New Parvosaurus study suffers from taxon exclusion
From the Freisem et al 2024 abstract:
“Here, we describe an almost complete skull of a new sphenodontian taxon from this formation (Norian, 227–208 Ma), making it the oldest known articulated sphenodontian skull from Europe and one of the oldest in the world. A phylogenetic assessment recovers it as a basal sphenodontian closely related to Planocephalosaurus robinsonae and to Eusphenodontia, making it the earliest-diverging sphenodontian known with an articulated skull.”
Parvosaurus is known from a tiny skull (Fig 3) that has been µCT scanned.
Figure 1. Freisem et al 2024 cladogram of sphenodontian lepidosaurs. Taxon exclusion mars this otherwise excellent study. Homoeosaurus is a squamate. Compare to the LRT subset in figure 2.
” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg?w=170″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg?w=579″ class=”size-full wp-image-84955″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg?w=584&h=1033″ alt=”Figure 1. Freisem et al 2024 cladogram of sphenodontian lepidosaurs. Taxon exclusion mars this otherwise excellent study. Homoeosaurus is a squamate. Compare to the LRT subset in figure 2.” width=”584″ height=”1033″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg?w=584&h=1033 584w, https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg?w=85&h=150 85w, https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg?w=170&h=300 170w, https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus-cladogram588-2.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Freisem et al 2024 cladogram of sphenodontian lepidosaurs. Taxon exclusion mars this otherwise excellent study. Homoeosaurus is a squamate. Compare to the LRT subset in figure 2.
The authors borrowed
the Simöes et al 2020 cladogram (Fig 1) and reported, “No outgroup was set.” That’s difficult to do because PAUP always assigns taxon number one to the outgroup. The authors included Prolacerta (Fig 1), an unrelated archosauromorph as their outgroup.
Figure 2. Subset of the LRT focusing on Sphenodontia with tested outgroups, not including protosquamates. Yellow taxa are tested in the LRT and Simöes et al 2024. Others are excluded from the 2024 study.
” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg?w=151″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg?w=515″ class=”size-full wp-image-84949″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg?w=584&h=1161″ alt=”Figure 2. Subset of the LRT focusing on Sphenodontia with tested outgroups, not including protosquamates. Yellow taxa are tested in the LRT and Simöes et al 2024. Others are excluded from the 2024 study.” width=”584″ height=”1161″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg?w=584&h=1161 584w, https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg?w=75&h=150 75w, https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg?w=151&h=300 151w, https://pterosaurheresies.files.wordpress.com/2024/03/sphenodonts.parvosaurus2024-588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. Subset of the LRT focusing on Sphenodontia with tested outgroups, not including protosquamates. Yellow taxa are tested in the LRT and Freisem et al 2024. Others are excluded from the 2024 study. Most workers consider rhychosaurs to be archoauromorphs, which is why Freisem et al. omitted them, but here Priosphenodon is a rhynchoaur. This is called cherry-picking taxa and trusting borrowed cladograms.
Taxon exclusion remains the number one problem
in paleontology, even when the Smithsonian’s own Hans Sues is a co-author. That’s why it is so important to build your own LRT to find out for yourself which taxa belong with others. Don’t trust a borrowed cladogram, especially one with cherry-picked taxa.
Figure 3. Parvosaurus skull from Simöes et al. 2024.
” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg?w=136″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg?w=465″ class=”size-full wp-image-84952″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg?w=584&h=1285″ alt=”Figure 3. Parvosaurus skull from Simöes et al. 2024.” width=”584″ height=”1285″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg?w=584&h=1285 584w, https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg?w=68&h=150 68w, https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg?w=136&h=300 136w, https://pterosaurheresies.files.wordpress.com/2024/03/parvosaurus.skull_.588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. Parvosaurus skull from Simöes et al. 2024. This taxon will be added to the LRT soon after colors have been adjusted to the DGS standard colors.
In all other regards, this study of a tiny skull
assigned to Parvosaurus harudensis MB.R.4520.2 was excellent. I will add this taxon to the LRT after the DGS colors have been adjusted to DGS standard colors.
References
Freisem LS, Müller J, Sues H-D and Sobral G 2024. A new sphenodontian (Diapsida: Lepidosauria) from the Upper Triassic (Norian) of Germany and its implicatons for the mode of sphenodontian evolution. BMC Ecology and Evolution 24:35. https://doi.org/10.1186/s12862-024-02218-1
Simões TR, Caldwell MW, Pierce SE 2020. Sphenodontian phylogeny and the
impact of model choice in Bayesian morphological clock estimates of
divergence times and evolutionary rates. BMC Biol. 2020;18:191. https://
doi. org/ 10. 1186/ s12915-020-00901-5.
wiki/Parvosaurus – not yet posted
Source: https://pterosaurheresies.wordpress.com/2024/03/20/new-parvosaurus-study-suffers-from-taxon-exclusion/
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