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Taxon exclusion and 'odd bedfellow' nestings.

Posted by DavidPeters1247 on 25 Mar 2015 at 14:25 GMT

The authors note problems with their tree, not only from a morphology vs. molecule perspective, but also by behavioral issues and other problems. They also find ‘rogue’ taxa that they delete. I find problems with many aspects of this study, chiefly from taxon exclusion to ‘odd bedfellow’ nesting.

The author’s taxon list includes a large number of living taxa and they nest appropriately in most cases. However basal members of sister clades, which should also share a large suite of traits, too often do not. I point, for example to the base of the Mosasauria with Adriosaurus, a mid-sized oceanic undulating lizard, oddly nesting next to Leptotyphlops, a tiny burrowing snake so derived that its mandibles open and close like doors. Such a derived snake should not nest at the base of the clade, nor should it nest anywhere near Adriosaurus. Such “odd bedfellow" issues mark problems that should have been reviewed prior to publication.

The authors do not realize that there are a large number of extinct taxa that nest between sphenodontids and squamates. One branch can be conveniently called proto-squamates and these include Lacertulus, Bavarisaurus, Meyasaurus, Carusia, Hoyalacerta, Homoeosaurus solnhofensis, Dalinghosaurus and Scandensia. The other branch begins with Tijubina, includes Huehuecuetzpalli, Macrocnemus, drepanosaurs, tanystropheids, fenestrasaurs and pterosaurs. Determining the correct outgroup for the Squamata affects ingroup relationships, particularly at the base of the clade. That was not done in this case.

The authors do not include Ardeosaurus, Eichstaettisaurus, Aphanizocnemus and Jucaraceps, four taxa that link snakes to geckos.

The authors do not include Euposaurus and Calanguban, two basal squamates, the former basal to iguania and the other basal the scleroglossa. Another basal scleroglossan, Liushusaurus, was not included. With it, Tchingisaurus nests at the base of the geckos, close to Ardeosaurus at the base of the snake clade. I don’t see Yabeinosaurus and Bahndwivici in the tree. Both are basal to Varanus and kin, Heloderma and kin and skinks, including Dibamus and Amphisbaena and kin.

The cladogram upon which these notes are made can be viewed at http://www.reptileevoluti...
A supporting MacClade nexus file can be requested on that web page.

In that cladogram Adriosaurus nests basal to snakes, but is not related to mosasaurs. Leptotyphlops nests as a derived terminal taxon. All sister taxa share a large number of traits and actually resemble one another, mirroring evolutionary events.

No competing interests declared.