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.

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.

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.

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.

Phylogeny, diversity and biogeography of Neotropical sipo snakes (Serpentes: Colubrinae: Chironius).

Neotropical sipo snakes (Chironius) are large diurnal snakes with a long tail and big eyes that differ from other Neotropical snakes in having 10 or 12 dorsal scale rows at midbody. The 22 currently recognized species occur from Central America south to Uruguay and northeastern Argentina. Based on the largest geographical sampling to date including ∼90% of all species, we analyzed one nuclear and three mitochondrial genes using phylogenetic methods to (1) test the monophyly of Chironius and some of its widely distributed species; (2) identify lineages that could represent undescribed species; and (3) reconstruct ancestral distributions. Our best hypothesis placed C. grandisquamis (Chocoan Rainforest) + C. challenger (Pantepui) as sister to all other species. Based on phylogeny and geographic distribution, we identified 14 subclades as putative species within Chironius fuscus, C. multiventris (including C. foveatus and C. laurenti), C. monticola, and C. exoletus. Under current taxonomy, these species show nearly twice as much genetic diversity as other species of Chironius for ND4. Biogeographical analyses using BioGeoBEARS suggest that current distribution patterns of Chironius species across South America resulted from multiple range expansions. The MRCA of the clade C. challenger + C. grandisquamis was most likely distributed over the Pantepui region, the Andes, and the Chocoan Rainforest, whereas the remaining lineages probably evolved from an Amazonian ancestor.

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

Abstract 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.

New records of the rare Troschel's Pampas Snake, Phimophis guianensis (Serpentes: Dipsadidae) in Brazil.

The Troschel's Pampas Snake, Phimophis guianensis (Troschel, 1848), is widely distributed in Amazonian Savannas at northern South America and a small portion of southern Central America, being recorded to Brazil based on three historical records, that ranged from 1997 to 2002, in Amapá and Pará states. In this study, we revise all known records of P. guianensis, providing an updated distribution map, and the first record to Roraima state.

A case of envenomation by neotropical Opisthoglyphous snake Thamnodynastes pallidus (Linnaeus, 1758) (Colubridae: Dipsadinae: Tachymenini) in Brazil.

This is a case report of a bite by an Opisthoglyphous snake Thamnodynastes pallidus (Linnaeus, 1758) in an undergraduate herpetologist observed at the Universidade Federal da Paraiba (Rio Tinto, PB, Brazil). The female victim was bitten in her left hand between the index finger and the middle finger and presented symptoms of local envenomation such as bleeding, itching, pain in the wound and swelling. The patient was first seen at the University and afterwards at home during the 36 hours following the incident, when the symptoms disappeared. This is the first case report of an accident by T. pallidus in a human being in Brazil.

The Biogeography of Deep Time Phylogenetic Reticulation.

Most phylogenies are typically represented as purely bifurcating. However, as genomic data have become more common in phylogenetic studies, it is not unusual to find reticulation among terminal lineages or among internal nodes (deep time reticulation; DTR). In these situations, gene flow must have happened in the same or adjacent geographic areas for these DTRs to have occurred and therefore biogeographic reconstruction should provide similar area estimates for parental nodes, provided extinction or dispersal has not eroded these patterns. We examine the phylogeny of the widely distributed New World kingsnakes (Lampropeltis), determine if DTR is present in this group, and estimate the ancestral area for reticulation. Importantly, we develop a new method that uses coalescent simulations in a machine learning framework to show conclusively that this phylogeny is best represented as reticulating at deeper time. Using joint probabilities of ancestral area reconstructions on the bifurcating parental lineages from the reticulating node, we show that this reticulation likely occurred in northwestern Mexico/southwestern US, and subsequently, led to the diversification of the Mexican kingsnakes. This region has been previously identified as an area important for understanding speciation and secondary contact with gene flow in snakes and other squamates. This research shows that phylogenetic reticulation is common, even in well-studied groups, and that the geographic scope of ancient hybridization is recoverable.

A new species of burrowing snake (Serpentes: Dipsadidae: Apostolepis ) from the state of Mato Grosso, Central-West region of Brazil

During a faunal rescue conducted at a hydroelectric power station constructed in a Cerrado savanna area in the state of Mato Grosso, a sample of five small stripe-patterned individuals of snakes of the genus Apostolepis Cope, 1862 document the existence of an undescribed species, which is named herein. The new species can be distinguished from its congeners by a combination of scale counts, number of maxillary teeth and color pattern. The new species is most similar to Apostolepis borellii Peracca, 1904, A. lineata Cope, 1887, A. nelsonjorgei Lema & Renner, 2004, A. nigroterminata Boulenger, 1896, A. serrana Lema & Renner, 2006 and A. underwoodi Lema & Campbell, 2017 in its coloration pattern. However, it is distinguished from these species by having a pair of triangular blotches covering portions of the third to sixth supralabials, a white nuchal collar, the shape of the fourth supralabial and the shape of the tip of tail, the number of supralabials in contact with parietals, the size of the anterior chinshields, the color pattern of the paraventral side, parietal and terminal scales, the width of dorsal stripes, and a distinct number of subcaudals. The new species occurs in areas within the Cerrado biome.(AU)

A new species of burrowing snake (Serpentes: Dipsadidae: Apostolepis ) from the state of Mato Grosso, Central-West region of Brazil

During a faunal rescue conducted at a hydroelectric power station constructed in a Cerrado savanna area in the state of Mato Grosso, a sample of five small stripe-patterned individuals of snakes of the genus Apostolepis Cope, 1862 document the existence of an undescribed species, which is named herein. The new species can be distinguished from its congeners by a combination of scale counts, number of maxillary teeth and color pattern. The new species is most similar to Apostolepis borellii Peracca, 1904, A. lineata Cope, 1887, A. nelsonjorgei Lema & Renner, 2004, A. nigroterminata Boulenger, 1896, A. serrana Lema & Renner, 2006 and A. underwoodi Lema & Campbell, 2017 in its coloration pattern. However, it is distinguished from these species by having a pair of triangular blotches covering portions of the third to sixth supralabials, a white nuchal collar, the shape of the fourth supralabial and the shape of the tip of tail, the number of supralabials in contact with parietals, the size of the anterior chinshields, the color pattern of the paraventral side, parietal and terminal scales, the width of dorsal stripes, and a distinct number of subcaudals. The new species occurs in areas within the Cerrado biome.

Evolutionary analysis of Chironius snakes unveils cryptic diversity and provides clues to diversification in the Neotropics.

Recent hypotheses to explain tropical diversity involves the Neogene and Quaternary geoclimatic dynamics, but the absence of unambiguous data permitting the choice between alternative hypotheses makes a general theory for the origin of tropical biodiversity far to be achieved. The occurrence of Chironius snakes in well-defined biogeographical regions led us to adopt Chironius as a model to unveil patterns of vertebrate diversification in the Neotropics. Here, we used molecular markers and records on geographic distribution to investigate Chironius evolution and, subsequently, providing hints on diversification in the Neotropics. To avoid analyzing nominal species that do not constitute exclusive evolutionary lineages, we firstly conducted a species delimitation study prior to carrying out the species distribution modeling analysis. We generated 161 sequences of 12S, 16S, c-mos and rag2 for 15 species and 50 specimens, and included additional data from GenBank yielding a matrix of 137 terminals, and performed the following evolutionary analyses: inference of a concatenated gene tree, estimation of gene divergence times, inference of the coalescent-based phylogeny of Chironius, estimation of effective population sizes and modeling potential distribution of species across the last millennia. We tested for species boundaries within Chironius by implementing a coalescent-based Bayesian species delimitation approach. Our analyses supported the monophyly of Chironius, although our findings underscored cryptic candidate species in C. flavolineatus and C. exoletus. The inferred timetree suggested that Chironius snakes have evolved in the early Miocene (ca. 20.2Mya) and began to diversify from the late Miocene to the early Pliocene, values that are much older than previously reported. Following genetic divergence of virtually all extant Chironius species investigated, the effective sizes of the populations have expanded when compared to their MRCAs. The evolutionary and SDM data from C. brazili and C. diamantina provided additional evidence of the origin of species in the Neotropics. We argue that temperature, instead of altitude, has been the major driving factor in the evolution of both species, and thus we present a case for the consequences of global warming.

Geographical features are the predominant driver of molecular diversification in widely distributed North American whipsnakes.

Allopatric divergence following the formation of geographical features has been implicated as a major driver of evolutionary diversification. Widespread species complexes provide opportunities to examine allopatric divergence across varying degrees of isolation in both time and space. In North America, several geographical features may play such a role in diversification, including the Mississippi River, Pecos River, Rocky Mountains, Cochise Filter Barrier, Gulf of California and Isthmus of Tehuantepec. We used thousands of nuclear single nucleotide polymorphisms (SNPs) and mitochondrial DNA from several species of whipsnakes (genera Masticophis and Coluber) distributed across North and Central America to investigate the role that these geographical features have played on lineage divergence. We hypothesize that these features restrict gene flow and separate whipsnakes into diagnosable genomic clusters. We performed genomic clustering and phylogenetic reconstructions at the species and population levels using Bayesian and likelihood analyses and quantified migration levels across geographical features to assess the degree of genetic isolation due to allopatry. Our analyses suggest that (i) major genetic divisions are often consistent with isolation by geographical features, (ii) migration rates between clusters are asymmetrical across major geographical features, and (iii) areas that receive proportionally more migrants possess higher levels of genetic diversity. Collectively, our findings suggest that multiple features of the North American landscape contributed to allopatric divergence in this widely distributed snake group.

A new species of Rhadinella (Serpentes: Colubridae) from the Sierra Madre del Sur of Guerrero, Mexico.

We describe a new species of Rhadinella from the Sierra Madre del Sur of Guerrero, Mexico, a region where the genus was previously unknown. This diminutive species is a member of a group of snakes previously allocated in the Rhadinaea godmani group, and more recently transferred to the genus Rhadinella. These snakes may have conspicuous dark longitudinal striping on a pale brown to orange background or may have dark brown to blackish dorsal ground coloration, which mostly or completely obfuscates a pattern of longitudinal striping. The new species is mostly dark with barely discernible slightly paler or darker striping (depending on how striping is interpreted). The closest relative of the new species, on the basis of morphological similarities and biogeography, appears to be Rhadinella donaji which occurs to the east in the Sierra Madre del Sur of Oaxaca about 275 km from the type-locality of the new species.

Molecular phylogeny of Caribbean dipsadid (Xenodontinae: Alsophiini) snakes, including identification of the first record from the Cay Sal Bank, The Bahamas.

We document the first specimen of a dipsadid snake from the Anguilla Cays, Cay Sal Bank, The Bahamas. We analyze 3,426 base pairs (bp) of sequence data derived from five mitochondrial loci and one nuclear locus using Maximum Likelihood (ML) and Bayesian Inference (BI) methods. Our molecular data agree with some aspects of morphology (e.g., scale counts, dentition, and color pattern) supporting identification of this specimen as the Cuban Racer, Cubophis cantherigerus cantherigerus (Bibron 1840), a species previously regarded as endemic to Cuba. This discovery provides another example of the strong Cuban affinities of the terrestrial vertebrate fauna of Bahamian islands.

A new species of Imantodes Duméril, 1853 (Serpentes, Dipsadidae) from the Eastern Cordillera of Colombia.

We describe a new species of Imantodes, morphologically similar to I. chocoensis, from the Eastern Cordillera of Colombia. This new species is distinguished from all congeners by the following combination of morphological characters: smooth dorsal scale rows 17/17/15; apical pits absent; infralabials 12-13; ventrals 227-236; subcaudals 147-148; presence of loreal scale; cloacal plate divided; dark temporal stripe on the suture between the lower edge of temporal scales and upper region of supralabials; dorsum of body light brown with dark brown transversal streaks, weakly evident in lateral view; hemipenis in situ extending to the level of 11th subcaudal and reaches the 10th subcaudal when everted; hemipenis with sulcus spermaticus expanded at the base of capitulum and extending distally. Additionally, we discuss the lateral expansion of the sulcus spermaticus in the new species, similar to that of species of Leptodeira.

A new species of Rhadinella (Serpentes: Colubridae) from the Pacific versant of Oaxaca, Mexico.

I describe a new species of Rhadinella from the Pacific versant of Oaxaca, Mexico, a region where the genus was previously unknown. This diminutive snake is a member of a group of snakes that have dark dorsal coloration, which mostly or completely obfuscates a pattern of longitudinal striping characteristic of most species of Rhadinella. The closest relative of the new species, on the basis of morphological similarities, appears to be Rhadinella pilonaorum which occurs to the east of the Isthmus of Tehuantepec about 800 km from the type-locality of the new species.

A new species of Chironius Fitzinger, 1826 from the state of Bahia, Northeastern Brazil (Serpentes: Colubridae).

We describe a new species of Chironius Fitzinger, 1826 from the highlands of Chapada Diamantina, state of Bahia, Brazil. The new species is distinguished from all currently recognized congeners by a unique combination of states of characters on coloration, scale counts, scale ornamentation, and hemipenis. The new species closely resembles Chironius flavolineatus (Jan, 1863) in color pattern, but differs from the later taxon by the presence of two to four posterior temporal scales; cloacal shield entire; six to ten rows of keeled dorsal scales at midbody; ventral scales with posterior dark edges forming conspicuous transverse bars along almost the entire venter; conspicuous dark longitudinal stripes (in "zigzag") in the midventral portion of subcaudals; region of medial constriction of hemipenis slightly covered with spinules separating calyces of apex from spines below region of constriction; and sulcus spermaticus situated on convex face of hemipenis in lateral view. The new species is apparently restricted to Chapada Diamantina, corroborating the biological importance of this region from a conservational perspective.

Morphological variation and taxonomy of Atractus latifrons (Günther, 1868) (Serpentes: Dipsadidae).

As currently understood Atractus latifrons is widely distributed in South America, occurring from Suriname to the east of the Andes in Bolivia. Throughout this widespread distribution, at least three distinct color patterns were previously reported in the literature. Here, we test whether quantitative variation and qualitative distribution of morphological characters are correlated with any color pattern displayed by the species along its range. We recognize three aposematic color patterns (bicolor in monads, tricolor in dyads, and tricolor in tetrads) for A. latifrons. We found no obvious correspondence between these patterns and any character systems analyzed herein. Additionally, we redescribe the holotype of A. latifrons and report on morphological variability (meristics, morphometrics, color patterns, and hemipenis) and geographical distribution (extending its distribution to the state Roraima, Brazil) of the species.