Molecular evidence for the paraphyly of Scolecophidia and its evolutionary implications

Abstract

The phylogenetic relationships between the three main clades of worm snakes remain controversial. This question is, however, crucial to elucidate the origin of the successful snake radiation, as these burrowing and miniaturized wormlike organisms represent the earliest branching clades within the snake tree. The present molecular phylogenetic study, intended to minimize the amount of missing data, provides fully resolved inter-subfamilial relationships among Typhlopidae. It also brings robust evidence that worm snakes (Scolecophidia) are paraphyletic, with the scolecophidian family Anomalepididae recovered with strong support as sister clade to the 'typical snakes' (Alethinophidia). Ancestral state reconstructions applied to three different traits strongly associated to a burrowing life-style (scolecoidy, absence of retinal cones and microstomy) provide results in favour of a burrowing origin of snakes, and suggest that worm snakes might be the only extant fossorial representatives of the primordial snake incursion towards an underground environment.

Fossil amphibians and reptiles from the Neogene locality of Maramena (Greece), the most diverse European herpetofauna at the Miocene/Pliocene transition boundary

“…As such, the two distinct scolecophidian clades that currently inhabit the northeastern Mediterranean, i.e., Typhlopidae (genera Letheobia Cope, 1869, andXerotyphlops Hedges, Marion, Lipp, Marin, andVidal, 2014), and Leptotyphlopidae (genus Myriop-holis Hedges, Adalsteinsson, and Branch in Adalsteinsson et al, 2009) cannot be reliably identified in the European fossil record. This is rather frustrating, given that typhlopids and leptotyphlopids are believed to have diverged from each other during the Mesozoic (Adalsteinsson et al, 2009;Miralles et al, 2018). Taking into consideration all these aspects, it is currently impossible to determine whether the new Maramena scolecophidians pertain to any of these genera or even represent a now locally or totally extinct lineage.…”

The bizarre skull of Xenotyphlops sheds light on synapomorphies of Typhlopoidea

“…The infraorder Scolecophidia sensu lato (see Miralles et al. ; Fig. ) consists of five families: Typhlopidae, Gerrhopilidae, Xenotyphlopidae (together constituting the superfamily Typhlopoidea), Anomalepididae, and Leptotyphlopidae (Vidal et al.…”

“…; Zheng & Wiens, ; Harrington & Reeder, ; Streicher & Wiens, ; Miralles et al. ). The question of scolecophidian monophyly is therefore putatively resolved (Miralles et al.…”

“…The question of scolecophidian monophyly is therefore putatively resolved (Miralles et al. ), but the morphology of scolecophidian lineages must be reconciled in light of phylogenetic evidence.…”

“…Although the relationships of the deep branches in the snake tree have not yet reached a point where they might be called ‘robust’, recent advances have promising support (Miralles et al. ).…”