SVP 2021 abstracts – 05: Are kuehneosaurids basal archosauromorphs? Still, no.

Sunday, November 7, 2021 13:17

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Pritchard 2021 wrote:
“Kuehneosaurids are a clade of rare, superficially lizardlike Triassic diapsids characterized by elongated ribs that are thought to support a patagium.”

As we learned earlier (2011), those are dermal rods, not ribs. The dorsal ribs are short and fused to the transverse processes (Figs 1, 2), hence Pritchard’s confusion (which is traditional and taught in college textbooks). No related taxa (Figs. 3, 4) have elongate transverse processes.

Triassic diapsids? Best to call these ‘Lepidosauriformes’ to differentiate them from unrelated, but convergent archosauromorph diapsids, like Petrolacosaurus.

Kuehneosaurids are not ‘superficially’ lizardlike. Basal kuehneosaurids are basal to lepidosaurs in the LRT, so their lizardlike traits are homologous.

Figure 1. Above, sample vertebrae from Pamelina. Below, the more derived Kuehneosaurus. True ribs are shown in yellow. Dermal struts are in blue.

Earlier Pritchard was a co-author on a paper
redescribing the osteology and relationships of Weigeltisaurus (Pritchard et al. 2021), a pseudo-rib glider related to kuehneosaurids in the LRT. Pritchard et al. mistakenly nested pseudo-rib gliders with aquatic archosauromorph taxa, as we looked at earlier here in May 2021 and some pseudo-rib gliders apart from others. Those should have been clear red flags to reexamine their data or add taxa.

Figure 2. Click to enlarge. The Triassic kuehneosaur gliders and their non-gliding precursors.

The Pritchard abstract continues:
“Since their discovery, kuehneosaurids have been considered close relatives of Lepidosauria owing to a suite of morphological characters including an incomplete lower temporal bar, a laterally bowed quadrate with a prominent lateral crest, and a subcircular thyroid fenestra in the puboischiadic plate.”

Yes! But don’t make the mistake of listing traits (= Pulling a Larry Martin).
Use the last common ancestor method to determine clades.

Figure 3. Derived lepidosauriformes. The clade Pseudoribia includes the pseudo-rib gliders

The Pritchard abstract continues:
“Early cladistic analyses of Diapsida supported this close relationship, such that kuehneosaurids hold an important role in discussions of lepidosaur origins.”

Yes! That’s what the large reptile tree (LRT, 1988+ taxa; subset Fig. 3) indicates. Cladograms that nest kuehneosaurids with aquatic taxa (e.g. Pritchard et al. 2021) are clear indicators of the need to add taxa in order to produce a gradual accumulation of traits, niches, etc.

Figure 4. Kuehneosaurid skulls from Palaegama to Coelurosauravus and Mecistotrachelos, and to Lanthanolania, Pamelina, Kuehneosaurus, Icarosaurus and Xianglong. Some of these taxa were not previously recognized as kuehneosaurids or their ancestors.

The Pritchard abstract continues:
“Discoveries over the past two decades have expanded the anatomical diversity of non-archosaurian archosauromorphs and non-saurian diapsids.”

Diapsid tetrapods are not monophyletic in the LRT.
Pritchard needs to add taxa to understand this.

“Recent phylogenetic studies have supported various alternative positions for kuehneosaurids as non-saurian diapsids, the sister taxon of Drepanosauromorpha, and as archosauromorphs close to Allokotosauria.”

Some studies nest kuehneosaurids close to aquatic taxa. Enough said.

“Herein, I present a revised phylogenetic analysis focused on early Sauria (339 characters, 61 taxa).”

Only 61 taxa? The LRT includes 1988 taxa.

“Parsimony and Bayesian analyses both support the hypothesis that kuehneosaurids are not lepidosauromorphs, but in fact nonarchosauriform archosauromorphs.

That is incorrect. Taxon exclusion is the problem, no doubt.

“The kuehneosaurid sample includes the North American Icarosaurus siefkeri and the European Kuehneosaurus latus and Kuehneosuchus latissimus.”

In the LRT several other taxa are included, so Pritchard is omitting them.

“The morphological characters that once supported a lepidosauromorph affinity for Kuehneosauridae are distributed among multiple early archosauromorph and
non-saurian taxa.”

Convergence like this is a bitch best tamed by adding taxa. Pritchard needs to add taxa.

“Characters supporting the position of kuehneosaurids within Archosauromorpha include a
postnarial process of the premaxilla, pendulous basal tubera of the basioccipital, a long and upturned retroarticular process, vertebral centra without a notochordal canal/pit, cervical vertebrae with prominent spine tables and epipophyses, a prominent post-glenoid process of the coracoid, and a horizontally oriented iliac blade with a prominent postacetabular process.”

Pritchard is ‘Pulling a Larry Martin’ here. Taxon exclusion has bedeviled him.

“This hypothesis removes a key outgroup to crown-group lepidosaurs, reduces the known diversity of nonlepidosaurian lepidosauromorphs, and obscures morphological transitions at the base of Lepidosauria.”

By contrast, the LRT illuminates the base of the Lepidosauria.
You can even throw out taxa and the topology remains the same. Remember, this topology was built with 260 taxa. Now it includes 1988.

“It also adds a clade with rib-mediated gliding adaptations to the rapidly expanding ecomorphological diversity of nonarchosaurian archosauromorphs during the Triassic
Period.”

Or not. (See phylogenetic explanations above).

References
Pritchard AC 2021. Revised phylogenetic analysis of Permo-Triassic diapsids supports kuehneosaurids as basal archosauromorphs. Journal of Vertebtate Paleontology abstracts.
Pritchard AC, Sues H-D, Scott D and Reisz RR 2021. Osteology, relationships and functional morphology of Weigeltisaurus jaekeli (Diapsida, Weigeltisauridae) based on a complete skeleton from the Upper Permian Kupferschiefer of Germany. PeerJ 9:e11413 DOI 10.7717/peerj.11413

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

https://pterosaurheresies.wordpress.com/2013/05/13/yes-theyre-all-kuehneosaurids-or-their-ancestors/

https://pterosaurheresies.wordpress.com/2012/11/13/rethinking-the-fused-ribs-of-triassic-gliders/

https://pterosaurheresies.wordpress.com/2021/05/22/weigeltisaurus-2021-taxon-exclusion-problems-again/

Source: https://pterosaurheresies.wordpress.com/2021/11/08/svp-abstracts-05-are-kuehneosaurids-basal-archosauromorphs-still-no/