Taxonomic status of the enigmatic Natrix sexcarinata Wagler, 1824 (Serpentes: Colubridae: Colubrinae).

Wagler described Natrix sexcarinata through a specimen collected on the banks of the Amazon River in Brazil, without citing a specific location. The species was later transferred to different Neotropical genera (Chironius, Herpetodryas, Phrynonax, and Pseustes) currently allocated in the Family Colubridae. The taxonomic instability of Natrix sexcarinata is probably due to its brief original description in combination with its supposedly inaccurate illustration. Despite the holotype being lost during World War II, some authors have pointed out that its description is somewhat similar to the widespread concept of Pseustes poecilonotus. More recently, a molecular study proposed the synonymy of the genera Pseustes with Spilotes, resurrecting the Phrynonax genus to allocate Ph. poecilonotus and Ph. polylepis. However, the taxonomic positioning of Natrix sexcarinata remains unsatisfactory with respect to the cis-Andean taxa placed in Phrynonax or even Spilotes throughout the Amazon. Considering the taxonomic and nomenclatural problems mentioned above, we investigated how many Phrynonax species occur along the Amazon Basin and what would be their applicable name. We examined the external morphology (meristic, morphometric, and color pattern data) of 118 Phrynonax specimens and prepared the hemipenes of seven specimens to understand geographic, sexual, and ontogenetic variability parameters. Our result suggests the synonymy of Ph. polylepis and N. sexcarinata under the combination Phrynonax sexcarinatus. Based on available evidence, we reinforce that Phrynonax sexcarinatus is the only congener that occurs along the Amazon Basin. We have also designated a Natrix sexcarinata neotype to stabilize its complex nomenclature.

Cryptic diversity and phylogeography of the Rhabdophis nuchalis group (Squamata: Colubridae).

Previous studies, have found that the rapid uplift of the Tibetan plateau accelerated the diversification of species. However, there are few relevant biogeographic data for the Colubridae in this region. We conducted a comprehensive study of the Rhabdophis nuchalis Group, which presently contains four nominal species, R. nuchalis, R. pentasupralabialis, R. leonardi, and R. chiwen. Building upon previous studies with specimens we have recently examined, greater interspecific and intraspecific diversity has been revealed. Here we address three questions: (1) Do the intraspecific differences represent only geographic variation within lineages, or are there cryptic species? (2) What are the interspecific relationships among members of the R. nuchalis Group? (3) What has been the biogeographic history of this species group? To resolve these questions we used four mitochondrial gene sequences and one nuclear sequence to investigate the molecular phylogenetic and geographic relationships among populations. Our molecular analysis reveals cryptic species diversity within the R. nuchalis Group, and seven clades were identified in the analysis. Ancestral area estimation suggests that the R. nuchalis Group originated in the Hengduan Mountains approximately 6.24 Mya and expanded its range northward to the Qinling-Daba Mountains. The Sichuan Basin appears to have been a barrier to migration. Species divergence seems to have been related to the rapid uplift of the Qinghai-Tibet Plateau.

A new snake species of the genus Gonyosoma Wagler, 1828 (Serpentes: Colubridae) from Hainan Island, China.

A new species of the genus Gonyosoma Wagler, 1828 is described herein based on six specimens from the Diaoluoshan Mountains, Hainan Island, Hainan Province, China. The new species, Gonyosoma hainanensesp. nov., is most similar to its continental sister species, Gonyosoma boulengeri (Mocquard, 1897). Both taxa have a scaled protrusion on the anterior portion of the rostrum, distinct from other congeners. However, Gonyosoma hainanensesp. nov. can be distinguished from G. boulengeri by two significant morphological characters: (1) black orbital stripe absent in adults (vs. present in G. boulengeri); and (2) two loreals (vs. one loreal in G. boulengeri). The new species is also genetically divergent and forms a unique clade from its sister species and all other congeners based on sequences of the mitochondrial gene cytochrome b (cyt b).

Systematic status of the rare Himalayan wolf snake Lycodon mackinnoni Wall, 1906 (Serpentes: Colubridae).

Lycodon mackinnoni is a poorly known Himalayan endemic snake known from Western Himalaya. Since the original description of L. mackinnoni almost 112 years ago, this species was not reported from its type locality and its phylogenetic position remain unknown. We herein, provide detail morphological description, comparison with type material, phylogenetic relationship with its congeners and new natural history information.

A new species of Ahaetulla Link, 1807 (Squamata: Colubridae) from the Mekong Delta, Vietnam.

A new vine snake, genus Ahaetulla, from Soc Trang Province, southern Vietnam is described based on morphological data and nucleotide sequences from COI and Cytb. Ahaetulla rufusoculara sp. nov. is diagnosed by the following morphological characters: bright red eyes; snout without dermal appendage; internasal separated from supralabial by loreal; body scale rows 15-15-13; ventrals 186190 in males and 182185 in females; subcaudals 143153 in males and 128 or 129 in females; 8 (rarely 9) supralabials, fourth and fifth or fourth to sixth entering orbit; 1214 maxillary teeth; hemipenis short, reaching 6th or 7th SC; cloacal plate divided; dorsum bright green; and yellow or white stripe along the lower flank. The new species differs from its congeners by an uncorrected p-distance in COI and Cytb sequences of at least 7.7% and 7.5%, respectively.

A new species of Boiga (Serpentes: Colubridae) from the Southern Western Ghats of India with a molecular phylogeny and expanded characterisation of related species.

We conducted a molecular phylogenetic study on the Boiga ceylonensis group from the Western Ghats of India, building on a recent morphology-based study. Our analysis supports previous work in elucidating the phylogenetic position of B. nuchalis and B. beddomei s. str. (of Matheran, Western Ghats) as clustering closely with B. ceylonensis, while B. flaviviridis clustered with the Sri Lankan taxon close to B. ranawanei. Additionally, our phylogenetic study revealed the presence of an undescribed taxon in the Southern Western Ghats, more closely related to B. ceylonensis than to any other sampled taxon, including sympatric congeners. This new taxon is described here as a new species Boiga whitakeri sp. nov. from the Devar MalaiAnaimalai hill complex. Based on molecular and morphometric studies, we expand the description of the recently described B. thackerayi as inhabiting almost the entire stretch of the Western Ghats. We also complement the diagnoses of B. nuchalis and B. flaviviridis, and determine the phylogenetic position of B. thackerayi with molecular data.

Night stalkers from above: A monograph of Toxicodryas/ tree snakes (Squamata: Colubridae) with descriptions of two new cryptic species from Central Africa.

The genus Toxicodryas, historically included with the renowned Australasian cat-eyed snakes of the colubrid genus Boiga, currently includes two widespread species (T. blandingii and T. pulverulenta) in western, central, and eastern Africa. We leverage findings from a recent phylogenomic and historical demographic analysis of this genus (based on 2848-4471 Rad-seq loci from across the genome), with robust sampling from throughout the ranges of both species, to define two additional taxonomic units, with species boundaries corresponding to river barriers. Additional morphometric data from scores of examined museum specimens and literature records bolster the recognition of these two new cryptic species. We hypothesize that T. blandingii occurs west of the confluence of the Congo and Ubangi rivers, whereas a cryptic new species that is found east of this biogeographic barrier has significantly higher numbers of ventral scale counts in both sexes, additional significant differences in several scale counts, and lower venom toxicity. Toxicodryas pulverulenta occurs west of the Niger Delta in West Africa, whereas a cryptic new species that is found east of this biogeographic barrier has significantly higher numbers of subcaudal scale counts in both sexes. A review of published information regarding morphological variation, ecology, natural history, habitat, and venom is summarized for these four Toxicodryas species.

The mitogenome of Ophidascaris wangi isolated from snakes in China.

Different species of the genus Ophidascaris (Baylis, 1921; Nematoda: Ascaridida, Ascaridoidea) are intestinal parasites of various snake species. More than 30 Ophidascaris species have been reported worldwide; however, few molecular genetic studies have been conducted on this genus. We sequenced the complete mitogenome of Ophidascaris wangi parasitizing two snake species of the family Colubridae, i.e., Elaphe carinata (Günther, 1864) and Dinodon rufozonatum. The mitogenome sequence of O. wangi was approximately 14,660 base pairs (bp) long and encoded 36 genes, including 12 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, and 22 transfer RNA genes. Gene arrangement, genome content, and transcription direction were in line with those in Toxascaris leonina (Linstow, 1902; Ascaridida: Ascarididae). Phylogenetics of O. wangi and other ascaridoids were reconstructed based on the concatenated amino acid sequences of 12 PCGs, and on nucleotide sequences of 12 PCGs and two rRNA genes. Phylogenetic analyses were performed using maximum likelihood and Bayesian inference methods, and the results suggested that O. wangi constitutes a sister clade of Ascaris, Parascaris, Baylisascaris, and Toxascaris within the family Ascarididae, which is a sister clade of Toxocaridae. The mitogenome sequence of O. wangi obtained from the present study will be useful for future identification of the nematode worms in the genus Ophidascaris and will increase the understanding of population genetics, molecular epidemiology, and phylogenetics of ascaridoid nematodes in snakes.

A revision of the dark-bellied, stream-dwelling snakes of the genus Hebius (Reptilia: Squamata: Natricidae) with the description of a new species from China, Vietnam and Thailand.

Species of the genus Hebius Thompson, 1913 with 17 or 19 dorsal scale rows at midbody and an overall dark venter are reviewed, including the two species previously known as Parahelicops annamensis Bourret, 1934 and Pararhabdophis chapaensis Bourret, 1934. Specimens with 17 scale rows are morphologically similar to Hebius venningi (Wall, 1910), which is here redefined based on external morphological characters such as scalation, and dorsal and ventral patterns. Consequently, Natrix nigriventer Wall, 1925 is resurrected from its synonymy with Hebius venningi, whereas Natrix taronensis Smith, 1940, previously considered a subspecies of H. venningi or a full species by some authors but without justification, is here confirmed to full species status. Another group of species, mostly similar in coloration and pattern to the H. venningi group but with 19 dorsal scale rows, includes H. modestus (Günther, 1875), H. deschauenseei (Taylor, 1934) and a new species which is described herein based on specimens from northern Vietnam, southern China and north-eastern Thailand due to distinct morphological differences. We also provide updated taxonomic accounts for the species of this group, including an identification key and distribution maps.

Phylogenetics of mud snakes (Squamata: Serpentes: Homalopsidae): A paradox of both undescribed diversity and taxonomic inflation.

Mud snakes (Serpentes: Homalopsidae) are a family of 55 described, mainly aquatic, species primarily distributed throughout mainland Southeast Asia and the Indo-Australian Archipelago. Although they have been the focus of prior research, the basic relationships amongst genera and species remain poorly known. We used a combined mitochondrial and nuclear gene dataset to infer their phylogenetic relationships, using the highest levels of taxon and geographic sampling for any homalopsid phylogeny to date (62% generic and 62% species coverage; 140 individuals). Our results recover two reciprocally monophyletic groups: the fangless Brachyorrhos and its sister clade comprised of all rear-fanged homalopsids. Most genera and interspecific relationships were monophyletic and strongly supported, but intergeneric relationships and intraspecific population structure lack support. We find evidence of both undescribed diversity as well as cases of taxonomic inflation within several species. Tree-based species delimitation approaches (mPTP) support potential new candidate species as distinct from their conspecifics and also suggest that many named taxa may not be distinct species. Divergence date estimation and lineage-through-time analyses indicate lower levels of speciation in the Eocene, with a subsequent burst in diversification in the Miocene. Homalopsids may have diversified most rapidly during the Pliocene and Pleistocene, possibly in relation to tectonic shifts and sea-level fluctuations that took place in Sundaland and the Sahul Shelf. Our analyses provide new insights on homalopsid taxonomy, a baseline phylogeny for the family, and further biogeographic implications demonstrating how dynamic tectonics and Quaternary sea level changes may have shaped a widespread, diverse family of snakes.

Contribution to the taxonomy of the genus Lycodon H. Boie in Fitzinger, 1827 (Reptilia: Squamata: Colubridae) in China, with description of two new species and resurrection and elevation of Dinodon septentrionale chapaense Angel, Bourret, 1933.

While considerable progress has been made in the taxonomic studies of the genus Lycodon in Asia, questions remain to be clarified regarding the taxonomy of certain groups, particularly those containing species in China. Not only do many regions in China remain overlooked by herpetologists, resulting in the possibility of undiscovered new species, but the surveyed areas also have suspicious records of recognized congeners that require taxonomic confirmations. Combining both morphological and genetic data, we tackle these outstanding issues in the taxonomy of Lycodon in China. In particular, we discover two new species of Lycodon: one from the previously neglected hot-dry valley in the northern Hengduan Mountain Region close to Tibet, and another recluse and cryptic species from the L. fasciatus complex in the downtown park of a major city in southern Sichuan Province. Additionally, we clarify the distribution of L. septentrionalis in China and resurrect and elevate its junior synonym subspecies, Dinodon septentrionale chapaense, as a full, valid species, and we synonymize the recently described L. namdongensis to the resurrected L. chapaensis comb. nov.. Lycodon chapaensis comb. nov. thus represents a new national record of reptilian fauna of China. Lastly, based on literature review, we also correct some of the erroneous records of L. fasciatus and L. ruhstrati in China, point out remaining taxonomic issues of the genus for future research, and update the dichotomous key and distribution of the 20 species of Lycodon currently recorded from China.

Taxonomic revision of the genus Xenopholis Peters, 1869 (Serpentes: Dipsadidae): Integrating morphology with ecological niche.

A reliable identification and delimitation of species is an essential pre-requisite for many fields of science and conservation. The Neotropical herpetofauna is the world's most diverse, including many taxa of uncertain or debated taxonomy. Here we tackle one such species complex, by evaluating the taxonomic status of species currently allocated in the snake genus Xenopholis (X. scalaris, X. undulatus, and X. werdingorum). We base our conclusions on concordance between quantitative (meristic and morphometric) and qualitative (color pattern, hemipenes and skull features) analyses of morphological characters, in combination with ecological niche modeling. We recognize all three taxa as valid species and improve their respective diagnosis, including new data on color in life, pholidosis, bony morphology, and male genitalia. We find low overlap among the niches of each species, corroborating the independent source of phenotypic evidence. Even though all three species occur in the leaf litter of distinct forested habitats, Xenopholis undulatus is found in the elevated areas of the Brazilian Shield (Caatinga, Cerrado and Chaco), whereas X. scalaris occurs in the Amazon and Atlantic rainforests, and X. werdingorum in the Chiquitanos forest and Pantanal wetlands. We discuss the disjunct distribution between Amazonian and Atlantic Forest snake species in the light of available natural history and ecological aspects. This study shows the advantages of combining multiple data sources for reliable identification and circumscription of ecologically similar species.

Out of the Hengduan Mountains: Molecular phylogeny and historical biogeography of the Asian water snake genus Trimerodytes (Squamata: Colubridae).

The Asian water snake genus Trimerodytes (formerly Sinonatrix) is endemic to East and Southeast Asia. Although several species have been included in various phylogenetic studies previously, the evolution and relationships among members of this genus as a whole remain unexplored. In this study, we report the sequencing two protein-coding mitochondrial gene fragments (MTCYB and ND2) and three nuclear genes (c-mos, NT3, and Rag1), reconstruct interspecific phylogeny, and explore biogeography for the genus Trimerodytes. Both Bayesian inference and maximum likelihood analyses consistently recover the monophyly of Trimerodytes with strong support, with T. yapingi the sister-group to the remaining species. The divergence date and ancestral area estimation suggest that Trimerodytes likely originated in Hengduan Mountains (eastern Tibetan Plateau) in western China at 23.93 Ma (95% HPD: 17.09-31.30), and intraspecific divergence began at about 4.23 Ma (95% HPD: 2.74-6.10). Analyses support the validity of T. yunnanensis.

Philodryas (Serpentes: Dipsadidae) Envenomation, a Neglected Issue in Chile.

Snakebite envenomation is considered a neglected tropical disease, although it also occurs outside the tropics. In this work, we analyzed the literature on Philodryas species in Chile (Philodryaschamissonis, P.simonsii, and P.tachymenoides) from 1834 to 2019, searching for epidemiological, clinical, and molecular aspects of envenomation. Ninety-one percent of the studies found regarded taxonomy, ecology, and natural history, suggesting that snakebites and venom toxins are a neglected issue in Chile. All snakebite cases reported and toxicological studies concerned the species Philodryaschamissonis. Using 185 distributional records from the literature and museum collections for this species, we show for the first time that the reported snakebite cases correlate with human population density, occurring in the Valparaiso and Metropolitan regions in Central Chile. The reduced number of snakebite cases, which were previously considered as having a low incidence in Chile, may be a consequence of under-reported cases, probably due to the inadequate publication or scarce research on this issue. Absence of information about official pharmacological treatment, post-envenoming sequels, clinical management of particular patient groups (e.g., with non-communicable diseases, pregnant women, and the elderly) was also detected. In conclusion, despite having over 185 years of literature on Chilean snakes, knowledge on the envenomation of Philodryas genus remains scarce, seriously affecting adequate medical handling during an ophidic accident. This review highlights the need to develop deep research in this area and urgent improvements to the management of this disease in Chile.

Discovery of a deeply divergent new lineage of vine snake (Colubridae: Ahaetuliinae: Proahaetulla gen. nov.) from the southern Western Ghats of Peninsular India with a revised key for Ahaetuliinae.

The Western Ghats are well known as a biodiversity hotspot, but the full extent of its snake diversity is yet to be uncovered. Here, we describe a new genus and species of vine snake Proahaetulla antiqua gen. et sp. nov., from the Agasthyamalai hills in the southern Western Ghats. It was found to be a member of the Ahaetuliinae clade, which currently comprises the arboreal snake genera Ahaetulla, Dryophiops, Dendrelaphis and Chrysopelea, distributed in South and Southeast Asia. Proahaetulla shows a sister relationship with all currently known taxa belonging to the genus Ahaetulla, and shares ancestry with Dryophiops. In addition to its phylogenetic position and significant genetic divergence, this new taxon is also different in morphology from members of Ahaetuliinae in a combination of characters, having 12-13 partially serrated keels on the dorsal scale rows, 20 maxillary teeth and 3 postocular scales. Divergence dating reveals that the new genus is ancient, dating back to the Mid-Oligocene, and is one of the oldest persisting monotypic lineages of snakes in the Western Ghats. This discovery adds to the growing list of ancient lineages endemic to the Agasthyamalai hills and underscores the biogeographic significance of this isolated massif in the southern Western Ghats.

Morphology-based intraspecific taxonomy of Oreocryptophis porphyraceus (Cantor, 1839) in mainland China (Serpentes: Colubridae).

In this study, a total of 106 individuals of Oreocryptophis porphyraceus from mainland China were morphologically examined and recorded. Differences between populations were compared by combining data from this study and other published research. The skulls of three specimens representing three proposed subspecies (i.e., O. p. pulchra, O. p. vaillanti, and O. p. hainana) were examined by computed tomography (CT) scanning. Both external morphological characters and skull comparisons consistently showed significant differences between the studied populations. Based on these data, we suggest that at least four subspecies of O. porphyraceus should be recognized in mainland China: i.e., O. p. porphyraceus, O. p. pulchra, O. p. vaillanti, and O. p. hainana. However, the taxonomical arrangement of the central Chinese populations with intermediate morphology remain unresolved.

A case of envenomation caused by Oxybelis fulgidus (Serpentes, Colubridae) in Brazilian Amazon.

A case of a bite inflicted by Oxybelis fulgidus in the wilds of Amazon is reported. The patient was a 67-year-old man who presented with dizziness, tachycardia and local pain, with erythema and bleeding in his left arm. The venom of Oxybelis fulgidus, a neotropical rear-fanged snake, contains one of the four three-finger toxins already isolated from colubrid snakes, called fulgimotoxin. He was treated with oral analgesics and returned to the ambulatory in 48 hours, with good evolution. We report tirst authenticated case of adult Oxybelis fulgidus with signs of mild local envenoming without evidence of systemic envenoming.

Hiding in the lianas of the tree of life: Molecular phylogenetics and species delimitation reveal considerable cryptic diversity of New World Vine Snakes.

The Brown Vine Snake, Oxybelis aeneus, is considered a single species despite the fact its distribution covers an estimated 10% of the Earth's land surface, inhabiting a variety of ecosystems throughout North, Central, and South America and is distributed across numerous biogeographic barriers. Here we assemble a multilocus molecular dataset (i.e. cyt b, ND4, cmos, PRLR) derived from Middle American populations to examine for the first time the evolutionary history of Oxybelis and test for evidence of cryptic lineages using Bayesian and maximum likelihood criteria. Our divergence time estimates suggest that Oxybelis diverged from its sister genus, Leptophis, approximately 20.5 million years ago (Ma) during the lower-Miocene. Additionally, our phylogenetic and species delimitation results suggest O. aeneus is likely a complex of species showing relatively deep species-level divergences initiated during the Pliocene. Finally, ancestral area reconstructions suggest a Central American origin and subsequent expansion into North and South America.

Ancient diversification, biogeography, and the role of climatic niche evolution in the Old World cat snakes (Colubridae, Telescopus).

The process of species diversification is often associated with niche shifts in the newly arising lineages so that interspecific competition is minimized. However, an opposing force known as niche conservatism causes that related species tend to resemble each other in their niche requirements. Due to the inherent multidimensionality of niche space, some niche components may be subject to divergent evolution while others remain conserved in the process of speciation. One such possible component is the species' climatic niche. Here, we test the role of climatic niche evolution on the diversification of the Old World cat snakes of the genus Telescopus. These slender, nocturnal snakes are distributed in arid and semiarid areas throughout Africa, southwest Asia and adjoining parts of Europe. Because phylogenetic relationships among the Telescopus species are virtually unknown, we generated sequence data for eight genetic markers from ten of the 14 described species and reconstructed a time-calibrated phylogeny of the genus. Phylogenetic analysesindicate that the genus is of considerably old origin that dates back to the Eocene/Oligocene boundary. Biogeographical analyses place the ancestor of the genus in Africa, where it diversified into the species observed today and from where it colonized Arabia and the Levant twice independently. The colonization of Arabia occurred in the Miocene, that of the Levant either in the Late Oligocene or Early Miocene. We then identified temperature and precipitation niche space and breadth of the species included in the phylogeny and examined whether there is phylogenetic signal in these climatic niche characteristics. Despite the vast range of the genus and its complex biogeographic history, most Telescopus species have similar environmental requirements with preference for arid to semiarid conditions. One may thus expect that the genus' climatic niche will be conserved. However, our results suggest that most of the climatic niche axes examined show no phylogenetic signal, being indicative of no evolutionary constraints on the climatic niche position and niche breadth in Telescopus. The only two variables with positive phylogenetic signal (temperature niche position and precipitation niche breadth) evolved under the Brownian motion model, also indicating no directional selection on these traits. As a result, climatic niche evolution does not seem to be the major driver for the diversification in Telescopus.

Exploring Chihuahuan Desert diversification in the gray-banded kingsnake, Lampropeltis alterna (Serpentes: Colubridae).

Within many biomes, the cause of phylogeographic structure remains unknown even across regions throughout North America, including within the biodiverse Chihuahuan Desert. For example, little is known about population structure or the timing of diversification of Chihuahuan endemics. This is due largely to the lack of population genomic studies within this region. We generated ultra-conserved element data for the gray-banded kingsnake (Lampropeltis alterna) to investigate lineage divergence and historical demography across the Chihuahuan Desert. We found three unique lineages corresponding to the Trans-Pecos and Mapimian biogeographic regions of the Chihuahuan Desert, and a distinct population in the Sierra Madre Occidental. Using several mutation rates to calibrate the timing of divergence among these lineages, we show that lineage divergence likely occurred during the Pleistocene, which indicates that careful consideration needs to be used when applying mutation rates to ultra-conserved elements. We suggest that biogeographic provinces within the Chihuahuan Desert may have served as allopatric refugia during climatic fluctuations of the Quaternary. This work serves as an important template for further testing biogeographic hypotheses within the region.