Figure 1
Phylogenetic context and methodological overview. (a) Traditional and (b) recent phylogenies of Squamata, derived from Rieppel9 and Zheng and Wiens135, respectively. Major differences include the paraphyly of ‘Scolecophidia’ and polyphyly of ‘Anilioidea’ and ‘Macrostomata’ in molecular phylogenies (b), as opposed to their respective monophyly under traditional, morphology-based views of snake evolution (a). The phylogeny in (b) also provides phylogenetic context for the specimens examined herein (see also Supplementary Table S1); note, however, that our analysis also examined four other anomalepidids—Anomalepis mexicanus, Helminthophis praeocularis, Liotyphlops argaleus, and L. beui—that are not included in (b) because equivalent taxa were not sampled in the source phylogeny135. (c) Overview of network modelling during anatomical network analysis (AnNA), showing how this method conceptualizes an anatomical system (in this case, the skull) as a set of interconnected ‘nodes’ (in this case, skull bones). First, the skeletal anatomy is coded into an adjacency matrix, in which scores of ‘1’ versus ‘0’ reflect the presence versus absence of a connection between two given bones; this allows the skull to be treated purely in terms of the topological relations among its constituent elements. This network is then analyzed via a clustering algorithm and partitioned into modules (see “Methods” section), each of which comprises a group of skull bones that interconnect more thoroughly among each other than they do with other such groups. Colours in (a–b) indicate corresponding higher taxa, and in (c) indicate corresponding modules. Anoma. Anomalepididae. Phylogeny in (b) and network in (c) generated in R [v.4.0.3]122 and RStudio [v.1.3.1093]123; specimen visualized in Dragonfly [v.4.1]114. MCZ scan data used by permission of the Museum of Comparative Zoology, Harvard University.
