A phantom on the trees: Integrative taxonomy supports a reappraisal of rear-fanged snakes classification (Dipsadidae: Philodryadini)

Heads and Tails: Comparative Osteology of Nearctic Dipsadid Snakes

Although numerous studies have addressed some aspects of the cranial osteology of Nearctic dipsadid species, only the species within the genera Heterodon and Carphophis have a formal published description of their skull. Similarly, vertebral data on such species are extremely scarce, and most of the available literature is focused on fossils. Such group has a complex phylogenetic history, being recovered as monophyletic or nonmonophyletic depending on the approach. In this paper, we provide detailed and comparative descriptions of the osteology of dipsadid species distributed in the Nearctic region based on 69 specimens of dry material and high-resolution computed tomography (CT) scans. Additionally, we explore the morphological variation of the skull and cervical vertebrae within the context of distinct phylogenetic hypotheses previously proposed. Only two suprageneric groups previously proposed shared exclusive morphological traits: (Carphophis amoenus + Contia tenuis), proposed by three studies, and (Diadophis punctatus (Ca. amoenus + Co. tenuis)), proposed by one study. Large and detailed studies on the skull, mandible, and vertebrae represent an important step toward the understanding of the evolution of species, especially when they also show intraspecific variation.

Metazoan endoparasites of snakes from Argentina: Review and checklist with distributional notes and remarks

This article presents a checklist of metazoan parasites of snakes from Argentina, along with a comprehensive review of the relevant literature published between 1922 and June 2023, covering various aspects of interest. We compiled 34 species of metazoan endoparasites from 28 studies. The subclass Digenea showed the highest number of species (n = 22 species), followed by the phylum Nematoda (n = 8 species), and the subclass Pentastomida (n = 3 species and 1 taxa inquirenda). Dipsadidae was the family of snakes with the most species examined for metazoan endoparasites (n = 20 species). In contrast, Viperidae had the largest number of specimens surveyed (n = 343). Of 23 provinces, 15 (65.2%) presented at least one report of metazoan endoparasites in snakes. The northeastern provinces showed the highest richness of metazoan endoparasites and host diversity. Many articles focused on taxonomy, but studies on parasite ecology were not found. Although taxonomic accuracy was high in most reports, some records were correctly deposited in zoological collections or geo-referenced. This is the first attempt to include all groups of metazoan endoparasites of snakes from Argentina in a single checklist in the last century.

Paedomorphosis and retention of juvenile diet lead speciation in a group of Neotropical snakes (Colubroides-Philodryadini)

Dipsadidae is one of the largest clades of extant reptiles, showing an impressive morphological and ecological diversity. Despite this fact, the developmental processes behind its diversity are still largely unknown. In this study, we used 3D reconstructions based on micro-CT data and geometric morphometrics to evaluate the skull morphology of Philodryas agassizii, a small, surface-dwelling dipsadid that consume spiders. Adult individuals of P. agassizii exhibit a cranial morphology frequently observed in juveniles of other surface-dwelling colubroideans, represented in our analysis by its close relative Philodryas patagoniensis. Large orbits, gibbous neurocranial roof and a relatively short jaw complex are features present in juveniles of the latter species. Furthermore, we performed an extensive survey about diet of P. patagoniensis in which we detected an ontogenetic dietary shift, indicating that arthropods are more frequently consumed by juveniles of this dietary generalist. Thus, we infer that P. agassizzii retained not only the ancestral juvenile skull morphology but also dietary preferences. This study reveals that morphological changes driven by heterochronic changes, specifically paedomorphosis, influenced the retention of ancestral life history traits in P. agassizii, and therefore promoted cladogenesis. In this way, we obtained first evidence that heterochronic processes lead speciation in the snake megadiverse clade Dipsadidae.

An annotated list of the reptiles of the highland grassland of Tandilia Mountains, Argentina

The study of biodiversity is a fundamental step to develop conservation strategies. Reptile populations are immersed in a global crisis, due to anthropic disturbances. Almost the entire Pampa ecoregion in Argentina was modified for agricultural and livestock activities, the only remnants of mountain native grasslands in Buenos Aires province being the Tandilia and Ventania mountain systems. Ventania reptiles have been exhaustively researched in last years, while Tandilia counts with fewer studies. We presented an actualized reptiles list of the Tandilia Mountain System. We used five data sources to collect presence records: literature, fieldwork, museum collection, citizen science, and a online database. The composition of reptiles from the Tandilia Mountain range includes 26 species in 12 families. Due to the presence of several endemic reptiles, and the representativeness of more than half of the reptiles of Pampa Ecoregion, Tandilia would be useful to determine conservation priority areas to conserve the native grassland and their reptile fauna.