Wapitisaurus reconstructed as a thalattosaur

Maish 2024
tested Wapitisaurus problelmaticus (Fig 1, Brinkman 1988, Bastiaans et al 2023, TMP 88.99.21, Early Triassic) in his thalattosaur (Fig 2) cladogram. It is known from a roadkill skull that may be what it seems, or may not be. Two prior authors weighed in on this specimen.

How much taphonomic shifting took place is the big question here.
None? or a great amount?

Figure 1. Wapitisaurus reconstructed on a Xinpusaurus Bauplan. ” data-image-caption=”

Figure 1. Wapitisaurus reconstructed on a Xinpusaurus Bauplan.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/wapitisaurus.skull_.recon588.gif?w=251″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/wapitisaurus.skull_.recon588.gif?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-88170″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/wapitisaurus.skull_.recon588.gif” alt=”Figure 1. Wapitisaurus reconstructed on a Xinpusaurus Bauplan.” width=”584″ height=”699″ />

Figure 1. Wapitisaurus reconstructed on a Xinpusaurus kohi Bauplan shown in figure 2. Note how the taphonomic shifting of the bones changes bone identities and reconstructions. If you’re going to re-identify sloughed off bones, use Photoshop to move them around like this to check your ideas.

Wapitisaurus was originally described
as a large weigeltisaurid, one of the so-called rib gliders (Fig 2). Brinkman wrote, “The skull of a new weigeltisaurid reptile, Wapitisaurus problematicus gen. et sp. nov., from the Lower Triassic Vega-Phoroso Member of the Sulphur Mountain Formation is described. It shares with Coelurosauravus, the only other known weigeltisaurid, the presence of an incomplete lower temporal arcade, a jugal with reduced postorbital process, and a squamosal crest ornamented with tooth-like projections. It differs from Coelurosauravus in its large size and in the structure and implantation of the teeth.”

Weigeltisaurus is shown in figure 2. Coelurosauravus is shown in figure 3.

Xinpusaurus kohi, the swordbill species. ” data-image-caption=”

Figure 3. Xinpusaurus kohi, the swordbill species.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/02/xinpusaurus588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/02/xinpusaurus588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-9102″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2013/02/xinpusaurus588.jpg” alt=”Xinpusaurus kohi, the swordbill species.” width=”584″ height=”179″ />

Figure 2. Xinpusaurus kohi, the swordbill thalattosaur.

Brinkman 1988 also wrote,
“Teeth like those of Wapitisaurus are also seen in two group of marine reptiles form the Triassic, the Thalattosauria and the Ichthyopterygia. Thus an alternative to the hypothesis that Wapitisaurus is related to Coelurosauravus is that it is a member of one of these groups.”

Like Brinkman, we should also explore all possibilities.

Figure 2. Weigeltisaurus illustrated. ” data-image-caption=”

Figure 2. Weigeltisaurus illustrated.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/05/weigeltisaurus2021recon588-2.jpg?w=163″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/05/weigeltisaurus2021recon588-2.jpg?w=558″ tabindex=”0″ role=”button” class=”size-full wp-image-56034″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/05/weigeltisaurus2021recon588-2.jpg” alt=”Figure 2. Weigeltisaurus illustrated. ” width=”584″ height=”1073″ />

Figure 2. Weigeltisaurus illustrated.

Brinkman accepted the in situ arrangement
of skull bones (Fig 1 frame 1) as their in vivo positions. Note the tooth-like projections on the squamosal crest of Weigeltisaurus (Fig 2) and Coelurosauravus (Fig 3) to understand Brinkman’s reasoning.

Interpretation is part of paleontology.

Coelurosauravus. ” data-image-caption=”

Figure 1. Coelurosauravus. It had ribs, but no transverse processes. The extradermal rods were more numerous than the ribs. Click to learn more.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/11/coelurosauravus588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/11/coelurosauravus588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-8168″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2012/11/coelurosauravus588.jpg” alt=”Coelurosauravus.” width=”584″ height=”363″ />

Figure 3. Coelurosauravus. It had ribs, but no transverse processes. The extradermal rods were more numerous than the ribs.

Bastiaans et al 2023 saw Wapitisaurus
more like a swimming thalattosaur (Fig 1), less like a glider, due to taphonomic shifting of several bones and patches.

I won’t be adding Wapitisaurus to the LRT,
(subset Fig 4) but wondered how this roadkill skull might have looked in vivo (Fig 1) using a Xinpusaurus kohi Bauplan (Fig 2). The less-disturbed mandible seems to be the key to understanding which interpretation is correct. Two skull reconstructions are shown in figure 1, frames 3 and 4. Some bones and patches are re-identified from Bastiaans et al.

Maish wrote,
“Family Thalattosauridae Merriam, 1904. Defined as the last common ancestor of Thalattosaurus alexandrae, Concavispina biseridens and all of its descendants.”

The last common ancestor of these two taxa in the LRT (subset Fig 4) is Clarazia. That omits a sister clade of widely recognized thalattosaurs plus two basal thalattosaurs. Perhaps a new definition is warranted for this clade based on adding several omitted taxa.

Figure 2. Aquatic younginiforms in the LRT include Sauropterygia, Ichthyopterygia, Mesosauria and Thalattosauria. ” data-image-caption=”

Figure 2. Aquatic younginiforms in the LRT include Sauropterygia, Ichthyopterygia, Mesosauria and Thalattosauria.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/thalattosaurialrt588.jpg?w=90″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/thalattosaurialrt588.jpg?w=307″ tabindex=”0″ role=”button” class=”size-full wp-image-88179″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/08/thalattosaurialrt588.jpg” alt=”Figure 2. Aquatic younginiforms in the LRT include Sauropterygia, Ichthyopterygia, Mesosauria and Thalattosauria.” width=”584″ height=”1949″ />

Figure 4. Aquatic younginiforms in the LRT include Sauropterygia, Ichthyopterygia, Mesosauria and Thalattosauria. Note the definition of Thallatosauria does not include all thalattosaurs in the LRT.

Maish concluded,
“A phylogenetic analysis, the most inclusive conducted on Thalattosauria so far, is preformed to evaluate the relevance of morphological variation within Xinpusaurus.”

Unfortunately,
Maisch omitted from his cladogram several thalattosaur taxa that appeared in the LRT back in 2018, and did not mention thalattosaur outgroup taxa, did not mention mesosaurs but did report, “As noted by Metz (2019) this morphology is highly derived within Diapsida, shown by archosaurs and lepidosaurs, but not by basal diapsids, and certainly not by ichthyosaurs or sauropterygians, with which thalattosaurs are currently allied. This requires further investigation, and a full publication of the results of Metz (2019) is desirable.”

Or Maisch could have added more taxa to his own studies. This is where the LRT comes in handy. It’s free. It’s online. It need not be cited. Just don’t omit taxa in your own focused studies or you’ll hear about it here.

References
Bastiaans D, Buffa V and Scheyer T M 2023. To glide or to swim? A reinvestigation of the enigmatic Wapitisaurus problematicus (Reptilia) from the Early Triassic of British Columbia, Canada. Royal Society Open Science, 10 (11): 231171.
Brinkman D 1988. A weigeltisaurid reptile from the Lower Triassic of British Columbia. – Palaeontology, 31: 951–956.
Maish MW 2024. Notes on thalattosaurs (Reptilia, Triassic) with special reference to the genus Xinpusaurus, from the Upper Triassic of SW-China. N. Jb. Geol. Paläont. Abh. 311/3 (2024), 229–280. Stuttgart.
Metz ET 2019. Description, phylogenetic analysis and taphonomy of a new Thalattosaur from the Brisbois member of the Vester Formation (Carnian/Norian) of central Oregon. – Doctoral dissertation.

wiki/Wapitisaurus