Processes leading to spectacular diversity of both form and species on islands have been well-documented under island biogeography theory, where distance from source and island size are key factors determining immigration and extinction resistance. But far less understood are the processes governing in situ diversification on the world's mega islands, where large and isolated land masses produced morphologically distinct radiations from related taxa on continental regions. Madagascar has long been recognized as a natural laboratory due to its isolation, lack of influence from adjacent continents, and diversification of spectacular vertebrate radiations. However, only a handful of studies have examined rate shifts of in situ diversification for this island. Here, we examine rates of diversification in the Malagasy snakes of the family Pseudoxyrhophiinae (gemsnakes) to understand if rates of speciation were initially high, enhanced by diversification into distinct biomes, and associated with key dentition traits. Using a genomic sequence-capture data set for 366 samples, we determine that all previously described and newly discovered species are delimitable and therefore useful candidates for understanding diversification trajectories through time. Our analysis detected no shifts in diversification rate between clades or changes in biome or dentition type. Remarkably, we demonstrate that rates of diversification of the gemsnake radiation, which originated in Madagascar during the early Miocene, remained steady throughout the Neogene. However, we do detect a significant slowdown in diversification during the Pleistocene. We also comment on the apparent paradox where most living species originated in the Pleistocene, despite diversification rates being substantially higher during the earlier 15 myr.

The use of environmental DNA (eDNA) has become an applicable noninvasive tool with which to obtain information about biodiversity. A subdiscipline of eDNA is iDNA (invertebrate-derived DNA), where genetic material ingested by invertebrates is used to characterize the biodiversity of the species that served as hosts. While promising, these techniques are still in their infancy, as they have only been explored on limited numbers of samples from only a single or a few different locations. In this study, we investigate the suitability of iDNA extracted from more than 3,000 haematophagous terrestrial leeches as a tool for detecting a wide range of terrestrial vertebrates across five different geographical regions on three different continents. These regions cover almost the full geographical range of haematophagous terrestrial leeches, thus representing all parts of the world where this method might apply. We identify host taxa through metabarcoding coupled with high-throughput sequencing on Illumina and IonTorrent sequencing platforms to decrease economic costs and workload and thereby make the approach attractive for practitioners in conservation management. We identified hosts in four different taxonomic vertebrate classes: mammals, birds, reptiles and amphibians, belonging to at least 42 different taxonomic families. We find that vertebrate blood ingested by haematophagous terrestrial leeches throughout their distribution is a viable source of DNA with which to examine a wide range of vertebrates. Thus, this study provides encouraging support for the potential of haematophagous terrestrial leeches as a tool for detecting and monitoring terrestrial vertebrate biodiversity.

The diversity of Anuran parasites is poorly surveyed, despite arguably being one of the most important threats to anuran populations worldwide. Additionally, parasites also interact with a number of other stressors, such as invasive species, pollution, sedimentation and changing light conditions, caused by anthropogenic disturbance in natural habitats. We aimed to explore the use of metabarcoding, a new, non-invasive tool to survey the parasite assemblages in frogs in different environments facing different levels of anthropogenic pressure. We collected fecal samples from frogs across three different transects in Ranomafana National Park, located in southeastern Madagascar, and then used the 18S metabarcoding technique to identify nematode species from the collected fecal samples. We were able to find four different putative species, which were all identified to the genus level. In comparison to the literature on previous surveys done with traditional methods, the metabarcoding approach seems to provide similar diversity estimates and taxonomical accuracy. Our results suggest that non-invasive sampling and metabarcoding can provide a suitable tool for intestinal parasite surveys in anuran host populations.

Few observations on living specimens of the Malagasy snake Liopholidophis grandidieri Mocquard have been previously reported. New field observations and specimens from Ranomafana National Park amplify knowledge of the natural history of this species. Liopholidophis grandidieri is known from above 1200 m elevation in pristine rain forests with a high diversity of hardwoods and bamboo. In some areas of occurrence, the forests are of short stature (15-18 m) as a result of lying atop well-drained boulder fields with a thin soil layer. Dietary data show that this species consumes relatively small mantellid and microhylid frogs obtained on the ground or in phytotelms close to the ground. A female collected in late December contained four oviductal eggs with leathery shells. One specimen formed a rigid, loose set of coils and body loops, and hid the head as presumed defensive behaviors; otherwise, all individuals were complacent when handled and showed no tendency to bite. I describe coloration and present photographs of living specimens from Ranomafana National Park. The ventral colors of L. grandidieri were recently said to be aposematic, but I discuss other plausible alternatives.

Abstract We present the first modern comprehensive systematic treatment of the Central American snake Dendrophidion paucicarinatum (Cope). We redescribe the species on the basis of a large sample from throughout its range, redescribe and illustrate the holotype, and provide a detailed treatment of its hemipenial morphology. Dendrophidion paucicarinatum is distinguished from other species of the genus by a combination of having more ventrals (>175), fewer subcaudals (<140), very weak keels on the dorsal scales, and distinct transverse dark lines across each ventral in adults. It is an upland species found almost exclusively above 1,000 m in mountainous regions of Costa Rica and western Panama, primarily in premontane and montane humid to wet forests and cloud forests. It is a large species attaining a total length of 1.5 m and is diurnal and anurophagous like other species of Dendrophidion. Known clutch sizes are 3–12. Evidence from the Monteverde region in Costa Rica suggests that populations of D. paucicarinatum declined after collapse of the frog fauna due to epidemic disease (chytridiomycosis). The hemipenis of D. paucicarinatum is similar to those of most other species of Dendrophidion in having reduced calycular structures and a largely nude apex; the sulcus spermaticus is centrolineal and undivided. The spinose region is delimited distally by a uniform row of distinctly enlarged spines, which is a character shared with D. dendrophis (sensu lato) and three species of the D. nuchale species complex, although these species are not thought to be closely related to D. paucicarinatum. Key words: Costa Rica, Panama, systematics, Central America, Dendrophidion, snakes, hemipenis, morphology Resumen Presentamos el primer estudio sistemático moderno de la serpiente centroamericana Dendrophidion paucicarinatum (Cope). Describimos de nuevo la especie en base de muchos ejemplares desde toda la distribución, redescribimos y ilustratamos el holotipo, y proveemos una descripción detallada de la morfología del hemipene. Dendrophidion paucicarinatum es una especie de tierras altas encontrada casi exclusivamente arriba de 1,000 m de elevación en las regiones montañosas de Costa Rica y Panama occidental, primariamente en los bosques lluviosos premontanos y montanos y bosques nubosos. Es una especie grande que alcanza una larga total hasta 1.5 m. Es diurna y anurofaga como otras especies de Dendrophidion. El número de huevos por puesta es 3–12. Observaciones desde la región de Monteverde en Costa Rica sugeren que la declinación de las poblaciones de D. paucicarinatum resulta del desplome de la anurofauna debido a enfermedad epidémica (chitridiomicosis). El hemipene de D. paucicarinatum es similar a la mayoría de otras especies de Dendrophidion al tener estructuras calyculares reducidas y un ápice mayormente nudo; el sulco espermático es centrolineal y no bifurcado. La región espinosa se limita distalmente por una fila uniforme de espinas distintamente agrandadas. Este último se comparte con D. dendrophis (sensu lato) y tres especias del complejo D. nuchale, aunque estas especies no se piensen relacionadas cercanamente a D. paucicarinatum.

The holotype of Drymobius heathii Cope (now Mastigodryas heathii) has remained unrecognized since the species was described in 1876. A review of specimens and associated data in the Academy of Natural Sciences of Philadelphia shows that one specimen, ANSP 11544, is very likely the holotype of this species. The presumptive holotype is redescribed and the coloration in life and natural history and other data for this species from northern Peru are presented. Mastigodryas heathii occurs in lowland coastal desert scrub and dry deciduous forests of the Pacific slope and interandean valleys. Its diet includes frogs, lizards, and rodents.

Snakes previously referred to Dendrophidion vinitor from southern Mexico to eastern Panama comprise three sibling species primarily distinguishable by substantial differences in hemipenial morphology and some subtle aspects of color pattern. Dendrophidion vinitor Smith is here restricted to populations from southern Mexico to Belize. Dendrophidion apharocybe new species is distributed from Honduras to Panama, primarily on the Atlantic versant. Dendrophidion crybelum new species is known from middle elevations of the Río Coto Brus valley in southwestern Costa Rica (Pacific versant). Hemipenes of D. vinitor and D. apharocybe are similar in overall shape (short, bulbous) but the former has a highly ornate apex with membranous ridges and an unusual apical boss, whereas D. apharocybe has a largely nude apex strongly inclined toward the sulcate side. Dendrophidion crybelum has an elongate cylindrical hemipenis with a large number of spines. In general, these species are not distinguishable by standard scutellation characters. Hemipenial and other characters suggest that these species are a monophyletic group within Dendrophidion and have the following relationships: (vinitor (apharocybe, crybelum)). Some aspects of the systematics and biogeography of Dendrophidion are discussed. Divergence among the three species is associated with two geological features important to speciation in Middle America, the northern Motagua–Polochíc fault zone (Guatemala–Belize) and the southern Cordillera Talamanca (Costa Rica–Panama).

Dendrophidion percarinatum (Cope) is redefined on the basis of standard and new characters to distinguish it from two new South American species with which it has previously been confused. The redefined D. percarinatum is distributed from Honduras through Central America to western Colombia, with a seemingly outlying locality in extreme western Venezuela. One new species, D. prolixum, is sympatric with D. percarinatum at a few localities in central western Colombia and the distribution of the new species continues southward into northwestern Ecuador. A second new species, D. graciliverpa, occurs throughout western Ecuador, where its distribution extensively overlaps that of D. brunneum (Günther). Hemipenes of the two new species are unusually long and slender (gracile morphotype), a morphology distinct from other described Dendrophidion hemipenes, which are shorter and more robust (robust morphotype). Additionally, the new species differ from D. percarinatum in color patterns but not in standard scutellation characters such as segmental counts. Similarly, the two new species differ from one another in coloration but not in scutellation or hemipenial morphology. Hemipenes of D. percarinatum and the new species are described in detail. The holotype of D. brunneum is redescribed to ensure the proper application of that name. New specimens document the widespread occurrence of D. brunneum in the lowlands of western Ecuador and apparent extensive pattern polymorphism, including unicolor, striped, crossbanded, and punctate forms; more data on coloration in life are needed. Some previous records of “D. percarinatum” from interandean valleys of the Río Cauca/Magdalena system are from mistaken identities. However, several specimens from the Río Magdalena resemble D. percarinatum in scutellation but differ in color pattern; their status needs further study.Dendrophidion percarinatum (Cope) se redefine sobre la base de caracteres estandarizados y nuevos para distinguirlo de dos nuevas especies sudamericanos con que se confundieron anteriormente. El redefinido D. percarinatum se encuentra desde Honduras por América Central hasta el oeste de Colombia, con una localidad aparentamente alejada en el extremo occidental de Venezuela. Una nueva especie, D. prolixum, es simpátrica con D. percarinatum a pocas localidades en el centro-occidental de Colombia; la distribución de la nueva especie continua hacia el sur hasta el noroeste de Ecuador. Una segunda nueva especie, D. graciliverpa, occurre en todo del Ecuador occidental, donde su distribución traslapa la distribución de D. brunneum (Günther). Los hemipenes de ambas nuevas especies son exceptionalmente alargados y delgados (morfotipo esbelto). Es una morfología distinta de los otros hemipenes de Dendrophidion, que son más corto y robusto (morfotipo robusto). Además, las nuevas especies se distinguen de D. percarinatum por la coloración pero no se distinguen en caracteres estandarizados de escutellación como cuentas segmentales. De modo parecido, las dos nuevas especies se distinguen por coloración pero no por la escutellación ni la morfología de los hemipenes. Se describen los hemipenes de D. percarinatum y las nuevas especies. Para asegurar la aplicación apropiada del nombre D. brunneum se redescribe el holotipo de esta especie. Nuevas especímenes documentan la ocurrencia amplia de D. brunneum en las tierras bajas del Ecuador occidental y también polimorfismo extenso de patrones, incluyendo patrones unicolor, rayado, con bandas, y con manchas; se necesitan más datos sobre la coloración de vida. Algunos registros anteriores de “D. percarinatum” desde los valles interandinos de la sistema Ríos Cauca/Magdalena son de identidades equivocadas. Sin embargo, existen especímenes del Río Magdalena que son parecidos a D. percarinatum en la escutellación pero son distintos en coloración; su estatus merece más estudio.

We review the systematics of the Dendrophidion nuchale complex in Central America and northern South America andrecognize three species. The names D. nuchale (W. Peters) and D. clarkii Dunn apply to two of the species. The third isdescribed as a new species, D. rufiterminorum. It differs from D. clarkii and D. nuchale in coloration and hemipenial char-acters but all three species of the nuchale complex are very similar in scutellation characters. Dendrophidion nuchale isdistributed in the coast ranges and adjacent foothills of northern Venezuela, and in a seemingly disjunct population in theSerranía de Perijá in western Venezuela. The name clarkii was recently applied to all populations of the nuchale complexfrom Belize and Guatemala in the north to western Colombia and Ecuador in the south. Herein, we restrict the name D.clarkii to populations in lower Middle America (Costa Rica and Panama) and west of the Andes in Colombia and Ecuador.Dendrophidion rufiterminorum is distributed in northern Central America (Belize, Guatemala, northern Honduras) fol-lowed by a broad disjunction without records of the species throughout most of Honduras and Nicaragua; thereafter, a fewspecimens and photographs document the presence of D. rufiterminorum on the Caribbean versant of southern Nicaraguaand Costa Rica, and uplands of northwestern Costa Rica (Pacific versant). Two localities of sympatry between D. rufiter-minorum and D. clarkii are known in Costa Rica (one on the Atlantic versant, the other on Pacific versant). Nonetheless,there is sparse documentation of either species in Costa Rica. The populations referred to D. clarkii in southwestern CostaRica, the eastern half of Panama, and western Colombia and Ecuador need further study. Hemipenes of species of thenuchale complex are described. All three species have a pair of enormously enlarged sulcate spines and a regular lineararray of enlarged spines (spinose annulus) encircling the base of the apical region. These characters are also shared with D. dendrophis sensu lato but not other members of the dendrophis species group.

Hemipenes of species in the North American colubrid genus Phyllorhynchus are described. Contrary to previous reports of a divided sulcus spermaticus, both species have an unusual morphology in which the lips of the sulcus diverge near the apex so that the sulcus groove opens into an extensive apical nude region. Two distinctive hemipenial morphologies were discovered within P. browni, which may signal unresolved systematic issues. Phyllorhynchus hemipenes are additionally unusual for colubrids in having calyces reduced (P. decurtatus) or absent (P. browni). These features resemble some natricid hemipenes, which are reviewed in order to make detailed comparisons. That review led to a reassessment of some hemipenial characters of natricids and the recognition of several novelties, including calyces in Rhabdophis and a peculiar lobular pocket in Xenochrophis cerasogaster. I conclude that the resemblance of the sulcus configurations in Phyllorhynchus and natricids is only superficial and therefore convergent. Other evidence supports the phylogenetic placement of Phyllorhynchus with Colubridae, for which the sulcus configuration, highly reduced calyces, and extensive apical nude areas are unusual. Relationships of Phyllorhynchus within Colubridae are unclear, but the genus shares with Salvadora an unusual morphology of the rostral scale and nude hemipenial apices. However, in other respects Salvadora and Phyllorhynchus differ greatly in morphology and ecology.

Systematic characters, distribution, natural history, and hemipenial morphology are described for Dendrophidion brunneum (Gunther), a poorly known snake from Ecuador and Peru. It has 17 midbody scale rows; 145-165 ventrals; 135-158 subcaudals; a tail 38-44% of total length; a relatively uniform green to brown dorsum; and a maximum length of 1370 mm (700-800 mm SVL). The species occurs from northern Ecuador to 8 S latitude in Peru, primarily on the Pacific slopes of the Andes but with a few documented lowland localities in Peru. Dendrophidion brunneum is diurnal, terrestrial, heliophilic, and oviparous. It occurs in humid montane forests or mixed puna grassland/highland forest. Recorded prey are small terrestrial frogs but a large individual possibly consumed a lizard. Defensive mechanisms include a pseudautotomic tail and behaviors such as striking, biting, and neck inflation. The hemipenis has a short, narrow base, a greatly expanded distal region, and a simple, centrolineal sulcus spermaticus. The expanded region is ornamented with spines, distal to which two flounces completely encircle the organ and another extends partially around one side. The flounces are unusual in being thin, membranous structures and in having mineralized rods (reduced spinules) completely embedded within the membranes. The apex is nude except for a few vestigial calyces. Unusual hemipenial characters are discussed.

We present a molecular phylogenetic analysis of caenophidian (advanced) snakes using sequences from two mitochondrial genes (12S and 16S rRNA) and one nuclear (c-mos) gene (1681 total base pairs), and with 131 terminal taxa sampled from throughout all major caenophidian lineages but focussing on Neotropical xenodontines. Direct optimization parsimony analysis resulted in a well-resolved phylogenetic tree, which corroborates some clades identified in previous analyses and suggests new hypotheses for the composition and relationships of others. The major salient points of our analysis are: (1) placement of Acrochordus, Xenodermatids, and Pareatids as successive outgroups to all remaining caenophidians (including viperids, elapids, atractaspidids, and all other "colubrid" groups); (2) within the latter group, viperids and homalopsids are sucessive sister clades to all remaining snakes; (3) the following monophyletic clades within crown group caenophidians: Afro-Asian psammophiids (including Mimophis from Madagascar), Elapidae (including hydrophiines but excluding Homoroselaps), Pseudoxyrhophiinae, Colubrinae, Natricinae, Dipsadinae, and Xenodontinae. Homoroselaps is associated with atractaspidids. Our analysis suggests some taxonomic changes within xenodontines, including new taxonomy for Alsophis elegans, Liophis amarali, and further taxonomic changes within Xenodontini and the West Indian radiation of xenodontines. Based on our molecular analysis, we present a revised classification for caenophidians and provide morphological diagnoses for many of the included clades; we also highlight groups where much more work is needed. We name as new two higher taxonomic clades within Caenophidia, one new subfamily within Dipsadidae, and, within Xenodontinae five new tribes, six new genera and two resurrected genera. We synonymize Xenoxybelis and Pseudablabes with Philodryas; Erythrolamprus with Liophis; and Lystrophis and Waglerophis with Xenodon.Este trabalho apresenta uma análise filogenética molecular das serpentes avançadas (Caenophidia), realizada com base na análise de seqüências de dois genes mitocondriais (rRNA 12S e 16S) e de um gene nuclear (c-mos; 1681 pares de bases no total) e com 131 táxons terminais, amostrados a partir das principais linhagens de Caenophidia, com ênfase nos xenodontíneos neotropicais. A análise de parcimônia dos dados mediante otimização direta resultou em uma árvore filogenética bem resolvida que, por um lado, corrobora alguns dos clados identificados em análises anteriores e por outro, estabelece novas hipóteses sobre a composição de outros grupos e do relacionamento entre eles. Os principais resultados obtidos salientam: (1) a alocação de Achrochordus, xenodermatídeos e pareatídeos como grupos externos sucessivos de todos os demais cenofídios (incluindo viperídeos, elapídeos, atractaspidídeos e todos os grupos de "colubrídeos"); (2) que, em relação ao último grupo, viperídeos e homalopsídeos podem ser considerados como clados irmãos dos demais; (3) a existência, dentro do grande grupo dos cenofidia, dos seguintes sub-grupos: psamophiídeos afro-asiáticos (incluindo o gênero Mimophis, de Madagascar), Elapidae (incluindo os hidrophiíneos, mas excluindo Homoroselaps, associado aos atractaspidídeos), Pseudoxyrhophiinae, Colubrinae, Natricinae, Dipsadinae e Xenodontinae. A análise sugere algumas alterações de cunho taxonômico dentro dos xenodontíneos, incluindo realocações genéricas para Alsophis elegans, Liophis amarali e modificações substanciais em relação a Xenodontini e à radiação dos xenodontíneos das Antilhas. Também é a aqui apresentada uma revisão da classificação de Caenophidia, baseada inicialmente nas análises moleculares, mas provendo diagnoses morfológicas para muitos dos clados incluídos, realçando os grupos que ainda merecem atenção especial no futuro. São aqui nomeados originalmente dois grandes clados dentro de Caenophidia, uma nova subfamília dentro de Dipsadidae e, dentro de Xenodontinae, cinco novas tribos e seis novos gêneros, sendo ainda dois gêneros revalidados. Os gêneros Xenoxybelis e Pseudablabes são considerados sinônimos de Philodryas; Erythrolamprus, sinônimo de Liophis; Lystrophis e Waglerophis, sinônimos de Xenodon.

Multilocus electrophoretic methods and microcomplement fixation comparisons of serum albumin are used to assess phylogenetic relationships among species of uropeltid snakes, to infer aspects of their population biology and biogeography, and to evaluate their relationships to other primitive snakes (Henophidia). There is very good agreement between phylogenetic inferences derived from the electrophoretic data and those derived from the albumin immunological data. Protein variation detected by electrophoresis is relatively high among 17 operational taxonomic units (OTUs) examined. The mean number of alleles per locus (5.1 across all OTUs), levels of polymorphism (25% of loci), and heterozygosity (4–6%), are typical of, or greater than, values reported for other snakes. Species of uropeltids are genetically highly differentiated, as measured by genetic distances (lowest interspecific Nei's unbiased genetic distances, 0.22-0.27 among several Sri Lankan species; 2.3 between Teretrurus of India and other uropeltines). The phylogenetic tree most consistent with both the immunological and electrophoretic data shows uropeltines from Sri Lanka to be monophyletic, but the Indian species are paraphyletic with respect to those from Sri Lanka. Rhinophis travancoricus of India is inferred to be the sister taxon to the Sri Lankan radiation. As the genera are presently understood, neither Rhinophis nor Uropeltis appears to be monophyletic. A biogeographic scenario derived from the phylogenetic hypothesis suggests an early diversification of uropeltids in India, followed by a single invasion into the lowlands of Sri Lanka. Subsequent evolution on Sri Lanka resulted in occupation of montane biotopes. Cylindrophis is the sister group to uropeltines and is considered a member of the Uropeltidae. The immunological data indicate no phylogenetic association between uropeltids and other ‘anilioid’ taxa, specifically Anilius, Loxocemus or Xenopeltis, although we cannot rule out a very remote relationship. We specifically reject the hypothesis that uropeltines and scolecophidians form a clade relative to henophidians. High levels of genetic variation and a trend toward negative FIS values for polymorphic loci in three populations suggest generally large effective population sizes and outbreeding in these species. The niche-width variation hypothesis for allozyme loci is not supported by the uropeltid data. In comparison to other vertebrates, the relationship between Nei's genetic distance and albumin immunological distance in uropeltids suggests either conservative albumin evolution or strong differentiation at electrophoretic loci.

Sibynomorphus, an assemblage of about a dozen species of South American gastropod-eating colubrids, has a peculiar distribution. Six species occur in northern Peru and southwestern Ecuador. The others are distributed south of the Amazon basin in Brazil, Bolivia, Paraguay, Uruguay, and Argentina. Species of Sibynomorphus known from Ecuador and Peru are reviewed. Sibynomorphus oligozonatus and S. petersi are reported from Peru for the first time. Study of existing collections considerably amplifies understanding of the geographic ranges and character variation within S. oligozonatus, S. oneilli, S. petersi, and S. williamsi. Sibynomorphus vagrans is known only from its type locality (Bellavista, Cajamarca Department, Peru), and S. vagus (type locality unknown) is known only from near the single historically reported locality for the species (Huancabamba, Piura Department, Peru). Sibynomorphus oligozonatus (four specimens known) is distributed in southwestern Ecuador (Azuay and Loja Provinces) and northern Peru (Piura Department). Sibynomorphus oneilli is distributed in the Cordillera Oriental and Cordillera Occidental of northern Peru from southern Ancash Department to southern Cajamarca and Amazonas Departments. Available specimens of S. petersi extend the known range from Azuay and Loja Provinces in southwestern Ecuador, along the western Andean slopes to southern Ancash Department, Peru (Pacific versant); a single specimen is also known from the upper Río Chotano in central Cajamarca Department, thus documenting that this species occurs on the Amazonian versant. Sibynomorphus williamsi is known from central Peru in Lima and Ancash Departments from near sea level to at least 2,900 m in the Andes (and perhaps as high as 3,600 m)—an elevational range unmatched in any other species of the genus. Two species (S. vagrans and S. vagus) are restricted to the Amazonian versant, two are restricted to the Pacific versant (S. oligozonatus and S. williamsi), and two are found on both versants (S. oneilli and S. petersi). A key to the species of Sibynomorphus in Peru and Ecuador is provided.Hemipenes are described for Sibynomorphus oligozonatus, S. petersi, S. vagrans, S. vagus, and S. williamsi. Their organs are similar to hemipenes of other Dipsadini in having a well-defined capitulum ornamented with papillate calyces, several rows of large spines encircling the organ proximal to the capitulum, an exceptionally large basal nude pocket, and the division of the sulcus spermaticus within the capitulum. In Sibynomorphus and in some other Dipsadini the branches of the sulcus spermaticus are centrolineal, but their tips pass somewhat to the lateral surface of the hemipenial lobe(s). The exceptional size of the nude pocket might be a synapomorphy of Dipsadini but further comparative studies are needed, especially because the pocket has probably been overlooked in many species.The natural history of all northern species of Sibynomorphus is summarized, but very little is known. Most localities are in relatively dry to arid habitats, such as dry deciduous forests or thorn forests, on the western Andean slopes or inter-Andean valleys. A few localities for S. petersi in northern Peru are in areas of mesic to humid forests, although specimens are from forest edge or ecotones in this area. Sibynomorphus williamsi is characteristic of the lomas formations on the central Peruvian coast, but it also occurs on the Andean slopes at higher elevations.Sibynomorphus shares with three other genera of Neotropical Dipsadinae (Dipsas, Sibon, Tropidodipsas) a behavioral propensity and associated morphological characteristics for consuming gastropods. In accordance with some previous authors, I suggest that the name Dipsadini be applied inclusively to this clade of four genera of Neotropical molluscivorous colubrids, notwithstanding previous arguments for excluding Tropidodipsas. Several external characters indicate that Sibynomorphus is most closely related to Dip

Abstract Dipsas nicholsi has been known from a handful of specimens collected during the final three-quarters of the 20th century. All came from a restricted lowland area (60–150 m) in central Panama, in the upper drainage of the Río Chagres. A recently identified specimen, the first known juvenile and only the second female, was found in 1997 in the Darién highlands (Serranía de Jingurudó, 855 m) of extreme eastern Panama, about 250 km from the clustered lowland localities in central Panama. It differs from central Panamanian specimens in some scutellation characters and especially in details of dorsal color pattern. The species' rarity makes it impossible to determine whether differences reflect geographic isolation or unknown aspects of ontogenetic, sexual, or individual variation. Distributional disruptions are commonplace in the Panamanian herpetofauna, although difficult to verify in the case of rare species. However, in the absence of a present-day habitat corridor, the Darién specimen of Dipsas nicholsi clearly represents a population widely separated and discontinuous from the one in central Panama. The Serranía de Jingurudó population, apparently a distributional relict, slightly closes the wide geographic gap between Dipsas nicholsi and its likely sister species, D. andiana, of western Ecuador. Commentary is provided on the cartographic names of several eastern Panamanian highlands. The Serranía de Jingurudó takes its name from a river, as shown by the Emberá suffix -dó. This highland was known for nearly half a century as the Sierra or Serranía de “Jungurudó”, probably a confused combination of a still-older map name (Sierra de “Jungururo”) and the Río Jingurudó.

The South American iguanian lizard genus Stenocercus includes 54 species occurring mostly in the Andes and adjacent lowland areas from northern Venezuela and Colombia to central Argentina at elevations of 0–4000m. Small taxon or character sampling has characterized all phylogenetic analyses of Stenocercus, which has long been recognized as sister taxon to the Tropidurus Group. In this study, we use mtDNA sequence data to perform phylogenetic analyses that include 32 species of Stenocercus and 12 outgroup taxa. Monophyly of this genus is strongly supported by maximum parsimony and Bayesian analyses. Evolutionary relationships within Stenocercus are further analyzed with a Bayesian implementation of a general mixture model, which accommodates variability in the pattern of evolution across sites. These analyses indicate a basal split of Stenocercus into two clades, one of which receives very strong statistical support. In addition, we test previous hypotheses using non-parametric and parametric statistical methods, and provide a phylogenetic classification for Stenocercus.

The systematics and biology of colubrid snakes from western Ecuador and northern Peru in the Dipsas oreas group, comprising the nominal taxa D. oreas (Cope), D. elegans (Boulenger), and D. ellipsifera (Boulenger), are reviewed. The last two species are resurrected from the synonymy of D. oreas. These species, especially D. elegans and D. ellipsifera, have been confused in previous literature because of inadequate attention to patterns of sexual dimorphism and geographic variation. Dipsas elegans and D. ellipsifera share a distinctive color pattern that is quite different from color patterns in D. oreas. Dipsas ellipsifera differs from both D. oreas and D. elegans in having lower ventral and subcaudal counts, but sexes must be analyzed separately to see the distinctions clearly. Other subtle characters of scutellation, coloration, and dentition aid in distinguishing these species. Dipsas elegans is unusual in that males have significantly more ventral scutes than females, the reverse of the more common colubrid pattern of sexual dimorphism, in which females have more ventrals than males; neither D. oreas nor D. ellipsifera is sexually dimorphic for this character.Dipsas ellipsifera is known only from the valley of the Río Mira in extreme northwestern Ecuador (Imababura Province). Dipsas elegans is known from the western versant of the Andes in Ecuador from just north of the equator to about latitude 2°S; it is also found in the inter-Andean valley of the upper Río Guayllabamba east of Quito. Dipsas oreas is known from southern Chimborazo and Guayas Provinces south to Loja Province in southern Ecuador, thence south along the western slopes of the Andes to at least the Río Zaña (6°51′S) in northern Peru. The occurrence and distribution of D. oreas in Peru is detailed for the first time. Most localities for D. oreas are on the Andean slopes, but the species is also recorded by specimens from the lowlands in the vicinity of Guayaquil, Ecuador. The type locality of D. oreas and many other South American amphibians and reptiles obtained by the naturalist James Orton is the “elevated Valley of Quito,” which has been erroneously interpreted narrowly as the vicinity of Quito, Ecuador. Orton's own writings show that a broader interpretation encompassing virtually all of the Ecuadorian highlands was intended. The ranges of D. elegans, D. ellipsifera, and D. oreas are very likely extremely fragmented because of significant destruction of forest habitats in western Ecuador and Peru.Hemipenes of Dipsas elegans, D. ellipsifera, and D. oreas are slightly bilobed, fully capitate, and have ornamentation similar to other species of the tribe Dipsadini (Dipsas, Sibon, Sibynomorphus, and Tropidodipsas). The capitulum is ornamented with papillate calyces and the sulcus spermaticus bifurcates within the capitulum. Proximal to the capitulum a battery of enlarged spines encircles the midsection of the organ. A large basal nude pocket is present on the hemipenis in all three species.Notes on coloration, natural history, and behavior are reported for the three species of the oreas group, although most observations are for Dipsas oreas. In northern Peru, D. oreas shows extensive intrapopulational variation in coloration, which could in part be sexually dimorphic. It is unclear whether this variation pertains to other parts of the distribution. Dipsas oreas is active nocturnally in low vegetation but seeks seclusion in leaf litter or under surface objects on the ground during the day. This diel behavior pattern is also reported for several other species of Dipsas and might be common in the genus. In northern Peru, the activity of adult D. oreas is strongly seasonal and coincides with the rainy season. A peculiar aggregation of Dipsas oreas encountered at a locality in northern Peru is described. Comprising one female and six males, this is the first reported case of “aggregation behavior” in any snake of the tribe Dipsadini and one of very few observations

The name Dipsas variegata (Dumeril, Bibron, and Dumeril) has been applied to snakes disjunctively distributed in northeastern South America and in Panama and western South America. The specific name variegata is here restricted to populations occurring from Venezuela to Trinidad and French Guiana, and seemingly to the mouth of the Amazon in Brazil. Records from Colombia are unsubstantiated.The name Dipsas nicholsi (Dunn) is revalidated for a Central American endemic with an exceptionally small range in central Panama. Specimens from western Ecuador previously assigned to "Dipsas variegata nicholsi" represent a different species-Dipsas andiana (Bou-lenger), which is resurrected from the synonymy of Dipsas oreas (Cope). Other records of Dipsas variegata from western Ecuador and southeastern Peru are based on misidentifications of species well known from those areas.Dipsas nicholsi and D. andiana differ in some scutellation, hemipenial, and color pattern characters. The two species share an unusual head pattern, but data are insufficient to conclude that they are sister species, although their disjunct distribution pattern (Panama and Chocoan South America) is one shared by many other organisms thought to be phylogenetically related.Hemipenes of Dipsas nicholsi and D. andiana are slightly bilobed and fully capitate; the sulcus spermaticus divides within the capitulum and has centrolineal branches. The capitulum is ornamented with papillate calyces. A battery of enlarged spines encircles the organ below the capitulum (with more spines in nicholsi than in andiana). There is all elongated basal nude pocket positioned laterally on the organ. Overall hemipenial morphology is similar to other species of the tribe Dipsadini (Dipsas, Sibon, Sibynomorphus, Tropidodipsas) for which organs have been described.The Dipsadini are docile snakes that, in the authors' experience, never defend themselves by biting or even striking with mouth closed. Defensive positional deportment is nonetheless widespread and varied, most commonly including acquisition of a triangular head shape in at least three genera of Dipsadini (and other snakes as well), which is brought about by dorsolateral spreading of the quadratomandibular articulations. Either asymmetrical or symmetrical coiling and head-hiding also occur in diverse species; there is evident individual variability in some species, whereas others possibly lack specialized behavior. A specimen of Dipsas nicholsi did not show the common head triangulation, but repeatedly exhibited stereotypic stages of defensive positioning that resulted in it taking the shape of a raised spiral coil.