Head Scalation Research Articles

Embryonic development of the neotropical pit viper Bothrops atrox (Serpentes: Viperidae: Crotalinae), with emphasis on pit organ morphogenesis and its evolution in snakes.

Bothrops atrox is a pit viper with a loreal pit organ, and its embryological development remains undescribed. Here, we provide a comprehensive description of the embryology of B. atrox, focusing on the loreal pit organ and cephalic scales. We characterized 13 developmental stages of B. atrox based on external features consistent with the embryogenesis of previously described snake species. The loreal pit organ originates from the circumorbital region and migrates to its final position. In Crotalinae, the pit organ first becomes visible at stage 28, whereas in Pythonidae labial, pit organs appear at Stage 35. Pit organs evolved independently three times in Serpentes, encompassing Boidae, Pythonidae, and Crotalinae. Boidae lacks embryological information for pit organs. Furthermore, we observed that head scalation onset occurs at Stage 33 in B. atrox, with fusion of scales surrounding the loreal pit organ. The embryology of pit organs in Pythonidae and Boidae species remains poorly understood. Our detailed embryological descriptions are critical for proposing developmental scenarios for pit organs and guiding future research on these structures.

Total-evidence phylogeny and evolutionary morphology of New World pitvipers (Serpentes: Viperidae: Crotalinae).

Crotalines (pitvipers) in the Americas are distributed from southern Canada to southern Argentina, and are represented by 13 genera and 163 species that constitute a monophyletic group. Their phylogenetic relationships have been assessed mostly based on DNA sequences, while morphological data have scarcely been used for phylogenetic inquiry. We present a total-evidence phylogeny of New World pitvipers, the most taxon/character comprehensive phylogeny to date. Our analysis includes all genera, morphological data from external morphology, cranial osteology and hemipenial morphology, and DNA sequences from mitochondrial and nuclear genes. We performed analyses with parsimony as an optimality criterion, using different schemes for character weighting. We evaluated the contribution of the different sources of characters to the phylogeny through analyses of reduced datasets and calculation of weighted homoplasy and retention indexes. We performed a morphological character analysis to identify synapomorphies for the main clades. In terms of biogeography, our results support a single colonization event of the Americas by pitvipers, and a cladogenetic event into a Neotropical clade and a North American/Neotropical clade. The results also shed light on the previously unstable position of some taxa, although they could not sufficiently resolve the position of Bothrops lojanus, which may lead to the paraphyly of either Bothrops or Bothrocophias. The morphological character analyses demonstrated that an important phylogenetic signal is contained in characters related to head scalation, the jaws and the dorsum of the skull, and allowed us to detect morphological convergences in external morphology associated with arboreality.

A new species of New Guinea Worm-Eating Snake (Serpentes, Elapidae, Toxicocalamus Boulenger, 1896) from Western Highlands Province, Papua New Guinea

We describe a new species of New Guinea Worm-Eating Snake (Elapidae: Toxicocalamus) from a specimen in the reptile collection of the Papua New Guinea National Museum and Art Gallery. Toxicocalamus longhagensp. nov. can be easily distinguished from other species of this genus by the presence of paired subcaudals, a preocular scale unfused from the prefrontal scale, a prefrontal distinct from the internasal scale that contacts the supralabials, a single large posterior temporal and two postocular scales. The new taxon is currently known only from one specimen, which was collected from Mt. Hagen Town in Western Highlands Province, Papua New Guinea in 1967. The new species was originally identified as T. loriae, but the unique head scalation and postfrontal bone morphology revealed through micro-computed tomography scanning easily distinguish the new species from T. loriaesensu stricto. This is the first species of this genus described from Western Highlands Province.

New Distribution Site and Supplementary Description on Variations of <i>Gloydius huangi</i> Wang, Ren, Dong, Jiang, Siler et Che, 2019 (Reptilia: Serpentes)

The newly described species Gloydius huangi Wang, Ren, Dong, Jiang, Siler et Che, 2019 were described based on only three specimens from two sites. We report a new distribution site from Markam County, Tibet Autonomous Region, China with supplementary description on variation of morphology and mitochondrial genetics of the species. The new specimen varies from types of G. huangi on head scalation, coloration patterns, and hemipenis morphology. A distinct genetical distance 1.9 – 2.2% based on Cytb gene fragment exist between the new specimen and types of the species.

A new species of Stoliczkia Jerdon, 1870 (Serpentes: Xenodermidae) from Mizoram, India.

We describe a new species of Stoliczkia from Mizoram, India. Stoliczkia vanhnuailianai sp. nov. is identified as a member of the genus Stoliczkia by distinct scale arrangements on the posterior of the head, and by scales on the body being separated by scaleless skin, and it differs from the two known congeners in body and head scalation. This is only the third specimen of Stoliczkia collected from India, and the sixth reported specimen for the genus. A revised key to the identification of the species of Stoliczkia is provided.

A new chameleon of the Trioceros affinis species complex (Squamata, Chamaeleonidae) from Ethiopia

A new species of chameleon, Trioceros wolfgangboehmeisp. nov., inhabiting the northern slopes of the Bale Mountains in Ethiopia, is described. It differs from its Ethiopian congeners by a combination of the following features: presence of a prominent dorsal crest with a low number of enlarged conical scales reaching along the anterior half of the tail as a prominent tail crest, a casque raised above the dorsal crest, heterogeneous body scalation, long canthus parietalis, rugose head scalation, high number of flank scales at midbody and unique hemipenial morphology. Based on morphological characteristics, phylogenetic discordances of previous studies and biogeographical patterns, this new species is assigned to the Trioceros affinis (Rüppell, 1845) species complex. An updated comprehensive key to the Trioceros found in Ethiopia is provided.

Genotyping validates the efficacy of photographic identification in a capture-mark-recapture study based on the head scale patterns of the prairie lizard (Sceloporus consobrinus).

Population studies often incorporate capture‐mark‐recapture (CMR) techniques to gather information on long‐term biological and demographic characteristics. A fundamental requirement for CMR studies is that an individual must be uniquely and permanently marked to ensure reliable reidentification throughout its lifespan. Photographic identification involving automated photographic identification software has become a popular and efficient noninvasive method for identifying individuals based on natural markings. However, few studies have (a) robustly assessed the performance of automated programs by using a double‐marking system or (b) determined their efficacy for long‐term studies by incorporating multi‐year data. Here, we evaluated the performance of the program Interactive Individual Identification System (I3S) by cross‐validating photographic identifications based on the head scale pattern of the prairie lizard (Sceloporus consobrinus) with individual microsatellite genotyping (N = 863). Further, we assessed the efficacy of the program to identify individuals over time by comparing error rates between within‐year and between‐year recaptures. Recaptured lizards were correctly identified by I3S in 94.1% of cases. We estimated a false rejection rate (FRR) of 5.9% and a false acceptance rate (FAR) of 0%. By using I3S, we correctly identified 97.8% of within‐year recaptures (FRR = 2.2%; FAR = 0%) and 91.1% of between‐year recaptures (FRR = 8.9%; FAR = 0%). Misidentifications were primarily due to poor photograph quality (N = 4). However, two misidentifications were caused by indistinct scale configuration due to scale damage (N = 1) and ontogenetic changes in head scalation between capture events (N = 1). We conclude that automated photographic identification based on head scale patterns is a reliable and accurate method for identifying individuals over time. Because many lizard or reptilian species possess variable head squamation, this method has potential for successful application in many species.

Kissing cousins: a review of the African genus Limnophis Günther, 1865 (Colubridae: Natricinae), with the description of a new species from north-eastern Angola

ABSTRACT The African natricine genus Limnophis is represented by two species: Limnophis bicolor Günther, 1865 and Limnophis bangweolicus (Mertens, 1936). They are stout-bodied, semi-aquatic snakes that mostly feed on fish and amphibians, and occur from Botswana and Namibia in the south throughout most of Zambia and Angola to the Democratic Republic of the Congo in the north. We gathered new material from the ranges of both species in Angola and Zambia in order to examine their taxonomic status and identify any overlooked diversity. We constructed a phylogenetic tree, based on three mitochondrial genes (16S, cytb, ND4) and one nuclear gene (cmos), which includes the first DNA sequence data for Limnophis. Three well-supported lineages were identified, each representing separate species. The taxonomic status of the two currently recognised species is validated, and we describe a new species of Limnophis from north-eastern Angola. The new species is distinguished from the others by the combination of distinct ventral and lateral head colouration and patterning, differences in head and ventral scalation, and uncorrected pairwise genetic distances to both L. bicolor and L. bangweolicus of 5.4–8.1% in cytb, 6.1–8.4% in ND4 and 2.7–8.3% in 16S.

New Morphological Data and Geographic Distribution of the Worm Lizard Amphisbaena littoralis (Squamata: Amphisbaenidae) in Northeastern Brazil

In this study, we provide new morphological data, update geographic distribution, and discuss some issues of conservation of Amphisbaena littoralis, a poorly known species of northeastern Brazil. Meristic characters and patterns of head scalation match the published species diagnosis, but we observed some deviations from the type series. Thus, on the basis of the type series (n = 13) and newly examined material (n = 12), we propose the following redefinitions in some diagnostic characters of A. littoralis: snout–vent length 143–278 mm; tail length 19.3–70 mm; body annuli 251–270; tail annuli 29–34; dorsal and ventral segments of midbody annulus 19–22 and 20–24, respectively; precloacal pores 5–6 (usually 6); and supralabials 3–4 (usually 4). The new records are from eight localities in six municipalities along the coast of Rio Grande do Norte state, extending the known geographic distribution of A. littoralis ca. 172 km south from the type locality. On the basis of the minimum convex polygon method, we estimated the extent of occurrence of the species to be around 5,448 km2.

Genotyping validates photo-identification by the head scale pattern in a large population of the European adder (Vipera berus).

Capture‐mark‐recapture procedures are a basic tool in population studies and require that individual animals are correctly identified throughout their lifetime. A method that has become more and more popular uses photographic records of natural markings, such as pigmentation pattern and scalation configuration. As with any other marking tool, the validity of the photographic identification technique should be evaluated thoroughly. Here, we report on a large‐scale double‐marking study in which European adders (Vipera berus) were identified by both microsatellite genetic markers and by the pattern of head scalation. Samples that were successfully genotyped for all nine loci yielded 624 unique genotypes, which matched on a one‐to‐one basis with the individual assignments based on the head scalation pattern. Thus, adders considered as different individuals by their genotypes were also identified as different individuals by their head scalation pattern, and vice versa. Overall, variation in the numbers, shape, and arrangement of the head scales enabled us to distinguish among 3200+ photographed individual snakes. Adders that were repeatedly sequenced genetically over intervals of 2–3 years showed no indication whatsoever for a change in the head scale pattern. Photographic records of 900+ adders that were recaptured over periods of up to 12 years showed a very detailed and precise match of the head scale characteristics. These natural marks are thus robust over time and do not change during an individual's lifetime. With very low frequency (0.3%), we detected small changes in scalation that were readily discernible and could be attributed to physical injury or infection. Our study provides a conclusive validation for the use of photo‐identification by head scale patterns in the European adder.

A new species of Wolf Snake of the genus Lycodon H. Boie in Fitzinger (Squamata: Colubridae) from the Aceh Province of northern Sumatra, Indonesia

Herein we describe a new species of Lycodon H. Boie in Fitzinger (Squamata: Colubridae) from Aceh Province, Sumatra. This brings the number of species known to occur on the Sunda Shelf to seven. The new species is readily diagnosed from the other congeners in the region by the lack of a preocular scale, the presence of keeled dorsal scales and a banded venter. It is superficially similar to L. butleri from the Malaysian Peninsula in coloration and to L. subcinctus in head scalation. Genetically, the new species is most similar to a group of species from Mainland Southeast Asia and China. We also note the presence of several deeply divergent lineages within Lycodon that may warrant the recognition as distinct genera. The genus is in need of a comprehensive molecular and morphological review.

A new species of kukri snake (Squamata: Colubridae: Oligodon Fitzinger, 1826) from Con Dao Islands, southern Vietnam.

We describe a new kukri snake, Oligodon condaoensis sp. nov., from Con Dao Islands, southern Vietnam based on the morphological characters of four specimens. It differs from other congeners by a combination of the following characters: medium size in adults (total length up to 552 mm); 17-17-15 dorsal scale rows; deeply forked hemipenes without spines and papillae, extending to subcaudal 13 or 14; 11-13 maxillary teeth, the posterior three being enlarged; cloacal plate undivided; head scalation complete; nasal divided; presubocular absent; 168-176 ventrals; 33-37 subcaudals; overall dorsal coloration dark gray, faint body stripes present or absent; and ventral coloration cream to dark gray without rectangular blotches. We also provide a list of 43 species of amphibians and terrestrial reptiles recorded from Con Dao Islands.

A new species of Chameleon (Sauria: Chamaeleonidae: Kinyongia ) highlights the biological affinities between the Southern Highlands and Eastern Arc Mountains of Tanzania

A new species of chameleon is described from the Livingstone and Udzungwa Mountains of Tanzania. The new species is morphologically most similar to Kinyongia vanheygeni . Furthermore, a single, short rostral appendage shows the species similarity to other Eastern Arc endemic Kinyongia species (e.g. K. uthmoelleri, K. oxyrhina, K. magomberae and K. tenuis ). Females of all these species lack any rostral ornamentation and are all very similar morphologically. Males of the new species, on which the morphological diagnosis is based, can be distinguished from other Kinyongia by a shorter rostral appendage that bifurcates at the tip. They are easily distinguished from K. vanheygeni , otherwise the most similar species, by differences in head scalation and the length and shape of the rostral appendage. The new species is associated with montane rainforest and is known from only four forest fragments of which two are in the Udzungwa and two in the Livingstone Mountains. Phylogenetically, the new species is sister to K. tenuis and K. magomberae, which together, form a clade that also contains K. oxyrhina . The disjunct distribution of the new species, in the Livingstone and Udzungwa mountains, stretches across the ‘Makambako Gap’ which is a putative biogeographical barrier separating the distinct faunas of the Southern highlands and Eastern Arc Mountains. Evidence from this species however, points to potentially closer biological affinities between the Livingstone and Udzungwa mountains.

A new green anole lizard of the "Dactyloa" clade (Squamata: Dactyloidae) from the Magdalena river valley of Colombia.

We describe a new species of Anolis from the Magdalena river valley in Colombia. The new species is morphologically similar to Anolis ibanezi and A. chocorum, but differs in body and dewlap color, and head scalation. We performed an exploratory multivariate analysis based on 15 morphological characteristics of the new species and A chocorum and found that differences between both species are mainly associated with head dimensions. A phylogenetic analysis based on morphological characters suggests that the new species is nested within the "Dactyloa" clade of Anolis. Finally, we discuss phylogenetic relationships and biogeographical affinities based in its distribution.

A new species of Bachia Gray, 1845 (Squamata: Gymnophthalmidae) from the Eastern Brazilian Cerrado, and data on its ecology, physiology and behavior.

A new species of Bachia of the bresslaui group, Bachia geralista sp. nov., is described from Planalto dos Gerais, an old and partially dissected plateau extending along the Cerrados of Bahia, Minas Gerais and Tocantins states, Brazil. The new species is morphologically similar to B. bresslaui, with which it has been confused; however head scalation resembles other species from sandy spots within the Cerrado (B. psamophila and B. oxyrhina). Like in B. psamophila and B. oxyrhina, the shovel-shaped snout of the new species is highly prominent, a typical trait of psammophilous habits in other gymnophthalmids. The examination of specimens of B. bresslaui from several populations within the Cerrado revealed great variation among localities, leading to the reidentification of a specimen from Utiariti, Mato Grosso, previously referred to in the literature as the second record of B. bresslaui, as the recently described B. didactyla, suggesting that cryptic diversity might remain still undiscovered within this genus in the Cerrado. Despite occurring in a relatively open Cerrado, thermal physiology of Bachia geralista sp. nov. restricts its occurrence to shaded microhabitats within this habitat.

A Contribution To the Knowledge of the Lizard Genus Alopoglossus (Squamata: Gymnophthalmidae)

We studied scutellation and morphometrics in the gymnophthalmid lizards of the genus Alopoglossus. Six species are recognized: Alopoglossus angulatus, A. atriventris, A. buckleyi, A. copii, A. festae, and A. lehmanni. We place the nominal species Alopoglossus andeanus Ruibal in the synonymy of A. angulatus. We provide detailed descriptions and head scalation illustrations of each species, an identification key, and a distribution map.Se estudia la folidosis y morfometría de las lagartijas gymnophthalmidas del género Alopoglossus. Se reconocen un total de seis especies: Alopoglossus angulatus, A. atriventris, A. buckleyi, A. copii, A. festae y A. lehmanni. La especie nominal Alopoglossus andeanus Ruibal es considerada como sinónimo de A. angulatus. Se provee ilustraciones de la escamación de las cabezas, claves de identificación y un mapa de distribución.

A new species of Sibon (Squamata: Colubridae) from the mountains of eastern Guatemala

A new species of snake of the genus Sibon (Squamata: Colubridae) is described from La Montaña de las Granadillas, partof the Sierra del Merendón in eastern Guatemala. Sibon merendonensis is part of the S. annulatus group, and differs fromother members of the group in its scale row formula, head scalation and body size. The new species is known only from the holotype and was collected from an isolated area of cloud forest near Zacapa, Department of Zacapa, Guatemala.

Morphology of Vipera palaestinae : Intraspecific Variability and Sexual Dimorphism

I present new data on intraspecific variations in external morphology and sexual dimorphism in different characteristics of Vipers, Vipera palaestinae in Israel. Corporal proportions and scalation pattern of museum specimens of this snake, the most common viperid species in Israel, were recorded and analyzed. Strong sexual dimorphism was found in tail measurements (its relative length, and number of subcaudal scales), head proportions and in the number of ventral scales. The sexual differences were evident in the head scalation – females have significantly more supralabial and sublabial scales; males, in turn exceed females in circumorbital scale counts. There is no sexual size dimorphism (SSD) in average body weight, snout-vent and total length. The sexes display a similar allometry between SVL/head and SVL/tail length; between tail length and the number of subcaudal scales (weak, but significant relationship). There is no correlation between SVL and the number of ventral or dorsal scales. The morphological plasticity caused by reproduction requirements is well registered and was evident in relating to tail measurements and body scalation, although the possible causes and selective forces of the pholidosis intersexual distinctions can be cleared up through future ecological studies.

Redescription of Tetradactyl Philippine Slender Skinks (Genus Brachymeles)

Abstract We redescribe the exceedingly rare, tetradactyl Philippine scincid lizards of the genus Brachymeles. Before the recent discovery of a second museum specimen of Brachymeles wrighti, and the rediscovery of B. elerae in the wild, these two species were known from a combined three museum specimens, all collected in the early 1900s. Since that time, biotic surveys in the region, including recent efforts focused at the recognized type localities for both species, resulted in the rediscovery of extant populations of B. elerae. Based on re-examination of type material, complete mensural and meristic data for a recently recovered museum specimen, as well as our recently collected material, we redescribe these two rare species, providing the first, complete diagnostic illustrations of head scalation and hand and foot morphology, and we comment on their taxonomic and phenotypic affinities, and conservation status.

Fluctuating asymmetry is a function of population isolation in island lizards

We measured the level of fluctuating asymmetry (FA) in head shape, head scalation and femoral pores in two lizard species (Podarcis bocagei and Podarcis hispanica) from 13 islands and 15 mainland localities in the Ria de Arosa archipelago of north-western Spain. Given the recent geological history of the region, the degree of isolation to which lizard populations have been subjected can be ordered along a spatio-temporal gradient, yielding the following hypotheses to be tested: FA will be higher (1) in island populations than in mainland populations; (2) on remote islands than on islands close to the mainland; (3) on small islands than on large islands. Molecular genetic data suggest that P. hispanica is autochthonous in the Ria de Arosa, whereas P. bocagei is a more recent arrival. Therefore, we predict also (4) a higher level of FA in P. hispanica than in P. bocagei. Statistically significant results were obtained for head-shape asymmetry, supporting the second and the fourth hypotheses. With an overall meristic asymmetry index, none of the hypotheses were corroborated, whereas for certain independent meristic traits, the first, the third and the fourth hypotheses were partially supported. Both head shape and meristic traits constitute precise measures of FA, but FA is more convincingly expressed in head shape and in single meristic traits than in overall meristic traits asymmetry. We conclude that FA reflects population isolation and may be a good indicator of developmental instability. It seems worthwhile to test for FA in a landlocked system under environmental and genetic stress, for the purpose of conservation biological assessments.