Revision to the LRT: basal tetrapods

Here’s a revision to the LRT
that is still being revised and studied (Fig. 1) following the addition of several taxa and two new characters.  I hope readers will report untenable relationships. Most of the taxa are still related to their prior sisters, but the order has changed here and there. It’s been interesting and enlightening going through this process.

Figure 1. Subset of the LRT focusing on the basal (anamniote) Tetrapoda. The last week has been spent reexamining data and letting the taxa sort themselves out again. Please report any untenable relationships.

Figure 1. Subset of the LRT focusing on the basal (anamniote) Tetrapoda. The last week has been spent reexamining data and letting the taxa sort themselves out again. Please report any untenable relationships.

A few novel nestings appear here.
As the days go by I will discuss and illustrate many of the interesting clades and sisters that were recovered here. For instance, earlier I reported Spathicephalus nesting with Tiktaalik.

Something that does not jump out immediately
is the genesis of tetrapods with fingers and toes deep enough into the Devonian to produce the highly derived near reptile with long digits, Tulerpeton, by the end of the Devonian, prior to the first appearance of nearly all tetrapod fossils with fingers and toes no sooner than the Early Carboniferous.

More reptile ancestors
Several more basal tetrapods are now in the direct lineage of the clade Reptilia. These formerly nested slightly elsewhere.

Middle Devonian tetrapod tracks
were reported earlier here. That trackmaker remains elusive. So the evidence for their presence is known, but the bones are not.

the web pages and their order will be updated this week. Currently the order does not reflect the tree topology shown above.


5 thoughts on “Revision to the LRT: basal tetrapods

  1. Please report any untenable relationships.

    That sentence is, in effect (I don’t know that’s not the intent), a Gish gallop: almost every relationship this tree consists of is untenable, and to explain why would take way more time and space than I can devote to a blog comment. Like… behold the size of my latest paper, and then remember that’s barely a start.

    I can quickly point out, though, that you have Brachydectes in your matrix twice: once as Brachydectes, and once as Lysorophus. Wellstead (1991), which I hope is your main source for the postcranium of Brachydectes, restricted Lysorophus to the undiagnostic holotype of its nomen dubium of a type species (2 1/2 vertebrae) and referred all the rest to Brachydectes where it has remained ever since.

    • Sorry, David, but Brachydectes elongatus (formerly Lysorophus tricarinatus; Cope 1877, Wellstead 1991; Permian, 250 mya;AMNH 6172 ) and Brachydectes newberryi (Wellstead 1991 Pardo and Anderson 2016; Latest Carboniferous; KUVP 49541) appear to be generically different. That these two nest together in the LRT -almost- falsifies your first opinion (almost every relationship this tree consists of is untenable). You cite Wellstead 1991 and suggest I should follow that authority, but science never relies on authority, especially if testing negates certain hypotheses of relationships. re: your latest paper… it would improve your paper to include reconstructions and smaller, more readily digested subsets of your cladograms with an eye toward using improved graphic techniques, like similar colors, to show relationships with more clarity to improve the user experience.

      • I agree there are at least two distinguishable taxa lurking within what Wellstead called Brachydectes. Probably they largely line up with what he called B. newberryi and B. elongatus. Part of the trouble is that the characters that differentiate them are not preserved in the type specimen of B. elongatus, and only one of them is preserved in the type of B. newberryi.

        The type of Lysorophus tricarinatus of course doesn’t preserve any of them, so neither can be referred to that species, and there’s no way to refer one but not the other to Lysorophus.

        And maybe B. should really be referred to Molgophis. Wellstead sort of left that question conspicuously open without mentioning it explicitly. Pardo & Anderson (2016) mentioned it, but didn’t develop it either and just lumped everything for the moment.

        In short, it’s a huge mess, and there’s no morphological justification for referring some material to Brachydectes and other (or any) material to Lysorophus.


        I cannot include reconstructions in my papers unless 1) I violate a lot of copyright, or 2) a coauthor or myself spend way too much time drawing them, or 3) a coauthor or myself spend money we don’t have.

        The colors that highlight taxa on the trees are completely consistent between all trees. They go by phylogenetic definitions, not by contents, so sometimes terminal taxa jump in and out of larger taxa; that’s only right & proper.

        Subsets of the trees, and of those from other papers, make up almost all figures in the Discussion. Maybe you gave up reading in the somewhat boring Results section? :-)

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