Numerous behaviors of natricine snakes are plausibly interpreted as antipredator mechanisms that are useful at different stages of an encounter with a predator. Several of these behaviors have been described in detail, often in the laboratory, but we know little about the factors that influence their expression and effectiveness in the field, especially against real predators. Thus, one question that we might ask is: How effective are humans and artificial stimuli as proxies for real predators? Other areas that would profit from further research include the role of color and pattern in avoidance of predation, the effect of injury on subsequent survival, growth, or other measures of demographic performance, the role of previous experience in shaping future antipredator behavior, and the links among fear, stress physiology, and antipredator behavior.

We studied the effects of relative prey mass and experience on prey-handling behaviors of 16 ingestively naïve Corn Snakes (Pantherophis guttatus) feeding on different categorical sizes of live House Mice (Mus musculus) over 11 feeding trials. We randomly assigned hatchlings to two categories of prey mass, relative to snake mass (small = 20–40% and large = 41–60%), and analyzed the effects of prey mass on capture position, prey-handling method, time to subdue prey, condition of prey at ingestion, direction of ingestion, and duration of ingestion. Prey mass significantly affected prey-handling behaviors. As snakes experienced larger prey, they used more complex prey-handling behaviors (hairpin loops and constriction). Snakes that had prior large-prey experience maintained constant subduing times across feeding trials, whereas snakes that had prior experience with small prey showed an increase in subduing time across trials. Snakes feeding on large prey took longer to ingest prey than snakes feeding on small prey; however, as snakes gained feeding experience, they maintained relatively constant ingestion times across trials. All snakes employed complex prey-handling behaviors prior to the point at which the prey could vigorously defend themselves, suggesting an advantage to employing complex behaviors before they are necessary. When prey reached a certain absolute size, all were constricted and killed, regardless of prior experience or relative prey size.

Hibernation is an important behavioral event in temperate-region reptiles for escaping periods of harsh winter temperatures. Generally considered a dormant period, observations of winter activity suggest that hibernating reptiles may be more active than initially thought. To examine winter activity in a species that commonly hibernates, Timber Rattlesnakes (Crotalus horridus), we monitored the detailed movements and body temperatures (T_bs) of free-ranging snakes over two winters. Hourly T_bs and movements of snakes throughout a five-month hibernation period were monitored for midwinter activity and potential thermoregulatory behavior. Environmental temperatures and snake operative temperatures were used to estimate time periods when snakes were at or on the surface. Visual observations of snakes basking on the surface were uncommon; however, hourly recorded snake T_bs revealed that 69% of the snakes emerged to the surface to bask two or more times for a total of 60 emergence events from 14 individuals. Snake T_bs (N = 53,041) during hibernation were 11.1 ± 3.5°C (mean ± SD) and ranged from 1.1–33.7°C. Counter to our prediction, calculated estimates of metabolic expenditure associated with increasing T_b (via basking or surface emergence) during hibernation had little effect on the total energy budget required to survive winter. Additional metabolic expenditure attributable to multiple basking events (e.g., 10 basking events) can be offset by acquiring as little as 1.0 g of rodent during the active season.

Reproduction involves costs and benefits to a female snake. Costs include increased predation risk as well as lower future survival and reproduction probability, whereas benefits are the current production of offspring. Reproduction also is highly energy demanding: at each reproductive event, a female must decide between the allocation of energy to female condition or to reproductive output. Moreover, energy allocation linked to reproduction may be influenced by environmental features, especially climate and food availability. During 2008 and 2009, we studied the female reproductive tactics of Thamnophis scaliger, a viviparous and earthworm-eating snake distributed at rather high altitudes in central México. Gravid females were collected in the field and maintained in captivity until giving birth. The low percentage of females that were gravid each year suggested they did not reproduce annually. This result probably was driven by the seasonal constrained availability and low-energy content of earthworms, which preclude females from acquiring sufficient energy to fuel more frequent reproduction. Females also produced rather large litter sizes, implying a significant investment in reproduction. Univariate and multivariate analyses (path analysis) found the expected relationships between maternal body size and litter size and mass, and there was no trade-off of energy allocation between postpartum females and their litters. We found, however, a noteworthy relationship between parturition date and postpartum female body condition. Females that reproduced later benefited most from foraging opportunities during the short rainy and high prey-availability period and remained in better body condition.

La reproducción implica costes y beneficios para una hembra de ofidio. Los costes incluyen el aumento del riesgo a ser depredada, así como la disminución de la probabilidad de supervivencia y reproducción en el futuro, mientras que los beneficios son la producción de descendencia en el presente. La reproducción también demanda mucha energía, y cada vez que una hembra se reproduce, debe decidir entre la asignación de energía a su condición corporal postparto o al rendimiento reproductivo. Estas tácticas en la reproducción de los ofidios pueden estar condicionadas por factores medioambientales, especialmente el clima y la disponibilidad de alimento. En 2008 y 2009, estudiamos la táctica reproductiva de las hembras de Thamnophis scaliger, un ofidio vivíparo, especialista en el consumo de lombrices, distribuido a bastante altitud en el centro de México. Se colectaron hembras grávidas que se mantuvieron en cautividad hasta el parto. El bajo número de hembras grávidas cada año sugirió que no se reproducían anualmente. Este resultado estuvo probablemente condicionado por la estacionalmente limitada disponibilidad y el bajo contenido energético de las lombrices, que impiden a las hembras adquirir suficiente energía para una reproducción más frecuente. Además, las hembras produjeron camadas relativamente numerosas, lo que implica elevada inversión en reproducción. Análisis univariantes y multivariantes (análisis de vías) encontraron la esperada relación entre tamaño corporal materno, y el tamaño y peso de la camada, pero no hubo una compensación entre la energía asignada a las hembras postparto y sus camadas. Si encontramos una notable relación entre la fecha de parto y la condición postparto de las hembras. Las hembras que se reproducían más tarde se beneficiaban de mayor oportunidad de forrajeo durante el corto periodo lluvioso y de alta disponibilidad de presas, por lo que quedaban con mejor condición corporal.

The effects of human disturbance on movements and concealment behavior of Western Diamondback Rattlesnakes (Crotalus atrox) were studied at the Arizona–Sonora Desert Museum near Tucson, Arizona. We predicted that C. atrox would move more frequently and greater distances, and show higher degrees of concealment in disturbed areas when compared to undisturbed areas. Twenty-five rattlesnakes were equipped with radio-transmitters between July 2005 and September 2011. During the active season, but excluding the mating season, C. atrox were less likely to move while in highly disturbed areas than when they were in undisturbed areas. During the mating season, however, C. atrox were significantly more likely to move while in highly disturbed areas than when they were in undisturbed areas. During the inactive season, disturbance had no significant effect on the probability of movement. In all seasons, C. atrox were more likely to be concealed in highly disturbed areas.

Nectophrynoides asperginis (Bufonidae) is a small toad endemic to the spray zone of the Kihansi River waterfall in Tanzania, Africa. This species was declared extinct-in-the-wild by the International Union for Conservation of Nature (IUCN) following construction of a hydroelectric dam that reduced the flow of the waterfall. The species is now limited to ex situ populations at the Wildlife Conservation Society's (WCS) Bronx Zoo, New York, the Toledo Zoo, Ohio, and two newer facilities in Tanzania. Much of the natural history of N. asperginis remains unknown, though it is known they are a sexually dimorphic species. Typically, males are smaller than females and possess distinctive dorsolateral inguinal patches (IP). Males appear to display these patches to conspecifics, but their function remains unknown. We created a five-grade schema to categorize the IPs by visual prominence accounting for both patch size and color, with Grade 1 being the least and Grade 5 being the most prominent. We hypothesized that a positive association exists between male IP grade and the snout–urostyle length (SUL) of females they amplexed. Therefore, we measured SUL and body mass in 91 pairs of amplexing N. asperginis and assessed the relationship of IP grade to female SUL in the amplexed pairs. Statistical analysis revealed a significant positive correlation (Spearman's rho = 0.250, P = 0.017) between male IP grade and the SUL of females being amplexed. This study suggests that IP grade is associated with mate assortment in N. asperginis, and it represents one of the first glimpses into the complex social interactions of this extinct-in-the-wild amphibian.

The availability of preferred habitat can have numerous effects on an individual's behavior and physiology and, in turn, can affect fitness. In Anolis lizards, different species have evolved specific limb lengths that enable them to perform well in habitats with specific perch characteristics. Indeed, perch width and height have been major drivers in the morphological diversification in this genus. Despite the extensive work on Anolis limb length/perch width relationships, however, the availability of perches (a preferred habitat characteristic) influences aspects of fitness is poorly known. In this study, we housed captive male/female pairs of Brown Anoles (Anolis sagrei) in cages with high and low availabilities of perches and quantified the effect of perch availability on perch use and reproductive variables (egg production, egg mass, interegg interval, yolk steroids, egg hatching success). In the low-perch availability treatment, females spent less time on perches than did females in the high-perch availability treatment. Despite this effect on perch use, however, perch availability had little to no effect on reproduction. Egg mass and yolk testosterone concentrations increased over the reproductive season, but perch availability had no effect on any temporal changes in reproductive variables over time. Despite the importance of perch characteristics in shaping the evolution of Anolis lizards, we found little evidence that perch availability affects maternal reproductive investment in A. sagrei under controlled laboratory conditions.

Previous studies found that two larvae of the family Ceratophryidae, Ceratophrys ornata (Ornate Horned Frogs) and Ceratophrys cranwelli (Cranwell's Horned Frogs), are able to produce underwater sounds as an antipredator strategy. Here, we determined whether tadpoles of another ceratophryid, Lepidobatrachus llanensis (Llanos Frogs), also produce underwater sounds in similar contexts of intraspecific interactions. Moreover, to compare the mechanism displayed by Ceratophrys spp. with related species, we tested the existence of an antipredator mechanism (= behavior) in L. llanensis tadpoles that diminishes the frequency of predation between conspecifics in the presence of heterospecific prey. Lepidobatrachus llanensis tadpoles exhibited an antipredator mechanism that is displayed on intraspecific interactions. Extensive trials failed to reveal sound production (in the 20 hertz [Hz]–20 kilohertz [kHz] range) in L. llanensis, contrasting our observations on Ceratophrys spp. Nevertheless, L. llanensis tadpoles recognized conspecifics because they consistently avoided each other. Under the experimental conditions described, we found L. llanensis tadpoles first eat all heterospecific prey and only then switch to cannibalism. Tadpoles began eating conspecifics only when prey were scarce and after a period of hunger. Moreover, cannibalistic events increased at higher predator-prey proportions. When comparing the number of events of cannibalism recorded for L. llanensis and the related C. cranwelli, under the same experimental conditions, we concluded that L. llanensis cannibalize 1.5 times more often. The genus Lepidobatrachus has distinctive and unique morphological characters that are divergent from its relatives (Ceratophrys, Chacophrys). The antipredator mechanism in L. llanensis contrasts those of Ceratophrys spp. and may be yet another differing characteristic of this group.

Relationships between behavioral regulation, environmental temperatures, and physiological tolerance are critical to conservation policy; however, these relationships may not be consistent among sister taxa. A species geographic range is influenced by various factors including physiological tolerance to temperature change. In this study, we investigated the effects of temperature variation on thermal preference and standard metabolic rates (SMR) of two species of larval salamanders, Eurycea cirrigera (Southern Two-Lined Salamander) and Eurycea wilderae (Blue Ridge Two-Lined Salamander). These species share similar life histories, but E. cirrigera is broadly distributed and E. wilderae occupies a smaller range. We measured SMR using volume of oxygen consumption during closed-circuit respirometery trials conducted at 5°C increments between 5°C and 25°C. Standard metabolic rates were influenced by temperature, with a range of temperature-independent SMRs observed at those temperatures above each species laboratory-determined thermal preference. Concordant with their thermal preference (15.70°C) and more-narrow geographic range, E. wilderae exhibited a smaller scope of temperatures at which SMR was temperature-independent, relative to E. cirrigera, and metabolic rates were depressed at 25°C. Therefore, preferred thermal temperatures corresponded with physiological maxima and environmental temperatures in each species. Our results support the importance of behavioral thermoregulation in maintaining optimal physiological function. Further, these findings indicate that the physiological specialization that occurs in species of narrow geographic ranges may preclude favorable responses to changing environmental temperatures caused by land-cover changes, including loss of riparian forest in the Eastern United States.

Aposematic coloration allows predators to use visual cues to avoid eating potentially toxic or distasteful prey. Predators across many animal taxa actively avoid aposematically colored prey and remember distasteful brightly colored prey longer than cryptically colored prey. Lizards of many species are known to use aposematic coloration when foraging; however, most previous studies investigating the recognition of aposematic coloration by lizards have used live prey. This factor makes it difficult to determine whether lizards rely solely on visual cues or use a combination of sensory cues in prey selection. To determine whether anoles can select prey relying on only visual cues, we investigated the foraging response of Ground Anoles (Anolis humilis) to aposematic prey. By using clay models, we were able to remove any natural olfactory or behavioral cues that lizards may use in prey selection. We presented anoles with aposematically and cryptically colored insect models and found that lizards recognized and avoided aposematic models. This study demonstrates that A. humilis are able to use visual cues alone when selecting prey items. Our findings support previous work demonstrating that aposematic coloration is advantageous for prey, as it decreases the risk of attack by predators. The coloration also benefits predators, as they are able to recognize aposematic prey by sight alone, and avoid expending energy on an unpalatable meal.

La coloración aposemática permite a los depredadores utilizar señales visuales con el fin de evitar el consumo de presas potencialmente tóxicas o de sabor desagradable. En varias taxa, los depredadores de animales evitan presas con colores aposemáticos. Además, recuerdan las presas desagradables por más tiempo si estas son de colores brillantes a que si son de colores crípticos. Muchas especies de lagartijas son conocidas por utilizar coloración aposemática al escoger su presa. Sin embargo, la mayoría de los estudios previos que investigan el reconocimiento de coloración aposemática por lagartijas han utilizado presas vivas, lo cual dificulta determinar si las lagartijas se basan únicamente en señales visuales o si usan una combinación de señales sensoriales en la selección de la presa. Para determinar si los anolis pueden seleccionar su presa basados solamente en señales visuales, estudiamos la respuesta de forraje de la lagartija Anolis humilis con presas aposemáticas. Usamos modelos de plastilina para eliminar cualquier señal olfativa o de comportamiento natural que usan las lagartijas para la selección de presas. Se presentaron modelos de insectos de colores aposemáticos o crípticos a los anolis y encontramos que las lagartijas reconocieron y evitaron los modelos aposemáticos. Este estudio demuestra que A. humilis es capaz de utilizar exclusivamente señales visuales al seleccionar presas. Nuestros hallazgos apoyan el trabajo previo que demuestra que la coloración aposemática es ventajosa para la presa y disminuye el riesgo de ataque de los depredadores. La coloración también beneficia a los depredadores, ya que son capaces de reconocer la presa aposemática exclusivamente por la vista y evitar gastar energía en una comida desagradable.

Amphibians are among the most endangered organisms on Earth; however, few monitoring studies have been conducted in the tropics despite high amphibian diversity in these regions. To help fill this gap, we completed fieldwork to reassess the status of the Bloody Bay Poison Frog (Mannophryne olmonae, an endemic from the island of Tobago), classified as “Critically Endangered” by the original IUCN Global Amphibian Assessment, though recently downgraded to “Vulnerable.” To assess occupancy patterns and population stability, we used occupancy modeling with three years of listening survey data (2011–2013) from 35 sites. To examine patterns of relative abundance and recruitment, we gathered frog encounter rate and body size data from 18 stream-side transects. To assess current distributional limits, we conducted listening surveys at and beyond the known range limits. Together, these data suggest that M. olmonae is more widely distributed than previously reported (we found 23 extralimital populations), is present at a high percentage of sites surveyed (>70%), and is successfully reproducing along all of the stream-side transects on which they were found. Also, we found M. olmonae in a variety of forest types including both degraded secondary forest and abandoned cacao plantations. These field data were instrumental in downgrading this species and emphasize that species of conservation concern need to be monitored on the ground after listing, and these efforts must be continued to detect ongoing change. Our study suggests that even brief surveys in limited areas can quickly provide useful conservation data.

Species with temperature-dependent sex determination (TSD) are more vulnerable to climate change than species with genetically based sex determination because an increase in average environmental temperature could lead to biased offspring sex ratios. In TSD species, the relationship between sex ratio and constant incubation temperature is characterized by two parameters: the pivotal temperature (T_piv) and the transitional range of temperature (TRT) that produces both sexes. Species with variation in either of these parameters should have more potential to adapt to new climatic conditions, therefore putting them at lower risk to global warming. In this study, we incubated eggs of the turtle Podocnemis lewyana (Testudines: Podocnemididae) from two geographically isolated populations (Magdalena and Sinú rivers) under controlled microclimatic conditions to corroborate the TSD pattern previously reported for this species and to estimate the degree of inter- and intrapopulation variation in T_piv and TRT. We used these estimates, together with information found in the literature on other life history traits of P. lewyana, to evaluate its adaptive potential or vulnerability to climate change. We found interpopulation variation in TRT and intrapopulation variation in T_piv. This latter parameter exhibited a high broad-sense heritability, demonstrating this species' potential to adapt to climate change; however, when considering the narrow TRT found in this study, the species' equatorial distribution and related adaptations to relatively more stable climates, its fragmented populations and low vagility that prevent gene flow, and its low genetic variability, we concluded that the ability of P. lewyana to adapt to climate change is limited.

Las especies con determinación sexual dependiente de la temperatura (DST) son más vulnerables al cambio climático que aquellas con determinación sexual genética, ya que un aumento en la temperatura ambiental puede llevar a sesgos en las proporciones sexuales de la progenie. En especies con DST la relación entre las proporciones sexuales y la temperatura constante de incubación, está caracterizada por dos parámetros: la temperatura pivotal (T_piv) y el rango de transición de temperaturas (RTT) en el que se producen ambos sexos. Las especies con más variación en alguno de estos parámetros tienen más potencial para adaptarse a nuevas condiciones climáticas, y en consecuencia ser menos vulnerables al calentamiento global. En este estudio incubamos huevos de la tortuga Podocnemis lewyana provenientes de dos poblaciones geográficamente aisladas (ríos Sinú y Magdalena) bajo condiciones microclimáticas controladas para corroborar la presencia de DST anteriormente registrada para esta especie, y para estimar el grado de variación en la T_piv y el RTT entre y dentro de las poblaciones. Usamos esos estimaciones con información publicada sobre otros rasgos de historia de vida de P. lewyana para evaluar su potencial adaptivo o vulneribilidad al cambio climático. Encontramos variación interpoblacional en el RTT y variación intrapoblacional en la T_piv. Este último parámetro exhibió un alto nivel de heredabilidad de sentido amplio demostrando el potencial que esta especie tiene para adaptarse al calentamiento global. Sin embargo considerando el RTT tan estrecho encontrado, su distribución tropical y en consecuencia adaptación a climas estables, la fragmentación de sus poblaciones y baja movilidad que previenen el flujo genético y su baja variabilidad genética, concluimos que la habilidad de P. lewyana para adaptarse al cambio climático es limitada.

Studies of resource selection at multiple scales are critical to understanding ecological and evolutionary attributes of a species. We analyzed relative abundance, habitat use, and oviposition site selection of Foothill Yellow-Legged Frogs (Rana boylii) at 11 localities across two geographic regions in California (northern Coast Range and Sierra Nevada) over 16 yr. We found narrow ranges for oviposition microhabitat characteristics (water depth, water velocity, and stream substrate) among study localities. At the Main and South forks of the Trinity River, variances of the habitat traits were lower for oviposition microsites than for random points within breeding areas, indicating fine-scale selection. On the South Fork Trinity, egg mass relative abundances were negatively associated with water depth and positively associated with distance from the shoreline, suggesting that breeding areas with high egg mass relative abundances generally occurred in wide shallow areas. We observed long-term repeated use of breeding sites. At the South Fork Trinity, 63% of potentially suitable breeding areas were used consecutively for 3 yr, and at Hurdygurdy Creek several areas were used in ≥11 yr. Oviposition site selection and microhabitat specificity may result in population stability even within the substantial temporal and spatial variability of stream environments. Management of stream environments and conservation plans for R. boylii could benefit by preserving hydrologic processes that produce these specific habitats and identifying and protecting high-use breeding areas.

Predator–prey interactions play an important role in structuring larval anuran communities in ephemeral wetlands. The type of interaction often depends on the predator species and the complexity of the aquatic habitat. We experimentally evaluated the effects of Panhandle Crayfish (Procambarus evermanni) predation on larval Southern Leopard Frogs (Lithobates sphenocephalus) and larval Ornate Chorus Frogs (Pseudacris ornata). We performed separate experiments for each anuran species and used multiple vegetation treatments to examine whether vegetation could provide refugia from crayfish predation. Our results indicate that crayfish are effective predators of anuran larvae regardless of the amount of vegetation present. Encounters between tadpoles and crayfish often resulted in nonlethal tail injury for tadpoles, suggesting that crayfish predation is prominent in ephemeral wetland communities. Leopard frog tadpoles in predator treatments also grew larger than their counterparts in nonpredator treatments, suggesting a reduction in intraspecific competition. Reduced competition and higher growth rates may allow anuran larvae to develop and metamorphose faster, allowing them to escape aquatic predators, drying wetlands, or both.

Travancore Tortoises (Indotestudo travancorica) are endemic to the Western Ghats, south India. Landscape level surveys showed no clear habitat selection by the species. Therefore, we used radiotelemetry to study home-range size and fine-scale spatial movement habitat use of four tortoises from 2008–10. Minimum convex polygon home-range sizes of four tortoises varied between 5.2 and 34 ha. Tortoises spent a majority of their time in evergreen forest edge that had bamboo–lantana–grass. Eighty-two percent of the locations in the evergreen forest, and 95% of the locations in the bamboo–lantana–grass habitat, were at the edge of these habitats. Therefore at a fine scale, tortoises used the forest edge, possibly because it provided opportunities for foraging and thermoregulation.

Invasive species are a threat to biodiversity, and understanding their impacts on native ecosystems is a research priority. Red Imported Fire Ants (Solenopsis invicta) are invasive in the southeastern United States and have multiple effects on a variety of native species. Some species and particular life stages (e.g., juveniles and eggs), may be especially vulnerable to fire ants, but research on these impacts has been limited. Fire ants occupy microhabitats used for nesting by Eastern Fence Lizards (Sceloporus undulatus) across much of their range. We examined the extent of fire ant predation on fence lizard eggs by constructing artificial nests at a fire ant–invaded location and monitoring their predation for up to 20 days. During this period, 24% of nests were predated by fire ants, and survival curves suggest 61% of nests may be vulnerable to fire ant predation over the entire incubation period. Distance of nests to the nearest fire ant mound and canopy cover above nests were not significant predictors of predation, indicating that nest site choice by fence lizards may not be able to avert fire ant predation. Invasive fire ants likely represent a novel level of predation pressure on many species, and these effects should be accounted for in management and conservation strategies.

Frogs in the genus Cycloramphus are endemic to the Brazilian Atlantic Forest domain and many are threatened or endangered. Cycloramphus species lay eggs either on moist rocks or in moist soil cavities on the ground. Tadpoles of only 8 of the 28 recognized Cycloramphus species are known. Herein we describe the tadpole of C. rhyakonastes on the basis of specimens collected at the type locality in southern Brazil. Cycloramphus rhyakonastes is an aquatic breeder with semiterrestrial tadpoles that live on moist rocks within the splash zone of high gradient streams. We compare the C. rhyakonastes tadpole with all congeneric tadpoles described to date and discuss adaptations in this specialized tadpole and those of other species that adhere to rocky substrates.

The origins of the two iguana species (Iguana delicatissima [Lesser Antillean Iguana] and Iguana iguana [Green Iguana]) occurring today in the Lesser Antilles are frequently questioned using mostly historical and genetic data. Osteological remains of iguanas are common in archaeological and paleontological deposits in the Lesser Antilles, however, and they could be important for understanding the past colonization processes of these two iguana species and subsequent sympatry. Unfortunately, although numerous questions exist about the past occurrence of those two species and their respective arrival dates, no osteological study has led to proper identification of subfossil iguana skeletal elements. Here we present a series of characters that allow for distinguishing the two species using isolated bones and emphasize the reliability of each recognized specific character. We also provide some comments about skeletal morphology of hybrids between both species and their identification based on osteology.

L'origine des deux espèces d'iguanes peuplant actuellement les Petites Antilles (Iguana delicatissima et Iguana iguana) est souvent sujette à question notamment via l'utilisation des sources historiques et génétiques. Cependant, les restes ostéologiques d'iguanes sont fréquemment retrouvés dans les sites archéologiques et paléontologiques des Petites Antilles et pourraient être de première importance pour comprendre les processus de colonisation de la zone par ces deux espèces. Malheureusement, bien que de nombreuses questions persistent quant à la présence passée et aux périodes d'arrivées de ces deux taxons, aucune étude ostéologique ne permet d'aboutir à une identification satisfaisante de leurs restes sub-fossiles. Nous présentons ici une série de caractères permettant d'identifier ces deux espèces via des fragments osseux isolés tout en discutant la fiabilité de chacun des caractères. Nous émettons également quelques commentaires relatifs à la morphologie squelettique des hybrides de ces deux espèces et à leur identification via des restes osseux.

We examined the osteology of Neogene Alligator, with a focus on fossils from the late Miocene (~8–7 million years ago [Ma]) Moss Acres Racetrack locality in Marion County, Florida, USA. These fossils have been referred previously to Alligator cf. A. mefferdi (early late Miocene, ~12–10 Ma, Nebraska), an extinct species that we and others have found to be lacking autapomorphic characters. Furthermore, numerous cranial polymorphisms, previously regarded as diagnostic autapomorphies or synapomorphies, exist in several species of Alligator, particularly in Alligator prenasalis (late Eocene–early Oligocene, ~36–33 Ma, South Dakota and possibly Nebraska), Alligator olseni (early Miocene, ~18–17 Ma, Florida), and the extant American Alligator (Alligator mississippiensis; southeastern United States). Except for minute differences in two scapular characters, the fossil Alligator from Moss Acres Racetrack is virtually indistinguishable from the A. mississippiensis morphotype, suggesting its referral to that lineage rather than to an extinct species. Cladistic analysis upholds this notion, with A. mississippiensis and the Moss Acres Racetrack Alligator being sister taxa in a unified clade isolated from A. mefferdi. This implies that the A. mississippiensis morphological lineage has existed in North America with very little change for the past 7–8 million years.

Tropidurus is a widespread genus of lizards in Brazilian biomes, particularly common in the state of Bahia, northeastern Brazil. However, genetic studies of populations and species of this group are still scarce. We used chromosomal and DNA barcoding analyses to examine 12 populations of five species of Tropidurus from semiarid (caatinga) and Atlantic forest portions of Bahia. All populations shared a karyotype with 2n = 36 divided into 12 metacentric and submetacentric chromosomes and 24 microchromosomes. The microchromosomes were acrocentric in most of species, but metacentric microchromosomes were observed in Tropidurus semitaeniatus, determining variation in fundamental number of arms from 48 to 52. One population of Tropidurus hispidus presented a supernumerary chromosome. Pericentromeric heterochromatin was detected in most microchromosomes and two pairs of macrochromosomes presented interstitial and pericentromeric C-bands. The nucleolar organizer regions (NORs) were single in Tropidurus erytrocephalus, T. semitaeniatus, and Tropidurus torquatus, and multiple in Tropidurus cocorobensis and T. hispidus. This is the first report of multiple NORs in both species. These results suggest a conserved pattern of karyotype macrostructure in Tropidurus, whereas microstructural features have undergone a more dynamic evolution, including non-Robertsonian rearrangements. DNA barcoding supported a clear distinction between analyzed species, except for the cryptic diversity indicated in the T. hispidus and T. torquatus cluster, in agreement with current taxonomic uncertainties. The diversity of this group of lizards is discussed based on their divergence and distribution patterns.

We describe a new species of anguid lizard of the genus Mesaspis from the Sierra de los Cuchumatanes of northwestern Guatemala. This species reaches a maximum snout–vent length of about 72 mm, making it much smaller than Mesaspis moreletii. In the Sierra de los Cuchumatanes it occurs sympatrically with Mesaspis moreletii temporalis, the only such instance of congeneric sympatry known in Nuclear Central America. The new species appears most similar to the widely distributed species M. moreletii, which may be polytypic. Mesaspis cuchumatanus may be distinguished from M. moreletii by usually having expanded supranasals, 16 longitudinal scale rows, small and granular scales covering the side of the neck from about the level of upper edge of auricular opening to ventrolateral fold, and smaller body size.

Se describe una nueva especie de lagartija del género Mesaspis de la Sierra de los Cuchumatanes al noroeste de Guatemala. Esta especie alcanza una longitud hocico-cloaca aproximada de 72 mm, por lo que es significativamente más pequeña que M. moreletii. Esta especie se encuentra en simpatria con M. moreletii temporalis en la Sierra de los Cuchumatanes, el único caso de simpatría del género en América Central Nuclear. La nueva especie parece ser más similar a Mesaspis moreletii que tiene una distribución más extensa y que puede ser politípico. Mesaspis cuchumatanus se puede diferenciar de M. moreletti por tener las supranasales usualmente expandidas, 16 filas de escamas longitudinales, escamas pequeñas y granulares cubriendo los lados del cuello desde el borde superior de la apertura auricular hasta el pliegue ventrolateral, y un cuerpo más pequeño.

We describe Pristimantis tinguichaca sp. nov., a member of the Pristimantis unistrigatus species group, from the cloud forests of Sangay National Park located on the eastern slopes of the Andes in southeastern Ecuador. The new species was collected in cloud forests and cattle pastures at 2,750–2,830 m elevation. It differs from other members of the P. unistrigatus group by the presence of small conical tubercles on the upper eyelids and heels, as well as by its reddish-colored iris. It is further distinguished by its small conical ulnar and tarsal tubercles. A single sharp metallic note composed of a modulated frequency characterizes the call. Stomach content analysis revealed a diet composed principally of beetles (51.7%).

Describimos a Pristimantis tinguichaca sp. nov. del grupo Pristimantis unistrigatus, de los bosques nublados del Parque Nacional Sangay de las estribaciones orientales de los Andes en el sureste de Ecuador, a elevaciones de 2,750–2,830 m. Difiere de otros miembros del grupo unistrigatus por la presencia de tubérculos cónicos pequeños en el párpado y talón, tubérculos ulnares y tarsales cónicos pequeños, e iris rojizo. El canto se caracteriza por un sonido metálico, grave; presenta llamados de frecuencia modulada, los mismos que están compuestos de una sola nota. El análisis de los contenidos estomacales reveló una dieta basada principalmente en coleópteros (51.7%).