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One goal of evolutionary developmental biology is to understand the role of development in the origin of phenotypic novelty and convergent evolution. Geckos are an ideal system to study this topic, as they are species‐rich and exhibit a suite of diverse morphologies—many of which have independently evolved multiple times within geckos.

We characterized and discretized the embryonic development ofLepidodactylus lugubris—an all‐female, parthenogenetic gecko species. We also used soft‐tissue μCT to characterize the development of the brain and central nervous system, which is difficult to visualize using traditional microscopy techniques. Additionally, we sequenced and assembled a de novo transcriptome for a late‐stage embryo as a resource for generating future developmental tools. Herein, we describe the derived and conserved patterns ofL. lugubrisdevelopment in the context of squamate evolution and development.

This embryonic staging series, μCT data, and transcriptome together serve as critical enabling resources to study morphological evolution and development, the evolution and development of parthenogenesis, and other questions concerning vertebrate evolution and development in an emerging gecko model.

 

In recent years, major changes have been proposed for the phylogenetic relationships within the Gymnophthalmoidea, including the description of Alopoglossidae. Recent studies relied primarily on molecular data and have not accounted for evidence from alternative sources, such as morphology. In this study, we provide a detailed bone‐by‐bone description of the skull ofPtychoglossus vallensisand compare this species with other gymnophthalmoideans. The description was based on 10 cleared‐and‐stained specimens, four disarticulated skulls, and computed microtomography data ofP. vallensis. Most recent phylogenetic hypothesis for the Gymnophthalmoidea was used as a framework to compare the skull ofP. vallensiswith other species of the Alopoglossidae, Gymnophthalmidae, and Teiidae. Marked similarities between alopoglossids and gymnophthalmids were observed in contrast to teiids, probably due to convergence generated by miniaturization. We also qualitatively analyzed the kinesis of the skull ofP. vallensisconcluding that is highly akinetic, a trait commonly evolved in fossorial, primarily burrowing squamates. We also describe one unique osteological feature for Alopoglossidae that is not known in any other squamate group. Anat Rec, 302:1074–1092, 2019. © 2018 Wiley Periodicals, Inc.

 

Abstract Determining the mechanisms that create and maintain biodiversity is a central question in ecology and evolution. Speciation is the process that creates biodiversity. Speciation is mediated by incompatibilities that lead to reproductive isolation between divergent populations and these incompatibilities can be observed in hybrid zones. Gecko lizards are a speciose clade possessing an impressive diversity of behavioral and morphological traits. In geckos, however, our understanding of the speciation process is negligible. To address this gap, we used genetic sequence data (both mitochondrial and nuclear markers) to revisit a putative hybrid zone between Sphaerodactylus nicholsi and Sphaerodactylus townsendi in Puerto Rico, initially described in 1984. First, we addressed discrepancies in the literature on the validity of both species. Second, we sampled a 10-km-wide transect across the putative hybrid zone and tested explicit predictions about its dynamics using cline models. Third, we investigated potential causes for the hybrid zone using species distribution modeling and simulations; namely, whether unique climatic variables within the hybrid zone might elicit selection for intermediate phenotypes. We find strong support for the species-level status of each species and no evidence of movement, or unique climatic variables near the hybrid zone. We suggest that this narrow hybrid zone is geographically stable and is maintained by a combination of dispersal and selection. Thus, this work has identified an extant model system within geckos that that can be used for future investigations detailing genetic mechanisms of reproductive isolation in an understudied vertebrate group. 

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. 

We identify a presumed specimen of Sphaerodactylus in amber from the Zoological Research Museum Alexander Koenig as being embedded in copal, rather than amber. Further, the specimen matches the morphology not of a Hispaniolan gecko, but of the extant Madagascan species Ebenavia boettgeri, which occurs in a known area of copal deposits. 

The Peruvian sphaerodactyl gecko, Pseudogonatodes barbouri, is among the smallest reptile species in South America. Morphological information about this species, or even the genus, is limited. In this study, we produced a bone-by-bone description from the skull and atlantoaxial complex to contribute new phenotypic information about this poorly known lizard. To achieve this objective, we employed a divide-and-conquer approach in which each author digitally isolated one or two bones from the skull and produced a written description of these elements, thereby reducing 3D imaging processing and description to a fraction of time. In addition to a reduced phalanx in the fourth toe of both the hand and foot, the genus is characterized by having nasal bones with a broad lateral wing, an ectopterygoid that clasps the pterygoid, and an anterior shifting of the paroccipital process and as consequence the position of the quadrate, and squamosal not participating in the quadrate suspension. There are also modifications in fenestration and foramina and a trend towards synostosis of the jaw bones (e.g., coronoid + splenial, compound bone + surangular). Pseudogonatodes bears four long processes on the intercentrum of the axis; which is a character of New World sphaerodactyls. 

Squamate remains from fossil-bearing deposits are difficult to identify on the basis of their morphology, because their modern relatives lack osteological description. In addition, intraspecific morphological variability of modern taxa is mostly understudied, making taxonomic identification of subfossil bones even more difficult. The aim of this study was to investigate osteological differences between two sympatric gecko species, Thecadactylus rapicauda and Hemidactylus mabouia, both currently occurring in the Lesser Antilles and in the subfossil assemblages of the region. Comparison of several modern museum specimens reveals the intraspecific osteological variability of these lizards and how difficult it is to distinguish between their bones, even though they are from two distant families. This study presents nine osteological characters, allowing for a fully reliable distinction of these two gecko species. These characters are applied to the specific identification of gecko species subfossil remains unearthed from the Pointe Gros Rempart 6 Hole (La De´sirade Island, Guadeloupe). Our results confirm the past occurrence of T. rapicauda as well as the historical introduction of H. mabouia on La De´sirade Island. 

Gekkota (geckos and pygopodids) is a clade thought to have originated in the Early Cretaceous and that today exhibits one of the most remarkable scansorial capabilities among lizards. Little information is available regarding the origin of scansoriality, which subsequently became widespread and diverse in terms of ecomorphology in this clade. An undescribed amber fossil (MCZ R–190835) from mid-Cretaceous outcrops of the north of Myanmar dated at 99 Ma, previously assigned to stem Gekkota, preserves carpal, metacarpal and phalangeal bones, as well as supplementary climbing structures, such as adhesive pads and paraphalangeal elements. This fossil documents the presence of highly specialized adaptive structures. Here, we analyze in detail the manus of the putative stem Gekkota. We use morphological comparisons in the context of extant squamates, to produce a detailed descriptive analysis and a linear discriminant analysis (LDA) based on 32 skeletal variables of the manus. The comparative sample includes members of 15 extant squamate families (Agamidae, Dactyloidae, Iguanidae, Leiosauridae, Liolaemidae, Polychrotidae, Tropiduridae, Diplodactylidae, Eublepharidae, Gekkonidae, Phyllodactylidae, Sphaerodactylidae, Gymnophthalmidae, Teiidae, and Scincidae). Although the fossil manus is qualitatively more similar to that of members of Gekkota, the LDA analysis places it in a morphozone shared by Gekkota and Scincomorpha. This result is particularly interesting, given that despite the presence of paraphalangeal structures had only been reported in extant geckos of the families Gekkonidae and Phyllodactylidae, the usage of an adhesive subdigital system to climb originated independently in Gekkota, Scincidae, and Dactyloidae.