(Relatively) Giant Tanytrachelos Specimens!

We’re just talking about bits and pieces here,
but the new, giant New Mexico Tanytrachelos specimens (Pritchard et al. 2015) are a close match to the much smaller New Jersey specimens (Fig. 1). When you restore all the bones in between using the tiny specimens as blueprints, there are no obvious proportional differences between the two versions of Tanytrachelos (but size IS a factor in speciation — but that is another paleo-heresy).

Figure 1. Giant Tanytrachelos from New Mexico along with the much smaller specimens from New Jersey. At top is the small specimen of Tanystropheus, all to scale.

Figure 1. Giant Tanytrachelos from New Mexico from Pritchard et al  2015, along with the much smaller specimens from New Jersey. Easier to imagine when all the parts are together and scaled to a blueprint. At top is the small specimen of Tanystropheus, all to scale.

Good description
by Pritchard et al (2015). And a good local nesting with Langobardisaurus and Tanystropheus and kin. Unfortunately, once you leave this vicinity in the Pritchard et al. cladogram (Fig. 2) sister taxa become wildly dissimilar (Mesosuchus, Teraterpeton and Macrocnemus together??). And the cladogram is missing several pertinent taxa (Fig. 3).

Figure 2. Pritchard et al. tree for Tanytrachelos. There are unrelated taxa here and related taxa are not included. See figure 3.

Figure 2. Pritchard et al. tree for Tanytrachelos. There are unrelated taxa here and related taxa are not included. See figure 3. Here two protorosaurs are widely separated. Other several purported sisters are indeed sisters in the large reptile tree, but others do not resemble one another and so could not have evolved from a common ancestor.

There is a much more gradual accumulation
of derived traits in the various sister cladded at the large reptile and large pterosaur trees, a subset of which is shown here (Fig. 3), where the lhyper-long-necked taxa are derived from long-necked taxa.

Figure 3. Tanytrachelos tree subset of the large reptile tree. Only a large gamut study can determine the inclusion set for more focused studies. You cannot rely upon tradition.

Figure 3. Tanytrachelos tree subset of the large reptile tree. Only a large gamut study can determine the inclusion set for more focused studies. You cannot rely upon tradition.

You can tell by the feet that tanystropheids are related to
fenestrasaurs and pterosaurs (Fig. 1). The very short metatarsal 5 along with a very long p5.1 is a shared trait of this clade that was named Characiopoda (“prop-footed ones” in Peters 2000). The clade includes Tanystropheidae + Langobardisaurus + Fenestrasauria.

Fenestrasauria = Cosesaurus, Sharovipteryx, Longisquama and Pterosauria (Peters 2000). This nomenclature and topology has been ignored by all workers for the last 15 years as they preferred to lump unrelated and dissimilar taxa together, preferring to pretend the origin of pterosaurs is a mystery, preferring NOT to look into this problem. When will reason return?

Also,
take a look at the skull of Tanystropheus (Fig. 1). All it is missing is an antorbital fenestra to become a pretty good pterosaur skull. You get such similarities through homology via relatedness.

As paleo-historians know,
the first specimens of Tanystropheus were considered pterosaurian largely due to their distinctive feet.

Good job!
to Pritchard et al. (2015) on their description and assessment for the giant Tanytrachelos.

It’s too bad
they were saddled with such a bad topology. I’m sure they realize that, like other lepidosaurs, Tanytrachelos has an ossified sternum and it is quite large, similar in shape to that of Huehuecuetzpalli, Langobardisaurus and Cosesaurus, three other tritosaur lepidosaurs. A large gamut study, like the large reptile tree, irons out all these problems.

Please, colleagues,
stop going with your gut, stop going with tradition and use the several times validated large reptile tree to help you determine inclusion sets for your more focused studies. Bigger (more taxa) is better. Or repeat the experiment yourself with a different set of characters and a large number of basal taxa. There is only one true tree of reptile evolution. Let’s find it together. Here is a good start with 580 taxa, fully resolved and with good bootstrap scores.

If anyone has Alan Turner’s ear
he disputed the ability of the large reptile tree to resolve 360 taxa with only 228 characters. There are now 220 more taxa here and no more characters, still fully resolved and going strong. Alan is not the only paleontologist who feels (and I used this word purposefully) this way. Most are anonymous referees. Alan was an editor on more than one of my manuscripts and contributed to the New Mexico Tanytrachelos paper (see refs).

References
Pritchard AC, Turner AH, Nesbitt SJ, Irims RB & Smith ND 2015. Late Triassic tanystropheids (Reptilia, Archosauromorpha) from northern New Mexico (Petrified Forest Member, Chinle Formation) and the biogeography, functional morphology, and evolution of Tanystropheidae. Journal of Vertebrate Paleontology 35(2):e911186, 20pp.

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