Unveiling the elusive: X‐rays bring scolecophidian snakes out of the dark

Abstract

Scolecophidian snakes have long posed challenges for scholars interested in elucidating their anatomy. The importance, and relative paucity, of highquality anatomical data pertaining to scolecophidians was brought into sharp focus in the late 20 th century as part of a controversy over the phylogeny and ecological origin of snakes. The basal position of scolecophidians in the phylogeny of snakes makes their anatomy, behavior, ecology, and evolution especially important for such considerations. The depauperate fossil record for the group meant that advances in understanding their evolutionary history were necessarily tied to biogeographic distributions and anatomical interpretations of extant taxa. Osteological data, especially data pertaining to the skull and mandible, assumed a dominant role in shaping historical and modern perspectives of the evolution of scolecophidians. Traditional approaches to the exploration of the anatomy of these snakes relied heavily upon serial-sectioned specimens and cleared-and-stained specimens. The application of X-ray computed tomography (CT) to the study of scolecophidians revolutionized our understanding of the osteology of the group, and now, via diffusible iodinebased contrast-enhanced computed tomography (diceCT), is yielding data sets on internal soft anatomical features as well. CT data sets replicate many aspects of traditional anatomical preparations, are readily shared with a global community of scholars, and now are available for unique holotype and other rare specimens. The increasing prevalence and relevance of CT data sets is a strong incentive for the establishment and maintenance of permanent repositories for digital data.

Variation in the cranial osteology of the amphisbaenian genus Zygaspis based on high‐resolution x‐ray computed tomography

“…X‐ray computed tomography is now well‐established as an excellent mechanism for studying cranial osteology of squamates, especially of smaller species. The technology replicates in many important ways the techniques used in the past for studying cranial morphology (Bell et al, 2021), and because it is nondestructive, efforts can be focused on specimens that do have relevant data on ontogenetic age, sex, and geographic location. This allows morphologists the ability to avoid many of the pitfalls associated with poor data quality in many collections of squamate skeletons preserved in museums (Bell & Mead, 2014).…”

An evolutionary paradox on threadsnakes: Phenotypic and molecular evidence reveal a new and remarkably polymorphic species of Siagonodon (Serpentes: Leptotyphlopidae: Epictinae) from Amazonia

“…The fossorial snakes known as 'Scolecophidia' Cope, 1864 are divided in three major lineages-Anomalepididae Taylor, 1939, Leptotyphlopidae Stejneger, 1892, and Typhlopoidea Romer, 1945-altogether comprising about 460 species that occur throughout the globe, except for Antarctica (Vidal et al 2010;Miralles et al 2018;Uetz et al 2022). These snakes have long posed challenges for researchers interested in elucidating their taxonomy, systematics, and consequently biogeography and evolution (Bell et al 2021). However, recent contributions-most of them boosted by the use of high resolution digital images (Rieppel et al 2009;Reis 2018, 2019;Koch et al 2019;Martins et al 2019a;Koch et al 2021;Lira and Martins 2021;Deolindo et al 2021;Martins et al 2021aMartins et al , 2021b-have repeatedly highlighted morphological data (mostly osteological) as fundamental for elucidating longstanding unresolved or disputed issues in the literature (see Miralles et al 2018).…”