SVP abstract 19: Hanging on to the invalid ‘Notoungulata’

Perini, Casali and Flynn 2020
try to resurrect an invalid clade in the LRT (subset Fig. 1), ‘Notoungulata‘. Either that or they never thought to test it for validity.

From their abstract:
“During most of the Cenozoic, South America (SA) was an isolated continent, leading to evolution of an unique and endemic fauna. Among these were the Notoungulata, an extinct group of ungulate-like mammals that included a wide array of species assigned to 14 families and more than 150 genera, occupying many distinct herbivorous niches and showing convergent morphologies with distantly related mammalian herbivore groups.”

That ‘wide array of species’ is a clue that this traditional clade is not monophyletic. The large reptile tree (LRT, 1751+ taxa, see Fig. 1) nests various traditional notogunulates in various disparate clades, some placental, others marsupial. This makes the Notoungulata invalid (in 2016, Fig. 1) due to polyphyly.

“Despite this diversity, few studies have addressed the evolution of morphological disparity among notoungulates.”

In counterpoint, the LRT addressed the evolution of morphological disparity in this traditional clade, and found its diversity spelled its doom.

“In this study, we applied modern comparative methods to investigate macroevolutionary patterns within the clade.”

...and that’s there main mistake. They assumed they had a monophyletic clade. Don’t assume! Test by adding taxa. Don’t cherry pick taxa, especially if those taxa are on traditional lists. Add taxa and add more taxa until all the taxa in your study nests in monophyletic clades, as shown online in the LRT. When this is done the traditional members of the Notoungulata fail to remain monophyletic (Fig. 1).

“We used a comprehensive morphological matrix to perform a Bayesian phylogenetic analysis, obtaining a fully resolved phylogeny and divergence time estimates for the major groups of notoungulates.”

Cherry-picking taxa makes this possible. Cherry-picking = cheating or laziness or reliance on others, none of which makes good science.

Figure 1. A selection of purported notoungulates (in amber) were added to the LRT and they did not nest together. That means they're not a clade.

Figure 1. From 2016: A selection of purported notoungulates (in amber) were added to the LRT and they did not nest together. That means they’re not a clade.

Perini, Casali and Flynn 2020 continue:
“This phylogeny supports the division of Notoungulata into Toxodontia and Typotheria, including many traditionally recognized families, as well as indicates paraphyly of some groups such as “Notohippidae”, “Notopithecidae”, and “Isotemnidae”. The diversity of Notoungulata rose steadily from the beginning of the Paleocene, reaching its apex by the end of the Oligocene, with marked decreases in the beginning, middle, and end of the Miocene, until final extinction in the Pleistocene. Toxodontia and Typotheria show no overlap, but occupy increasingly more distinct areas of the morphospace over time. Etc.”

Some traditional notoungulates are marsupials. Others are placentals in the LRT. You can weed out convergence by adding taxa. I’ll keep saying that until it becomes rote and the standard operating principle.

Figure 3. Toxodon and the much smaller Eurygenium to scale.

Figure 2. Toxodon and the much smaller Eurygenium to scale.

Nothing should proceed in detail
until a valid phylogenetic context is present. Otherwise you are wasting your time. Once you have your wide gamut cladogram, the kind that minimizes taxon exclusion, like the LRT, you will have a tool that you can use over and over again with little additional effort. It’s like a Periodic Table of Elements you can refer to. If you never have such a tool you will always risk taxon exclusion and the specter of convergence.


References
Perini FA, Casali DD and Flynn J 2020. Notoungulata, an endemic radiation of extinct South American herbivorous mammals. SVP abstracts 2020.

wiki/Notoungulata

 

SVP abstracts 18: Palatal foramina and the origin of baleen in mysticetes

Peredo and Pyenson 2020 discuss
the origin of baleen in mysticetes by looking at palatal foramina.

“Baleen whales (mysticetes) filter-feed using specialized keratinous plates, called baleen, to sieve large quantities of prey laden water. Baleen represents a wholly novel integumentary structure, with no apparent homologous structure in any living animal. The origins of baleen, and filter-feeding in whales, have been the topic of much debate. In particular, the lack of osteological correlates for baleen makes it unclear which (if any) stem mysticetes first had keratinous structures for filter feeding.”

The origin of baleen in whales is found in traditionally overlooked nearly toothless desmostylians like Desmostylus (Fig. 2) and Behemotops (Fig. 3), taxa nesting basal to mysticetes in the large reptile tree (LRT, 1751+ taxa; subset Fig. 1).

Figure 3. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

Figure 1. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

“One potential osteological correlate are palatal foramina and sulci: structures in the roof of the mouth that may vascularize the baleen plates.”

Peredo and Pyenson are “Pulling a Larry Martin” by looking for a few ‘key’ traits rather than running a phylogenetic analysis of all traits without excluding pertinent taxa, such as Desmostylus and Behemotops.

“Palatal foramina are present and well developed in extant and fossil crown mysticetes and are preserved in some stem mysticetes as well. Here, we report the presence of numerous and well-developed palatal foramina in non-filter-feeding cetaceans, including crown and stem odontocetes and in stem cetaceans (so-called archaeocetes).”

Peredo and Pyenson are excluding pertinent taxa.

“Additionally, we observe the presence of palatal foramina in 61 observed species of terrestrial artiodactyls.”

Peredo and Pyenson are excluding pertinent taxa. No artiodactyls are basal to any whales in the LRT. Hippos are not artiodactyls in the LRT. Toothed whales arise from tenrecs and anagalids.

Figure 1. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

Figure 2. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

The Peredo and Pyenson abstract continues:
“CT scanning demonstrates consistent internal morphology across all observed palatal foramina, suggesting that the palatal foramina observed in extant mysticetes are homologous to those of terrestrial artiodactyls.”

This sounds like cherry-picking taxa. Perhaps palatal foramina are typical of non-arboreal mammals? What do tenrec and desmostylian foramina look like?

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 3. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

The Peredo and Pyenson abstract continues:
“The presence of palatal foramina in non-filter-feeding whales (odontocetes and archaeocetes) and in terrestrial artiodactyls suggest that the structures are more probably associated with an elaborate gingiva or other oral tissue and are alone not reliable osteological correlates for the presence of baleen in fossils.”

Next time, just add pertinent taxa and run the analysis… then see what turns up. The origin of baleen in whales was answered here in 2016. ResearchGate.net has an unpublished paper to read on the triple origin of whales here.


References
Peredo CM and Pyenson N 2020. Palatal foramina in stem whales and terrestrial artiodactyls obfuscate their potential for inferring baleen in stem mysticetes. SVP abstracts 2020.

wiki/Baleen_whale

SVP abstracts 17: Pederpes is a junior synonym for Whatcheeria

Otoo et al. 2020 bring us
a new reconstruction of Whatcheeria (Figs. 1, 2), evidently updated from a 2018 abstract by the same authors (less one).

Figure 1. Whatcheeria fossil.

Figure 1. Whatcheeria fossil.

From the Otoo et al. abstract:
“The early tetrapod Whatcheeria is represented by hundreds of specimens from the Mississippian Delta locality (Iowa, U.S.A.). Research on the postcranial anatomy allows a full-body reconstruction to be produced for the first time. The ribcage is strongly regionalized, with long anterior trunk ribs bearing large uncinate processes, and short posterior trunk ribs. The girdles and limbs are massive; in particular, the processes of the humerus are very large, and imply bulky forelimb and shoulder musculature, especially relating to the retraction of the forelimb. The cervical region is elongated and the tail is reduced in length relative to contemporary tetrapods such as embolomeres and colosteids.”

Whatcheeria nests in the large reptile tree (LRT, subset Fig. 3) alongside Pederpes (Fig. 4). The two share all traits scored in the LRT and are coeval in the Early Carboniferous.

Figure 2. Whatcheeria skull.

Figure 2. Early Carboniferous Whatcheeria skull.

More from the Otoo et al. abstract:
“The resulting proportions are more similar to terrestrial taxa such as Seymouria and Eryops. These taxa also share with Whatcheeria robust humeri with large processes, large olecranon processes, large scapular blades, and regionalized ribcages. Such similarities suggest convergent life habits, with an anteriorly stiffened trunk to increase the effectiveness of the powerful forelimbs and reduce lateral motion of the body.”

Figure 4. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Figure 3. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

More from the Otoo et al. abstract:
“We hypothesize that Whatcheeria represents an independent experiment in appendicular-dominated locomotion, with improved ability to explore terrestrial environments The large (>2 m maximum) body size of Whatcheeria is larger than most Mississippian tetrapods, particularly those for which there is the most compelling evidence of terrestriality (e.g., Balanerpeton, Westlothiana). Aquatic locomotion may have been accomplished by bottom-walking, or rowing with the forelimbs.”

“Our new data include additional synapomorphies between Whatcheeria and Pederpes, and suggest that the latter is a juvenile.

Whatcheeria and Pederpes nest together in the LRT (Fig. 4). Of 235 traits, none differ between the two. Based on scale bars the two are identical in size, with 10cm measuring the snout to the posterior orbit on both. Pederpes (Clack 2002) is thus a junior synonym for Whatcheeria (Lombard and Bolt 1995). Hmmm. Wonder how this one got away from the experts over the last 18 years. Whatcheeria entered the LRT in 2017, so I had three years to see this, too.

Figure 3. Pederpes is a basal taxon in the Whatcheeria + Crassigyrinus clade.

Figure 4. Early Carboniferous Pederpes is a basal taxon in the Stegocephalia.

More from the Otoo et al. abstract:
These data contribute to a new diagnosis for the Whatcheeriidae and a reassessment of material and taxa referred or compared to the family; significantly, Ossinodus is not a whatcheeriid and represents a distinct morphotype.

The LRT (subset Fig. 3, Fig. 5) agrees with this.

Figure 2. Ossinodus, Pederpes were more primitive than the more aquatic Icthyostega.

Figure 5. Ossinodus,is more primitive than the more aquatic Icthyostega. Pederpes is more derived, but close. The black areas of Ossinodus are known. The rest is restoration.

More from the Otoo et al. abstract:
“However, these data do move Whatcheeria crownward in phylogenetic analyses. Rather, our findings highlight the disparity of stem tetrapods, and emphasizes Whatcheeria’s status as an early-diverging experiment in a morphology later revisited by crown tetrapods.”

The LRT (subset Fig. 3) does not agree with this conclusion. Ossinodus (Fig. 5) nests basal to both stegocephalians (including Whatcheeria) and crown tetrapods. It is the most basal tetrapod with substantially larger limbs than those of basalmost tetrapods like Trypanognathus. Ichthyostega and Pederpes are taxa leaving no Permian and Mesozoic descendants.


References
Ahlberg PE and Milner AR 1994. The origin and early diversification of tetrapods. Nature 368, 507-514.
Clack JA 2002. Gaining Ground: The origin and evolution of tetrapods. Indiana University Press.
Clack JA 2002. An early tetrapod from ‘Romer’s Gap’. Nature. 418 (6893): 72–76. doi:10.1038/nature00824
Lydekker R 1890. On two new species of labyrinthodonts. Quarterly Journal of the Geological Society, London 46, 289-294.
Lombard RE and Bolt, J.R 1995. A new primitive tetrapod, Whatcheeria deltae, from the Lower Carboniferous of Iowa. Palaeontology 38(3):471–495.
Otoo B, Bolt J, Lombard E and Coates M 2020. A new reconstruction of Whatcheeria and the ecomorpholigcal disparity of early tetrapods. SVP abstracts 2020.
Otoo BK, Bolt JR, Lombard E 2018. A leg up: Whatcheeria and its new contributions to tetrapod anatomy. SVP abstracts.
Panchen AL 1991. The early tetrapods: classification and the shapes of cladograms in: Origins of the Higher Groups of Tetrapods: Controversy and Consensus. Eds. Schultze HP and Trueb L. Comstock Publishing Associates, Cornell University Press, Ithaca and London.

wiki/Pederpes
wiki/Whatcheeria

https://pterosaurheresies.wordpress.com/2018/10/30/svp-2018-new-whatcheeria-data-from-nearly-100-specimens/

SVP abstracts 16: A 3D aïstopod points to yet another transition to land

Marjanović and Jansen 2020 suggest
a transition to terrestrial life independent from any crown-group tetrapods in the snake-like microsaur aîstopod clade. In the LRT that clade includes extant aquatic snake-like caecilians. In the LRT terrestrial and fossorial snakes likewise had aquatic ancestors by convergence.

From the Marjanović and Jansen 2020 abstract:
“A complete, articulated, three-dimensional and stunningly well-prepared skeleton from the Saar-Nahe basin (western Germany) phenetically resembles Oestocephalus, but achieves a lower head-to-body length ratio by possessing more elongate and more numerous vertebrae.”

Figure 1. Ophiderpeton (dorsal view) and two specimens of Oestocephalus (tiny immature and larger mature).

Figure 1. Ophiderpeton (dorsal view) and two specimens of Oestocephalus (tiny immature and larger mature).

Continuing from the Marjanović and Jansen 2020 abstract:
“Despite the rather young ontogenetic age indicated by size and skull proportions, the shape range of the dorsal scales is that of Colosteus, including rhombic scales around the dorsal midline.”

Figure 5. Colosteus is covered with dermal skull bones and osteoderms. Those vestigial forelimbs are transitional to the limbless condition in Phlegethontia.

Figure 2. Colosteus is covered with dermal skull bones and osteoderms. Those vestigial forelimbs are transitional to the limbless condition in Phlegethontia.

Continuing from the Marjanović and Jansen 2020 abstract:
“As in the “nectridean” Keraterpeton, the dorsal scales bear microscopic honeycombed sculpture; we also report this in Oestocephalus.”

Figure 3. Keraterpeton, basal to the Diplocaulus clade in the LRT.

Figure 3. Keraterpeton, basal to the Diplocaulus clade in the LRT.

Continuing from the Marjanović and Jansen 2020 abstract:
“Such sculpture is also seen on the ventral scales of the new specimen, which are nonetheless as narrow as in other aïstopods.”

Figure 4. Phlegethontia overall with neck and sacral bones colored red. The 'gill bones' are removed. They are gastralia.

Figure 4. Phlegethontia overall with neck and sacral bones colored red. The ‘gill bones’ are removed. They are gastralia.

Continuing from the Marjanović and Jansen 2020 abstract:
“The presence of the braincase and the first complete, undistorted aïstopod palate is confirmed by μCT; hyobranchial bones, endochondral girdles or a tail-fin skeleton are absent. The tail tapers to a point, is not laterally flattened, and the scales do not leave room for a soft-tissue tail fin; no gill slit is apparent in the scale cover behind the head.”

These indicators of terrestrial life contrast with the mandibular lateral-line canal previously identified in Coloraderpeton and suggest that the new specimen, together with the phlegethontiids from the contemporaneous fossil forest floor of Chemnitz (eastern Germany), represents a transition to terrestrial life independent from any crown-group tetrapods.”

The basalmost taxon in this legless clade is nearly legless Acherontiscus, (Fig. 5) considered an aquatic animal due to a few lateral lines on the skull. Living legless microsaurs, the caecilians, are also secondarily aquatic. The authors consider their new taxon and Phlegethontia (Fig. 4) secondarily terrestrial.

In a similar fashion 
extant snake ancestors in the LRT were aquatic, making most living snakes secondarily terrestrial, by convergence. Derived sea snakes and others, like the water moccasin, went back to an aquatic existence making the snake-like morphology rather flexible with regard to niche.

Figure 6. Acherontiscus is a basal taxon in the aïstopod clade.

Figure 5. Acherontiscus is a basal taxon in the legless aïstopod clade.

Continuing from the Marjanović and Jansen 2020 abstract:
“Yet, despite the stem-tetrapodomorph plesiomorphies in the braincase, lower jaw and scales of Aïstopoda, a preliminary phylogenetic analysis of an improved and greatly enlarged dataset finds no support for a whatcheeriid-grade position, and less support for a more crownward colosteid-grade position (as recently proposed) than for an amphibian one.”

Figure 4. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Figure 6. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Continuing from the Marjanović and Jansen 2020 abstract:
“Only Andersonerpeton, an isolated lower jaw described as an aïstopod, joins Densignathus in the whatcheeriid grade. Redescriptions of additional “nectrideans” and other supposed “lepospondyls” will be needed to resolve this conundrum.”

Figure 6. Living caecilian photo.

Figure 7. Living caecilian photo.

According to Wikipedia,
Aïstopoda include: Lethiscus, Ophiderpeton, Oestocephalus, Coloraderpeton and Phlegethontia among taxa tested by the large reptile tree (LRT, subset Fig. 6) nesting in the clade Microsauria. Aïstopods have been variously grouped with other lepospondyls, or placed at or prior to the batrachomorph-reptiliomorph divide. However, a cladistic analysis by Pardo et al. (2017) recovered Aistopoda at the base of Tetrapoda.

The aîstopod, Lethiscus, is from Viséan strata 340 mya,
coeval with Silvanerpeton, the last common ancestor of all reptiles in the LRT. There are no legless taxa proximal to reptiles in the LRT (subset Fig. 6).


References
Marjanović D and Jansen M 2020. A complete, three-dimensional early Permian aïstopod (Tetrapodomorpha) illuminates the phylogeny, ontogeny and terrestrialization of early limbed and limbless vertebrates. SVP abstracts 2020.

wiki/Aistopoda

SVP abstracts 15: Gigantic recumbirostran and reptile herbivory

At first this abstract sounded like
Asaphestera, which the lead author, Mann et al. 2020 mistakenly reassessed their ‘microsaur’, Asaphestera platyris (Fig. 1), as ‘the earliest synapsid’.

Earlier in May, the LRT nested Asaphestera as a microsaur after demonstrating interpretation and reconstruction errors. However, the term ‘gigantic recumbirostran’ should probably not be applied to Asaphestera with a 4cm skull length. Oddly, given the headline, the actual size of the ‘gigantic’ skull was is not mentioned in this abstract.

Figure 1. Asapehestera platyris in situ, traced by Mann et al. 2020, then traced and reconstructed using DGS methods.

Figure 1. Asapehestera platyris in situ, traced by Mann et al. 2020, then traced and reconstructed using DGS methods.

From the Mann, Calthorpe and Maddin 2020 abstract:
“Currently, it is thought that the establishment of a modern trophic structure with widespread herbivory occurred in the Permian. Herbivorous adaptations in tetrapods that allow for expanded niche exploitation include modifications to craniodental morphology and expansion of the postcranial skeleton (ribs, girdles) to accommodate large guts stocked with microbial endosymbionts to aid in digestion of cellulose. The earliest tetrapod clades to experiment with herbivory (e.g., diadectids, edaphosaurids, and captorhinids), have their origins in the terminal Carboniferous but did not diversify until the Permian.”

Need to add the Cephalerpeton clade (Middle Pennsylvanian), the Stephanospondylus clade (Early Permian) and Caseasauria (Early Permian) to that list.

“Here we present a new large pantylid recumbirostran ‘microsaur’ known from a single skull found in a lycopsid tree stump from the Pennsylvannian-aged Sydney Mines Formation on Cape Breton Island, Nova Scotia. Phylogenetic analysis recovers the new taxon as sister-taxon to Pantylus.”

Pantylus (Fig. 1) and its sister Stegotretus (Berman, Eberth and Brinkman 1988; Fig. 2) are from the Early Permian and Earliest Permian respectively.

Pantylus

Figure 2. The microsaur Pantylus. Click to learn more.

Figure 2. Stegotretus from Berman, Eberth and Brinkman 1988. Scale bar not known.

Figure 3. Stegotretus from Berman, Eberth and Brinkman 1988. Scale bar not known.

Continuing from the Mann, Calthorpe and Maddin 2020 abstract:
“MicroCT analysis reveals complex craniodental specializations that are interpreted as adaptations related to an herbivorous lifestyle. The morphology of the marginal and palatal teeth is similar to the bulbous, durophagous dentition of fossil tetrapods including Pantylus, Euryodus, Opisthodontosaurus, but are also similar to that of modern omnivorous squamates (e.g., Tiliqua tiliqua). However, the palatal teeth are further organized into dense dental fields that together with dentition on the coronoids of the lower jaw form occluding dental batteries, similar to those seen in Permian-aged animals interpreted as herbivores, such as other pantylids, moradisaurines and edaphosaurids.”

“This suggests that the dental apparatus seen in the new taxon functioned similarly in facilitating both grinding and shearing of plant material, consistent with the interpretations made for the other taxa. Our new taxon, however, substantially predates these later occurrences, thus providing the earliest evidence for tetrapod herbivory, and possibly represents the first example of an herbivore for amniotes, if recent phylogenetic hypotheses that recumbirostrans are reptiles are accurate.”

Those hypotheses are not supported by the large reptile tree (LRT, 1751 taxa) where members of the clade Recumbirostra, continue to nest within Microsauria, which includes the extant clade Caeciliidae. Recumbirostra appears to be a junior synonym for Microsauria. Adding taxa resolves this issue.

“The early occurrence and extent of development of a complex dental apparatus in this unexpected data point indicates a far earlier diversification of diet and niche exploitation by early tetrapods than previously recognized.”

Actually not ‘a far earlier diversification… than previously recognized’. We had this nailed far earlier, in 2012.


References
Berman DS, Eberth DA and Brinkman DB 1988. Stegotretus agyrus, a new genus and species of microsaur (amphibian) from the Permo-Pennsylvanian of New Mexico. Annals of Carnegie Museum. 57: 293–323.
Cope ED 1882. Third contribution to the history of the Vertebrata of the Permian formation of Texas. Proceedings of the American Philosophical Society 20:447-461.
Mann A, Calthorpe AS and Maddin HC 2020. A gigantic recumbirostran from the Carboniferous of Nova Scotia reveals adaptations to herbivorous feeding. SVP abstracts 2020.
Mann A et al. (7 co-authors) 2020. Reassessment of historic ‘microsaurs’ from Joggins, Nova Scotia, reveals hidden diversity in the earliest amniote ecosystem. Papers in Palaeontology 2020:1–17.

https://pterosaurheresies.wordpress.com/2020/05/11/asaphestera-the-earliest-amniote-no/

https://pterosaurheresies.wordpress.com/2020/06/21/origin-of-tetrapod-herbivory-effects-on-local-plant-diversity/

wiki/Pantylus
wiki/Stegotretus

SVP abstracts 14: Phylogeny of the Eosauropterygia reviewed

Lin et al. 2020 bring us a new phylogeny
of the Eosauropterygia (defined as: Pachypleurosaurus (Fig. 1) and descendants, or Sauropterygia sans Placodontia).

Pachypleurosaurus had more than two sacrals all converging on a tiny ilium.

Figure 1. Pachypleurosaurus had more than two sacrals all converging on a tiny ilium.

From the Lin et all 2020 abstract:
“During the last two decades, abundant Triassic sauropterygians have been reported from Europe and southwestern China, which greatly improve our understanding of the diversity and stratigraphic, as well as paleogeographic, distribution of Triassic sauropterygians. The phylogeny of Sauropterygia was also repeatedly analyzed with the description of each new species. Except for Placodontia, however, various analyses of sauropterygian interrelationships have yielded incongruent results, especially with regards to the monophyly of Pachypleurosauridae and Eusauropterygia (= Eosauropterygia sans Pachypleurosauridae) which were alternatively supported or rejected by different analyses.”

“The incongruent results of these analyses were probably caused by the implementation of different character codings, based primarily on the same data matrix taken from a global parsimony analysis by Rieppel about 20 years ago, which was based almost exclusively on European material. Since we have a large number of new specimens from the rest of the world, it is high time to reexamine the phylogeny of the entire group, or at least of the eosauropterygians, in order to assess whether and how the newly described taxa affect overall tree topology.”

Figure 3. Aquatic younginiform subset of the LRT demonstrating relationships within the Enaliosauria (=Sauropterygia + Ichthyosauria)

Figure 2. Aquatic younginiform subset of the LRT demonstrating relationships within the Enaliosauria (=Sauropterygia + Ichthyosauria)

Continuing from the Lin et all 2020 abstract:
“Given that the ingroup relationships of Placodontia is well established, we herein focus on reanalyzing the interrelationships of Eosauropterygia, which is the sister clade of the Placodontia within the Sauropterygia. We present a comprehensive phylogenetic hypothesis for Eosauropterygia based on a cladistic analysis of 137 characters coded for four outgroup and 49 ingroup taxa, including nearly all currently recognized Triassic eosauropterygian genera. This is the most inclusive phylogenetic analysis of Eosauropterygia to date.”

Does it include the taxa listed above (Fig. 1). If not, add them.

“The new phylogenetic hypothesis of Eosauropterygia suggests that Pachypleurosauridae is the sister taxon of Eusauropterygia, and their monophyly as traditionally upheld is reestablished.”

Which taxon is the last common ancestor? In the large reptile tree (LRT, 1751+ taxa, subset Fig. 2) indicates that Eusauropterygia is indeed monophyletic and arises from a series of pachypleurosaurs. This is distinct from the Lin et al. results which recovers a monophyletic Pachypleurosauridae.

“Furthermore, the monophyly of the genus Nothosaurus as traditionally conceived is not supported, whereas the monophyly of Lariosaurus is obtained if the lariosaurian affinity of N. juvenilis, N. youngi, and N. winkelhorsti is accepted. In this study, the monophyletic Pistosauroidea excludes Corosaurus and Cymatosaurus. The latter two genera are found to form a clade that represents the basal-most members of Eusauropterygia. The new phylogenetic hypothesis is mostly in good accordance with the stratigraphic distribution of the genera.”

I cannot comment further on a cladogram I have not seen. Overall the LRT recovers a traditional cladogram, with the exception of a short list of non-tradtional outgroups, like the Mesosauria, Thalattosauria and Ichthyosauria along with a long list of basal aquatic diapsids. The clade Enaliosauria is traditionally considered obsolete, but the LRT recovers it as a monophyletic clade. Turtles are not closely related when the valid, tested turtle sisters and ancestors are included in the taxon list. The initial radiation of sauropterygians evidently occurred prior to the Early Triassic given the diversity present in the Early Triassic and the diversity of mesosaurs in the Late Permian.


References
Lin W, Jiang D, Rieppel O, Motany R, Tintori A, Sun Z and Zhou M 2020. Phylogeny of the Eosauropterygia (Diapsida: Sauropterygia) incorporating recent discoveries from South China.  SVP Abstracts 2020.

wiki/Sauropterygia

SVP abstracts 13: Tiny Tiktaalik-like tetrapod

Lembert et al. 2020 bring us
a much smaller Tiktaalik-like tetrapod.

From the Lembert et al. abstract:
“The elpistostegalian stem-tetrapod Tiktaalik roseae (Fig. 1) is known from a single locality (NV2K17) within the Fram Formation of Ellesmere Island, Nunavut Territory, Canada. Specimens from this locality represent subadult to adult specimens, including specimens up to 61% larger than the holotype specimen (NUFV 108) and reaching an estimated 3 meters in length.”

Figure 3. Tiktaalik specimens compared to Ossinodus.

Figure 1. Tiktaalik specimens compared to Ossinodus.

“Here we present fossil material of a much smaller elpistostegalian specimen (NUFV 137) from a second, slightly older locality within the Fram Formation on Ellesmere Island (NV0401), possibly representing a juvenile T. roseae specimen or a new taxon.”

Not mentioned in this abstract, tiny Koilops (Figs. 2, 3) nests basal to Tiktaalik in the large reptile tree (LRT, 1251 taxa).

Figure 2. Koilops is a flat-headed sister to Spathicephalus, but with teeth, larger orbits and a shorter snout

Figure 2. Koilops is a flat-headed sister to Spathicephalus, but with teeth, larger orbits and a shorter snout

Figure x. The fin to finger transition in the LRT with the addition of Elpistostege.

Figure 3. The fin to finger transition in the LRT with the addition of Elpistostege.

Continuing from the Lembert et al. abstract:
“Preserved remains of NUFV 137 include fragmentary lower and upper jaws, gular plates, fragments of the rostrum, articulated body scales, articulated pectoral fin elements, and several other currently unidentified endoskeletal pieces. Linear proportions between homologous landmarks of lower jaws of NUFV 137 and NUFV 108 suggest an animal approximately 61% smaller than the holotype of T. roseae, and, with a reconstructed total jaw length of approximately 12.4 cm, NUFV 137 is similar in size to one of the smallest known elpistostegalian taxa (Rubrognathus kuleshovi).”

Taxon exclusion has evidently excluded the even smaller Koilops (Fig. 2) from the Lembert et al. studies.

“If NUFV 137 represents a juvenile T. roseae individual, it would expand the known size range of T. roseae specimens, with implications for understanding allometric growth in a tetrapodomorph taxon.

Figure 4. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Figure 4. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Continuing from the Lembert et al. abstract:
“While lower jaw characters appear to be similar to those in T. roseae, it is uncertain if some features, such as a posteriorly displaced postsplenial pit line, reduced adsymphyseal dentition, and varying postcranial proportions, are the result of differences in ontogeny or warrant a separate taxonomic grouping. These differences, and the presence of a potential operculum, indicate NUFV 137 might represent a distinct but similar, Tiktaalik-like taxon.”


References
Lemberg JB, Stewart TA, Daeschler E and Shubin NH 2020. Tomography of a tantalizingly tiny Tiktaalik-like taxon. SVP abstracts 2020.

SVP abstracts 12: Conoryctes, still not a taeniodont

Kynigopoulou Z et al. 2020
make another ill-fated attempt at nesting a taxon in a polyphyletic (= invalid) clade. Earlier (part of a 4-part series) the large reptile tree (LRT, subset Fig. 1) split up putative members of the Taeniodonta into several clades, making it invalid due to polyphyly.

Figure 3. Subset of the LRT labeling several traditional taeniodonts in red, indicating the traditional clade Taeniodonta is polyphyletic and should therefore be abandoned.

Figure 1. Subset of the LRT labeling several traditional taeniodonts in red, indicating the traditional clade Taeniodonta is polyphyletic and should therefore be abandoned.

From the Kynigopoulou Z et al. 2020 abstract:
“Conoryctes belongs to the Taeniodonta, a group of Paleogene mammals with unique dentition, suitable for an abrasive diet, and specialized postcranial skeletons.”

No it doesn’t. There is no monophyletic clade Taeniodonta. Conoryctes (Fig. 2) nests in the LRT as a carnivorous marsupial close to Early Cretaceous Vincelestes.

Figure 1. Conoryctes fossil and drawing from Schoch 1986.

Figure 2. Conoryctes fossil and drawing from Schoch 1986.

Continuing from the Kynigopoulou Z et al. 2020 abstract:
“Taeniodonts are among few eutherian clades with fossil evidence indicating they crossed the Cretaceous–Paleogene mass extinction boundary. They are traditionally divided into two families: the more ‘generalist’ Conoryctidae and anatomically derived Stylinodontidae.”

Whoa! Stylinodonts aren’t taeniodonts either. They are placental carnivorans.

“Here we report new specimens of Conoryctes from the Paleocene Nacimiento Formation of the San Juan Basin, New Mexico, U.S.A. These consist of numerous vertebrae, a pelvis, sacrum, partial forelimb and hindlimb, with phalanges and unguals, comprising the first relatively complete associated postcranium of the genus.”

Fantastic! Post-crania! Should look like Vincelestes post-crania.

“The new specimens allowed us to add new postcranial characters to a large phylogenetic analysis of early eutherian mammals (622 characters, 125 taxa), which we analysed using parsimony and Bayesian techniques. The results find Onychodectes as a basal taeniodont outside of the sister groups Conoryctidae (Conoryctes, Conoryctella, Huerfanodon) and Stylinodontidae (Wortmania, Psittacotherium, Ectoganus, Stylinodon).”

Missing a TON of taxa here (Fig. 1). I wonder if these taxa were united by teeth traits? If so, don’t do that. The value of quantity (in the LRT) comes up once again. Colleagues: let’s get the overall picture right, then add details.

“We also examined the anatomy and locomotor adaptations of the hindlimb, using multivariate analysis of 11 linear pes measurements to assess foot posture. Three representative taeniodonts (Onychodectes, Conoryctes, Stylinodon) were compared to a suite of extant mammals with known postural grades of the foot, as well as eight Paleogene taxa. Onychodectes and Conoryctes exhibit a more plantigrade posture whereas Stylinodon is more digitigrade, plotting next to the aardvark (Orycteropus).”

Do these authors know the aardvark is an armor-less armadillo?  Did they include Vincelestes (Fig. 3) in their taxon list?

Figure x. Vincelestes overall.

Figure 3. Vincelestes overall.

Continuing from the Kynigopoulou Z et al. 2020 abstract:
“Qualitatively, in Conoryctes, the astragalus features a relatively well-developed trochlear surface indicating cruropedal movement was more limited to the parasagittal plane. The articular surfaces on the astragalus and calcaneum with the navicular and cuboid respectively, show a degree of rotational movement within the middle pes suggestive of moderate supination during pedal flexion. The calcaneal tuber is robust indicative of a powerful foot stroke. These features, in combination with other features of the skeleton, support digging abilities in Conoryctes. Our study suggests that a plantigrade foot posture and digging behaviors are ancestral for Conoryctidae and perhaps all taeniodonts. It is likely their ability to burrow, and feed on tough vegetation, was essential to their survival in the early Paleocene and subsequent radiation.”

The LRT suggests you compare Conoryctes to Vincelestes, if you haven’t done so already. And add more taxa to see if your Taeniodonta remains monophyletic.


References
Kynigopoulou Z, Shelley S, Williamson T and Brusatte S 2020. The anatomy, paleobiology, and phylogeny of the Paleocene Taeniodont Conorycties. SVP abstracts 2020.

https://pterosaurheresies.wordpress.com/2018/12/24/taeniodonta-is-polyphyletic-part-3-conoryctes/

SVP abstracts 11: Palacrodon returns as a drepanosauromorph?

Jenkins et al. 2020 review
“the phylogenetic placement of an enigmatic reptile from the Early Triassic Transantarctic Mountains.” This reptile has gone through some name changes, but the large reptile tree (LRT, 1751+ taxa) nested it in 2016 with similar, big-eyed, basal placodonts like Palatodonta and Pappochelys (Fig. 1). Co-authors Jenkins and Lewis (2016) nested it with rhynchocephalians, but limited their taxon list to rhynchocephalians and procolophonids. There is no indication that they included basal placodonts in 2020.

Originally
(Broom 1906) considered what little is known of Palacrodon browni (= Fremouwsaurus geludens; Early Triassic; Fig. 1) a member of the Rhynchocephalia.

Figure 1. A comparison of basal placodonts to scale (and Paraplacodus reduced to one-third shows how Fremouwsaurus (Palacrodon) is transitional between the small spike-tooth ancestors like Palatodonta and Pappochelys and the pavement toothed Paraplacodus.

Figure 1. A comparison of basal placodonts to scale (and Paraplacodus reduced to one-third shows how Fremouwsaurus (Palacrodon) is transitional between the small spike-tooth ancestors like Palatodonta and Pappochelys and the pavement toothed Paraplacodus.

From the Jenkins et al. 2020 abstract:
“The phylogenetic placement of Palacrodon has been contentious since its initial description, with workers naming it as either a rhynchocephalian, lizard, procolophonid, eosuchian, or archosauromorph.”

Taxon inclusion nests it with basal placodonts.

“The uncertainty surrounding the phylogenetic affinity of Palacrodon in large part stems from the fact that nearly all the specimens found are teeth and fragmentary portions of tooth-bearing bone. Palacrodon bears characteristic labio-lingually elongate, molariform, cuspidate teeth reminiscent of herbivorous reptiles like extinct trilophosaurs and polyglyphanodonts and modern shell-crushing lizards.”

“Because previous workers lacked any other skeletal material, Palacrodon has never been placed within a phylogeny.”

Never? The LRT placed it in 2016,

“Though its phylogenetic affinity is uncertain, Palacrodon is a cosmopolitan genus spanning most of the Triassic, with specimens found in the Early Triassic of Antarctica, Early-Middle Triassic of South Africa, and the Late Triassic of Arizona. The only specimen of Palacrodon possessing more than dentition is from the Early Triassic lower Fremouw Formation of Antarctica (specimen number BP/1/5296). That formation is the sedimentary sequence immediately preceding the Permian-Triassic mass extinction boundary in the Transantarctic Mountains and represents the only known Early Triassic paleopolar deposit with abundant tetrapod material. The Antarctic specimen of Palacrodon was described from the impression of a latex peel as a partial small skull belonging to an unknown diapsid reptile initially named Fremouwsaurus geludens, which was later synonymized with Palacrodon.”

“We CT scanned the Antarctic specimen and found that previously undescribed skeletal elements are preserved in BP/1/5296. These include limb bones, ribs, phalanges, caudal vertebrae, ankle bones, and an ilium. Of the cranial elements, portions of the right maxilla, lacrimal, prefrontal, jugal, postorbital, ectopterygoid, and dentary are preserved. Both parsimony and Bayesian analyses found Palacrodon to be a stem saurian with close affinities to drepanosauromorphs.”

See figure 2 for known drepanosaurs (all Late Triassic) and their ancestor, Jesairosaurus (Early to Middle Triassic) in the LRT.

Figure 3. Drepanosaurs and their ancestor sisters, Jesairosaurus and Palaegama to scale.

Figure 3. Drepanosaurs and their ancestor sisters, Jesairosaurus and Palaegama to scale.

From the Jenkins et al. 2020 abstract:
“This finding suggests that Palacrodon is the earliest known drepanosaur, extending the temporal range of the clade by nearly 20 million years. Palacrodon is also the only known drepanosauromorph from the southern hemisphere. Further analysis of these new skeletal elements will now allow a more thorough understanding of the behavior and niche of Palacrodon and primitive drepanosuars generally.”

Excluding far fewer taxa, in the large reptile tree (LRT, 1749+ taxa) moving Palacrodon from the base of the Placodontia to the base of the Drepanosauromorpha adds 8 steps based on very few skull traits. Of course the post-crania could change things, but usually taxon exclusion changes things more.

Figure 2. The head of Palacrodon and the headless body of the Majiashanosaurus compared.

Figure 2. The head of Palacrodon and the headless body of the Majiashanosaurus compared.

References
Broom R 1906. On a new South African Triassic rhynchocephalian. Transactions of the Philosophical Society of South Africa 16:379-380.
Gow CE 1992. An enigmatic new reptile from the Lower Triassic Fremouw Formation of Antarctica. Palaeontologia Africana 29:21-23.
Gow CE 1999. The Triassic reptile Palacrodon brown Broom, synonymy and a new specimen.
Jenkins K, Lewis P, Choiniere J and Bhullar B-A 2020. The phylogenetic placement of an enigmatic reptile from the Early Triassic Transantarctic Mountains. SVP abstracts 2020.
Jenkins KM and Lewis PJ. 2016. Triassic lepidosaur from southern Gondwana. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
Neenan JM, Li C, Rieppel O, Bernardini F, Tuniz C, Muscio G and Scheyer TG 2014. Unique method of tooth replacement in durophagous placodont marine reptiles, with new data on the dentition of Chinese taxa. Journal of Anatomy 224(5):603-613.

https://pterosaurheresies.wordpress.com/2016/10/30/is-palacrodon-a-rhynchocephalian-svp-abstract-2016/

 

SVP abstracts 10: Scottish Middle Jurassic pterosaur, back again this year

Revised November 4, 2020
with the news that two Skye pterosaurs have been presented in SVP abstracts, not the one I assumed. Neither has been published yet, so I don’t know if the accompanying illustrations represent one or the other.

This is the second time
the wonderful Skye, Scotland pterosaur has entered the SVP abstracts. The first was in 2019, covered here. Evidently, this specimen is still unnamed and unnumbered, so I wondered, what progress does the new set of authors bring to this specimen this year?

Figure 1. Skye pterosaur from traced from in situ specimens found online.

Figure 1. Skye pterosaur from traced from in situ specimens found online.

From the Jagielska et al. 2020 abstract:
“An incomplete fossil record limits understanding of pterosaurian macroevolution during the Middle Jurassic, a period associated with diversification of many major pterosaur clades.”

By contrast, the fossil record in the large pterosaur tree (LPT, 251 taxa) has no large gaps during the Middle Jurassic (Fig. 2) or otherwise. The fossil record is more complete than the authors realize, evidently due to taxon exclusion.

“The European Middle Jurassic pterosaurian record, until now, has consisted of numerous non-taxon specific specimens and included a single named genus, based on a partially preserved dentary.”

Are we forgetting all the many Dorygnathus specimens (Fig. 2)? Several are transitional to higher pterodactyloid-grade taxa, either directly (ctenochasmatids and azhdarchids) or indirectly through Scaphognathus (the rest of them; Peters 2007).

Figure 8. Click to enlarge. The descendants of Sordes in the Dorygnathus clade and their two clades of pterodactyloid-grade descendants.

Figure 2. Click to enlarge. The descendants of Sordes in the Dorygnathus clade and their two clades of pterodactyloid-grade descendants.

Continuing from the Jagielska et al. 2020 abstract:
“Here we describe a new three-dimensionally preserved partial skeleton from the Bathonian Lealt Shale Formation of Skye, Scotland, that helps fill the Middle Jurassic pterosaur gap. It is the most complete fossil from the Jurassic sequence of the Scottish Hebrides, which commonly yields ichnofossils but only fragmentary archosaur remains, and the first nearly complete Middle Jurassic pterosaur from outside of China. The new pterosaur is mostly articulated and includes the skull (which retains delicate palatal, hyoid, and neurocranial elements), complete cervical and caudal vertebral series, fully preserved paired forelimbs with partially preserved wing phalanges, a disarticulated dorsal vertebral series and ribcage, and a poorly preserved sacral, pelvis and hindlimb region. It is the largest non-pterodactyloid on record, with an estimated 2 m wide wingspan.”

We also heard this in 2019. Since the authors have changed, perhaps no one told Jagielska et al. that this specimen was featured in an SVP abstract a year ago.

“The specimen represents a new genus and species diagnosed by several autapomorphies, including slender, curved humeral shaft; large teardrop-shaped lower temporal fenestra; a novel “jugo-lacrimal” fossa, and unique palatal arrangement with trident-shaped anterior vomer.”

As Larry Martin was quick to note, most autapomorphies can be found in other tetrapod taxa by convergence. So first, run the analysis. Then start describing some interesting traits.

“We conducted a phylogenetic analysis by combining several published datasets, which placed the new Scottish pterosaur within the paraphyletic array of non-monofenestratans commonly called the Rhamphorhynchinae, where it shares cranial similarities to the similarly-aged Chinese Angustinaripterus longicephalus.”

Sometimes more data nests taxa elsewhere, but their ‘several published datasets’ don’t include the LPT (subset Fig. 3). Borrowing other datasets usually absolves authors from mistakes made by prior authors, especially taxon exclusion issues. Colleagues, students: create your own datasets. Create your own reconstructions. By the way, in 2019 the earlier set of authors nested the Skye pterosaur with Darwinopterus and Wukongopterus, far from Angustinaripterus. The LRT nests the Skye pterosaur basal to the clade of wukongopterids (Fig. 3).

“We imaged the skull using microCT, which reveals a brain endocast with a large cerebellum and floccular region wrapped by thin, curved semi-circular canals of the inner ear, similar to closely related Rhamphorhynchus muensteri.”

The 2019 abstract likewise mentioned µCT scans. None of the above taxa are closely related to R. muensteri.

Figure 3. Subset of the LPT showing the nesting of the Skye pterosaur from available data (Fig. 1).

Figure 3. Subset of the LPT showing the nesting of the Skye pterosaur from available data (Fig. 1).

Continuing from the Jagielska et al. 2020 abstract:
“Along with the highly diverse but fragmentary Tayton Limestone Formation assemblage of England, the new specimen challenges the long-considered notion that the European Middle Jurassic was a time of low pterosaur diversity and anatomical disparity.”

One more specimen that we knew about last year will not challenge a ‘long considered notion’ that was never a notion to begin with. Hate to be snippy here, but hyperbole is not appropriate in science simply to elevate a notion or a cladogram, especially if it lacks dozens of pertinent taxa.


References
Jagielska N et al. (9 co-authors) 2020. An exceptionally well preserved pterosaur from the Middle Jurassic of Scotland. SVP abstracts 2020.
Martin-Silverstone E, Unwin DM and Barrett PM  2019. A new, three-dimensionally preserved monofenestratan pterosaur form the Middle Jurassic of Scotland and the complex evolutionary history of the scapulo-vertebrael articulation. SVP abstracts 2019. Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

https://pterosaurheresies.wordpress.com/2019/11/01/svp-abstracts-the-skye-pterosaur/