Assembling the Squamate Tree of Life – part 1

Some of the heaviest hitters in paleontology joined forces to produce a 300-page paper (including tons of photos and the data matrix) of squamate phylogeny, including several fossil taxa. Gauthier et al. (2012) takes the reader through the history of squamate studies, discusses some of long standing problems and some of the new molecular studies. 141 extant and 51 extinct species were included. The outgroup consisted of three Rhynchocephalians. 610 characters were tested. 112 trees were recovered, chiefly at the base of the Iguania. The homoplasy index was 0.82, so a great deal of homoplay was present. This was a huge study and powerful due to its size.

Happily most of the Gauthier (2012) tree echoed the results of prior trees and the large reptile tree. At the base of both: Huehuecuetzpalli followed by Iguania and Scleroglossa with the latter divided into Gekkota, Scincomorpha and Anguimorpha. Major differences include: 1) Mosasaurs and their kin at the base of the Scleroglossa. 2) Eichstattisaurus at the base of the Gekkota, 3) Amphisbaenia as the sister to a 4) monophyletic Serpentes (snakes). The large reptile tree found 1) mosasaurs to nest with varanids, 2) Eichstattisaurus to nest with basal snakes close to mosasaurs and their kin, far from the Gekkota, 3) amphisbaenids as sisters to skinks, 4) and diphyletic clades of snakes arising from sisters to Lanthanotus and Adriosaurus.

The Gauthier et al. 2012 family tree of the squamates

Figure 1. Click to enlarge. The Gauthier et al. 2012 family tree of the squamates, color added for large clades.

We’ll look at these differences point by point in coming blogs and attempt to dissect the differences and why they occurred.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Gauthier, JA, Kearney M, Maisano JA, Rieppel O and Behkke ADB 2012. Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record. Bulletin of the Peabody Museum of Natural History 53(1):3-308. online here.

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