Molecular phylogeny of the New World Dipsadidae (Serpentes: Colubroidea): a reappraisal

Highly conserved and extremely variable: The paradoxical pattern of toxin expression revealed by comparative venom-gland transcriptomics of Phalotris (Serpentes: Dipsadidae)

Although non-front fanged snakes account for almost two-thirds of snake diversity, most studies on venom composition and evolution focus exclusively on front-fanged species, which comprise most of the clinically relevant accidents. Comprehensive reports on venom composition of non-front fanged snakes are still scarce for several groups. In this study, we address such shortage of knowledge by providing new insights about the venom composition among species of Phalotris, a poorly studied Neotropical dipsadid genus. Phalotris are known for their specialized venom delivery system and toxic venoms, which can cause life-threatening accidents in humans. We evaluate the venom-gland transcriptome of Phalotris, comparing the following three South American species: P. reticulatus for the Araucaria Pine forests, P. lemniscatus for the Pampa grasslands, and P. mertensi for the Brazilian Cerrado. Our results indicate similar venom profiles, in which they share a high expression level of Kunitz-type inhibitors (KUNZ). On the other hand, comparative analyses revealed substantial differences in the expression levels of C-type lectins (CTL) and snake venom metalloproteinases (SVMP). The diverse set of SVMP and CTL isoforms shows signals of positive selection, and we also identified truncated forms of type III SVMPs, which resemble type II and type I SVMPs of viperids. Additionally, we identified a CNP precursor hosting a proline-rich region containing a BPP motif resembling those commonly detected in viperid venoms with hypotensive activity. Altogether, our results suggest an evolutionary history favoring high expression levels of few KUNZ isoforms in Phalotris venoms, contrasting with a highly diverse set of SVMP and CTL isoforms. Such diversity can be comparable with the venom variability observed in some viperids. Our findings highlight the extreme phenotypic diversity of non-front fanged snakes and the importance to allocate greater effort to study neglected groups of Colubroidea.

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.

The Venom Composition of the Snake Tribe Philodryadini: 'Omic' Techniques Reveal Intergeneric Variability among South American Racers

Snakes of the Philodryadini tribe are included in the Dipsadidae family, which is a diverse group of rear-fanged snakes widespread in different ecological conditions, including habitats and diet. However, little is known about the composition and effects of their venoms despite their relevance for understanding the evolution of these snakes or even their impact on the occasional cases of human envenoming. In this study, we integrated venom gland transcriptomics, venom proteomics and functional assays to characterize the venoms from eight species of the Philodryadini tribe, which includes the genus Philodryas, Chlorosoma and Xenoxybelis. The most abundant components identified in the venoms were snake venom metalloproteinases (SVMPs), cysteine-rich secretory proteins (CRISPs), C-type lectins (CTLs), snake endogenous matrix metalloproteinases type 9 (seMMP-9) and snake venom serinoproteinases (SVSPs). These protein families showed a variable expression profile in each genus. SVMPs were the most abundant components in Philodryas, while seMMP-9 and CRISPs were the most expressed in Chlorosoma and Xenoxybelis, respectively. Lineage-specific differences in venom composition were also observed among Philodryas species, whereas P. olfersii presented the highest amount of SVSPs and P. agassizii was the only species to express significant amounts of 3FTx. The variability observed in venom composition was confirmed by the venom functional assays. Philodryas species presented the highest SVMP activity, whereas Chlorosoma species showed higher levels of gelatin activity, which may correlate to the seMMP-9 enzymes. The variability observed in the composition of these venoms may be related to the tribe phylogeny and influenced by their diets. In the presented study, we expanded the set of venomics studies of the Philodryadini tribe, which paves new roads for further studies on the evolution and ecology of Dipsadidae snakes.

A new species of Dipsas (Serpentes, Dipsadidae) from central Panama

A new species of Dipsas Laurenti, 1768, from Central Panama is described based on molecular analyses, hemipenial morphology, and external characters. This is the sixth species of Dipsas to be described for the country; the snake has been suspected to exist since 1977 and has not been thoroughly studied until now. Additionally, morphological comparations including scale counts are done with other species within the genus, and the current geographic distribution of Dipsas temporalis (Werner, 1909), the sister species, is updated. Finally, a key to the species of Dipsas currently known from Middle America is presented.

Revealing the cryptic diversity of the widespread and poorly known South American blind snake genus Amerotyphlops (Typhlopidae: Scolecophidia) through integrative taxonomy

Morphological stasis is generally associated with relative constancy in ecological pressures throughout time, producing strong stabilizing selection that retains similar shared morphology. Although climate and vegetation are commonly the main key factors driving diversity and phenotypic diversification in terrestrial vertebrates, fossorial organisms have their morphology mostly defined by their fossorial lifestyle. Among these secretive fossorial organisms, blind snakes of the South American genus Amerotyphlops are considered poorly studied when compared to other taxa. Here, we evaluate the cryptic diversity of Amerotyphlops using phylogenetic and multivariate approaches. We based our phylogenetic analysis on a molecular dataset composed of 12 gene fragments (eight nuclear and four mitochondrial) for 109 species of Typhlopidae. The multivariate analysis was implemented using 36 morphological variables for 377 specimens of Amerotyphlops. Additionally, we contrast our phylogenetic result with the morphological variation found in cranial, external and hemipenial traits. Our phylogenetic results recovered with strong support the following monophyletic groups within Amerotyphlops: (1) a clade formed by A. tasymicris and A. minuisquamus; (2) a clade composed of A. reticulatus; (3) a north-eastern Brazilian clade including A. yonenagae, A. arenensis, A. paucisquamus and A. amoipira; and (4) a clade composed of A. brongersmianus and a complex of cryptic species. Based on these results we describe four new species of Amerotyphlops from north-eastern and south-eastern Brazil, which can be distinguished from the morphologically similar species, A. brongersmianus and A. arenensis.

Increasing taxon sampling suggests a complete taxonomic rearrangement in Echinantherini (Serpentes: Dipsadidae)

Although the recent advances on the relationship of its major groups, the systematics of the rich fauna of Neotropical snakes is far from being a consensus. In this sense, derived groups presenting continental distributions have represented a main challenge. The taxonomy of the snake tribe Echinantherini is one of the most contentious among the diverse family known as Dipsadidae. The tribe is poorly sampled in phylogenetic studies, resulting in conflicting hypotheses of relationships among its taxa. Moreover, several rare and micro endemic species of Echinantherini have never been evaluated within a comprehensive phylogenetic framework. Here, we assess for the first time the phylogenetic position of the rare Echinanthera amoena within Echinantherini. We based our analyses on a comprehensive multilocus dataset including 14 of the 16 species described for the tribe. Our results support the monophyly of Echinantherini and strongly indicate E. amoena as a unique lineage, phylogenetically positioned apart from all other congeners. From the three current genera (Echinanthera, Taeniophallus, and Sordellina) our results indicate that Echinanthera and Taeniophallus are paraphyletic, since the T. affinis species group is positioned as sister to Echinanthera (except E. amoena) clustering apart from the clade formed by the T. brevirostris and T. occipitalis groups. We describe new genera for the T. affinis and T. occipitalis species groups and an additional monospecific genus for E. amoena. Although we did not evaluate the phylogenetic position of T. nebularis, we described a new genus and removed it from Echinantherini since its morphology strikingly departs from all species now included in the tribe. Finally, we redefine the genera Echinanthera and Taeniophallus and we provide comments about further directions to study the biogeography and the evolution of morphological traits in Echinantherini.

Leaving no stone unturned: three additional new species of Atractus ground snakes (Serpentes, Colubridae) from Ecuador discovered using a biogeographical approach

The genus Atractus includes 146 species of cryptozoic snakes occurring from Panama to northeastern Argentina. Here, a molecular phylogeny of this genus is presented, which encompasses 29% (= 42; six are included here for the first time) of the species currently recognized. Morphological and phylogenetic support is found for three new species of ground snakes, which are described here based on their unique combination of molecular, meristic, and color pattern characteristics. The name A.arangoi Prado, 1939 is revalidated for a Colombian snake species previously subsumed under A.major Boulenger, 1894 based on new material collected in Ecuador. Reidentifications are provided for Atractus voucher specimens and sequences deposited in GenBank. With these changes, the number of Atractus reported in Ecuador increases from 27 to 31 species. Finally, attention is given to the importance of using a biogeographical framework that includes molecular data and a comprehensive geographic sampling when proposing species limits in complex taxonomic groups.

Evolution of the rostral scale and mimicry in the genus Xenodon Boie, 1826 (Serpentes: Dipsadidae: Xenodontinae)

Snakes are a stimulating life form from an evolutionary perspective. Despite the basic morphological body shape (limbless, with a tubular body), these vertebrates are extremely diverse. The Neotropical region is one of the most diverse regions for snakes in the world, with >650 known species. Within this great diversity, the genus Xenodon includes 12 species with interesting adaptations to terrestrial and semi-fossorial habitats. Members of this genus are mostly diurnal and terrestrial, feed mainly on anurans and exhibit Batesian mimicry of venomous snakes of the genera Bothrops or Micrurus. Here, through phylogenetic analysis and ancestral state estimation, we explore the evolution of the rostral scale and mimicry within the genus Xenodon. Our results suggest that the ancestral lineage of Xenodon had a rounded rostral scale and exhibited Bothrops mimicry. The evolution of the rostral scale in Xenodon might be related to abiotic factors, as an adaptation for open and forested habitats, and mimicry is likely to be related to biotic factors, as a defensive strategy resembling those of venomous snakes.

The smallest area shaped a big problem: a revision of the placement of the Ventania sky island in the biogeography of South America

The placement of the southern border of the Neotropical region, called the Subtropical Line, is a long-lasting point of discussion. Its most debatable section runs around the Pampean province, where an isolated mountain system called Ventania has Andean connections surrounded by Neotropical biota. To answer where to place the Subtropical Line, a thorough revision of the biogeography of Ventania is needed. Thus, we characterized Ventania as an area of endemism and conducted a similitude analysis to compare it with surrounding systems using stenoic taxa. Then we compiled the disjunct distributions in Ventania and the phylogenetic information of its endemic taxa to know with which other areas it is related. We also compared the biogeographic differences with Tandilia, the nearest mountain system. We found that Ventania is a small but well-defined area of endemism mostly related to the Andean and South American Transition Zone (SATZ) provinces. Relatedness with the Pampean province is less than had been thought. We suggest that Ventania is a SATZ sky island province, and the smallest continental province of the world. The Subtropical Line should therefore be placed in the southern border of the Pampean province, with Ventania as a SATZ island inside the Neotropical region.

A new species of Phalotris (Serpentes, Colubridae, Elapomorphini) from Paraguay

A new species of Phalotris from the nasutus group, Phalotris shawnellasp. nov., is described. It can be distinguished from the other members of the group by having the following combination of characters: 1) fifth supralabial in contact with parietal, 2) vertebral stripe present, 3) yellowish nuchal collar (2 or 3 dorsal scales long), 4) dull reddish color of head, 5) broad, solidly or near solidly dark, lateral bands, 6) red-orange ventral scales lightly and irregularly spotted with black mainly on the posterior half of the body and 7) a bilobed, extremely asymmetrical hemipenis, with enlarged, curved, lateral spines. The species is only known from a recent specimen collected in the Cerrado zone of northeastern Paraguay at Rancho Laguna Blanca, San Pedro department, and two photographic records of live specimens from this and an additional locality. Limited ecological data based on observations of a captive individual, and a wild record, are provided, and a conservation assessment is performed for this extremely limited range Paraguayan endemic snake.

An integrative view of the toxic potential of Conophis lineatus (Dipsadidae: Xenodontinae), a medically relevant rear-fanged snake

Most traditional research on snake venoms has focused on front-fanged snake families (Viperidae, Elapidae, and Atractaspididae). However, venom is now generally accepted as being a much more broadly possessed trait within snakes, including species traditionally considered harmless. Unfortunately, due to historical inertia and methodological challenges, the toxin repertoires of non-front-fanged snake families (e.g., Colubridae, Dipsadidae, and Natricidae) have been heavily neglected despite the knowledge of numerous species capable of inflicting medically relevant envenomations. Integrating proteomic data for validation, we perform a de novo assembly and analysis of the Duvernoy's venom gland transcriptome of the Central American Road Guarder (Dipsadidae: Xenodontinae: Conophis lineatus), a species known for its potent bite. We identified 28 putative toxin transcripts from 13 toxin families in the Duvernoy's venom gland transcriptome, comprising 63.7% of total transcriptome expression. In addition to ubiquitous snake toxin families, we proteomically confirmed several atypical venom components. The most highly expressed toxins (55.6% of total toxin expression) were recently described snake venom matrix metalloproteases (svMMPs), with 48.0% of svMMP expression contributable to a novel svMMP isoform. We investigate the evolution of the new svMMP isoform in the context of rear-fanged snakes using phylogenetics. Finally, we examine the morphology of the venom apparatus using μCT and explore how the venom relates to autecology and the highly hemorrhagic effects seen in human envenomations. Importantly, we provide the most complete venom characterization of this medically relevant snake species to date, producing insights into the effects and evolution of its venom, and point to future research directions to better understand the venoms of 'harmless' non-front-fanged snakes.

Historical biogeography of the genus Rhadinaea (Squamata: Dipsadinae)

Multiple geological and climatic events have created geographical or ecological barriers associated with speciation events, playing a role in biological diversification in North and Central America. Here, we evaluate the influence of the Neogene and Quaternary geological events, as well as the climatic changes in the diversification of the colubrid snake genus Rhadinaea using molecular dating and ancestral area reconstruction. A multilocus sequence dataset was generated for 37 individuals of Rhadinaea from most of the biogeographical provinces where the genus is distributed, representing 19 of the 21 currently recognized species, and two undescribed species. Our analyses show that the majority of the Rhadinaea species nest in two main clades, herein identified as "Eastern" and "Southern". These clades probably diverged from each other in the early Miocene, and their divergence was followed by 11 divergences during the middle to late Miocene, three divergences during the Pliocene, and six divergences in the Pleistocene. The ancestral distribution of Rhadinaea was reconstructed across the Sierra Madre del Sur. Our phylogenetic analyses do not support the monophyly of Rhadinaea. The Miocene and Pliocene geomorphology, perhaps in conjunction with climate change, appears to have triggered the diversification of the genus, while the climatic changes during the Miocene probably induced the diversification of Rhadinaea in the Sierra Madre del Sur. Our analysis suggests that the uplifting of the Trans-Mexican Volcanic Belt and Chiapan-Guatemalan highlands in this same period resulted in northward and southward colonization events. This was followed by more recent, independent colonization events in the Pliocene and Pleistocene involving the Balsas Basin, Chihuahuan Desert, Pacific Coast, Sierra Madre Occidental, Sierra Madre Oriental, Sierra Madre del Sur, Trans-Mexican Volcanic Belt, and Veracruz provinces, probably driven by the climatic fluctuations of the time.

Amphibians and reptiles from the Parque Nacional da Tijuca, Brazil, one of the world’s largest urban forests

Abstract: The Parque Nacional da Tijuca in Rio de Janeiro, Brazil, is considered to be one of the world’s largest urban forests, however no systematic inventory of its herpetofauna is available. In the present study, we surveyed the amphibians and reptiles of this park to assess its species composition (including secondary data) and obtain estimates of species richness and abundance. We conducted active searches (460 hours) between January 2013 and December 2015. We identified the taxa endemic to either the Atlantic Forest or Rio de Janeiro state, and verified the conservation status of each species in the international, Brazilian, and state red lists. We also estimated the species richness and sampling sufficiency by rarefaction curves and Bootstrap richness estimator, and analyzed the distribution of the species abundance in Whittaker plots. We recorded 3,288 individuals over 36 months, representing 24 species of amphibians and 25 reptiles. The cumulative species curves, rarefaction, and the richness estimated indicated that sampling effort was adequate. Species abundance adjusted to the log-series model in both amphibians and reptiles. The four most abundant amphibians represented 70% of the individuals recorded in this group, while the two most abundant reptiles represented 60% of the total individuals. The inclusion of the secondary data raised the number of amphibian species to 38, and the number of reptiles to 36. Approximately 80% of the amphibian species and 28% of the reptile species recorded are endemic to the Atlantic Forest, and six of the amphibian species are endemic to Rio de Janeiro state. Six amphibian species and one reptile species are classified under some threat of extinction, and two reptile species were exotic. The considerable diversity of the herpetofauna of the Parque Nacional da Tijuca, which includes endemic and threatened species, reflects the effectiveness of the reforestation of this protected area and emphasizes the importance of its conservation.

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.

A morphological and molecular study of Hydrodynastes gigas (Serpentes, Dipsadidae), a widespread species from South America

BACKGROUND

Studies with integrative approaches (based on different lines of evidence) are fundamental for understanding the diversity of organisms. Different data sources can improve the understanding of the taxonomy and evolution of snakes. We used this integrative approach to verify the taxonomic status of Hydrodynastes gigas (Duméril, Bibron & Duméril, 1854), given its wide distribution throughout South America, including the validity of the recently described Hydrodynastes melanogigas Franco, Fernandes & Bentim, 2007.

METHODS

We performed a phylogenetic analysis of Bayesian Inference with mtDNA 16S and Cytb, and nuDNA Cmos and NT3 concatenated (1,902 bp). In addition, we performed traditional morphometric analyses, meristic, hemipenis morphology and coloration pattern of H. gigas and H. melanogigas.

RESULTS

According to molecular and morphological characters, H. gigas is widely distributed throughout South America. We found no evidence to support that H. gigas and H. melanogigas species are distinct lineages, therefore, H. melanogigas is a junior synonym of H. gigas. Thus, the melanic pattern of H. melanogigas is the result of a polymorphism of H. gigas. Melanic populations of H. gigas can be found in the Tocantins-Araguaia basin.

A new species of Oxyrhopus Wagler, 1830 (Serpentes: Dipsadidae) from the Bolivian Andes

We describe a new dipsadine snake species, of the genus Oxyrhopus Wagler, 1830, from the highlands of Bolivia. Oxyrhopus emberti sp. n. is diagnosed from its congeners based on external and hemipenial morphology. The new species inhabits the humid forests of Yungas and Tucumano-Bolivian Forest highlands, between 1.200 - 1.800 meters above sea level, and is likely to be a Bolivian endemic. We also discuss the relationships of the new species with Andean congeners and provide a key to the identification of the Oxyrhopus species from the Central Andes of Bolivia and Peru.

Hidden diversity in two widespread snake species (Serpentes: Xenodontini: Erythrolamprus) from South America

The spatial distribution of genetic diversity of widely distributed Neotropical tetrapods has been an active research field during the last decade, although it has focused on lowland (mostly Amazonian) taxa. In this paper we use phylogenetic analyses to explore the diversity within two widely distributed snake species, Erythrolamprus epinephelus and E. reginae. Specifically, we focus on Andean populations of the former and lowland samples of the latter. Our results show that Erythrolamprus epinephelus is paraphyletic and support recognition of the subspecies albiventris, fraseri and lamonae as distinct species. Regarding E. reginae, our results are in conflict with recent taxonomic proposals in that (1) E. reginae is paraphyletic, and (2) E. zweifeli from Trinidad and E. reginae from Amazonian Ecuador are not reciprocally monophyletic. Finally, we recommend caution when proposing taxonomic changes based on incomplete geographic and/or character sampling of widespread Neotropical taxa.

Species richness and composition of snake assemblages in poorly accessible areas in the Brazilian Amazonia

Abstract: Snakes are a diverse group of terrestrial vertebrates of the order Squamata. Despite that, in the Amazonian biome, information about distribution and identification of snakes is limited when compared to other groups. Additionally, in Amazonia there is a sampling bias towards areas geographically close to urban centers and more densely populated areas. This in turn leads to false distribution gaps in poorly accessible areas of Amazonia. In this article we report the composition of snake assemblages in six areas of the Brazilian Amazonia, based on field sampling conducted over four years using standardized methods. We sampled 70 species from eight families: Typhlopidae (n=1), Leptotyphlopidae (n=1), Anillidae (n=1), Boidae (n=5), Colubridae (n=15), Dipsadidae (n=35), Elapidae (n=7), and Viperidae (n=5). The largest number of species was recorded in the Trombetas River area and the lowest in the Jatapu River area. The total beta diversity was 0.40 and the snake assemblages were structured mainly by replacement (72.5%). The time-limited search was the method that recorded the greatest number of individuals in the studied areas (44.1%) and also the greatest number of species (n=40). However, some species were recorded only by other methods such as interception by pitfall traps with directional fences. Despite the large number of species sampled in the study, no particular area comprised more than 40% of species registered in all the areas, indicating that snakes are poorly detected even with large sampling effort across multiple areas of a species distribution.

Snakes in a seasonally dry tropical forest in northeastern Brazil

Abstract: This study aimed to provide information on composition, abundance, and estimated snakes richness in an area of arboreal Caatinga (seasonally dry tropical forest) and analyze patterns of faunistic similarity between assemblages of snakes in the semiarid region of northeastern Brazil. The snakes found within the Fazenda Almas Natural Private Reserve (RPPN Fazenda Almas) were sampled during a 10-year period, with monthly monitoring, employing time constrained search, pitfall traps with drift fences, and donations from local collectors. Twenty-two snake species were recorded, with a predominance of terrestrial species with diurnal-nocturnal activity patterns. The species accumulation curves reached its asymptote, indicating that all possible species in the study area had been recorded. Our results indicated that the snake fauna in the study area is similar to other snake assemblages in localities with Caatinga vegetation in the Sertaneja Depression (“Depressão Sertaneja”) drylands, and that those assemblages constitute faunistic units typical of the interior of northeastern Brazil.

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.

Observations on reproduction in captivity of the endemic long-tailed snake Philodryas chamissonis (Wiegmann, 1835) (Reptilia, Squamata, Dipsadidae) from Chile

The long-tailed snake Philodryas chamissonis is an oviparous rear-fanged species endemic to Chile, whose reproductive biology is currently based on anecdotic reports. The characteristics of the eggs, incubation time, and hatching are still unknown. This work describes for the first time the oviposition of 16 eggs by a female in captivity at Zoológico Nacional in Chile. After an incubation period of 59 days, seven neonates were born. We recorded data of biometry and ecdysis of these neonates for 9 months. In addition, a review about parameters of egg incubation and hatching for Philodryas species is provided.

Barcoding Analysis of Paraguayan Squamata

Paraguay is a key spot in the central region of South America where several ecoregions converge. Its fauna (and specifically its herpetofauna) is getting better studied than years before, but still there is a lack of information regarding molecular genetics, and barcoding analyses have proven to be an excellent tool in this matter. Here, we present results of a barcoding analysis based on 16S rRNA gene sequences, providing valuable data for the scientific community in the region. We based our fieldwork in several areas of Paraguay. We analyzed 249 samples (142 sequenced by us) with a final alignment of 615 bp length. We identified some taxonomic incongruences that can be addressed based on our results. Furthermore, we identify groups, where collecting efforts and research activities should be reinforced. Even though we have some blanks in the geographical coverage of our analysis—and there is still a lot to do towards a better understanding of the taxonomy of the Paraguayan herpetofauna—here, we present the largest genetic dataset for the mitochondrial DNA gene 16S of reptiles (particularly, Squamata) from Paraguay, which can be used to solve taxonomic problems in the region.

Distribution extension of Phimophis guerini (Serpentes: Dipsadidae: Xenodontinae) in the Brazilian Amazon

Phimophisguerini Duméril, Bibron & Duméril, 1854 is a Xenodontinae snake distributed in Argentina, Brazil and Paraguay. In Brazil, the species is broadly distributed, occurring mainly in open areas of the Cerrado, but also in the Amazon, Atlantic forest and Caatinga. We provide a new record for this species from the municipality of Santarém in the western portion of the state of Pará (Brazil). Five specimens were collected in a small area covered with Amazonian Savanna vegetation. We also provide the description of the morphological variation for the collected specimens. The new record extends the northern limit of the distribution by some 640 km (from Floresta Nacional de Carajás, Parauapebas municipality, eastern Pará). The record from Santarém provides a third locality for P.guerini within the Amazon biome and supports the hypothesis of a past ecological corridor linking the Cerrado and the open habitats within the Amazon.

Large-scale molecular phylogeny, morphology, divergence-time estimation, and the fossil record of advanced caenophidian snakes (Squamata: Serpentes)

Caenophidian snakes include the file snake genus Acrochordus and advanced colubroidean snakes that radiated mainly during the Neogene. Although caenophidian snakes are a well-supported clade, their inferred affinities, based either on molecular or morphological data, remain poorly known or controversial. Here, we provide an expanded molecular phylogenetic analysis of Caenophidia and use three non-parametric measures of support-Shimodaira-Hasegawa-Like test (SHL), Felsentein (FBP) and transfer (TBE) bootstrap measures-to evaluate the robustness of each clade in the molecular tree. That very different alternative support values are common suggests that results based on only one support value should be viewed with caution. Using a scheme to combine support values, we find 20.9% of the 1265 clades comprising the inferred caenophidian tree are unambiguously supported by both SHL and FBP values, while almost 37% are unsupported or ambiguously supported, revealing the substantial extent of phylogenetic problems within Caenophidia. Combined FBP/TBE support values show similar results, while SHL/TBE result in slightly higher combined values. We consider key morphological attributes of colubroidean cranial, vertebral and hemipenial anatomy and provide additional morphological evidence supporting the clades Colubroides, Colubriformes, and Endoglyptodonta. We review and revise the relevant caenophidian fossil record and provide a time-calibrated tree derived from our molecular data to discuss the main cladogenetic events that resulted in present-day patterns of caenophidian diversification. Our results suggest that all extant families of Colubroidea and Elapoidea composing the present-day endoglyptodont fauna originated rapidly within the early Oligocene-between approximately 33 and 28 Mya-following the major terrestrial faunal turnover known as the "Grande Coupure" and associated with the overall climate shift at the Eocene-Oligocene boundary. Our results further suggest that the caenophidian radiation originated within the Caenozoic, with the divergence between Colubroides and Acrochordidae occurring in the early Eocene, at ~ 56 Mya.

Reproductive aspects of the semi-aquatic snake Erythrolamprus miliaris (Dipsadidae: Xenodontini) in the state of Rio de Janeiro, southeastern Brazil

We analyzed some aspects of reproduction and sexual dimorphism of the semi-aquatic dipsadid snake Erythrolamprus miliaris in the state of Rio de Janeiro, southeastern Brazil. We detected sexual dimorphism in body size (snout-vent length), with females averaging larger than males, but no sexual dimorphism in the relative length of the tail. Oviductal eggs and secondary follicles were found in all seasons, suggesting that female reproductive cycles are continuous, in spite of the tropical seasonal climate in the region. Reproductive males were present throughout the year, suggesting a continuous cycle for males as well. Clutch size averaged 10.3 ± 4.8 (range 4-21) and there was a positive and significant relationship between clutch size and female size. Compared to conspecific populations previously studied in other Atlantic Rainforest areas, populations of E. miliaris from the state of Rio de Janeiro appear more similar overall in their reproductive traits to a more northern population from the state of Bahia than to populations from further south in the states of São Paulo and Paraná.

A new species of Erythrolamprus from the oceanic island of Tobago (Squamata, Dipsadidae)

Tobago is a small island on the southeast edge of the Caribbean Plate with a continental flora and fauna. Using DNA sequences from Genbank, new sequences, and morphological data from the snakes Erythrolamprusepinephalus, E.melanotus, E.reginae, and E.zweifeli, the species status of specimens of a Tobago snake previously considered to be Erythrolamprusreginae was assessed. Erythrolampruszweifeli, long considered a subspecies of E.reginae, was found to be a northern Venezuela-Trinidad endemic and the sister to E.reginae. The trans-Andean species E.epinephalus is shown to be non-monophyletic while the Costa Rican lineage of E.epinephalus is weakly supported as the sister to the Tobago population. The Tobago Erythrolamprus is described as a distinct taxon based upon five specimens from four localities in lower montane rainforest. Much of the new species range includes the Main Ridge Forest Reserve of Tobago, the oldest protected forest in the Western Hemisphere. All known locations fall within a 400-ha area, and its total geographic distribution is likely to be less than 4,566 ha. The restricted distribution of this new snake makes it a likely candidate for threatened status. The new species also becomes another biogeographic link between northern Venezuela and Tobago.

Composition and natural history of the snakes from the Parque Estadual da Serra do Papagaio, southern Minas Gerais, Serra da Mantiqueira, Brazil

The Serra da Mantiqueira is one of the least inventoried physiographic areas of southeastern Brazil. There is great potential for detection of endemic species for which little or nothing is known about basic aspects of natural history. The Parque Estadual da Serra do Papagaio (PESP) within the Serra da Mantiqueira is an area of extreme biological importance because it houses mixed formations of grasslands, ombrophilous forests, and enclaves of Araucaria forests (mixed ombrophilous forest). Currently, the mixed ombrophilous forest covers less than 5% of its original range and areas occupied by this forest type, and associated ecosystems constitute refuges, housing several endemic, high altitude species. Between September 2015 and April 2016, field samplings were performed in the PESP using four distinct methods. The objective was to determine the composition and natural history of snakes from an isolated, high altitude area of the Serra da Mantiqueira. In PESP and surrounding areas, 80 individuals representing 24 species, 19 genera, and three families were recorded. Data are presented on abundance, habitat, daily activity, diet, reproduction, and defense. Comparison of the PESP snake assemblage with 30 other Atlantic Forest areas in southeastern Brazil indicate the Serra da Mantiqueira presents particular characteristics regarding snake composition.

Biochemical characterization of venom from Pseudoboa neuwiedii (Neuwied's false boa; Xenodontinae; Pseudoboini)

In this work, we examined the proteolytic and phospholipase A₂ (PLA₂) activities of venom from the opisthoglyphous colubrid Pseudoboa neuwiedii. Proteolytic activity (3 and 10 μg of venom) was comparable to that of Bothrops neuwiedii venom but less than Bothrops atrox. This activity was inhibited by EDTA and 1,10-phenanthroline but only slightly affected (≤30% inhibition) by PMSF and AEBSF, indicating it was mediated by snake venom metalloproteinases (SVMPs). The pH and temperature optima for proteolytic activity were 8.0 and 37 °C, respectively. The venom had no esterase activity, whereas PLA₂ activity was similar to B. atrox, greater than B. neuwiedii but less than B. jararacussu. SDS-PAGE revealed venom proteins >100 kDa, 45-70 kDa, 21-24 kDa and ~15 kDa, and mass spectrometry of protein bands revealed SVMPs, cysteine-rich secretory proteins (CRISPs) and PLA₂, but no serine proteinases. In gelatin zymography, the most active bands occurred at 65-68 kDa (seen with 0.05-0.25 μg of venom). Caseinolytic activity occurred at 50-66 kDa and was generally weaker than gelatinolytic activity. RP-HPLC of venom yielded 15 peaks, five of which showed gelatinolytic activity; peak 7 was the most active and apparently contained a P-III class SVMP. The venom showed α-fibrinogenase activity, without affecting the β and γ chains; this activity was inhibited by EDTA and 1,10-phenanthroline. The venom did not clot rat citrated plasma but reduced the rate and extent of coagulation after plasma recalcification. In conclusion, P. neuwiedii venom is highly proteolytic and could potentially affect coagulation in vivo by degrading fibrinogen via SVMPs.

Systematics of South American snail-eating snakes (Serpentes, Dipsadini), with the description of five new species from Ecuador and Peru

A molecular phylogeny of the Neotropical snail-eating snakes (tribe Dipsadini) is presented including 43 (24 for the first time) of the 77 species, sampled for both nuclear and mitochondrial genes. Morphological and phylogenetic support was found for four new species of Dipsas and one of Sibon, which are described here based on their unique combination of molecular, meristic, and color pattern characteristics. Sibynomorphus is designated as a junior subjective synonym of Dipsas. Dipsas latifrontalis and D. palmeri are resurrected from the synonymy of D. peruana. Dipsas latifasciata is transferred from the synonymy of D. peruana to the synonymy of D. palmeri. A new name, D. jamespetersi, is erected for the taxon currently known as Sibynomorphus petersi. Re-descriptions of D. latifrontalis and D. peruana are presented, as well as the first photographic voucher of an adult specimen of D. latifrontalis, along with photographs of all known Ecuadorian Dipsadini species. The first country record of D. variegata in Ecuador is provided and D. oligozonata removed from the list of Peruvian herpetofauna. With these changes, the number of Dipsadini reported in Ecuador increases to 22, 18 species of Dipsas and four of Sibon.