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 Dipsastemporalis (Werner, 1909), the sister species, is updated. Finally, a key to the species of Dipsas currently known from Middle America is presented.

ResumenDescribimos una nueva especies de Dipsas Laurenti, 1768 de la región central de Panamá en base a análisis moleculares, morfología hemipenial y caracteres de morfología externa. Esta es la sexta especie del género Dipsas descrita para el país. Se sospechaba su existencia desde 1977 pero no había sido estudiada exhaustivamente hasta ahora. Adicionalmente, presentamos comparaciones morfológicas (incluyendo lepidosis) con otras especies del género y actualizamos la distribución geográfica de su especie hermana Dipsastemporalis (Werner, 1909). Finalmente, presentamos una clave para las especies de Dipsas distribuidas en Centroamérica.

Phylogenetic and morphological evidence reveals the association between diet and the evolution of the venom delivery system in Neotropical goo-eating snakes

Advanced endoglyptodont snakes share a complex but homologous venom delivery system associated with the upperjaw and its dentition. Recently, a remarkable novel lower jaw venom delivery system was described for the Neotropicaldipsadine radiation of goo-eating snakes. While most dipsadines are opistoglyphous and exhibit large, mainly serousvenom glands associated with the upper jaw and supralabial glands, goo-eating dipsadine snakes are aglyphous and lackserous upper labial venom glands. Here, we provide new morphological and histological information on the oral glandsand maxillary dentition of representatives of the major lineages of dipsadines that help trace the evolutionary steps thatshaped the venom delivery system of dipsadines. We performed a maximum likelihood analysis on a molecular datasetthat includes 443 terminals and seven loci. Our results show that goo-eating dipsadines form a monophyletic assemblagethat includes the genusAdelphicosfor the first time, along withGeophis,Atractus,Ninia,Chersodromus,Tropidodipsas,Sibon, andDipsas. We also provide the first evidence of a complete shift from an upper jaw to a lower jaw venomdelivery system associated with their specialized feeding behaviour. Unlike other dipsadines who exhibit typicalendoglyptodont anteroposteriorly ridged posterior maxillary teeth, goo-eating dipsadines have uniform lateromediallyridged teeth throughout their maxilla. Our results indicate that the loss of the endoglyptodont venom delivery systemoccurred in the most recent common ancestor of goo-eating dipsadines, probably resulting from the loss of theembryonic posterior maxillary lamina responsible for the development of the venom delivery system.

Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata.

The skeleton of the middle ear of lizards is composed of three anatomical elements: columella, extracolumella, and tympanic membrane, with some exceptions that show modifications of this anatomy. The main function of the middle ear is transforming sound waves into vibrations and transmitting these to the inner ear. Most middle ear studies mainly focus on its functional aspects, while few describe the anatomy in detail. In lizards, the morphology of the columella is highly conservative, while the extracolumella shows variation in its presence/absence, size, and the number of processes present on the structure. In this work, we used diaphanized and double-stained specimens of 38 species of lizards belonging to 24 genera to study the middle ear's morphology in a comparative framework. Results presented here indicate more variation in the morphology of the extracolumella than previously known. This variation in the extracolumella is found mainly in the pars superior and anterior processes, while the pars inferior and the posterior process are more constant in morphology. We also provide new information about the shape of gekkotan extracolumella, including traits that are diagnostic for the iguanid and gekkonid middle ear types. The data collected in this study were combined with information from published descriptive works. The new data included here refers to the length of the columella relative to the extracolumella central axis length, the general structure of the extracolumella, and the presence of the internal process. These characters were included in ancestral reconstruction analysis using Bayesian and parsimony approaches. The results indicate high levels of homoplasy in the variation of the columella-extracolumella ratio, providing a better understanding of the ratio variation among lizards. Additionally, the presence of four processes in the extracolumella is the ancestral state for Gekkota, Pleurodonta, and Xantusiidae, and the absence of the internal processes is the ancestral state for Gekkota, Gymnophthalmidae, and Scincidae; despite the fact that these groups convergently develop these character states, they could be used in combination with other characters to diagnose these clades. The posterior extension in the pars superior and an anterior process with some small and sharp projections is also a diagnostic trait for Gekkota. A more accurate description of each process of the extracolumella and its variation needs to be evaluated in a comprehensive analysis, including a greater number of species. Although the number of taxa sampled in this study is small considering the vast diversity of lizards, the results provide an overall idea of the amount of variation of the middle ear while helping to infer the evolutionary history of the lizard middle ear.

Hemipenial morphology of nine South American species of Mabuya (Scincidae: Lygosominae) with comments on the morphology of the family.

Species of the genus Mabuya are barely recognizable because of their highly conservative external morphology, resulting in unstable systematic and taxonomic status. Considering that hemipenial morphology has been extensively used as a source of systematic information for several groups of Squamata, we described the hemipenial morphology of nine species of Mabuya, searching for diagnostic features useful to taxonomic and systematic studies. To have comparative parameters within the family, we also presented the description of the hemipenes of two other Scincidae species (i.e., Trachylepis atlantica and Tiliqua rugosa). This information, together with the available literature, was analyzed in a comparative framework, allowing us to define some variation for the genus and family. The hemipenial morphology of the species of Mabuya studied is very conservative; features that show subtle variation were the shape of the protuberances present on the asulcate face of the hemipenial body and the presence and type of a lateral fold, on the body. Also, within the family, some variation was found in the shape and length of lobes, length of branches of the sulcus spermaticus, and in the kind of folds and protuberances in both faces of the lobes and hemipenial body. Although these features were not tested in a systematic context, this information suggested variations in hemipenial morphology that could contribute to taxonomic diagnostics and phylogenetic characters. The importance of obtaining proper preparations for gathering accurate information is emphasized, and the use of fresh-killed specimens that shows fewer difficulties for the procedures of preparation is highly recommended.