Juan D. Daza

Diffusible iodine-based contrast-enhanced computed tomography (diceCT) : an emerging tool for rapid, high-resolution, 3-D imaging of metazoan soft tissues.

Morphologists have historically had to rely on destructive procedures to visualize the three‐dimensional (3‐D) anatomy of animals. More recently, however, non‐destructive techniques have come to the forefront. These include X‐ray computed tomography (CT), which has been used most commonly to examine the mineralized, hard‐tissue anatomy of living and fossil metazoans. One relatively new and potentially transformative aspect of current CT‐based research is the use of chemical agents to render visible, and differentiate between, soft‐tissue structures in X‐ray images. Specifically, iodine has emerged as one of the most widely used of these contrast agents among animal morphologists due to its ease of handling, cost effectiveness, and differential affinities for major types of soft tissues. The rapid adoption of iodine‐based contrast agents has resulted in a proliferation of distinct specimen preparations and scanning parameter choices, as well as an increasing variety of imaging hardware and software preferences. Here we provide a critical review of the recent contributions to iodine‐based, contrast‐enhanced CT research to enable researchers just beginning to employ contrast enhancement to make sense of this complex new landscape of methodologies. We provide a detailed summary of recent case studies, assess factors that govern success at each step of the specimen storage, preparation, and imaging processes, and make recommendations for standardizing both techniques and reporting practices. Finally, we discuss potential cutting‐edge applications of diffusible iodine‐based contrast‐enhanced computed tomography (diceCT) and the issues that must still be overcome to facilitate the broader adoption of diceCT going forward.

Skull anatomy of the miniaturized gecko Sphaerodactylus roosevelti (Squamata: Gekkota)

A detailed description of the skull and jaw of the gecko Sphaerodactylus roosevelti is presented. The bones are described articulated and isolated with special consideration given to the type of suture among joining elements. S. roosevelti was compared with 109 gekkotan species to evaluate the osteological variation and to find characters for cladistic analysis. Changes in the skull associated with the miniaturization process are discussed within the sphaerodactylid geckos. A noticeable increase of overlapping sutures was observed in the snout of the smallest sphaerodactylids compared to other gekkotans. This pattern is convergent with that in miniaturized pygopodids and may be attributed to adaptations for decreasing mechanical resistance of the cranium during feeding or burrowing. New cranial characters support Sphaerodactylinae as a monophyletic group and should be useful for resolving questions such as their relationship with other gekkotans. J. Morphol. 269:1340–1364, 2008.

Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards

Exquisitely preserved fossil lizards from 99-million-year-old Burmese amber provide new insights into paleotropical diversity. Modern tropical forests harbor an enormous diversity of squamates, but fossilization in such environments is uncommon and little is known about tropical lizard assemblages of the Mesozoic. We report the oldest lizard assemblage preserved in amber, providing insight into the poorly preserved but potentially diverse mid-Cretaceous paleotropics. Twelve specimens from the Albian-Cenomanian boundary of Myanmar (99 Ma) preserve fine details of soft tissue and osteology, and high-resolution x-ray computed tomography permits detailed comparisons to extant and extinct lizards. The extraordinary preservation allows several specimens to be confidently assigned to groups including stem Gekkota and stem Chamaleonidae. Other taxa are assignable to crown clades on the basis of similar traits. The detailed preservation of osteological and soft tissue characters in these specimens may facilitate their precise phylogenetic placement, making them useful calibration points for molecular divergence time estimates and potential keys for resolving conflicts in higher-order squamate relationships.

On the Fossil Record of the Gekkota

Gekkota is often interpreted as sister to all remaining squamates, exclusive of dibamids, or as sister to Autarchoglossa. It is the only diverse lineage of primarily nocturnal lizards and includes some of the smallest amniotes. The skeleton of geckos has often been interpreted as paedomorphic and/or “primitive” but these lizards also display a wide range of structural specializations of the postcranium, including modifications associated with both scansorial locomotion and limb reduction. Although the concept of “Gekkota” has been variously applied by different authors, we here apply a rigorous apomorphy based definition, recent advances in gekkotan morphology and phylogenetics, and diverse comparative material to provide a comprehensive assessment of 28 known pre‐Quaternary geckos, updating the last such review, published three decades ago. Fossils evaluated include both sedimentary fossils and amber‐embedded specimens. Known Cretaceous geckos are exclusively Asian and exhibit character combinations not seen in any living forms. Cenozoic gekkotans derive from sites around the world, although Europe is especially well represented. Paleogene geckos are largely known from disarticulated remains and show similarities to Sphaerodactylidae and Diplodactylidae, although resemblances may be plesiomorphic in some cases. Many Neogene gekkotans are referable to living families or even genera, but their geographic occurrences are often extralimital to those of modern groups, as is consistent with paleoclimatic conditions. The phylogenetic placement of fossil gekkotans has important repercusions for timetree calibration, but at present only a small number of fossils can be confidently assigned to even family level groupings, limiting their utility in this regard. Anat Rec, 297:433–462, 2014.

A New Amber-Embedded Sphaerodactyl Gecko from Hispaniola, With Comments On Morphological Synapomorphies of the Sphaerodactylidae

Abstract A new species of Sphaerodactylus (Squamata: Gekkota: Sphaerodactylidae) is described from an amber inclusion from the late Early Miocene or early Middle Miocene (15 to 20 million years ago) of the Dominican Republic. Unlike earlier amber-embedded specimens assigned to this genus, the new specimen is largely skeletal, with some integument remaining. A combination of 258 (of 674) osteological and external characters could be scored for the new species in a cladistic analysis of 21 gekkotan species, including representatives of all sphaerodactylid genera. The most parsimonious trees obtained confirm the placement of the amber gecko within the genus Sphaerodactylus and a comparison with extant Hispaniolan and Puerto Rican congeners suggests phenetic similarity both with members of S. difficilis complex and the S. shrevei species group. Character mapping on the basis of the phylogenetic analysis permits the preliminary identification of morphological characters diagnostic of the Sphaerodactylidae, Sphaerodactylini, and Sphaerodactylus. Osteological features of the new species are discussed in the broader context of sphaerodactyl, sphaerodactylid, and gekkotan variation. Extant Hispaniolan Sphaerodactylus display significant ecomorphological variation and it is likely that the many known, though not yet described, amber-embedded specimens will eventually reveal similar patterns in their Miocene congeners.

The Circumorbital Bones of the Gekkota (Reptilia: Squamata)

The enormous variation of the orbit in lepidosaurs is better conceptualized in terms of composition and configuration. Broadly, the orbit varies from having totally closed rim to being open posteriorly. Two processes are responsible for changes in the components of the circumorbital series, element loss and fusion. The resulting contacts among elements are the main factors determining orbital configuration. Here, we present a revision of the gekkotan circumorbital bones in the general context of the Lepidosauria. From observations of a sample of 105 species of gekkotans prepared using different techniques, we describe the main changes in the orbit and corroborate the presence or absence of some of the ambiguous elements such as the lacrimal and the jugal. The supraorbital bones of squamates are reviewed and some problems of homology are evaluated using recent phylogenenetic hypothesis. Anat Rec, 2010.

Cladistic Analysis of Iguania and a Fossil Lizard from the Late Pliocene of Northwestern Argentina

Abstract A fragmentary fossil lizard from Uquía Formation (Late Pliocene), Jujuy Province, Argentina, is described. The material consists of disarticulated cranial bones from the snout and jaw that were part of a microvertebrate fossil assemblage generated by accumulation of predatory birds pellets. The phylogenetic analysis of 396 morphological characters indicates a sister-group relationship between the new taxon and a clade formed by the families Liolaemidae, Leiocephalidae, and Tropiduridae. Its uncertain position and substantial morphological differences justify its placement in a new genus. We present a detailed osteological description of the material, and compare the morphological features with other Iguanoidea. In the context of this new analysis of Iguania, we included Pristiguana brasiliensis, the oldest know iguanian from South America. The results of this analysis support the monophyletic status of Iguanoidea and other groups within Iguania that are named and diagnosed. Resumen Describimos restos fragmentarios de un lagarto fósil procedente de la Formación Uquía (Plioceno Tardío) en la Provincia de Jujuy, Argentina. El material consiste de huesos craneales desarticulados del hocico y la mandíbula que fueron recuperados de un ensamble fósil de microvertebrados, el cual es una acumulación de egagrópilas generado por la actividad trófica de aves depredadoras. El análisis filogenético de 396 caracteres morfológicos indica que el nuevo taxón es el grupo hermano de un clado formado por las familias Liolaemidae, Leiocephalidae y Tropiduridae. La posición dudosa de este fósil y las substanciales diferencias morfológicas justifican clasificarlo como un género nuevo. Incluimos una descripción morfológica detallada del material fósil y comparamos su anatomía con otros miembros de Iguanoidea. En el contexto de este nuevo análisis de Iguania, incluimos a Pristiguana brasiliensis, el cual hasta hoy es el iguanio más viejo que se conoce de América del Sur. Los resultados de este análisis filogenético apoyan el estatus monofilético de Iguanoidea y de otros grupos dentro de Iguania, los cuales se definen y diagnostican.

A redescription and phylogenetic reinterpretation of the fossil lizard Hoburogekko suchanovi Alifanov, 1989 (Squamata, Gekkota), from the Early Cretaceous of Mongolia

ABSTRACT Additional information about one of the oldest known gecko-like lizards, Hoburogekko suchanovi from the Early Cretaceous of Mongolia, is provided in light of recent advances in the understanding of gekkotan osteology. The phylogenetic affinities of this taxon were assessed by adding it into an existing morphological data set of 224 taxa coded for 364 characters. The effects of character ordering and scoring on tree topology and the composition of Gekkonomorpha were also explored. The results of the analysis indicate that Gekkonomorpha is highly unstable and additional revision of stem gekkotans (e.g., Parviraptor, Gobekko) is required to refine the basal relationships of this clade. Like modern gekkotans, Hoburogekko possess a tubular frontal bone. In contrast to extant gekkotans, the Meckelian canal is only partially fused and may represent an incipient form of the gekkotan condition. The posterior shelf of the maxilla is wider than in modern gekkotans, perhaps related to a plesiomorphically large jugal. The short, rounded snout may indicate a lifestyle as found in some modern gekkotans found in equivalent xeric environments to the inferred paleoenviroment of the Höövor (Mongolia) locality during the Early Cretaceous.

Jaw Adductor Muscles across Lepidosaurs: A Reappraisal

The exact homologies of tetrapod jaw muscles remain unresolved, and this provides a barrier for phylogenetic analysis and tracing character evolution. Here, lepidosaur jaw muscles are surveyed using direct examination of species from 23 families and published descriptions of species from 10 families. A revised nomenclature is applied according to proposed homologies with Latimeria. Among lepidosaurs, variation was found in many aspects of jaw muscle anatomy. The superficial layers mm. levator and retractor anguli oris (LAO and RAO) are present in Sphenodon but not all squamates. The external jaw adductor muscles universally present in lepidosaurs are homologous with the main adductor muscle, A2, of Latimeria and include four layers: superficialis (A2‐SUP), medialis (A2‐M), profundus (A2‐PRO), and posterior (A2‐PVM). The A2‐SUP appears divided in Agamidae, Gekkota, Xantusiidae, and Varanidae. The A2‐M is layered lateromedial in lizards but anteroposterior in snakes. The names pseudotemporalis (PS) and pterygomandibularis (PTM) are recommended for subdivisions of the internal adductors of reptiles and amphibians, because the homology of this muscle with the A3′ and A3 ″ of Latimeria remains inconclusive. The intramandibularis of lepidosaurs and Latimeria (A‐ω) are homologous. The distribution of six jaw muscle characters was found to plot more parsimoniously on phylogenies based on morphological rather than and molecular data. Character mapping indicates that Squamata presents reduction in the divisions of the A2‐M, Scincoidea presents reduction or loss of LAO, and two apomorphic features are found for the Gekkota. Anat Rec, 2011.

Naming and rediagnosing the Cretaceous gekkonomorph (Reptilia, Squamata) from Öösh (Övörkhangai, Mongolia)

http://zoobank.org/urn:lsid:zoobank.org:pub:F16D073A-A0E2-4CA6-B797-756847D7C5AD