Abstract. Cutaneous sensory organs (sensilla) are mechanoreceptive structures present in the skin of squamate reptiles. In gekkotan lizards these structures are characterized by a raised eminence, the button, which bears one or more elongate hair-like bristles as well as a field of shorter spinules. Variation in the dimensions of these structures and in the number and elaborations of the bristles have been well characterized in the limbless pygopodid gekkotans and their tetrapodal relatives in the Diplodactylidae and Carphodactylidae, but patterns of variation in the Gekkonidae, by far the most diverse and species-rich clade of gekkotans, remain unexplored. We used scanning electron microscopy to examine and characterize the sensilla of 47 species representing 11 major clades of gekkonids, as well as representatives of other gecko families. Variation in morphology across gekkonid sensilla exceeds that observed in other gecko families, with bristle number varying from zero to 29 and bristle length from 3 to 50 lm. There is some phylogenetic signal in sensillar morphology, particularly within genera, but there is no association between mechanoreceptor dimensions and overall body size. In some taxa there is evidence that bristle length and bristle number are inversely related. Intraspecific variation in receptor size and configuration, both between individuals and across different body regions, is clearly present but remains insufficiently documented.
Abstract. A population freed from a constraining interspecific interaction (e.g., competition or predation) may experience niche shifts and expansions. This phenomenon, termed ecological release, is an eco-evolutionary process driven by individual behaviors and interindividual interactions. However, empirical studies of these interactions seldom observe them directly, instead inferring process from pattern. Here, we set up experimental conditions for ecological release of the lizard Anolis carolinensis (green anole) from constraining interactions with its congener, Anolis sagrei (brown anole), by constituting populations of lizards on small islands. We monitored individual and population habitat use along three niche axes (perch height, perch diameter, and lateral movement between perches) on one experimental (one-species) and one control (two-species) island, for three time periods: 1) preremoval, when both islands had both species; 2) postremoval, shortly after A. sagrei were cleared from the experimental island; and 3) delayed postremoval, 7 months later, when long-lived lizards were joined by a second generation born in the intervening months. We found that green anole perch height decreased on the one-species island and increased on the two-species island. These shifts did not occur during postremoval but were evident by delayed postremoval, when both generations on the one-species island were perching nearly 130 cm lower than their counterparts on the two-species island. We also documented correlated changes in perch diameter at both the individual and population level but no changes in the extent of individuals' lateral movement. Lastly, changes in population-level niche width (i.e., perch height and diameter variances) occurred without detectable changes in niche overlap among individuals. Our results demonstrate that that the dynamics of ecological release in nature need not be inferred, because experiments can observe them directly in individuals, across generations, and along multiple niche axes.
Abstract. We describe through integrative taxonomy a new species of snouted treefrog of the genus Scinax from white-sand forests of the Rio Negro Sustainable Development Reserve in Central Amazonia, Brazil. The new species is phylogenetically related to other Scinax with striped eyes and pulsed advertisement calls. It differs from other Amazonian species mainly by having snout–vent length 21.6–25.4 mm (n= 11) in adult males and 24.8–27.0 mm (n= 9) in females, snout subacuminate in dorsal view, a dark brown lateral stripe on each flank (fading posteriorly), brown tadpoles with labial keratodont row formula 2(2)/3 and keratodont row P-2 longer than P-1 and P-3, and an advertisement call consisting of a single pulsed note with a call duration of 502–652 ms, 79–105 pulses/note and a dominant frequency of 3,811–4,543 Hz. The new species clusters within a major, well-supported phylogenetic clade grouping several candidate and recently described species as well as species previously included in the former Scinax staufferi species group (viz., S. cruentomma, S. fuscomarginatus, S. staufferi, and S. wandae). The phylogenetic relationships and structural pattern in the advertisement calls of these species highlight the need for a redefinition and reevaluation of the monophyly of the S. staufferi species group.
I reaffirmed the existence of a red-bellied snake, Storeria occipitomaculata (Storer, 1839), collected in an allopatric locality in eastern Nebraska, U.S.A., in the 19th century. I utilized data associated with this snake, MCZ Herpetology R-135 (Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts), to determine it was probably collected in the 1850s, approximately 170 years ago, either in the eastern portion of the Platte River Valley in western Douglas County or in the Missouri River Valley in eastern Washington County, bordering Iowa. I used this information to discuss the biogeographic and conservation implications for populations of S. occipitomaculata occurring in the Prairie Peninsula of the American Midwest and in the grassland-dominated plains. Moreover, I demonstrate the importance of reevaluating historic specimens in collections and the data associated with them to generate critical insights into species biogeography, ecology, and conservation.
Abstract. Treefrogs of the genus Osteocephalus have been the focus of several taxonomic and phylogenetic studies, especially in the last two decades. These recent studies have shown that the diversity of this charismatic Amazonian genus is still largely underestimated. Through the evidence of morphological and molecular data, we describe a new species of the Osteocephalus alboguttatus species group from the Purus-Madeira Interfluve, southwestern Brazilian Amazonia. The new species differs from other Osteocephalus by having a small body size (snout–vent length 32.1–44.1 mm), skin texture non-sexually dimorphic, dorsum smooth with a few scattered small tubercles, vocal sac single and subgular, frontoparietal ridges not externally visible, and a dark tan brown iris with lighter vermiculation. The rapid increase in the number of new frog species described from the Purus-Madeira Interfluve highlight the importance of sampling poorly explored and remote areas in Amazonia, as well as the value of supporting taxonomic research to accelerate species documentation in face of the biodiversity crisis.
Thirteen species of West Indian boas (Chilabothrus) are distributed across the islands of the Greater Antilles and Lucayan Archipelago. Hispaniola is unique among this group of islands in having more than two species of Chilabothrus—three are currently recognized. Here we describe a fourth species from Hispaniola, a newly discovered distinctive species of small boa from the dry forest of the Barahona Peninsula, southwestern Dominican Republic, near the border with Haiti. This new species resembles in body size and in other aspects its closest relative Chilabothrus fordii (Günther 1861), with which it appears to be allopatric. The new species, which we describe as Chilabothrus ampelophis sp. nov., differs from C. fordii in body, head, and snout shape; in scalation; in both coloration and color pattern; and in phylogenetic uniqueness. Some relevant meristic characters from C. ampelophis sp. nov. fall between C. fordii and C. gracilis (Fischer 1888), accentuating the morphological and likely ecological differences from its sister species C. fordii. The discovery of this new species is especially important as it appears to be among the smallest boid (Boidae) species, has an arboreal specialization, and is found in a very restricted and highly threatened habitat.
Describing the relationships among morphology, behavior, and ecology is central to understanding the processes of evolutionary diversification. Anolis lizards are an excellent group for studying such ecomorphological relationships. Extensive research on anole ecological morphology has been conducted in the Caribbean, where sympatric species have repeatedly and convergently evolved to partition habitat through differential perch use. Six ecomorphs have been described, each with particular behavioral, morphological, and ecological characteristics well-suited for the microhabitat it occupies. However, little research has been conducted in mainland Central or South America, and a few case studies suggest that mainland anoles may not conform to the ecomorph classes recognized for Greater Antillean anoles. In this study, we examine the ecological morphology of sympatric mainland species of Anolis in a tropical lowland rainforest in Costa Rica and compare these species to the Caribbean ecomorphs. Our results show overlapping niches and substantial variability in habitat use across many species. Moreover, the relationship between relative hindlimb morphology and habitat use in Anolis humilis and Anolis limifrons does not conform to that of Caribbean species. Predation and fluctuating environmental conditions likely structure morphological variation differently in the mainland, leading the independent radiation of mainland anoles to produce divergent ecomorphological relationships compared with the Caribbean islands.
Parabrotula (Zugmayer 1911a), included in the family Bythitidae (Ophidiiformes), is a genus of small viviparous mesopelagic fishes with two valid species. Parabrotula plagiophthalmus is known from collections made worldwide except in the eastern Indian, eastern Pacific, and western South Atlantic Oceans; most specimens are from the North Atlantic Ocean. Most anatomical data for P. plagiophthalmus are limited to aspects of external anatomy, the reproductive system, and meristic data that can be gathered through radiographs; virtually no data on other aspects of the osteology of P. plagiophthalmus are available. In this study, we describe the skeleton of P. plagiophthalmus from cleared and stained specimens and computed tomography data. Many aspects of the skeleton of P. plagiophthalmus are reduced (subopercle; ceratobranchial 5; gill rakers; gill filaments; distal radials of median pterygiophores; caudal skeleton; posttemporal; supracleithrum; scapula; distal pectoral radials; pelvic girdle and fins; scales) or absent (mesethmoid; nasal; pterosphenoid; intercalar; infraorbital bones; endopterygoid; coronomeckelian; supramaxilla; pharyngeal toothplates). All bones of the skull are extremely thin dermal or perichondral ossifications, with little to no endochondral components. The vomer supports a variable number of teeth (0–3). The pars autopalatina and its ossification are separated from the pars metapterygoidea and pars quadrata and their ossifications; the thin ectopterygoid bridges these elements of the suspensorium. The lower jaw is very large compared with all other elements of the viscerocranium. The pectoral radial plate was never observed to be divided into separate radial elements. We discuss the skeleton of Parabrotula in the context of other taxa but call attention to the need for further comparative studies of the anatomy of ophidiiform fishes.
Museum of Comparative Zoology (MCZ) VPM-4225, a carnivoran dentary, is described here for the first time, 82 years after it was collected in the Duchesnean (late middle Eocene) portion of the Galisteo Formation in New Mexico. It evidently corresponds to the specimen—never identified by its catalog number, never described, and considered missing for the last 41 years—that formed the basis for the purported occurrence of the early carnivoraform Uintacyon in the formation reported in 1943. The specimen is here reidentified as one of the earliest amphicyonids, Angelarctocyon, which was previously known from only two specimens from the Chambers Tuff of Texas. With this reidentification, there is no longer a valid occurrence of Uintacyon postdating the Uintan North American Land Mammal Age, adding to the evidence for rapid replacement of ancient carnivoramorphan lineages by early crown-clade carnivorans in the late middle Eocene, across a period of severe climatic fluctuations 42–40 million years ago.
The brown anole (Anolis sagrei) is a widespread neotropical lizard found on many islands in the West Indies as well as the coast of Central America. Across their range, brown anole populations show extensive ecomorphological trait variation and substantial genetic divergence. It is unclear, however, whether this genetic and morphological divergence is indicative of reproductive isolation between populations. We investigated variation in mating behavior across populations by analyzing 4 h of video for each of 234 captive male-female pairs encompassing all 36 possible pairings from six sampled islands. For each pair of individuals, we tested for an association between the occurrence of mating, morphological traits, and genetic relatedness of their populations. We found no support for the hypotheses of ecological divergence, nonecological divergence, or both ecological and nonecological divergence driving premating reproductive isolation in A. sagrei. We did find that males with relatively short heads tend to mate more quickly and hypothesize potential explanations that warrant future investigation.
In polygynous lizards, male–male competition is an important driver of morphologic and behavioral traits associated with intraspecific dominance. The extent to which females engage in aggressive behavior and thus contribute to competition-driven morphologic variation is not well studied. We used injury frequencies of brown anoles (Anolis sagrei) in 16 island populations to test the hypothesis that injury-inducing aggressive encounters increase with population density in both male and female lizards. We further asked whether intraspecific competition is a potential driver of phenotypic traits related to dominance by using population density as proxy for intraspecific competition. We found that the proportion of individuals with injuries was greater in populations with higher densities, suggesting that agonistic competitive interactions increase with population density. Size-adjusted head length of male and female lizards increased with population density, suggesting that larger heads might be advantageous when intraspecific competition is strong. We detected differences in morphology and injury frequency among islands for both males and females, which suggests that agonistic competitive interactions among females may be stronger than previously appreciated. Further research is needed to determine whether aggressive encounters involving females are restricted to intrasexual competition or whether they also involve males, and how morphologic traits of females are related to competitive dominance and reproductive success.
Abstract. The Chañares Formation (latest Middle–earliest Late Triassic) of northwestern Argentina is part of the Ischigualasto–Villa Unión Basin and preserves a rich fossil vertebrate record discovered by a crew of the Museum of Comparative Zoology (Harvard University) led by Alfred Romer. A diverse non-dinosaurian dinosauromorph assemblage has been described from this formation and includes the iconic, small-sized “proto-dinosaur” Lagosuchus talampayensis Romer, 1971. This species has been crucial to understand the body plan of dinosaur precursors and the higher-level phylogenetic relationships of dinosaurs. More recently, authors considered this genus and species as nomina dubia. The aim of this contribution is to reassess the taxonomic validity of L. talampayensis. New observations indicate that the holotype of L. talampayensis differs from other avemetatarsalians, but not from the hypodigm of Marasuchus lilloensis, in the presence of a globose femoral head (strongly convex proximal and medial surfaces) with a distinctly dorsal orientation and a sub-oval outline in proximal view as a result of incipient posterior and posteromedial tuberosities. Thus, Lagosuchus talampayensis is here considered a senior synonym of “Marasuchus lilloensis” (Romer, 1972). Our conclusions have implications in the knowledge about early dinosauromorph diversity and the taxonomic richness of the group in the Chañares Formation.
Within the lizard genus Anolis, color variation in the dewlap, an important signaling trait, can indicate local adaptation or divergence between populations. Most research on anole dewlaps has taken aim at males rather than females. Despite several publications of unrelated lizard genera with links between female signal color polymorphisms and fecundity, variation in female anole dewlaps has received less inquiry. We compiled dewlap photographs of females from several populations of the Anolis lemurinus group, characterized color variants through visual assignment, and tested for associations of dewlap color to body size and dewlap area. We describe the first case of polymorphic dewlap color in females and relatively monomorphic dewlap color in males within a group of anoles. Our survey found that female dewlap color variation in the group is more similar between geographically proximate northern populations of A. lemurinus and A. bicaorum than between populations ascribed to A. lemurinus from different regions. Additionally, we provide evidence that female body size in this group may correlate with dewlap coloration. Our findings support the need for further taxonomic research within the A. lemurinus group, as well as research into the potential mechanisms driving and maintaining color polymorphism in female signaling traits.
The ecomorph concept of the adaptive radiation of Caribbean anoles is characterized by a suite of behavioral, ecological, and morphological traits that are tightly linked to microhabitat use in lizards. However, most studies on the adaptive radiation of anoles have been conducted in a single macrohabitat type—lowland tropical forests. Because behavior can help organisms cope with different environmental conditions, we can predict that there will be key shifts in behavior within ecomorphs when examined across different macrohabitats, although this idea remains empirically underexplored. Here we utilized the replicated evolution of montane endemics from a primarily lowland species in a clade of trunk–ground Anolis lizards to test the hypothesis that shifts in basking behavior, wariness, and display behavior accompany divergence into montane habitats. The montane specialists A. armouri and A. shrevei each independently evolved from the primarily lowland dwelling A. cybotes in two widely separated mountain chains on the island of Hispaniola. We found evidence for a convergent behavioral response to the high-altitude macrohabitat: A. armouri and A. shrevei spend more time basking, utilize more open environments, and are warier than lowland A. cybotes. We also found divergence in display behavior in A. shrevei. We detected no evidence of divergence in locomotor behavior with elevation among active lizards. Together, our results suggest that the ecomorph concept would be enriched by extending observations of behavior (and other aspects of the phenotype) into different macrohabitats. Future work should focus on whether the observed behavioral shifts are clinal, reflecting local adaptation within A. cybotes, or fixed differences between the lowland generalist and montane species. Adaptation to the macrohabitat has previously been underappreciated as a source of behavioral diversity in Anolis lizards; this study is the first step toward documenting intraecomorph behavioral variation across divergent habitats.
Gregory's diverticulum is a conspicuous digestive tract element found in selected sand dollar (Echinoidea: Clypeasteroida) species. This organ, a transitory structure of the juvenile organism, was named after the American zoologist Emily R. Gregory (1863–1946). Although it had been observed before by the renowned echinoid researcher and former director of the Museum of Comparative Zoology Alexander E. Agassiz, Gregory was the first to describe the organ as a distinct entity on the basis of the ubiquitous sand dollar species Echinarachnius parma. However, despite presenting her discovery at several national and international conferences, as well as in short papers, Gregory's find remained largely unmentioned by contemporary echinoderm researchers. With the erroneous assessment of one of the most eminent authorities on echinoid taxonomy and systematics Theodor J. Mortensen that the organ she discovered does not exist, Gregory's work seemed destined to fall into oblivion. However, in the second half of the 20th century, several unpublished master's theses provided unequivocal evidence for the existence of the organ, thus reviving interest in research on Gregory's diverticulum. The present article gives a historical overview of studies related to Gregory's diverticulum, provides the first comprehensive biography of Emily R. Gregory, describes the circumstances of the organ's discovery, and explores why the research of a female zoologist was seemingly not met with much enthusiasm during her lifetime.
We report the discovery of a new genus and species of amber-preserved lizard from the mid-Cretaceous of Myanmar. The fossil is one of the smallest and most complete Cretaceous lizards ever found, preserving both the articulated skeleton and remains of the muscular system and other soft tissues. Despite its completeness, its state of preservation obscures important diagnostic features. We determined its taxonomic allocation using two approaches: we used previously identified autapomorphies of squamates that were observable in the fossil; and we included the fossil in a large squamate morphological data set. The apomorphy-based identification of this specimen, including comparative data on trunk elongation in squamates, suggests its allocation to the stem-group Anguimorpha. Results from the phylogenetic analysis places the fossil in one of four positions: as sister taxon of either Shinisaurus crocodilurus or Parasaniwa wyomingensis, at the root of Varanoidea, or in a polytomy with Varanoidea and a fossorial group retrieved in a previous assessment of squamate relationships. It is clear that this fossil has many similarities with anguimorph squamates and, if this taxonomic allocation is correct, this fossil would represent the first amber-preserved member of stem Anguimorpha ever recorded, and the smallest known member of that group. It further emphasizes the role of amber inclusions in expanding our understanding of the diversity of Cretaceous lizard communities.
