A year ago
Martill et al. 2015 described the stem snake, Tetrapodophis (Fig. 1) and considered it a burrowing squamate. A new paper by Lee et al. 2016 reports that Tetrapodophis had aquatic adaptations.
Figure 1. Tiny Tetrapodophis at full scale if your monitor produces 72 dpi images (standard on many monitors).
This new study confirms
what you read here, here and here when we nested Tetrapodophis with the following aquatic pre-snaketaxa: Pontosaurus, Adriosaurus and Aphanziocnemus in the large reptile tree (subset Fig. 2).
From the Lee et al abstract
“The exquisite transitional fossil Tetrapodophis – interpreted as a stem-snake with four small legs from the Lower Cretaceous of Brazil – has been widely considered a burrowing animal, consistent with recent studies arguing that snakes had fossorial ancestors [not so here]. We reevaluate the ecomorphology of this important taxon using a multivariate morphometric analysis and a reexamination of the limb anatomy. Our analysis shows that the body proportions are unusual and similar to both burrowing and surface-active squamates. We also show that it exhibits striking and compelling features of limb anatomy, including enlarged first metapodials and reduced tarsal/carpal ossification – that conversely are highly suggestive of aquatic habits, and are found in marine squamates. The morphology and inferred ecology of Tetrapodophis therefore does not clearly favour fossorial over aquatic origins of snakes.”
Figure 2. Scleroglossan subset of the large reptile tree. Generalists taxa duplicated in the Yi and Norell tree are shown in bright green. Burrowers shared in the Yi and Norell tree are in dark green. Legless taxa are black. Vestiges are in gray. Unknown are striped.
prior workers have not performed a phylogenetic analysis on this taxon that includes the above named aquatic squamates and Jucaraseps?
Lee MSY, Palci A, Jones MEH, Caldwell MW, Holme JD & Reisz RR 2016. Aquatic adaptations in the four limbs of the snake-like reptile Tetrapodophis from the Lower Cretaceous of Brazil. Cretaceous Research (advance online publication)
Martill DM, Tischlinger H and Longrich NR 2015. A four-legged snake from the Early Cretaceous of Gondwana. Science 349 (6246): 416-419. DOI: 10.1126/science.aaa9208