Aurélien et al. 2018 bring us
molecular evidence for the paraphyly of Scolecophidia (burrowing miniaturized worm-snakes, Fig. 2), which they claim “represent the earliest branching clades within the snake tree.” Like others making the same claim before, this is a preposterous statement given the highly derived skulls of various burrowing snakes and the major lack of fossil stem snakes in their cladogram. The Aurélien et al. cladogram includes Varanus, Lacertidae and Anolis sp. as progressively more distant outgroup taxa, omitting (as in all DNA studies) even more fossil taxa.
We looked at
the previous DaSilva et al. 2018 study that took on the origin of snakes using DNA and a few fossils earlier here (and see figure 1.)
The LRT ancestors of snakes
were recovered here (subset Fig. 1) five years ago.
Distinct from DNA studies
the large reptile tree (LRT, 1308 taxa; subset in Fig. 1) employs fossil taxa and skeletal traits. In doing so burrowing snakes are recovered as a derived monophyletic clade displaying a gradual accumulation of derived traits in derived taxa (Fig. 2). And that makes sense. We expect a gradual accumulation of derived traits in derived taxa, and that’s exactly what you get in the snake section of the LRT. We learned earlier to distrust DNA studies when dealing with distantly related tetrapods, and this is yet another case of the same problem.
Aurélian M et al. (5 co-authors) 2018. Molecular evidence for the paraphyly of Scolecophidia and its evolutionary implications. Journal of Evolutionary Biology DOI: 10.1111/jeb.13373 online here.
DaSilva FO et al. (7 co-authors) 2018. The ecological origins of snakes as revealed by skull evolution. Nature.com/Nature Communications (2018)9:376 1–11. DOI: 10.1038/s41467-017-02788-3 pdf