgroups, how do they know? They don’t.

“However, in the Azhdarchoidea⁴, a clade that exhibits gigantism, we test the hypothesis that there was a decreased reliance on flight^5,6,7 and find evidence for reduced selection on flight efficiency in this clade.”

Odd that these authors do not include the many examples of flightless pterosaurs, including derived and sometimes giant members of the Azhdarchidae.  They only say ‘there was a decreased reliance on flight.’

“Our approach offers a blueprint to objectively study functional and energetic changes through geological time at a more nuanced level than has previously been possible.”

There is no ‘blueprint’ here, only more misdirection and mythology. Sad that the works of professor Mike Benton have now become suspect following the present continuation of his long-standing pattern of cherry-picking and taxon exclusion favoring the textbooks and lectures that provide his income.

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References
Andres B, Clark J and Xu, X 2014. The earliest pterodactyloid and the origin of the group. Current Biology 24:1011–1016 (2014).
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. Hist Bio 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Venditti C, Baker J, Benton MJ, Meade A and Humphries S 2020. 150 million years of sustained increase in pterosaur flight efficiency. Nature https://doi.org/10.1038/s41586-020-2858-8

From the Nature comments section:
“The ancestors of pterosaurs were recovered twenty years ago (in Peters 2000) by simply adding Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama to four previously published analyses. Peters (2007) nested these bipedal taxa within the Lepidosauria by once again simply adding taxa. Omitting citations and omitting taxa results in statements like the following found in the Venditti et al. 2020 abstract: “in the absence of proto-pterosaur fossils, it is difficult to study how flight first evolved in this group.” Had the authors included Cosesaurus they would have known this taxon was flapping without flying due to a locked down, stem-shaped coracoid otherwise found only in birds and pterosaurs. Bats flap anchored by an analogous clavicle.”

 

SVP abstracts 28: Were pachycormiformes predators and suspension feeders?

Wretman, Liston and Kear 2020 bring us
their views on the Pachycormiformes, a clade named for Early Jurassic Pachycormus (Fig. 1). These are typically large fish (Fig. 2) with living relatives (Fig. 3) among the Osteoglossiformes (= bony tongues), like the arowana (Osteoglossum).

From the Wretman et al. abstract:
“Pachycormiforms are an extinct radiation of Mesozoic actinopterygian fishes that occupy a key transitional position along the Holostei-Teleostei stem.”

Figure 1. Pachycormus macropterus has a new skull reconstruction. Originally I did this without template or guidance. Now osteoglossiformes provide a good blueprint.

From the Wretman et al. abstract:
“The group first appears in the fossil record with an explosive diversification into two morphologically distinct lineages: ‘toothless’ suspension-feeders (SFP) including the famously gigantic Leedsichthys; and ‘tusked’ carnivorous pursuit predators, such as the superficially sword-fish like Protosphyraena (Fig. 2).

Figure 2. Protosphyraena museum mount. Length about 3m. Note the advanced placement of the pelvic fins.

From the Wretman et al. abstract:
“Pachycormiforms characteristically trended towards reduced ossification in the skeleton, especially amongst the larger-bodied suspension-feeding forms, which tend to be represented by fragmentary and enigmatic remains. Nevertheless, pachycormiform fossils have been recognized worldwide in strata of Early–Late Jurassic and Late Cretaceous age. In contrast, stratigraphically intermediate Early Cretaceous pachycormiforms are virtually unknown, with the exception of the Protosphyraena-like taxon Australopachycormus from the late Albian of Australia.”

Figure 3. Subset of the LRT focusing on fish. Here Pachycormiformes are highlighted.

From the Wretman et al. abstract:
“Here we report on a new Early Cretaceous pachycormiform taxon from the late Albian Allaru Mudstone of northwestern Queensland in Australia. Surprisingly, this specimen is edentulous and consists of a skull with the anterior half of the body, representing an individual of about 1.0-1.5 m SL — approximately equivalent in length to the Dresden juvenile specimen of Asthenocormus.”

“Significantly, the Allaru Mudstone pachycormiform is both the first SFP identified from Australia, and the first Early Cretaceous SFP globally. Moreover, while our multiple cross-referencing parsimony and Bayesian phylogenetic analyses decisively place it as a basally branching member of the suspension-feeding clade, the Allaru Mudstone pachycormiform possesses a curious character state mosaic incorporating traits that are more consistent with pursuit predator pachycormiform taxa of equivalent body-size.”

Figure 4. The arowana, an Amazon River predator, nests with Late Jurassic Dapedium in the LRT.

From the Wretman et al. abstract:
“This observation raises questions about whether Cretaceous pachycormiforms manifested repeated convergence, or perhaps mask a more complex evolutionary history of secondarily-derived extreme feeding specializations.”

The living pachycormiform, Osteoglossum (Fig. 4), is a large (2m), slow-moving, surface predator, bony-tongue, not a suspension feeder. It is also a facultative air breather. So maybe the feeding strategy traditions of extinct taxa need to be reconsidered in this light.

Pachycormiforms/osteoglossiformes are some of the closest living relatives of spiny sharks (acanthodians). Note the sharp-pointed, bony pectoral fins of clade members (Figs. 1, 2, 4).

And that’s the last of the SVP abstracts.
Regular news and views will return to the standard once-a-day schedule.

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References
Wretman L, Liston J and Kear B 2020. First record of an edentulous suspension-feeding pachycormiform fish from the Lower Cretaceous of Australia. SVP abstracts 2020.

SVP abstracts 27: Plesiosaur breathing

Wintrich and Vanoefer 2020
bring us a look at plesiosaur breathing, but do not consider the vertical feeding configuration (Fig. 1) and bubble-net blowing hypothesis.

Figure 3. Click to enlarge. Albertonectes reconstructed. This 11 m elasmosaur is the longest thusfar recorded. This may be the breathing pose, swallowing air, then submerging the neck. When horizontal the air could be passed back to the lungs, as hypothesized for Dinocephalosaurus.

From the Wintrich and Vanoefer 2020 abstract:
“Plesiosaurs are enigmatic marine reptiles known from the Late Triassic to the Late Cretaceous and represent the most derived group of sauropterygians.

Why ‘enigmatic’? Plesiosaurs are readily identified without argument.

“Among plesiosaurs, there are several lineages showing an extremely long neck, which raises different biomechanical questions dealing with use and function, up to the breathing mechanism. Furthermore, for aquatic tetrapods, buoyancy control is an important adaptation to support the body in the water column. The respiratory system and its influence on buoyancy control have been discussed only briefly, and no mathematical approach has been taken so far. However, the breathing mechanism and therefore the respiratory system of highly aquatic tetrapods has to be specialized in different ways to enable life in a pelagic environment.”

“Here, we follow different mathematical approaches based on the metabolism (work of breathing), the trachea, and the morphology of the skull and trunk, in order to reconstruct the breathing mechanism, respiratory system, and lung volume in plesiosaurs, and then discuss the most plausible respiratory anatomy.”

“Furthermore, we find support for the hypothesis of a functional secondary palate from the reconstructed respiratory system as well as for the use of gastroliths, especially in the Elasmosauridae.”

“In addition to this, we calculated the center of mass to reconstruct buoyancy control in plesiosaurs.”

“In general, we studied four different long-necked plesiosaurs (Cryptoclidus, Albertonectes, Rhaeticosaurus, Rhomaleosaurus) and included Augustasaurus as the most derived pistosaur for which the entire neck is known.”

“Our results demonstrate that the lung volume was larger than suspected for an aquatic tetrapod. However, plesiosaurs showed an adaption similar to that of marine turtles, which have shifted the lung to the dorsal side of the trunk. The influence of the long trachea on breathing is not as great as suggested before. However, especially in the elasmosaurid, the long neck influences the center of mass. This supports the hypothesis of gastroliths functioning in buoyancy control in elasmosaurs. Furthermore, based on an ancestral state reconstruction, we show that the specialized plesiosaurian respiratory systems probably evolved in early sauropterygians.”

‘Influences’. ‘Supports’. ‘Probably’. Conclusions?
I didn’t see any here. Did I miss something? Seems like this is all old news. Earlier we looked at the possibility that plesiosaurs were vertical hunters (Fig. 1), expressing bubble nets as they rose beneath fish schools, as in modern mysticetes. Let’s see that ‘specialized’ hypothesis tested in the 2021 abstracts.

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References
Wintrich T and Vanhoefer J 2020. A specialized respiratory system in plesiosaurs (Sauropterygia): breathing with the long neck. SVP abstracts.

SVP abstracts 26: Pterosaur fibers or lack thereof, again

Unwin and Martill 2020
published on this abstract earlier last year and this year (2020).

“Fiber-like structures are frequently preserved in association with fossilized remains of the pterosaur integument. Several fiber types have been recognized. Among the commonest are aktinofibrils, typically 40–100+ μm in breadth and present throughout the flight patagia, exhibiting the same patterns of alignment across Pterosauria.

“Occasionally partially mineralized in distal regions of the patagia, aktinofibrils were composite, helically-wound structures composed of much finer filaments a few microns in diameter.

“Comparable in size to aktinofibrils, but less common, are single-stranded, hair-like pycnofibers, seemingly branched in two specimens of the anurognathid Jeholopterus, that supposedly adorned parts of the cranium, neck, and body. Fiber-like structures have also been reported in cranial crests, foot webs, and tail flaps. The identity, homology, composition, and function of integumentary fibers is fiercely disputed.”

‘Fiercely’? Hyperbole. This issue was just raised by Unwin and Martill and I have yet to see their evidence. Here’s the evidence for pycnofibers on the fluffiest pterosaur of all, the owl-like holotype of Jeholopterus (Fig. 1) and a reconstruction of same (Fig. 2).

Figure 1. Wing and other extra dermal membranes surrounding Jeholopterus.

Figure 2. Jeholopterus in dorsal view. Here the robust hind limbs, broad belly and small skull stand out as distinct from other anurognathids. Click to enlarge.

Unwin and Martill 2020 abstract continues:
“This study aimed to resolve these issues through analysis of 150+ specimens where the integument is preserved, representing >25% of known pterosaur species, 15 of the 20 principal lineages, and almost the entire temporal range of the clade. Details of the macro- and microstructure of fibers was obtained using light, UV and laser-UV photography, and binocular and scanning electron microscopy.”

Missing from their taxon list are any outgroups of the Pterosauria (Cosesaurus, Sharovipteryx and Longisquama, Fig. 3), all of which also have extradermal membranes and fibers, some of which form precursor wing fibers (Peters 2009).

Figure 3. Longisquama in situ. See if you can find the sternal complex, scapula and coracoid before looking at figure 2 where they are highlighted.

Unwin and Martill 2020 abstract continues:
“Results of this study provide broad support for a new model in which pterosaur integumentary fibers of all types had a single common origin: dermal collagen. This idea is consistent with:

1. exceptionally preserved examples of cranial crests, wing membranes, and integument associated with the neck and body, which demonstrate that fibers were embedded within the integument, and formed part of the dermis;
2. calcification of fibers in the cranial crest and, occasionally, in distal parts of the flight patagia;
3. the composite construction of fibers, which were composed of much finer, helically-wound fibrils.

There’s no argument there. Nothing fiercely disputed. Everyone agrees.

“Multiple specimens with soft tissues preserved in four different preservational modes, show that the integument had a glabrous, fine granular, or even polygonal external texture. Aktinofibrils and other collagenous dermal fibres (e.g., in cranial crests and skin associated with the neck and body) exposed by decay of the remarkably thin epidermis have frequently been misinterpreted as pycnofibers.”

The word ‘misinterpreted’ here should have been the leading sentence followed by evidence. Not the penultimate one followed by no evidence. Unwin and Martill should have taken the strongest evidence against their hypothesis and knocked it down with evidence. They had the opportunity, and they were paid to do this, but failed to do their job.

Figure 4. Here is the Vienna specimen of Pterodactylus in situ and with matrix removed. Where are the pycnofibers here? I see skin, but no fibers. Then again, the fluffiness of Jeholopterus gave it owl-like silent flight characteristics not needed in a beach combing wader.

Unwin and Martill 2020 abstract continues:
“External fibers fringing the jaws of anurognathids may be an exception, although branching, reported in one specimen, is likely an artifact of preservation.”

Only this one extremely minor exception? Let’s talk about the other major exceptions (Figs. 1, 2). And let’s talk about the lack of similar fibers on wading pterosaurs like Pterodactylus (Fig. 4). The fact that Unwin and Martill got the wing membranes wrong and continue to deny the lepidosaur ancestry of pterosaurs lead one to distrust and discredit everything else they say (= invalid phylogenetic context). And that’s something that should never happen to a couple of pterosaur experts.

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References
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Unwin D and Martill D 2019. When the Mesozoic got ugly – naked, hairless, (and featherless) pterosaurs. SVPCA abstracts.
Unwin D and Martill D 2020. Identity, homology, and composition of fiber-like structures associated with the pterosaur integument. SVP abstracts 2020.

https://pterosaurheresies.wordpress.com/2019/10/02/unwin-and-martill-2019-find-pterosaurs-naked-and-ugly/

https://pterosaurheresies.wordpress.com/2020/09/30/naked-pterosaurs-or-feathered-phds-clash/

SVP abstracts 25: Acanthodians misunderstood

Schnitz et al. 2020 attempt to bring
a new understanding to the spiny sharks, the acanthodians (Fig. 1, left column). In the large reptile tree (LRT, 1751+ taxa; subset Fig. 2) acanthodians are basal bony fish transitional taxa leading to several clades of other basal bony fish.

Figure 1. Click to enlarge. Acanthodians and their spiny and non-spiny relatives in the LRT (subset Fig. 2), not to scale.

From the abstract:
“Acanthodians are a poorly understood paraphyletic group of extinct fishes from the Paleozoic.”

They are better understood now after nesting them in the LRT, which minimizes taxon exclusion. I hate to keep repeating this, but all I add to do was add taxa.

“While they show comparatively little diversity in lifestyle and range of body shape, they play a prominent part in our understanding of vertebrate evolution as part of the chondrichthyan stem-group.”

This is false. Spiny sharks are osteichthyans in the LRT, not basal to sharks. Taxon exclusion has been a continuing problem with fish workers.

Figure 2. Subset of the LRT focusing on basal vertebrates (= fish) highlighting acanthodians (=spiny sharks).

“Their evolutionary history, however, is poorly understood, largely due to the limited preservation of their mostly cartilaginous skeleton that results in a bias towards isolated remains such as fin spines and scales.”

This is false. The LRT provides a complete evolutionary history back to headless Cambrian chordates.

“Thus, considerable uncertainties remain in how the completeness of acanthodian fossils impact on the phylogenetic narrative of both chondrichthyans and other vertebrates.”

This is false. The LRT provides the certainties that come from minimizing taxon exclusion.

“Here, we address these issues by using a variation of the previously defined Skeletal Completeness Metric (SCM), an approach that calculates how complete the skeletons of individuals are compared to their theoretical complete skeleton, to quantify the quality of the acanthodian fossil record.”

This might be the next step after first recovering a valid phylogeny from the more complete acanthodian fossils.

“Acanthodians show a significantly lower completeness distribution than many tetrapods, including theropods, plesiosaurs, sauropodomorphs, ichthyosaurs, pelycosaurs and parareptiles, but a similarly low distribution to bats. Analysis of completeness distribution between acanthodian orders reveals significant differences, with the Acanthodiformes and Diplacanthiformes showing highest overall completeness. Our assessment of completeness reveals only weak spatial biases influencing the acanthodian fossil record while temporal biases are much higher.”

In other words, no phylogenetic conclusions and sort of a waste of time because no valid phylogeny was created. Don’t follow authorities, textbooks or invalid traditions. When you minimize taxon exclusion you’ll understand acanthodian phylogeny. THEN proceed with more detailed studies.

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References
Schnitz L, Butler RJ, Coates MI and Sansom IJ 2020. Skeletal and soft tissue completeness of the acanthodian fossil record through time. SVP abstracts 2020.

wiki/Acanthodii
wiki/Mesacanthus
wiki/Climatius

SVP abstracts 24: Macrocnemus revisited

Scheyer et al. 2020 bring us
a review of the tanystropheid, tritosaur, lepidosaur, Macrocnemus (Fig. 1), a genus known from several specimens, not all of which are congeneric in the large reptile tree (LRT, 1752+ taxa; subset Fig. 2).

Figure 1. M. fuyuanensis GMPKU-P-3001 overall. This specimen nests with T2472.

Figure 2. Subset of the LRT focusing on the relatives of Macrocnemus.

From the abstract:
“Over the past decades, an increasing number of mostly marine reptiles have been described from the Triassic of southern China. Many of these taxa had a Tethys-wide distribution, whereas terrestrial reptile taxa known from both western and eastern margins of the Tethys are exceptionally rare.”

“One such terrestrial animal is the small to medium sized tanystropheid archosauromorph Macrocnemus from the Middle Triassic. The genus is represented by two European species, the well-known M. bassanii and M. obristi, known only from posterior postcranial remains, and the slightly younger M. fuyuanensis, known from two complete specimens from southwestern China.”

The LRT finds the several members of the traditional genus, Macrocnemus (Fig. 2), are not congeneric. One tested specimen from China (Fig. 1, GMPKU-P-3001) is congeneric with several European specimens. The BES SC 111 specimen is small, leading to the clade Fenestrasauria and Pterosauria. It is not a juvenile as workers assume prior to running a phylogenetic analysis.

“Species recognition in the genus classically relied on proportional differences of the limb bones.”

The LRT scores the entire specimen and proportional differences of the limb bones are not  relied upon. That would be “Pulling a Larry Martin.” Scheyer et al. should reconstruct the various specimens to discover the diversity in the shapes of skull, pedal and all other skeletal elements.

“M. fuyuanensis was recently tentatively proposed to be present also in Europe, based on a single specimen from the Besano Formation of Monte San Giorgio, southern Switzerland/northern Italy. Further analysis, however, was hampered due to limited original description of the holotype specimen of M. fuyuanensis and insufficient understanding of the cranial anatomy of M. bassanii, despite being known from several complete and well-preserved specimens in European collections.”

As noted above in the LRT.

“To clarify the relationships among Macrocnemus species, we re-described both the holotype of M. fuyuanensis and a well-preserved skull of M. bassanii, the latter using high-resolution synchrotron micro-computed tomography, which allowed us to reconstruct and describe the configuration of the skull, including the braincase for the first time, in high detail. Our findings reveal that the osteology of both species is very similar and no clear differences were found in the cranium.”

As noted above in the LRT without benefit form µCT scans.

“The skull of Macrocnemus has a rigid, tightly fitting squamosal-quadrate joint allowing little, if any, cranial kinesis. The configuration of the palatal bones with the tooth-bearing pterygoids, palatines and vomers could be reconstructed for the first time.”

No, Kuhn-Schnyder 1962 did this earlier (Fig. 3). So did Miedema et al. 2020 (Fig. 4), but that specimen, PIMUZ T 2477, is not congeneric with other European Macrocnmeus specimens. That is something you only find out by running a wide gamut phylogenetic analysis, evidently missing from Scheyer et al. 2020.

Figure 3. Palate of Macrocnemus from Kuhn-Schnyder 1962.

Figure 4. The PIMUZ T 2477 specimen wrongly traditionally assigned to Macrocnemus.

“In the postcranium, besides the limb ratios, we confirmed the identification of the interclavicle as the most important bone for species recognition.”

This is, by definition, “Pulling a Larry Martin.” Don’t do that! Run the analysis.

“The interclavicle of M. fuyuanensis can be distinguished from M. bassanii, among other features, by its short and fusiform posterior process and anterior facing rod-like processes that extend from a common base enclosing a narrow V-shaped median notch. The presence of M. fuyuanensis at Monte San Giorgio confirms its widespread distribution over the entire Tethys realm.”

You heard it here first (Fig. 2) using phylogenetic analysis. The same analysis nests Macrocnemus within Lepidosauria, far from Archosauromorpha. Add taxa to resolve this issue for yourself. That’s all you have to do.

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References
Kuhn-Schnyder E 1962. Ein weiterer Schädel von Macrocnemus bassanii Nopcsa aus der anisischen Stufe der Trias des Monte San Giorgio (Kt. Tessin, Schweiz). Palaeontologische Zeitschrift 36:110-133.
Scheyer T, Miedema F, Wang W, Li C, Spiekman S, Fernandez V and Reumer J 2020. Standard osteological and virtual 3D anatomical re-investigation of Macrocnemus (Tanystropheidae Archosauromorpha), a rare Middle Triassic terrestrial reptile with a Tethys-wide distribution. SVP abstracts 2020.

https://pterosaurheresies.wordpress.com/2018/11/18/antorbital-fenestrae-and-lizardy-epipterygoids-in-macrocnemus/

https://pterosaurheresies.wordpress.com/2020/07/26/pimuz-t-2477-not-quite-macrocnemus-despite-appearances/

https://pterosaurheresies.wordpress.com/2018/11/24/a-small-bipedal-macrocnemus-pmuz-t4823/

https://pterosaurheresies.wordpress.com/2018/11/18/antorbital-fenestrae-and-lizardy-epipterygoids-in-macrocnemus/

https://pterosaurheresies.wordpress.com/2020/10/11/tiny-enigmatic-feralisaurus-nests-with-a-giant-bizarre-sister/

SVP abstracts 23: Alvarezsaurids identified as termite eaters again

Qin et al. 2020 suggest
alvarezsaurids, tiny theropods with odd hook-like hands, were termite eaters. According to tradition and Qin et al. alvarezsaurids would have used their strong, hook-like fore claws to rip open termite nests.

By contrast,
earlier a tick bird analog (Figs. 1, 2) was proposed here.

Figure 3. Giant Deinocheirus, a contemporary of Mononykus, might have served as the host and dining room for a series of ever smaller and more specialized parasite eaters.

From the Qin et al. abstract:
“Alvarezsauroidea is a group of bizarre theropods with highly specialized anatomy. Some of the late-branching members of this clade evolved extremely small body size—as small as early birds.”

“Alvarezsauroids until now have generally been overlooked in studies of theropod body mass evolution because they lacked sufficient lineage sampling and because the evidence for skeletal maturity of tiny specimens was lacking. Moreover, unlike the evolution of flight in paravians, the phylogenetically independent reduction in alvarezsauroid body mass lacks an obvious functional correlate.”

Unless they became parasite pluckers, like tick birds.

“The recent discoveries of early-branching alvarezsauroid fossils from China make a more thorough investigation of body mass evolution in this clade possible.”

Haplocheirus (Fig. 1) nests at the base of the alvarezaurids in the large reptile tree (LRT, 1751+ taxa) and in all other studies. These close relatives of velociraptors are traditionally portrayed as capable of leaping on the backs of larger dinosaurs. That’s where the ticks are, hiding among the feathers. That explains the phylogenetic miniaturization of alvarezsaurids, widely recognized as convergent with birds.

“We conducted detailed osteohistological analysis and bone co-ossification comparisons for Chinese alvarezsauroids, including the Late Jurassic Haplocheirus sollers, Aorun zhaoi, and Shishugounykus inexpectus, the Early Cretaceous relatively large-sized alvarezsauroids Xiyunykus pengi and Bannykus wulatensis, and the Late Cretaceous alvarezsauroid Xixianykus zhangi.”

In the LRT Aorun does not nest with alvarezsaurids, but at a much more basal node. Several of the others have not yet been tested due to their partial and often post-cranial only remains. Often these authors consider the large fore claws ideal for ripping open termite mounds.

“Together with previously published histological data and observations of anatomical characters such as bone ossification, we present a general age and ontogeny estimation for alvarezsauroid specimens. We use our results to estimate adult body mass of all alvarezsauroids and to critically assess the hypothesis of lineage-specific size decrease in Alvarezsauroidea.”

Figure 2. Tickbirds sitting atop a pair of rhinos, perhaps a modern analog for mononykids.

“Our results reveal that size evolution within alvarezsauroids had an initially divergent start followed by a single body size miniaturization event. This miniaturization process started at around 90 million years ago, had a significantly high rate, and culminated in parvicursorines that attained the smallest non-paravian dinosaur body masses in its final stage. Alvarezsauroid lineage richness increased after the miniaturization began, and potentially involved a secondary radiation of small-sized taxa at the end of the Cretaceous. Our results also support the idea that these late-branching small-sized alvarezsauroids occupied an obligate myrmecophagous (termite-eating) ecological niche. This hypothesis is also supported by their unusual low growth rates strategies revealed by our osteohistological studies, and their highly specialized anatomical features indicated by previous research.”

Analog extant termite eaters (anteaters, pangolins) are not tiny, bird-shaped taxa. Analog extant tick pluckers (Fig. 2) are bird-shaped taxa. Authors Michael Benton and David Hone, are part of the contingent promoting the unlikely termite-eater hypothesis.

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References
Qin Z, Zhao Q, Choiniere J, Benton M and Xu X 2020. Comparative osteohistology of alvarezsaurs informs hypotheses for their body size evolution. SVP abstracts 2020.

https://pterosaurheresies.wordpress.com/2020/05/21/mononykus-and-shuvuuia-cretaceous-tickbirds/

https://www.smithsonianmag.com/science-nature/a-new-ant-eating-dinosaur-xixianykus-67587048/

SVP abstracts 22: Weigeltisaurus reexamined

Pritchard, Sues, Reisz and Scott 2020
promise to bring us a look at the ‘osteology and phylogenetic affinities of the early gliding reptile Weigeltisaurus jaekeli” (Fig. 1).

Unfortunately,
no phylogenetic analysis, or any hint thereof, is to be found in the abstract.

We looked at Weigeltisaurus earlier
here when the skull (Fig. 1) was described by Bulanov and Sennikov 2015.

Figure 1. Weigeltisaurus skull reconstructed by Bulanov and Sennikov (gray scale), and using DGS techniques (color). They did not attempt to trace the occiput, nor did they understand that the posterior crest is the supratemporal, displaced in situ and that the main portion is a very large squamosal that sweeps up. This skull is nearly identical to that of sister taxa, with the exception of the extended posterior elements, probably for secondary sexual selection. The same cannot be said of the Bulanov and Sennikov reconstruction which is, unfortunately, unique as is.

Weigeltisaurus is a relative of Coelurosauravus 
(Fig. 2) and other pseudo-rib gliders. The ribs are dermal in nature, extending from the tips of the dorsal and lumbar ribs, whether few or many.

Figure 2. Click to enlarge. The Triassic kuehneosaur gliders and their non-gliding precursors. Note the icarosaurs are not rib gliders. Their actual ribs are fused to mimic transverse processes as demonstrated around the neck and anterior torso.

From the Pritchard et al. 2020 abstract:
“Weigeltisauridae is a clade of small-bodied Permian diapsids that represent the oldest known vertebrates with skeletal features for gliding. It is characterized by a cranium with a posterior bony casque, prominent horns on the temporal arches, and a series of elongate bony spars projecting from the ventrolateral surface on both sides of the trunk. Definitive specimens are known from upper Permian of Germany, Russia, and Madagascar, but the quality of their preservation previously limited understanding of the skeletal structure and phylogenetic affinities of these reptiles.”

All you have to do is add taxa (= minimize taxon exclusion) and let the software determine where these Permian pseudo-rib gliding lepidosauriforms nest. In the large reptile tree (LRT, 1752+ taxa; subset Fig. 3) these arboreal gliders nest at the base of the lepidosauriformes. (The Diapsida is now limited to just archosauromorphs with a diapsid-skull morphology, by convergence with lepidosauriformes). Only here, in the LRT, among all prior pertinent cladograms, is the clade of pseudo-rib gliders surrounded by arboreal taxa with weigeltosaurs nesting with kuehneosaurs. Usually they nest apart and too often close to marine taxa.

Figure 2. Derived lepidosauriformes. The clade Pseudoribia includes the pseudo-rib gliders

The Pritchard, Sues, Reisz and Scott abstract continues:
“Here, we present a revised account based on a nearly complete skeleton of Weigeltisaurus jaekeli from the Kupferschiefer of central Germany and a revised phylogenetic analysis of early Diapsida and early Sauria.”

That analysis must have been part of the oral presentation. There is no hint of it here. Sauria is an invalid clade. Diaspsida is restricted to the Archosauromorpha in the LRT.

“The specimen preserves all elements of the skeleton, save for the braincase, palate, some dorsal vertebrae, the carpus, and the tarsus. The well-preserved teeth in the maxilla are not conical but leaf-shaped, resembling those in the middle portion of the maxillae of the Russian weigeltisaurid Rautiania. The parietals bear rows of dorsolaterally oriented horns similar to those on the squamosals. The quadrate is a dorsoventrally short element with a tapering dorsal margin that lacks a cephalic condyle. The squamosal appears to cover the quadrate both laterally and posterodorsally. The manual and pedal phalanges are elongate and slender, similar to those of extant arboreal squamates. The unguals have very prominent flexor tubercles. A patagium was supported by elongate, slender bony rods. They are situated superficial to the preserved dorsal ribs and gastralia, corroborating the hypothesis that these structures represent dermal ossifications independent of and greater in number than the bones of the dorsal axial skeleton.”

Excellent description. But that was provided earlier (Bulanov and Sennikov 2015).

Phylogenetic conclusions? 
I guess we’ll have to wait for the paper.

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References
Bulanov VV and Sennikov AG 2015. Substantiation of validity of the Late Permian genus Weigeltisaurus Kuhn, 1939 (Reptilia, Weigeltisauridae) Paleontological Journal 49 (10):1101–1111.
Pritchard A, Sues HD, Reisz R and Scott D 2020. Osteology and phylogenetic affinities of the early gliding reptile Weigeltisaurus jaekeli. SVP abstracts.

https://pterosaurheresies.wordpress.com/2011/09/26/icarosaurus-kuehneosaurus-and-the-so-called-rib-gliders/

https://pterosaurheresies.wordpress.com/2015/12/17/weigeltisaurus-skull-reconstructions/

Prior citations
Colbert, Edwin H. (1966). A gliding reptile from the Triassic of New Jersey. American Museum Novitates 2246: 1–23. online pdf
Evans SE 1982. Gliding reptiles of the Late Permian. Zoological Journal of the Linnean Society, 76:97–123.
Evans SE and Haubold H 1987. A review of the Upper Permian genera  Coelurosauravus, Weigeltisaurus and Gracilisaurus (Reptilia: Diapsida). Zool J Linn Soc, 90:275–303.
Fraser NC, Olsen PE, Dooley AC Jr and Ryan TR 2007. A new gliding tetrapod (Diapsida: ?Archosauromorpha) from the Upper Triassic (Carnian) of Virginia. Journal of Vertebrate Paleontology 27 (2): 261–265. doi:10.1671/0272-4634(2007)27[261:ANGTDA]2.0.CO;2.
Frey E, Sues H-D and Munk W 1997. Gliding Mechanism in the Late Permian Reptile Coelurosauravus. Science Vol. 275. no. 5305, pp. 1450 – 1452
DOI: 10.1126/science.275.5305.1450
Li P-P, Gao K-Q, Hou L-H and Xu X. 2007. A gliding lizard from the Early Cretaceous of China. PNAS 104(13): 5507-5509. doi: 10.1073/pnas.0609552104 online pdf
Modesto SP and Reisz RR 2003. An enigmatic new diapsid reptile from the Upper Permian of Eastern Europe. Journal of Vertebrate Paleontology 22 (4): 851-855.
Modesto SP and Reisz RR 2011. The neodiapsid Lanthanolania ivakhnenkoi from the Middle Permian of Russia, and the initial diversification of diapsid reptiles. SVPCA abstract.
Robinson PL 1962. Gliding lizards from the Upper Keuper of Great Britain. Proceedings of the Geological Society London 1601:137–146.
Stein K, Palmer C, Gill PG and Benton MJ 2008. The aerodynamics of the British Late Triassic Kuehneosauridae. Palaeontology, 51(4): 967-981. DOI: 10.1111/j.1475-4983.2008.00783.x
Piveteau J 1926. Paleontologie de Madagascar, XIII. Amphibiens et reptiles permiens: Annales de Paleontologie, v. 15, p. 53-128.

SVP abstracts 21: Vancleavea: ~3x larger than we thought

Price 2020 presents
new larger specimens of Vancleavea campi (Fig. 1; Parker and Barton 2008; Nesbitt et al. 2009), a derived thalattosaur close to Helveticosaurus in the large reptile tree (LRT, 1751 taxa).

Figure 1. The Thalattosauria and outgroups (Wumengosaurus and Stereosternum) to scale.

From the Price 2020 abstract:”
“The basal archosauriform Vancleavea campi has long been thought to represent a relatively small, semi-aquatic, predator from the Late Triassic ecosystems found in the entire Upper Triassic strata of western North America.”

Orginally Vancleavea was considered an archosauriform, but it resembles no other archosauriformes. Adding taxa shifts Vancleavea to the Thalattosauria. This has been online since 2011. So, Price should add taxa to clear up this decade-old problem.

“Here, I describe four partial dentaries recovered from the Duke Ranch Member of the Redonda Formation of eastern New Mexico. All specimens are referred to Vancleavea campi on the basis of a number of characters of the dentary shared with a complete individual of the taxon, here postulated to represent autapomorphies of Vancleavea campi.”

“These dentaries show that Vancleavea was a much larger animal than previously thought, and an estimate of the total minimum length is presented using isometric scaling. The total length of the largest individual is estimated close to four meters.”

That would make Vancleavea the largest thalalattosaur (Fig. 1).

“This size may have allowed Vancleavea to hunt larger prey within its environment and therefore shifts its role in the ecosystem to that of a semi-aquatic apex predator. I interpret the size increase as a growth series within the taxon, but acknowledge that further evidence is needed in support of this hypothesis.”

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References
Nesbitt SJ, Stocker MR, Small BJ and Downs A 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157 (4): 814–864. doi:10.1111/j.1096-3642.2009.00530.x.
Parker WG and Barton B 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Palaeontologia Electronica 11 (3): 20p.
Price R 2020. New specimens of the Archosauriform Vancleavea campi from the Upper Triassic (Rhaetian) Redonta Formation of Eastern New Mexico indicates Vancleavea campi was an apex predator. SVP abstracts 2020.

wiki/Vancleavea

SVP abstract 20: Squamate variability within a single species

Petermann and Gauthier 2020 bring us their views on the 
“potential consequences of our inability to assess intraspecific variability in growth rates.”

From the Petermann and Gauthier abstract:
“An investigation of life-history parameters in the extant iguanian lizard Sauromalus ater (the Common Chuckwalla), a sexually dimorphic species from the SW U.S.A., revealed remarkable intraspecific variability.”

“We found expected differences in growth strategies between males and females, but also within each sex, relating to body size and the timing of sexual maturity. Males and females can grow rapidly to size-at-sexual-maturity, producing above-average adult body sizes. Or, they can grow slowly to size-at-sexual-maturity, yielding adults at or below average body sizes. Neither growth strategy influences longevity. As a result, we found that body size of similar-aged individuals varied by 53% for males and 38% for females, and maximum differences in ‘adults’ of 64% for males and 38% for females.”

Further ranging results were found here earlier in the large pterosaur tree (LPT, 251 taxa) for the lepidosaur pterosaurs, Pteranodon (Fig. 1) and Rhamphorhynchus (Fig. 2). These both became fully resolved in phylogenetic analysis.

Figure 2. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen.

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row.

Continuing from the Petermann and Gauthier abstract:
“Our results add to previous reports of intraspecific variability in extant and extinct vertebrates. High levels of intraspecific size-variability have multiple implications for vertebrate paleontology.

1. Morphologically similar specimens from the same locality could belong to the same species even if the size difference among adult individuals exceeds 50%, which is a higher level than previously thought.
2. Specimens that have been analyzed skeletochronologically and have been found to be similar or identical in chronological age, may not exhibit similar sizes.
3. Variability in growth strategies may lead to mistaking males and females (especially among sexual dimorphs), or individuals using different growth strategies, as belonging to separate species.”

This is the way evolution works in all vertebrate communities, including humans, where some are taller, some are robust, some are more colorful or sexier, some are brilliant, distinct from the others. In both Rhamphorhynchus and Pteranodon, no two specimens are alike.

“We previously presented evidence that a sequence of sub-terminal skeletal suture fusions relates to maximum body size in squamates, and not to chronological age. This indicates that late-ontogenetic, suture-fusion events could be used to evaluate whether two or more specimens of similar morphology and chronological age are differently-sized conspecifics. Likewise, skeletal suture fusions may aid discerning different growth strategies within a single species, as opposed to the presence of two morphologically similar, but nonetheless separate, species in a single taphonomic assemblage.”

This follows the work of Maisano 2002, who found fusion patterns were phylogenetic in lepidosaurs. a pattern continued in pterosaurs, where fusion patterns are also phylogenetic, distinct form archosaur growth patterns.

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References
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Petermann H and Gauthier JA 2020. Intrespecific variability in an extant squamate and its implications for use in skeletochronology in extinct vertebrates. SVP abstracts 2020.