Biology, including herpetology, has made greater strides in recent decades than in any time in history. It has progressed from a largely inductive science performed on an expeditionary basis to a laboratory-based discipline in which preformed hypotheses are tested empirically. My research has spanned that change in paradigm and an example of expeditionary biology, the study of habitat selection by amphibians and reptiles in the Darien Gap, Panama, is described. The study of Sea Snakes is used to illustrate the transition. Analysis of the offerings to two herpetological journals, Herpetologica and the Journal of Herpetology, also demonstrates changes in different topical emphases. A prominent trend in herpetology has been a shift from basic biology to conservation in the face of environmental degradation and the need to preserve the biodiversity of amphibians and reptiles. The unified biology of antiquity had fragmented into separate, specialized disciplines that seldom related to each other in more than a general way, despite the encompassing generalization of adaptation through evolution. In the past decade there has been a great melding of disciplines and a return to a more-holistic melding of disparate areas of biological endeavor.

Understanding how habitat heterogeneity influences the genetic structure of populations is an important goal of conservation genetics. Species with different evolutionary histories may respond differently to contemporary habitat loss and fragmentation. Recent genetic analyses have shown high levels of genetic structure in two subspecies of Massasauga Rattlesnakes of conservation concern (Eastern Massasaugas, Sistrurus catenatus catenatus and Desert Massasaugas, Sistrurus catenatus edwardsii) living in highly fragmented habitats. Here, we complement those results with an analysis of the genetic structure of the third subspecies (Western Massasaugas, Sistrurus catenatus tergeminus), which has a largely continuous distribution in Kansas but with some isolated populations in Missouri. We found no evidence of genetic structure among the Kansas populations of Western Massasaugas, though our STRUCTURE analysis did identify the two Missouri populations as distinct clusters from each other and from the Kansas populations. Population differentiation estimates were much lower across all Western Massasauga populations compared to those observed in Eastern and Desert Massasaugas. Quantitative analyses of habitat availability and fragmentation confirm that the Kansas landscape is less fragmented than the range occupied by Eastern Massasaugas; this supports a possible influence of habitat fragmentation on genetic structure of these snakes. The more-continuous distribution and relative genetic uniformity of Western Massasaugas found in Kansas contrast with the isolated nature of Desert and Eastern Massasaugas, making the Western subspecies unique within the Massasauga complex.

We conducted nocturnal surveys in the insular and coastal areas of Coiba National Park (CNP) and its mainland buffer zone in Panama (Chiriquí conservation site) from 2009–2012 to determine the conservation status of Crocodylus acutus. In 99 nights, we surveyed 147.2 km and captured 185 animals during nocturnal transects inspection with headlamps. Overall, sex ratio was 1.00:1.01 female/male with significant differences by size/age class and year. Females were slightly larger in total length than males (115.1 ± 56.9 cm-females, 105.4 ± 71.8 cm-males). The encounter rate was calculated based on number of animals captured per km of surveyed transect. The C. acutus encounter rate per year was 1.8 ind/km (60 ind/33.5 km/12 places visited) in 2009, 1.0 ind/km (90 ind/87.4 km/18 places visited) in 2010, and 1.3 ind/km (35 ind/26.3 km/8 places visited) in 2012. Based on our spatial analysis, the animals showed a dispersed pattern in most sites on CNP. Captured C. acutus were found in 581.1 km² total area within 78% natural habitat, including mangroves and beaches, and 22% disturbed habitat on both the mainland and the islands. In addition, the spatial analysis showed reduction in natural land cover; crocodile habitat showed limited conversion to agricultural land use; and we found correlation between crocodile population size and protected areas. The differences between mainland and island populations regarding ecology suggest that a long-term monitoring program for American Crocodiles is necessary to distinguish between natural fluctuations and anthropogenic changes on population dynamics and conservation status.

Entre 2009 al 2012 hicimos varias expediciones en la parte insular y en las áreas costeras del Parque Nacional Coiba y su zona de influencia en Panamá (Sitio de conservación para la diversidad), para determinar el estado de conservación de Crocodylus acutus y sus hábitats asociados. En 99 noches recorrimos 147.2 km y capturamos 185 animales usando linternas de cabeza. La proporción de sexos fue 1.00:1.01 hembra/macho, la cual fue significativamente diferente cuando los animales fueron clasificados por grupo etario y año. Las hembras fueron un poco más grandes que los machos (115.1 ± 56.9 cm-hembras, 105.4 ± 71.8 cm-machos). La tasa de encuentro fue calculada con base en el número de animales capturados por kilómetro. La tasa de encuentro para C. acutus por año fue de 1.8 ind/km (n = 60; 33.5 km; lugares visitados: 12) en 2009, 1.0 ind/km (n = 90; 87.4 km; lugares visitados: 18) in 2010 y 1.3 ind/km (n = 35; 26.3 km; 26.3; lugares visitados: 8) en 2012. El análisis espacial mostró a C. acutus distribuido en la isla de Coiba en un patrón disperso, excepto en El María y el Playa Blanca donde el patrón de dispersión fue de agrupamiento. Los animales capturados se encontraban en un área total de 581.12 km² cubierta por un 78% de manglares y playas y un 22% por hábitats modificados. Comparando la cobertura vegetal de 1992 y 2000, nuestros resultados mostraron baja densidad poblacional asociada a la reducción de hábitat. Las diferencias en la ecología poblacional entre los sitios continentales y los insulares sugieren que un programa de monitoreo a largo plazo del Cocodrilo Americano permite distinguir entre las fluctuaciones naturales y los cambios antropogénicos sobre la dinámica poblacional y el estado de conservación.

The island of Aruba is home to several endemic species, and has been colonized recently by the invasive boa, Boa constrictor. We present data for a multiple-year sampling effort on one of Aruba's endemic species, the Aruban Whiptail Lizard (Cnemidophorus arubensis). Our sampling began before the invasion of B. constrictor and ended after their firm establishment, thus affording us the unique opportunity to document the potential effects of this invasive snake on the endemic lizard. Additionally, we compare our data with earlier studies with an average lizard density of 235.1/ha (SE = 73.42, n = 11). After the invasion of the B. constrictor we calculated densities of C. arubensis as high as 2,185/ha. Although B. constrictor regularly preys upon C. arubensis, the relationship between B. constrictor and C. arubensis likely represents ecological facilitation of the lizard species. Herein, we further develop a hypothesis that may explain how the invasive B. constrictor has caused an increase in the population of this endemic lizard. Additionally, we suggest and discuss a few alternative hypotheses that may also account for this observed pattern of increased density. This study identifies a need for continued monitoring of Aruba's native fauna, as well as the need for further experimental approaches to understand the mechanism by which invasive predators ecologically interact with native prey.

The direct and indirect effects of fire on different life stages of amphibians are poorly understood and difficult to predict given interspecific variation in physiology and life history. We investigated how time-since-fire (TSF) of seasonal ponds embedded within Florida scrub habitat affected growth, development, and survival of larval Oak Toads (Anaxyrus quercicus). We selected 12 ponds at Archbold Biological Station on the southern Lake Wales Ridge, Florida: four burned within the last 4 mo, four burned 3–4 yr ago, and four burned 11 yr ago. We hatched and reared three clutches of Oak Toads in the laboratory for 2 wk and then sorted larvae into groups of 24 having equal representation from each clutch. We randomly assigned groups of larvae to 0.22-m³ mesh field enclosures in each pond (n = 2–3 enclosures per pond) and measured environmental variables that might contribute to observed amphibian responses including pH, temperature, and periphyton growth. After 15 d, when larvae began metamorphosing, mean survival was significantly higher in the most-recently burned ponds. The TSF did not have a significant effect on developmental stage or tadpole size, although Oak Toad larvae tended to develop faster in the most-recently burned ponds. Although all ponds were acidic (pH < 4.3), there was a trend toward higher pH in the more-recently burned ponds, and survival was significantly positively correlated with pH. Overall our results suggest that performance and recruitment of larval Oak Toads are higher in recently burned ponds.

Contrasting movements and habitat use may occur among snakes, and these differences may reflect important local responses to habitat variation and/or signify that broad, unimodal approaches to species conservation are too coarse. Fine-scale differences in these behaviors (e.g., between neighboring conspecifics) may be underappreciated because studies either focus exclusively on one (sub)population, and/or the animals are not compared across relevant ecological boundaries. We report on a striking dichotomy of seasonal migration behavior between Rattlesnakes (Crotalus oreganus) using two neighboring den sites. The snakes at one site undertook long-distance (2.9 ± 0.57 km [mean ± SD], highly directional migratory behavior that was consistent across years and individuals. These movements carried them out of the habitat normally associated with these animals in this region (grassland steppe) and into higher elevation forests, a habitat not previously reported for these animals. Conversely, snakes at another den only 21 km away were nonmigratory (0.97 ± 0.54 km) and remained in grassland habitat throughout the year. Landscape and other environmental factors may have been responsible for the difference in the behavior of these two denning groups, suggesting that our knowledge of what dictates the migratory behavior of animals such as snakes is far from complete. Stereotyping the habitat use and behavior of any snake population is potentially misleading, and more thorough exploration is needed on how these animals alter their local movement patterns in response to changes in landscapes and habitat configurations, including potential climate change effects.

Many snake species make lengthy linear migrations between overwintering sites and summer foraging or mating habitats. Although mountainous topography may restrict migratory movements, most previous studies on migratory snake populations have occurred in areas with low to moderate topographic relief. The objectives of this study were to describe the movement patterns of Prairie Rattlesnakes (Crotalus v. viridis) in a mountainous landscape, compare those patterns to those of migratory snake populations from areas with lower topographic relief, and test for variation in movement patterns between sexes and among years. We used radiotelemetry to monitor the movements of 21 male and 6 nonpregnant female Prairie Rattlesnakes in the Frank Church Wilderness in central Idaho during the summers of 2006–2008. Mean total distance moved during the entire activity season in 2008 was 4.46 km (range 1.38–7.67); mean maximum distance moved from the hibernaculum was 1.46 km (range 0.69–2.71). Although the movement distances reported here are intermediate to those reported for other migratory snake populations, they are similar to some distances reported from areas with low to moderate topographic relief. This suggests that rattlesnakes are capable of making considerable movements in a mountainous landscape, although factors such as prey availability could also contribute to differences in reported movement distances. Rattlesnakes displayed moderate fidelity to summer activity areas but had similar mean bearings during outbound migration across multiple years. We hypothesize that linear migrations reported from rattlesnakes in many populations actually represent the most-direct movement to annual foraging areas rather than true searching movements.

Social behaviors often are context dependent; behaviors at high density may change or disappear at lower population densities. We analyzed spatial dispersion patterns and habitat associations at high and low population densities of male Espadarana (Centrolene) prosoblepon that declined following the invasion of a pathogenic fungus, Batrachochytrium dendrobatidis (Bd). We mapped the spatial location of male frogs on four permanent 200-m stream transects over 4 pre- and 7 postdecline yr. We calculated distances between nearest neighbors and between hot spots—defined as areas of high male density—and compared habitat associations of frogs at high and low densities. Average predecline density across transects was 0.034 ± 0.02 males m⁻¹ (mean ± SE) and dropped to 0.019 ± 0.02 males m⁻¹ postdecline. Nearest neighbor and between cluster distances did not change significantly between pre- and post-decline yrs. Nine of 21 hot spots persisted in the same location across 12 yrs, whereas 8 hot spots disappeared and 4 new hot spots appeared postdecline. We determined male abundance was correlated with the amount of leafy vegetation and stream width at high density, but we found no associations at low densities. Overall, spatial dispersion patterns were highly conserved for over a decade, despite a new cohort of individuals, a decline in abundance, and changes in physical structure associated with natural forest dynamics. Our results suggest spatial dispersion is density independent and that male hot spots are influenced by both physical habitat and social interactions.

Parasitized hosts frequently experience behavioral side effects associated with pathology. Although this phenomenon is fairly well documented, we do not fully understand the relationship between changes in host behavior and parasite infection intensity. Building upon previous research on Batrachochytrium dendrobatidis (hereafter “Bd”) and feeding efficiency in anuran tadpoles, we conducted a laboratory experiment using Bd-infected tadpoles of the Green Frog (Lithobates [=Rana] clamitans). We allowed tadpoles to feed during a 5-h trial and tested whether Bd-infection intensity was a significant predictor of the amount of food that tadpoles consumed during the trial. As predicted, tadpole feeding efficiency decreased linearly with Bd-infection intensity. Our results indicate that Bd-infected tadpoles suffer a reduced potential to obtain food and that feeding performance is correlated with Bd-infection intensity. Our result indicates that, if tadpoles cannot clear low-level Bd infections, their health might decline at a rapid rate, which could further reduce their ability to defend themselves from other micro- and macroparasites.

Demilitarized zones may aid in the protection of endangered wildlife. We compared relative abundance of the endangered Chinese Pond Turtle (Mauremys reevesii) among water bodies on the Kinmen Islands, a recently demilitarized zone between Taiwan and China. Vegetation and wildlife on the two islands, located 2 km from the Chinese coastline, were degraded by bombardment and military occupation between 1958 and early 2000s. However, natural habitats gradually recovered after military forces withdrew. More than 100 ponds, mostly produced during the occupation to provide freshwater for the soldiers, are now abandoned and provide habitat for aquatic turtles. We sampled 41 ponds and found that presence of M. reevesii was tightly associated with vegetation coverage around the pond, whereas its relative abundance was associated with aquatic vegetation and distance from roads. Comprehensive protection and management of this species should consider both vegetation coverage and road effects in certain vulnerable areas where establishment of a natural reserve might be considered.

Agassiz's Desert Tortoises (Gopherus agassizii) spend >95% of their lives underground in cover sites that serve as thermal buffers from temperatures, which can fluctuate >40°C on a daily and seasonal basis. We monitored temperatures at 30 active tortoise cover sites within the Soda Mountains, San Bernardino County, California, from February 2004 to September 2006. Cover sites varied in type and structural characteristics, including opening height and width, soil cover depth over the opening, aspect, tunnel length, and surficial geology. We focused our analyses on periods of extreme temperature: in summer, between July 1 and September 1, and winter, between November 1 and February 15. With the use of multivariate regression tree analyses, we found cover-site temperatures were influenced largely by tunnel length and subsequently opening width and soil cover. Linear regression models further showed that increasing tunnel length increased temperature stability and dampened seasonal temperature extremes. Climate change models predict increased warming for southwestern North America. Cover sites that buffer temperature extremes and fluctuations will become increasingly important for survival of tortoises. In planning future translocation projects and conservation efforts, decision makers should consider habitats with terrain and underlying substrate that sustain cover sites with long tunnels and expanded openings for tortoises living under temperature extremes similar to those described here or as projected in the future.

Concordant phylogeographic patterns among species indicate similar ecological and/or evolutionary histories. A concordant phylogeographic pattern exists among two fossorial skinks inhabiting Florida scrub habitat on the Lake Wales Ridge in central Florida. We evaluate whether the Peninsula Crowned Snake (Tantilla relicta relicta), a fossorial species similarly adapted to xeric upland habitats in central Florida, follows the same phylogeographic pattern. We collected 51 Peninsula Crowned Snakes from 13 sites on the Lake Wales Ridge. The sites spanned Josephine Creek, a location identified as a potential phylogeographic break-point for the species studied previously. We screened the genetic variation of a portion of the mitochondrial cytochrome-b gene and the mitochondrial control region. Phylogenetic analysis indicated that the Peninsula Crowned Snake has central and southern groups, which is similar, yet not identical, to other reptiles on the Lake Wales Ridge. Tests of differentiation detected population structure among three Peninsula Crowned Snake populations within 10 km of Archbold Biological Station. Our results support the presence of at least two major phylogeographic segments for scrub reptiles on the Lake Wales Ridge and suggest that the Peninsula Crowned Snake may have a genetic population structure, even in connected habitats.

We investigated the spatial ecology of the California Kingsnake (Lampropeltis californiae) in unfragmented and fragmented habitat with varying patch sizes and degrees of exposure to urban edges. We radiotracked 34 Kingsnakes for up to 3 yr across four site types: interior areas of unfragmented ecological reserves, the urbanized edge of these reserves, large habitat fragments, and small habitat fragments. There was no relationship between California Kingsnake movements and the degree of exposure to urban edges and fragmentation. Home range size and movement patterns of Kingsnakes on edges and fragments resembled those in unfragmented sites. Average home-range size on each site type was smaller than the smallest fragment in which snakes were tracked. The persistence of California Kingsnakes in fragmented landscapes may be related directly to their small spatial movement patterns, home-range overlap, and ability to use urban edge habitat.

There is a surprising lack of data available on snake demography. This is largely because snakes are cryptic and difficult to detect. To address this problem, researchers often use nonrandom sampling methods (which can result in sampling artifacts) or pool capture occasions (which results in a loss of information). We conducted two spatially and temporally overlapping mark–recapture studies on Milksnakes (Lampropeltis triangulum). Both studies used fixed trap locations (artificial cover objects) but varied in their sampling duration and intensity. We used multimodel inference within an information-theoretic approach to estimate adult annual survival (0.72 ± 0.160 standard error [SE]) and abundance (N = 85 ± 35.2 SE). To estimate density, we used a spatially explicit model (1.19 individuals/ha ± 0.331 SE). We applied a novel approach to address sampling bias that resulted from the use of fixed trap locations. This involved modeling maximum detection frequency as a covariate, which better accounted for individual heterogeneity in detection probabilities than did mixtures, sex, behavior, or month. This approach allowed for the recovery of information that was lost when capture occasions were pooled to account for low detection. We found support for this technique via reanalysis of datasets of known population size. This approach may be useful for mark–recapture studies that rely on fixed trap locations.

Western Pond Turtles (Actinemys marmorata) are endemic to western North America and are found in a diversity of aquatic habitats. To date, few studies have examined the ecology of populations in ephemeral or intermittent ponds. Here, we studied the terrestrial habitat requirements of Western Pond Turtles in an intermittent pond that dries in years with below-average rainfall. We tracked terrestrial movements of Western Pond Turtles in an ephemeral pond at the San Joaquin Experimental Range in Madera County, California, USA, in the western foothills of the Sierra Nevada. We used radiotelemetry in 2012–13 to record their terrestrial locations and timing of departure from, and return to, the pond. Also, we examined the terrestrial microhabitat turtles selected for aestivation and overwintering. Turtles began leaving the pond as it dried in the late spring and early summer, spending an average of 235 d out of water, and their return to the pond was correlated with increasing rainfall during late winter. The majority of terrestrial locations were concealed completely in litter or duff and 95% of terrestrial locations during the study occurred within 187 m of the pond edge. Turtles in our study generally exhibited terrestrial habitat use similar to that of populations in intermittent lotic systems such as the many snow-melt and rain-fed rivers in northern California. Our results reinforce the importance of terrestrial habitat in the life history of Western Pond Turtles and the context-dependence of their habitat needs.

Habitat size and heterogeneity are among the main factors determining local species richness. However, distinguishing between them is critical to discriminate stochastic from the habitat-driven processes underlying local patterns of species distribution. Here, we test the individual effects and interaction of habitat size and heterogeneity in driving the occurrence of species in water bodies in the Brazilian Caatinga dry forest. We surveyed sites of different sizes and degrees of physical heterogeneity (i.e., margin architecture and plant stratification) and performed univariate and multivariate analyses to test the effect of these factors on species richness and composition. We found a clear habitat size effect but a negligible influence of habitat heterogeneity on the species richness at breeding sites. Specific habitat features may be important for few species, however. Our findings suggest an overall stochastic usage of water bodies by the anurans in the Caatinga and highlight the need of distinguishing the effects of habitat availability from those of habitat heterogeneity when investigating the structure of anuran assemblages.

In some herbivores, home range size is correlated negatively with the primary productivity of their environments. Although the South African Succulent Karoo is arid, it receives relatively predictable winter rainfall and therefore relatively predictable primary production toward the following spring. Lush springs may alternate with occasional drought years. Over five spring seasons with variable rainfall patterns, I studied home range size in 21 male and 31 female Namaqualand Speckled Tortoises (Homopus signatus) in the Succulent Karoo using opportunistic sightings, thread-trailing, and radio telemetry. In addition, daily movement distances were determined for 8 males and 28 females with the use of thread-trailing over three spring seasons. The average home range size for H. signatus was 3,470 m², much smaller than home ranges for tortoises in other arid regions. Home range size did not differ between the sexes, but was negatively correlated with rainfall. Daily movement distances were also similar between sexes, but tortoises moved greater distances in a relatively warm spring. It appears that temporary mesic conditions in spring enable male and female H. signatus to meet their nutritional needs in a relatively small area, and the flexible response to variable environmental conditions may enhance tortoise survival during drought years.

We studied the effects of sex, body size, and season on the diet of two populations of the Blue-Bellied Poison Frog Andinobates minutus (Anura: Dendrobatidae) along the Pacific coast of Colombia. Andinobates minutus had a specialist diet, with preference for Acari (mites), Formicidae (ants), Collembola (springtails), and Holometabolous larvae. No differences in diet composition were noted between populations or between seasons. However, prey volume was higher in frogs from Bahía Málaga than those from Isla La Palma, and both populations experienced a decrease in the number of prey items in November, caused possibly by the low prey availability in that month. A differential effect of body size on diet was noted between populations. The total volume of prey, the volume and number of ants, and the volume of mites increased with snout–vent length (SVL), whereas the number of springtails decreased with SVL only in the Bahía Málaga population but not in the Isla La Palma population. This differential effect could be caused by the difference in distributions of the individuals' body sizes between populations. A significant effect of sex on diet was noted in both populations. Females from both populations showed higher preference for ants than did males. However, the importance of Formicidae showed temporal fluctuations in both populations. The diet of A. minutus in both populations had an important phylogenetic component, because closely related species have similar diets. Although other factors affected diet, the differential effects observed between populations could be caused by the spatiotemporal dynamic of each population.

In animals with internal fertilization, the male genitalia often vary greatly, have complex morphology, and show fast rates of evolution. In studies of the evolution of such male genitalia, static allometric relationships have been used extensively. Static allometry is an intraspecific measure of proportional size of a particular structure with respect to the body size. We examined the static allometric pattern of the genitalia of two allopatric subspecies of a Jamaican Anolis lizard, Anolis grahami grahami and A. grahami aquarum, and compared our findings to observed patterns in nongenitalian traits: limbs and the dewlap. Limb and dewlap traits showed similar allometric slopes, with some variation in the intercept, whereas hemipenial traits showed different slopes. The hemipenial traits of Anolis g. grahami exhibited a statistically significant negative allometry, while A. g. aquarum showed slope values that were not statistically different from isometry. Our results corroborate the idea that genital traits evolve faster than other morphological body traits.

Accurate descriptions of gonadogenesis are necessary to have a baseline to detect abnormalities during development and to assess the time a species may be more vulnerable to the action of pesticides, endocrine disruptors, and pharmaceuticals to which abnormal conditions have been attributed. Here, I describe the histomorphological changes during gonadal differentiation in the Snouted Treefrog Scinax fuscovarius. I sexed and measured a total of 302 tadpoles between Gosner stages 26–46 and 21 juvenile and adults. The results show that 1) the species possesses the undifferentiated type of gonadal differentiation—ovaries differentiate much earlier (at stage 26) than testes (stage 36); 2) oogenesis begins almost simultaneously with ovarian differentiation; and 3) ovaries and testes exhibit different rates of gonadal differentiation with respect to somatic development—the ovaries have an accelerated rate (the ovarian cavity differentiates early during larval development and previtellogenic oocytes develop at early premetamorphic stages), whereas the testes have a decelerated rate (seminiferous tubules differentiate at the juvenile stage). The comparison of these characteristics with those of other co-occurring anuran species reveals important interspecific variation in the relative timing of gonadogenesis. Finally, and as a byproduct of the extensive sampling, I describe several cases of gonadal malformations.

The New World direct-developing frogs (Brachycephaloidea = Terrarana) comprise nearly a thousand species that share direct development among other putative synapomorphies, yet embryonic development in this group has been thoroughly described in only about 20 species. Here we describe the early ontogeny of the craugastorid Haddadus binotatus, making special emphasis on tail structure and development, and its differences and similarities with that of other terraranans. The morphological changes during embryonic development of H. binotatus and those of other Neotropical direct-developing species are alike, with some variation including the absence of external gills, timing of limb differentiation, and tail configuration. The tail with a rotated core axis and lateral and asymmetric fins that cover the posterior half of the embryo represents an outstanding case of developmental repatterning. We present some interpretations of the evolution of the tail and its three major aspects, the rotation of the core axis, and the origin and extensions of the fins, and pinpoint that those mechanisms underlying fin development should be fairly plastic, allowing the ontogenetic and evolutionary variation within the Brachycephaloidea clade.

Las ranas de desarrollo directo del Nuevo Mundo (Brachycephaloidea = Terrarana) incluyen cerca de mil especies que comparten el desarrollo directo entre otras sinapomorfías putativas; sin embargo el desarrollo embrionario en este grupo ha sido descripto en no más de 20 especies. Aquí describimos la ontogenia temprana del craugastórido Haddadus binotatus, con especial énfasis en la estructura y el desarrollo de la cola y sus diferencias y similitudes con la de otros terraranas. Los cambios morfológicos durante el desarrollo embrionario de H. binotatus son similares a los de otras ranas neotropicales con desarrollo directo, con algunas variaciones que incluyen la ausencia de branquias externas, los tiempos de diferenciación de las extremidades y la configuración de la cola. La cola con su eje rotado y aletas laterales y asimétricas que cubren la mitad posterior del embrión representa un caso excepcional de cambio en los patrones del desarrollo. Aquí presentamos algunas interpretaciones sobre la evolución de la cola y sus tres aspectos principales: la rotación del eje y el origen y extensión de las aletas, y señalamos que los mecanismos que subyacen al desarrollo de la aleta parecen ser lo suficientemente plásticos como para permitir la variación ontogenética y evolutiva presente en el clado Brachycephaloidea.

Varanus (Soterosaurus) monitors recently received increased scrutiny from herpetologists, resulting in identification of previously unrecognized morphologic and genetic diversity. These advances rendered Varanus salvator salvator as one of the most narrowly distributed monitors, because most populations are reassigned to existing or newly identified species. No diagnostic skeletal characters are known for those species. Two skeletonized specimens of the recently named Varanus palawanensis are in the collection of the U.S. National Museum of Natural History, but are labeled V. salvator. Here, I offer some observations on those skeletons, make comparisons with some other Varanus(Soterosaurus) monitors, and update the diagnosis of the species with some probable osteological autapomorphies. Varanus palawanensis differs from other Varanus (Soterosaurus) in possessing a unique combination of character states. The premaxilla extends to the level of the frontal, the frontal and parietal lack dermal sculpturing, the lacrimal anteroposteriorly narrow, the vidian canal entirely within the parabasisphenoid, and the anterostapedial process is tab-like. I contend that species should be holophyletic even in the face of taxonomic upheavals created by newly identified diversity.

The parthenogenetic triploid lizard Aspidoscelis neotesselata originated from a hybridization event between a female of diploid parthenogenetic Aspidoscelis tesselata (pattern class C) and a male of Aspidoscelis sexlineata viridis, and A. neotesselata is morphologically more similar to its maternal progenitor, A. tesselata. The geographic distribution of A. neotesselata is characterized by localized arrays of individuals located within a four-county area in southeastern Colorado, and postorigin divergence is visually evident in its four allopatric color pattern classes (A, B, C, and D). A fundamental pattern of morphological divergence was revealed by a multivariate partitioning of its four color pattern classes into two basic groups: an A group (pattern classes A and D) and a B group (pattern classes B and C). A problem introduced by this grouping is the incongruence between the multivariate similarity of pattern classes A and D and the closer geographic proximity of other color pattern classes to each of A and D. All four color-pattern classes of A. neotesselata had a modified triploid karyotype of 69 1 chromosomes (3n = 70). Electrophoretic assessment of 31 nuclear gene loci across the four color-pattern classes revealed postorigin genetic variation only at the mannose-6-phosphate isomerase (MPI) locus, but A. neotesselata had a remarkable heterozygosity of 71% based on these loci.