Morphological basis of the feeding mechanics in the shingle-back lizard Trachydosaurus rugosus (Scincidae, Reptilia)

This report details certain morphological aspects of the feeding system of the lizard Trachydosaurus rugosus , an opportunistic omnivore, as a first step toward a functional characterization of its masticatory system. The skull is relatively solid and internally well braced; its anterodorsal elements are tightly tied to the integument and covering osteoderms. There is potential for intracranial kinesis and streptostyly. At small gapes, mandibular movements seem to be restricted to relatively simple, hingelike actions by a series of mechanical stops. The dentition features a progression of smaller to larger teeth posteriorly along the tooth row. The jaw adductor musculature is massive; other jaw muscles are relatively simple. The external adductor mass is particularly noteworthy in that it is subdivided into four mechanical units by a complex internal tendon tract (the coronoid aponeurosis). The internal adductor is composed of two separate gross muscles, pseudotemporalis (PST) and pterygoideus (PT). Each of these is subdivided into two main units by aponeurotic sheets, the PST by parts of the coronoid aponeurosis and the PT by a separate series. The form of the aponeurotic system in Trachydosaurus confounds the separation and identification of the adductor muscles and their component parts along the lines of traditional nomenclature, and underscores the need for separating criteria based on homology from those reflecting morphological and possibly functional divisions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50278/1/1051810303_ftp.pd

Separating sexual dimorphism from other morphological variation in a specimen complex of fossil marine reptiles (Reptilia, Ichthyosauriformes, Chaohusaurus).

The Early Triassic Chaohu Fauna from Anhui Province, China, contains the oldest record of Mesozoic marine reptiles, such as Cartorhynchus and Sclerocormus. Most specimens from the fauna belong to the ichthyosauriform Chaohusaurus, more specifically resembling C. chaoxianensis. However, a wide range of morphological variation exists within about 40 skeletons that have been prepared, likely reflecting mixed signals from both sexual and taxonomic differences. We test whether the sexual and taxonomic signals are separable based on quantification, aided by the knowledge of sexual dimorphism in extant marine tetrapods. There are two different suites of dimorphism that divide the specimens differently from each other yet consistently within each suite, resulting in four morphotypes in combination, likely representing two sexes of two taxa. Presumed males have larger organ of prehension sensu Darwin, specifically limbs in the present case, for a given body length. This sexing criterion is supported by the only specimen of a gravid female, which belongs to the morphotype with short limbs. Males also have larger skulls for the trunk length compared to females. This study demonstrates that sexual and taxonomic signals are separable in fossil reptiles, with a sufficient sample size and careful analyses

Introduction: The Entangled Histories of Science and Capitalism

This volume revisits the mutually constitutive relationship between science and capitalism from the seventeenth century to the present day. Adopting a global approach, this introduction rejects the notion that either science or capitalism can be understood as stages of modernity that emerged in the West and subsequently engendered a “Great Divergence” with the rest of the world. Instead, both science and capitalism were historical institutions that arose in an imperial context of global exchange and whose entanglement has been continuously remade. Rather than seek to explain either the development of modern science as a product of economic forces or the divergence of capitalist economies as a result of technical innovation, we want to emphasize the knowledge work that has been a central feature of both modern science and capitalism across the globe

“Living fossils” and the mosaic evolution of characters

The modern discussion of living fossils turns mostly on the persistence of archaic, or ancestral, traits in extant organisms. Prime examples mentioned by Darwin already—who also coined the term “living fossil”—include the platypus and the extant lungfishes. However, the identification of archaic traits in extant organisms requires a basis of comparison, i.e., it requires an estimate of the phylogenetic interrelationships of the living fossil in question. Phylogenetic relationships are determined not on the basis of the persistence of archaic traits, but on the basis of shared derived characters. The identification of persistent traits in an organism requires the same organism to also exhibit advanced, or specialized traits that allow its proper classification. The occurrence of such a mixture of primitive (plesiomorphic) or derived (apomorphic) traits in an organism, or species, is called the heterobathmy of characters. Willi Hennig recognized the heterobathmy of characters as quite a universal phenomenon, and made it the basis of his phylogenetic systematics

The earliest herbivorous marine reptile and its remarkable jaw apparatus

Newly discovered fossils of the Middle Triassic reptile Atopodentatus unicus call for a radical reassessment of its feeding behavior. The skull displays a pronounced hammerhead shape that was hitherto unknown. The long, straight anterior edges of both upper and lower jaws were lined with batteries of chisel-shaped teeth, whereas the remaining parts of the jaw rami supported densely packed needle-shaped teeth forming a mesh. The evidence indicates a novel feeding mechanism wherein the chisel-shaped teeth were used to scrape algae off the substrate, and the plant matter that was loosened was filtered from the water column through the more posteriorly positioned tooth mesh. This is the oldest record of herbivory within marine reptiles

Comparative Skull Morphology of Uropeltid Snakes (Alethinophidia: Uropeltidae) with Special Reference to Disarticulated Elements and Variation

Uropeltids form a diverse clade of highly derived, fossorial snakes that, because of their phylogenetic position among other alethinophidian lineages, may play a key role in understanding the early evolution of cranial morphology in snakes. We include detailed osteological descriptions of crania and mandibles for eight uropeltid species from three nominal genera (Uropeltis, Rhinophis, and Brachyophidium) and emphasize disarticulated elements and the impact of intraspecific variation on previously proposed morphological characters used for phylogenetic analysis. Preliminary analysis of phylogenetic relationships strongly supports a clade composed exclusively of species of Plectrurus, Uropeltis, and Rhinophis. However, monophyly of each of those genera and Melanophidium is not upheld. There is moderate support that Sri Lankan species (e.g., Rhinophis and Uropeltis melanogaster) are monophyletic with respect to Indian uropeltids. Previously proposed characters that are phylogenetically informative include the shape of the nasals, length of the occipital condyle, level of development of the posteroventral process of the dentary, and participation of the parietal in the optic foramen. Additionally, thirty new features that may be systematically informative are identified and described, but were not verified for their utility. Such verification must await availability of additional disarticulated cranial material from a larger sample of taxa. All characters require further testing through increased focus on sources and patterns of intraspecific variation, inclusion of broader taxonomic samples in comparative studies, and exploration of skeletal development, sexual dimorphism, and biogeographic patterns. Additionally, trends in the relative enlargement of the sensory capsules, reduction in cranial ossification and dentition, fusion of elements, and the appearance of novel morphological conditions, such as the structure and location of the suspensorium, may be related to fossoriality and miniaturization in some uropeltid taxa, and may complicate analysis of relationships within Uropeltidae and among alethinophidian snakes

Calabaria and the phytogeny of erycine snakes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73563/1/j.1096-3642.1993.tb00290.x.pd