Digging into blindsnakes' morphology: Description of the skull, lower jaw, and cervical vertebrae of two Amerotyphlops (Hedges et al., 2014) (Serpentes, Typhlopidae) with comments on the typhlopoidean skull morphological diversity

Abstract

Scolecophidians are small fossorial snakes that exhibit several osteological innovations, most of which driven by their extreme body miniaturization. Considering that data on skull morphology has proven to be relevant in terms of scolecophidian systematics and morphofunctional evolution, herein, we aim to describe in detail the skull, lower jaw, and cervical vertebrae of Amerotyphlops brongersmianus and A. reticulatus. Our results suggest that the investigated osteology of Amerotyphlops resembles several new world typhlopid species, with reduced interspecific variation in the basicranium, lower jaw and cervical vertebrae. Both species exhibit characters states that are typically conserved intragenerically amongst typhlopoids, such as the presence of a single parietal, paired supraoccipitals, and otooccipitals that are in contact medially, and the basioccipital participating in the formation of the foramen magnum. We discuss possible systematically important osteological skull variations among typhlopoids and provide a comprehensive comparison of these taxa based on literature and data gathered herein.

Underground Down Under: Skull anatomy of the southern blind snake Anilios australis Gray, 1845 (Typhlopidae: Serpentes: Squamata)

“…The number of foramina in the plate is asymmetrical and variable between the two specimens, but this plate exhibits more than 10 foramina. This type of fenestration has not been reported in any previous detailed description of blindsnake cranial anatomy, including Liotyphlops (Rieppel et al, 2009), Typhlops (Thomas, 1976), and Xenotyphlops (Chretien et al, 2019), but see (Deolindo et al, 2021;Lira & Martins, 2021). The septomaxilla has a tall medial vertical flange (Figure 15e, f,k,l).…”

“…Narrow snouts are common among members of Leptotyphlopidae and some anomalepids (e.g., Koch, Martins, & Schweiger, 2019;Martins et al, 2019;Pinto & Fernandes, 2012;Santos, 2018;Santos & Reis, 2019), and to some degree in A. kunuaensis. The snout of Anilios australis is very similar to A. bicolor (Palci et al, 2016) and A. ligatus (Lee & Scanlon, 2002) in having a bulbous appearance, but is less expanded than the snout of Ramphotyphlops lineatus, R. flaviventer, and Sundatyphlops polygrammicus (List, 1966- The roofing bones across "Scolecophidia" show a high degree of variation in fusion patterns (Figure 1; Lira & Martins, 2021). Combinations of fused elements are generally more frequently observed in Anomalepididae and Leptotyphlopidae, while among Typhlopidae (e.g., List, 1966;Cundall & Irish, 2008;Palci et al, 2016;also Deolindo et al, 2021;Lira & Martins, 2021;Torki, 2017) and Xenotyphlopidae (Chretien et al, 2019) fusion is less frequent.…”

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

“…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). For instance, several studies (e.g., Koch et al 2019Koch et al , 2021Martins et al 2019a) have taken advantage of µCT data to overcome the challenges imposed by the overall highly conserved external morphology of scolecophidians, demonstrating the informativeness of skull and lower jaw characters for systematic studies .…”