Squamate Taxa Research Articles

Early Miocene squamate assemblage from the Mokrá-Western Quarry (Czech Republic) and its palaeobiogeographical and palaeoenvironmental implications

Two fossiliferous karstic fissures from the Mokrá-Western Quarry, MWQ (1/2001 Turtle Joint; 2/2003 Reptile Joint) provided a diverse vertebrate fauna from the early Miocene (Burdigalian, MN 4) including squamates. The rather warm climatic conditions during the Miocene Thermal Maximum (17.8-17.7 Ma) enabled dispersal of thermophilic lizards and snakes throughout Central Europe. In total, ten major clades have been identified in MWQ localities, including: Lacertidae (Lacertidae indet., Lacertidae tooth morphotype 1 and 2); Amphisbaenia (Amphisbaenia indet.); ? Scincoidea (? Scincoidea indet.); Anguidae (Pseudopus laurillardi (Lartet, 1851), Pseudopus sp., Ophisaurus sp., and Anguinae indet.); Varanidae (Varanus mokrensisIvanov, Klembara, Ruta & Böhme, 2018); Boidae (Bavarioboa cf. hermiSzyndlar & Schleich, 1993); Pythonidae (Python sp.); Colubridae (Colubridae gen. et sp. indet., Coluber [s.l.] sp., and “Colubrinae” indet., type 1), Natricidae (Natrix sp. and “Natricinae” indet.); Viperidae (Viperinae [‘Oriental vipers' group], Vipera sp. [‘European vipers' group]); and Elapidae (Elapidae gen. et sp. indet.). Python sp. from the MWQ represents the first known occurrence of this most thermophilic Neogene squamate taxon within the area of Central Paratethys and we assume that MAT did not fall below 18-19 °C in the vicinity of this locality during the late Burdigalian stage. These humid subtropical to paratropical climatic conditions, also documented by several full-aquatic and semi-aquatic amphibians and reptiles, were suitable for the occurrence of other thermophilic lizard and snake taxa reported from MWQ, including Varanus mokrensis, Pseudopus laurillardi, Bavarioboa, large Elapidae and ‘Oriental vipers'.

The first record of Wormian bones in lizards

ABSTRACTWormian bones are accessory bones found between cranial elements. These rare bones vary greatly in size, shape and placement. Wormian bones are well-known in mammals, notably in humans and chimpanzees, but not in lizards. Here we examine the genus Zygaspis, a southern African amphisbaenian with complex cranial sutures, for the presence of Wormian bones. Skulls from seven of the eight species of Zygaspis were examined for the presence of Wormian bones. Because of their small size, complex sutures and delicate nature, high-resolution X-ray computed tomography was used to produce 3D models of the skulls. We discovered three Wormian bones in the interdigitated frontoparietal suture of Z. kafuensis. This discovery is the first known record of Wormian bones in a lizard and it is one of the few reports of them in the Squamata. The presence of Wormian bones in a head-first, burrowing squamate allows for a possible functional role to be hypothesised. Additional studies on a variety of squamate taxa are now needed, particularly in burrowing groups with interdigitated sutures, to improve our understanding of these rare cranial elements.

Molecular Identification and Geographic Origin of an Exotic Anole Lizard Introduced to Brazil, with Remarks on Its Natural History

Abstract. Introduced species are major drivers of biodiversity loss worldwide. Several squamate taxa have become established outside of their native ranges after human-mediated transportation, becoming a conservation concern. We report on the occurrence of an exotic anole lizard in the Baixada Santista region in coastal Brazil. To clarify the species' identity and examine the geographic source of its introduction, we generated sequences of one mitochondrial DNA marker. The anole is genetically closest to species in the Anolis carolinensis group (Dactyloidae), which does not occur naturally in South America. Phylogenetic analyses found that samples from Brazil nest within A. porcatus, a Cuban species that has also been introduced into Florida and the Dominican Republic. Results indicate that Brazilian A. porcatus are nested among samples from La Habana, Matanzas, and Pinar del Rio, which may suggest a western Cuban source of introduction. Nevertheless, Brazilian samples also cluster closely with a sample f...

A tiny lizard (Lepidosauria, Squamata) from the Lower Cretaceous of Spain

Abstract: The smallest living amniotes are all lizards, but the fossil history of this size trait in Squamata is difficult to follow because small skeletons have low preservation potential and are often hard to detect in the field. A new squamate taxon,Jucaraseps grandipesgen. et sp. nov., is here described on the basis of an articulated skeleton from the Early Cretaceous Spanish lagerstätten of Las Hoyas. It differs from other known Mesozoic lizards in combining very small body size with a short rostrum, low maxillary tooth count, a relatively slender and elongated body, and short limbs with large hind feet. Phylogenetic analysis using TNT places it on the stem of a clade encompassing scincomorphs, gekkotans, snakes, amphisbaenians and anguimorphs. Comparison with modern lizards suggests it was probably a cryptic surface or subsurface ground dweller but not a burrower.

Palaeoenvironment and palaeoclimate of the Mousterian–Aurignacian transition in northern Iberia: The small-vertebrate assemblage from Cueva del Conde (Santo Adriano, Asturias)

The transition from the Middle Palaeolithic (Mousterian) to the Upper Palaeolithic (Aurignacian) has been one of the prominent themes in the archaeology of the European Palaeolithic for more than 20 years. One of the most controversial questions concerning this period is the extinction of the Neanderthals and their replacement by modern humans. In this context, Cueva del Conde, located in the northern part of the Iberian Peninsula, is an archaeo-palaeontological site that records the Mousterian to Aurignacian transition. It has been excavated since the beginning of the 20th century, first by the Conde de la Vega del Sella and systematically by a team from the University of Oviedo since 2001. Three main zones have been identified: the External Zone, dated to approximately 39 110 ± 520 BP (level N104); the Entrance Platform, dated between 38 250 ± 390 BP and 34 730 ± 500 BP; and Gallery A with a radiocarbon date of approximately 31 540 ± 400 BP (level N2a2). The small-vertebrate assemblages recovered from the water-screening of all sediment from the excavation campaigns represent at least 21 small mammal, amphibian and squamate taxa. The small-vertebrate associations in the three zones suggest a patchy landscape, dominated by humid meadows and woodland areas with the existence of water in the vicinity of the cave. The climate shows a more continental pattern during the Mousterian, though it was milder during the Aurignacian. The small vertebrates of the Cueva del Conde Mousterian and Aurignacian levels suggest a climate that differed from modern day temperatures, between −1.1 and −4.4 °C (mean annual temperature), placing these assemblages during Interstadials 9 to 7 (Is9 to 7).

Fine structure of the vomeronasal organ in the grass lizard, Takydromus tachydromoides

The squamates are composed of many taxa, among which there is morphological variation in the vomeronasal organ (VNO). To elucidate the evolution of chemoreception in squamate reptiles, morphological data from the VNO from a variety of squamate species is required. In this study, the morphology of the VNO of the grass lizard Takydromus tachydromoides was examined using light and electron microscopy. The VNO consists of a pair of dome-shaped structures, which communicate with the oral cavity. There are no associated glandular structures. Microvilli are present on the apical surfaces of receptor cells in its sensory epithelium, as well as on supporting cells, and there are centrioles and ciliary precursor bodies on the dendrites. In addition to ciliated cells and basal cells in the non-sensory epithelium, there is a novel type of non-ciliated cell in T. tachydromoides. They have constricted apical cytoplasm and microvilli instead of cilia, and are sparsely distributed in the epithelium. Based on these results, the variation in the morphology of the VNO in scincomorpha, a representative squamate taxon, is discussed.

Examining the utility of categorical models and alleviating artifacts in phylogenetic reconstruction of the Squamata (Reptilia)

Reconstruction artifacts are a serious hindrance to the elucidation of phylogenetic relationships and a number of methods have been devised to alleviate them. Previous studies have demonstrated a striking disparity in the evolutionary rates of the mitochondrial (mt) genomes of squamate reptiles (lizards, worm lizards and snakes) and the reconstruction artifacts that may arise from this. Here, to examine basal squamate relationships, we have added the mt genome of the blind skink Dibamus novaeguineae to the mitogenomic dataset and applied different models for resolving the squamate tree. Categorical models were found to be less susceptible to artifacts than were the commonly used noncategorical phylogenetic models GTR and mtREV. The application of different treatments to the data showed that the removal of the fastest evolving sites in snakes improved phylogenetic signal in the dataset. Basal divergences remained, nevertheless, poorly resolved. The proportion of both fast-evolving and conserved sites in the squamate mt genomes relative to sites with intermediate rates of evolution suggests rapid early divergences among squamate taxa and at least partly explains the short internal relative to external branches in the squamate tree. Thus, mt and nuclear trees may never reach full agreement because of the short branches characterizing these divergences.

Weak founder effect signal in a recent introduction of CaribbeanAnolis

Species introductions provide a rare opportunity to study rapid evolutionary and genetic processes in natural systems, often under novel environmental pressures. Few empirical studies have been able to characterize genetic founder effects associated with demographic bottlenecks at the earliest stages of species introductions. This study utilizes prior mitochondrial DNA information which identifies the putative source population for a recently established (c. 7 years between import and sampling) species introduction. We investigated the evidence for a founder effect in a highly successful introduction of a Puerto Rican Anolis species that has established itself on Dominica to the localized exclusion of the native, endemic anole. Five highly polymorphic microsatellite loci were used to explore the partitioning of genetic diversity within and between native source, native nonsource, and introduced populations of Anolis cristatellus. Group comparisons reveal significantly lower allelic richness and expected heterozygosity in introduced populations compared to native populations; however, tests for heterozygosity excess relative to allelic richness failed to provide consistent evidence for a founder effect within introduced populations. Significant levels of within-population genetic variation were present in both native and introduced populations. We suggest that aspects of the reproductive ecology of Anolis (high fecundity, sperm storage and multiple paternity) offer an important mechanism by which genetic variation may be maintained following demographic bottlenecks and founder events in some squamate taxa.

The early Cretaceous lizard genus Yabeinosaurus from China: Resolving an enigma

Synopsis The lizard genus Yabeinosaurus was originally described more than 60 years ago from deposits of the Early Cretaceous Jehol Group of northeastern China. Its morphology and phylogenetic position have remained enigmatic for several reasons, not least the inaccessibility of the type and figured material, now lost, and the immaturity of all previously documented specimens. Recent work on the Jehol Biota has yielded a series of well‐preserved Yabeinosaurus skeletons, ranging from juvenile to adult. Contrary to previous interpretations, Yabeinosaurus was not a small, weakly ossified lizard with gekkotan affinities. The adult reached a size in excess of 300 mm snout‐pelvis length and had a large, heavily ossified and strongly sculptured skull. Phylogenetic analysis highlights some of the difficulties involved in determining the systematic positions of early squamate taxa. Nevertheless, the overall results suggest a position close to the iguanian‐scleroglossan dichotomy (just above or just below). As such, Yabeinosaurus may represent a relict taxon in the Jehol Biota, a survivor of the Pan‐Laurasian lizard fauna of the Jurassic.

Appendicular Skeleton in Amphisbaenians (Reptilia: Squamata)

Abstract The appendicular skeletal elements in 32 species from all 23 extant genera of amphisbaenians were surveyed via the preparation and study of radiographs, dry skeletons, and cleared-and-stained specimens. Here I report on the presence or absence of those elements, describe their morphology, and make comparisons to several other limbless or limb-reduced squamate taxa that have previously been suggested as close relatives to amphisbaenians. Variability found here in the appendicular skeleton provides a new source of character data for ongoing phylogenetic studies of the group. Comparisons of these elements to those found in potential squamate sister groups indicate that some amphisbaenians share plesiomorphic similarities with limbed squamates such as gymnophthalmid lizards, whereas others share only absence or reduction features with other limbless or limb-reduced squamates, such as dibamid lizards and snakes. This pattern is considered potentially inconsistent with previously proposed hypotheses of...

Geographic and Annual Variation in Life-History Traits in a Temperate Zone Australian Skink

Life-history theory seeks to explain patterns of variation between species or populations of the same species. Studies of squamates in general, and lizards in particular, have assumed a prominent place in the understanding of such variation. However, to date, there have been surprisingly few studies of the Scincidae, a major squamate taxon. We investigated geographic and interannual variation in life-history traits in two populations of the Tasmanian spotted snow skink, Niveoscincus ocellatus, living at the climatic extremes of the species' distribution. Within each population, there were no interannual or intersexual differences in adult body size. However, mature individuals from a cold subalpine/alpine site were significantly larger at maturity, and had a larger maximum body size than mature individuals from a warmer coastal site. These findings are consistent with current predictions of the proximate effect of the thermal environment on lizard growth and size and age at maturity. In both populations, female fecundity was size-related. Litter size did not vary between years at either site, but, contrary to expectations, females from the cold site had the same or higher size-adjusted reproductive output as those from the warm coastal site. We suggest that resource availability is high at both sites and that a high reproductive output by females from the cold site does not confer a significantly higher survival risk than a lower reproductive commitment. Offspring were largest at the cold site, which is consistent with variation in offspring size of other widespread species and may occur because of strong selective pressures on early survival and growth at the cold site.

A new lizard from the Lower Cretaceous of Shandong, China

ABSTRACT A new squamate taxon is described from the Lower Cretaceous Doushan Formation, Qingshan Group, Laiyang, Shandong Province, China. Two incomplete mandibles represent a morphologically peculiar lizard taxon, which has heavily built jaws and highly specialized crushing teeth in a greatly shortened tooth row. Results of phylogenetic analysis show that the new taxon is a member of the Scincomorpha, and can be grouped with the Lacertiformes on the basis of character states related to jaw structures.

The ethmoidal region ofDibamus taylori(Squamata: Dibamidae), with a phylogenetic hypothesis on dibamid relationships within Squamata

The nasal capsule and nasal sac ofDibamus tayloriare described based on a plate reconstruction of serially sectioned material and are compared with several other squamate taxa. The ethmoidal region ofD. tayloriis characterized by a short nasal vestibule, a well developed concha, a much reduced and nearly functionless Jacobson's organ, an incomplete nasal roof, and a true nasopharyngeal duct with a complicated secondary palate. Cartilaginous and epithelial structures of the ethmoidal region provide many informative and useful characters for a phylogenetic analysis. Different anatomical features ofD. tayloriare compared with other burrowing forms (Acontias meleagris,Anniella, pulchra Voetzkowia mira,Feylinia currori) and discussed functionally and phylogenetically. Phylogenetic analysis of all higher squamate taxa using 144 available data derived from many regions of the body indicates relative relationships as (((Dibamidae, Amphisbaenia) Serpentes) Scleroglossa).

Oviducal structure in four species of gekkonid lizard differing in parity mode and eggshell structure.

Oviducal structure was analysed in vitellogenic females from four species of gekkonid lizard exhibiting variation in parity mode and eggshell structure: Hemidactylus turcicus (oviparous) which produces a hard, calcareous eggshell; Saltuarius wyberba (oviparous) which produces a soft, parchment-like eggshell; and Hoplodactylus maculatus and Hoplodactylus duvaucelii (both viviparous). Oviducts were analysed by light, scanning electron and transmission electron microscopy. The uterus exhibited differences among species that were directly attributable to parity mode. H. turcicus and S. wyberba (oviparous) had numerous uterine shell glands; H. maculatus and H. duvaucelii (viviparous) had very few. The uterus also exhibited differences between the two oviparous species (H. turcicus and S. wyberba) which may be related to the type of eggshell produced. Variations were noted in the staining properties of the uterine glandular and epithelial cells. The structure of the infundibulum, uterine tube, isthmus and vagina also differed among species, but differences could not be directly related to parity mode or eggshell structure. Instead, the differences may be related to how prepared the oviduct is for ovulation in individuals analysed from the different species. This study confirms, in the Gekkonidae, aspects of oviducal structure that have been associated with parity mode in other squamate taxa.

Production of antibodies to putative pheromone receptors in rat vomeronasal organ

The squamates are composed of many taxa, among which there is morphological variation in the vomeronasal organ (VNO). To elucidate the evolution of chemoreception in squamate reptiles, morphological data from the VNO from a variety of squamate species is required. In this study, the morphology of the VNO of the grass lizard Takydromus tachydromoides was examined using light and electron microscopy. The VNO consists of a pair of dome-shaped structures, which communicate with the oral cavity. There are no associated glandular structures. Microvilli are present on the apical surfaces of receptor cells in its sensory epithelium, as well as on supporting cells, and there are centrioles and ciliary precursor bodies on the dendrites. In addition to ciliated cells and basal cells in the non-sensory epithelium, there is a novel type of non-ciliated cell in T. tachydromoides. They have constricted apical cytoplasm and microvilli instead of cilia, and are sparsely distributed in the epithelium. Based on these results, the variation in the morphology of the VNO in scincomorpha, a representative squamate taxon, is discussed.