Amerotyphlops brongersmianus (Vanzolini, 1976) (Typhlopidae, Serpentes) as a model for scolecophidian ontogenetic shifts of heart topography and relative size

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.

Section: Commentarymentioning

confidence: 99%

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

Bell

Daza

Stanley³

et al. 2021

“…Thirty-four species of Scolecophidia occur in Brazil (Costa et al, 2022), of which six are allocated in the genus Amerotyphlops (Typhlopidae) as proposed by Hedges et al (2014). The type species, Amerotyphlops brongersmianus (Vanzolini, 1976), has brownish, yellow-brownish, or red-brownish color (Dixon & Hendricks, 1979), 20 scales around the body (Hedges et al, 2014), and inhabits different biomes in Brazil (Wallach et al, 2014), including Restinga areas (Martins et al, 2010). Restinga areas are part of the Atlantic Rainforest, and are known to have herbaceous/shrubby coastal sand-dune habitats that cover most of Rio de Janeiro State coast (Myers et al, 2000;Rocha et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Reproductive maturity and sexual dimorphism of a population of Amerotyphlops brongersmianus from a Restinga area in southeastern Brazil (Serpentes: Typhlopidae)

Khouri

Almeida‐Santos

Fernandes

2023

Natural history data are important for a better understanding of distinct aspects of snake biology, and this information in scarce on Scolecophidia. Here we focus on sexual maturity and sexual dimorphism within a population of Amerotyphlops brongersmianus from the Restinga de Jurubatiba National Park, Rio de Janeiro state, Brazil. The smallest sexually active male and female showed snout‐vent length of 117.5 and 158.4 mm, respectively. Females had statistically significant larger body and head length sizes, whereas males had longer tails. Juveniles showed no sexual dimorphism for any analyzed feature. Secondary vitellogenic follicles had a more opaque, yellowish/darker aspect, being larger than 3.5 mm. We reinforce that in addition to traditional features for determining sexual maturity, morphological and histological characteristics of kidneys should be evaluated in males, as well as the morphology of the infundibulum in females. Histological data show development of seminiferous tubules and presence of spermatozoa in males, and infundibulum receptacles and uterine glands in females as a sign of sexual maturity. This type of information is essential for a more accurate description of data on sexual maturity, allowing access to information on the development of reproductive structures that are not available macroscopically.

“…The genus Amerotyphlops currently comprises 15 recognized species that occur through Central America, in the Lesser Antilles, and South America, having A. brongersmianus as its type species. Even though the last 10 years have witnessed an increase in morphological contributions for the genus since the works of Thomas (1976) (e.g., Graboski et al, 2018;Martins, Silva, & Gonzalez, 2020), detailed descriptive studies of the skull, lower jaw and cervical morphology are still absent for any of the Amerotyphlops currently recognized, including its type species. Osteological data-in particular skull morphology-has proven to be relevant in terms of scolecophidian systematics and also their morphofunctional evolution (e.g., Cundall & Irish, 2008;Koch, Martins, & Schweiger, 2019;Martins et al, 2019, Deolindo et al, this volume, Martins et al, this volume).…”

Section: Introductionmentioning

confidence: 99%

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

Lira

Martins

2021

Self Cite

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.