Recent studies on the systematics and phylogeny of the blue-tailed skinks in the Plestiodon brevirostris group identified a population from the Sierra Madre del Sur of eastern Guerrero, Mexico, that appeared to represent an undescribed species. Here, we formally describe this lineage as a new species, compare it with the other species in the P. brevirostris group, identify a specimen from western Oaxaca that belongs to the new species, and provide an updated key to the group. The new species is morphologically similar and closely related to P. ochoterenae , but molecular and morphological data support its evolutionary independence. The new species is distinguished from the other species in the P. brevirostris group, except for P. ochoterenae , by the presence of a primary temporal, a well-defined lateral pale line on the neck, and a well-defined dorsolateral pale line that extends posteriorly to the level of the hind limbs. It differs from P. ochoterenae by having longer limbs and a well-defined lateral pale line on the neck. The present study further highlights the relevance of the Sierra Madre del Sur as a hotspot of endemism and undescribed diversity.

We describe a new species of the genus Abronia from the La Sepultura Biosphere Reserve in western Chiapas, México. The new species is known only from the vicinity of the type locality in the Sierra Madre de Chiapas. It is readily distinguished from all congeners by the following combination of characters: lack of protuberant or spine-like supra-auricular scales, lack of protuberant or casque-like posterolateral head scales, 30–35 transverse dorsal scale rows, lateralmost row of ventral scales enlarged relative to adjacent medial row, dorsum brown with 8–10 transverse dark crossbands, and dark lateral bar on the neck extending from the shoulder to near the auricular opening. We tentatively assign the new species to the subgenus Lissabronia pending the availability of a robust, comprehensive molecular phylogeny for the genus. We discuss regional Abronia biogeography and comment on the conservation implications of our discovery for the imperiled highland forests of the Sierra Madre de Chiapas, a globally important center of endemism.

A new species of Gerrhonotus , previously confused with G. infernalis , is described from the Cuatro Ciénegas Basin, Coahuila, Mexico. The new species is known from the type locality only and is characterized by the following combination of characters: a cantholoreal scale usually present, a dark mark extending anteriorly from the lower temporal scales through the lower border of the orbit to the preocular or cantholoreal scales, keeled dorsal scales, dorsal body pattern usually composed of cross-bands mostly interrupted or barely discernible on middorsum, usually indiscernible vertical dark bars on the lateral fold (few, faint bars occasionally present), and black flecks scattered on the venter. The new species is geographically closest to G. lugoi and G. infernalis but morphologically most similar to G. infernalis .

We describe a new species of Phrynosoma from central northeastern Guerrero, México; perform a phylogenetic analysis of mitochondrial and nuclear sequence data to estimate its phylogenetic relationships; and investigate the monophyly of Phrynosoma asio , P. braconnieri , and P. taurus . The new species can be distinguished from all of its congeners by the possession of a unique combination of morphological characteristics. The molecular genetic data include three fragments of the mitochondrial genome and six nuclear genes (2419 and 3909 base pairs in total, respectively) for 31 samples belonging to the 16 previously recognized species of Phrynosoma and the new species. The new species is strongly supported in maximum likelihood analyses of both the concatenated mitochondrial and nuclear data as a monophyletic, distinct evolutionary lineage sister to, and moderately divergent from, P. taurus , and highly divergent from all of the other species of Phrynosoma . A Bayesian species tree analysis also strongly supports the monophyly of the Brevicauda clade, and a sister relationship between P. taurus and the new species.

A new species of the colubrid genus Geophis from northern Puebla, Mexico, is described. The new species possesses most of the diagnostic characters of the G. dubius group but differs from all other species of Geophis by having the loreal shorter than the combined prenasal and postnasal length, one postocular scale, one supraocular scale, the fifth supralabial and parietal in contact, dorsal scales in 17 rows, dorsal scales smooth throughout the length of the body or, if keeled, not anteriorly to the posterior fourth of the body, 129–140 ventrals in females and 125–139 in males, 26–31 subcaudals in females and 34–39 in males, 159–170 ventrals plus subcaudals in females and 161–174 in males, 9 maxillary teeth, anterior tip of the maxilla toothless, an overall dark dorsum, a predominantly cream venter, and a short tail in males. A Bayesian phylogenetic analysis of mtDNA sequences of the cytochrome b and tRNA Trn genes, including representatives of the new species, G. carinosus , G. dubius , and G. juarezi supported the distinctness of the new species.

A bstract A new species of the colubrid genus Geophis is described from the Sierra Madre del Sur of Guerrero, Mexico. The new species possesses all of the diagnostic characters of the sieboldi group, but differs from all of the other species in the group by having dorsal scales arranged in 17 rows, 133–139 ventrals in females and 130–137 in males, 24–31 subcaudals in females and 34–39 in males, keeled dorsal scales on at least the posterior three-fourths of the body, apparently no apical pits, and a light nuchal collar in juveniles. The new species fills a gap in the distribution of the sieboldi group between Michoacán and Oaxaca, and is the first Mexican species of the genus reported to exhibit both a unicolor (uniformly dark) and a bicolor (with dark markings on a red background color) body and tail dorsal patterns, a polymorphism similar to that previously documented in few lower Central American species.

Demographic data are essential to determine the probability that species will persist over time. Unfortunately, demographic studies are rarely part of the initial evaluation of potentially threatened or endangered species. Here, we studied the population dynamics of a poorly known knob-scaled lizard species ( Xenosaurus sp.) from México with the use of a population matrix modeling approach. We measured annual fecundity and survival over three consecutive years (2001–2004) and used these data to generate transition matrices. From these matrices we estimated annual variability in finite population growth rate (λ), stable stage structure, and the relative importance of the life-cycle components for λ (elasticity values). In 2 of the 3 yr population growth rates indicated a tendency toward population increase (λ 01–02 = 1.20 and λ 02–03 = 1.14), whereas in 1 of the 3 yr population growth rate indicated population decrease (λ 03–04 = 0.78). The negative population trend observed during 2003–2004 was explained by warmer and drier environmental conditions that caused the lowest observed survival rates in all size classes. We examined this annual demographic variability using stochastic simulations. This allowed us to project population trends under hypothetical scenarios with increasing frequency of unfavorable years, manifest through reduced survival, fecundity, or both. Our simulations revealed that small increases in the frequency of harsh annual conditions vastly increased extinction risk in this species. Given the highly restricted geographic distribution of this species and its susceptibility to extinction, we recommend that it be given a high priority for conservation.

The treefrog genus Hyla (Anura: Hylidae) consists of at least 31 species found in North America, Central America, Europe, and Asia and is the only genus of hylids that occurs outside the New World. Despite intensive work on the phylogeny of the genus in the past few years, several problems still exist regarding relationships within Hyla. These problems include the unusual placements of H. gratiosa and H. walkeri in some recent studies and the relatively limited taxon sampling of Asian species. In the present study, we revisit the phylogeny of Hyla to address some of these problems. First, we tested the unexpected placements of H. gratiosa and H. walkeri by sampling additional individuals of these species. Our results show that the unusual placements of H. gratiosa and H. walkeri in previous studies were most likely due to a mislabelled tissue sample and a misidentified specimen, respectively. Second, we included two species of Asian Hyla not included in previous phylogenies. Our study provides additional evidence for two separate colonizations of Hyla from the New World into Asia, and suggests an unusual biogeographic pattern in the Asian Hyla clades.

I describe a new species of the Geophis dubius group from the northern slopes of the Sierra de Juárez of Oaxaca, Mexico. The new species is most similar to G. carinosus . A previously unknown population of the G. dubius group from the Isthmus of Tehuantepec in Oaxaca is also reported.

We describe a new species of Barisia from the oak-pine and cloud forests on the southern slopes of the central Transvolcanic Belt in the states of Mexico and Morelos, Mexico, and report on variation in a sample of 21 specimens of the poorly known B. rudicollis . The new species and B. rudicollis appear to have allopatric distributions and to be sister taxa. Because of increasing fragmentation and destruction of their habitat, we suggest that these species be regarded as threatened. We discuss synapomorphies for the genus Barisia . Resumen Se describe una especie nueva de Barisia de los bosques húmedos de pino-encino y de neblina de la vertiente meridional del Eje Neovolcánico Tranversal en los estados de México y Morelos, México, y se reporta la variación en una muestra de 21 ejemplares de la poco conocida B. rudicollis . La nueva especie y B. rudicollis parecen tener distribuciones alopátricas y ser especies hermanas. Debido a la creciente fragmentación de su hábitat, sugerimos que estas especies sean consideradas como amenazadas. Se discuten las sinapomorfías para el género Barisia .