Weigeltisaurus 2021: taxon exclusion problems again

Pritchard et al. 2021
took another look at one of the pseudo-rib gliders, Weigeilitsaurus jaekeil (originally Palaeochameleo jaekeli Weigelt 1930; Figs. 1, 2), an arboreal, crested, basal lepidosauriform (Fig. 4) from the Late Permian.

Unfortunately
the authors did not increase the size of their way-too-short taxon list borrowed from an earlier study by two of the authors (Pritchard and Sues 2019, Fig. 5).

Pertinent taxa omitted
from both studies include (also see Fig. 4):

  1. Paliguana
  2. Coletta
  3. Sophineta
  4. Pintosaurus
  5. Contritosaurus
  6. Tridentinosaurus (Fig. 1)
  7. Mecistotrachelos (Fig. 1)
  8. Lanthanolania (Fig. 1)
  9. Xianglong (Fig. 1)
  10. Saurosternon (Fig. 1)
  11. Palaegama (Fig. 1)
  12. Owenetta
  13. Candelaria
  14. Barasaurus
  15. Kitchingnathus
  16. Santaisaurus
  17. Sauropareion
  18. and dozens of other basal reptile taxa that separate diapsid-grade lepiosauromorphs from diapsid-grade archosauromorphs, which Pritchard et al. were unable to do with their abbreviated taxon list

Sadly, and once again,
this is what happens when paleontologists cherry-pick their taxon list rather than let a wide gamut cladogram, like the large reptile tree (LRT, 1865+ taxa) provide a list of taxa, neither too few nor too many, pertinent to the more focused study.

Figure 1. Click here for a larger image at ReptileEvolution.com. The Triassic kuehneosaur gliders and their non-gliding precursors.

The authors also lack sufficient taxa
to split diapsid-grade Archosauromorpha from diapsid-grade Lepidosauromorpha (#18 from the list above), so they mistakenly include a long list of unrelated archosauriformes, like lumbering Erythrosuchus.

Figure 2. Weigeltisaurus reconstruction from Pritchard et al. Manus and pes reconstructions added here. Compare the manus and pes to Icarosaurus, then tell us all these two are not related.

Pritchard et al. report,
Patagia that support a gliding membrane independently evolved several times in diapsid reptiles, with weigeltisaurids representing only the oldest known example of such a system. However, in all other cases the homologies of the bones supporting the patagium are well understood.”

Ironically, this is not well understood by Pritchard et al. Their basic misunderstanding is based on the following error: “The most common patagium supports represented in extinct reptiles are elongated dorsal ribs (e.g., Kuehneosauridae, Mecistotrachelos apreoros, Xianglong zhaoi) that extend laterally or posterolaterally from their articulations with trunk vertebrae.”

Note to Pritchard et al: Look more closely. And add taxa.
Those are not long ribs on Icarosaurus (Fig. 3), Kuehneosaurus (Fig. 1) and Xianglong (Fig. 1). Those pseudo-ribs are dermal in origin, as in Weigeltisaurus and Coelurosauravus (Fig. 1). What the authors thought were elongate transverse processes are actually short ribs fused to each vertebrae, except anteriorly where the pattern is revealed.

No related taxa have elongate transverse processes.
That’s what you learn from adding taxa in analysis. The gliding mechanisms on all the above taxa (Fig. 1) are all dermal in origin, as in Weigeltisaurus.

Pritchard et al. report,
“A rib-supported patagium is also present in the extant gliding iguanians of the genus Draco of southeast Asia.”

Draco does have elongate ribs (and no transverse processes). This is a basic difference from the Permian through Cretaceous gliders (Fig. 1). We call this convergence. The interrelated taxa in figure 1 with pseudo-ribs all present homology, not convergence. Look at all the traits from head to toe, not just one or two ‘special’ traits.

Figure 3. Icarosaurus. Note the tiny ribs near the shoulders. The bases for the strut-like dermal bones are the ribs themselves flattened and transformed by fusion to act like transverse processes, which sister taxa do not have. Note the length of the hands corresponds to the base of the anterior wing strut.
Figure 3. Icarosaurus. Note the tiny ribs near the shoulders. The bases for the strut-like dermal bones are the ribs themselves flattened and transformed by fusion to act like transverse processes, which sister taxa do not have. Note the length of the hands corresponds to the base of the anterior wing strut.
Figure 2. Derived lepidosauriformes. The clade Pseudoribia includes the pseudo-rib gliders
Figure 4. Derived lepidosauriformes. The clade Pseudoribia includes the pseudo-rib gliders

We looked at Coelurosauravus and the other pseudo-rib gliders
earlier here in 2011. So this has been online for ten years.

Pritchard et al. did not do a superb job
of describing their taxon in detail (Figs. 7–10) with many oversights and errors published. It seems they attempted to trace Photoshop images either with outlines or colors, but did not always do so well.

Figure 2. Cladogram from Pritchard and Sues 2019 showing the nesting of Teraterpeton with Trilophosaurus. The yellow taxa are lepidosauromorphs and the green taxa are archosauromorphs in the LRT. Taxon exclusion folds them together like a deck of cards.
Figure 5. Cladogram from Pritchard and Sues 2019 showing the nesting of Teraterpeton with Trilophosaurus. The yellow taxa are lepidosauromorphs and the green taxa are archosauromorphs in the LRT. Taxon exclusion folds them together like a deck of cards.
Figure 6. From Pritchard et al. 2021. Colors added. Massive taxon exclusion mars this cladogram as in their previous cladogram Fig. 5). See figure 4 for a cladogram with relevant taxa included.

Digital Graphic Segregation (DGS)
was used (Fig. 7 left) to find the pelvic and sacral elements only partially identified by Pritchard et al. 2021, who had firsthand access to the fossil. The reconstruction based on the tracing at left is closer to bone shapes found in sister taxa (Fig. 1).

Figure 7. Weigeltisaurus pelvis tracing and reconstruction using DGS (left) and by Pritchard et al. 2021.
Figure 8. Weigeltisaurus manus and reconstruction using DGS and PILs here.
Figure 9. Weigletisaurus pes and reconstruction using DGS and PILs here. Note the broken mt5 overlooked by Pritchard et al. 2021.
Figure 10. Weigeltisaurus skull. Frame 1: as traced by Pritchard et al. Frame 2: colors changed to those used here for homologous bones. Frame 3. Parts of the supratemporal, premaxilla, frontal, lacrimal and prefrontal added, jugal rotated to in vivo position.

If you’re going to build a cladogram, do yourself a favor.
Add pertinent taxa. Look more closely at related taxa. Don’t blindly follow out-of-date traditions and myths based on short taxon lists. Study your cladogram. Sometimes it will tell you exactly where there are errors in scoring. The LRT is here for you, either to use or to act as a suggestion box.

References
Pritchard AC, Sues H-D. 2019. Postcranial remains of Teraterpeton hrynewichorum (Reptilia:
Archosauromorpha) and the mosaic evolution of the saurian postcranial skeleton. Journal of
Systematic Palaeontology 17(20):1745–1765 DOI 10.1080/14772019.2018.1551249.
Pritchard AC, Sues H-D, Scott D, 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
Weigelt J 1930. Palaeochameleo jaekeli nov. gen., nov. sp., ein neuer Rhynchocephale aus dem Mansfelder Kupferschiefer. Leopoldina 6:625–642.

wiki/Weigeltisaurus

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