Sexual dimorphism in Louisiana pine snakes (Pituophis ruthveni).

The Louisiana pine snake, Pituophis ruthveni, is a cryptic, federally threatened snake species with several fragmented populations in Louisiana and Texas, USA. There are currently four captive breeding populations in zoos in the USA; however, little scientific data exists on their life history and anatomy. Accurate sex determination and identification of normal reproductive anatomy are an essential part of a veterinary exam and conservation programs. The authors had encountered various cases of sex misidentification in this species that were attributed to lack of lubrication of the sexing probes and enlarged musk glands. Anecdotal observation led to a hypothesis of sexual dimorphism based on body and tail shape. To test this hypothesis, we measured body length, tail length and width, and body to tail taper angle in 15 P. ruthveni (9 males and 6 females). We also obtained tail radiographs of all animals to document the presence of mineralized hemipenes. Significant dimorphism was identified in relative tail length, width, and taper angle; females consistently exhibited a more acute taper angle. Contrary to previous studies in other Pituophis species, a male-biased sexual size dimorphism was not identified. Mineralized hemipenes were confirmed in all males (a newly described trait in this species), and we found that the lateral view was consistently more reliable for identification of hemipenes compared to the ventrodorsal view. This information contributes to the scientific community's understanding of this species and is of use to biologists and veterinarians working toward conservation of this threatened species.

First evidence of hemiclitores in snakes.

Female genitalia are conspicuously overlooked in comparison to their male counterparts, limiting our understanding of sexual reproduction across vertebrate lineages. This study is the first complete description of the clitoris (hemiclitores) in female snakes. We describe morphological variation in size and shape (n = 9 species, 4 families) that is potentially comparable to the male intromittent organs in squamate reptiles (hemipenes). Dissection, diffusible iodine contrast-enhanced micro-CT and histology revealed that, unlike lizard hemiclitores, the snake hemiclitores are non-eversible structures. The two individual hemiclitores are separated medially by connective tissue, forming a triangular structure that extends posteriorly. Histology of the hemiclitores in Australian death adders (Acanthophis antarcticus) showed erectile tissue and strands/bundles of nerves, but no spines (as is found in male hemipenes). These histological features suggest the snake hemiclitores have functional significance in mating and definitively show that the hemiclitores are not underdeveloped hemipenes or scent glands, which have been erroneously indicated in other studies. Our discovery supports that hemiclitores have been retained across squamates and provides preliminary evidence of differences in this structure among snake species, which can be used to further understand systematics, reproductive evolution and ecology across squamate reptiles.

Resurrection of Anolis ustus Cope, 1864 from synonymy with Anolis sericeus Hallowell, 1856 (Squamata, Dactyloidae).

In this study, based on a morphological analysis, the resurrection of the name Anolis ustus Cope 1864, is proposed for populations from the Yucatán Peninsula (Campeche, Yucatán, and Quintana Roo, Mexico, and Belize), formerly referred as Anolis sericeus Hallowell, 1856. Anolis ustus differs from Anolis sericeus by its mean snout-vent length and number of gorgetal scales in males, in tibia length and head width in females, and dorsal and ventral scales for both sexes. In addition, Anolis ustus has a small dewlap of similar size between males and females, whereas in Anolis sericeus males have a dewlap much larger than that of the females. These characteristics allow Anolis ustus to be identified within the Anolis sericeus complex. In this study, a description of the characteristics of the hemipenis is also provided, and its importance in the taxonomy of Anolis is discussed.

A large and unusually colored new snake species of the genus Tantilla (Squamata; Colubridae) from the Peruvian Andes.

A new colubrid species of the genus Tantilla from the dry forest of the northern Peruvian Andes is described on the basis of two specimens, which exhibit a conspicuous sexual dimorphism. Tantilla tjiasmantoi sp. nov. represents the third species of the genus in Peru. The new species is easily distinguished from its congeners by the combination of scalation characteristics and the unusual transversely-banded color pattern on the dorsum. A detailed description of the skull morphology of the new species is given based on micro-computed tomography images. The habitat of this new species is gravely threatened due to human interventions. Conservation efforts are urgently needed in the inter-Andean valley of the Maranon River.