13 research outputs found
Bird-Like Anatomy, Posture, and Behavior Revealed by an Early Jurassic Theropod Dinosaur Resting Trace
BACKGROUND: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. METHODOLOGY/PRINCIPAL FINDINGS: Here we describe a well-preserved theropod trackway in a Lower Jurassic ( approximately 198 million-year-old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. CONCLUSIONS/SIGNIFICANCE: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods
Equatorial paleolatitude for Northeast Africa in the Late Triassic: paleomagnetic study on the Gezira and Bir-Umhebal [229â223Â Ma] ring complexes, Southeastern Desert, Egypt
New archosauromorph fragments from the Dockum Group of Texas and assessment of the earliest dinosaurs in North America
Species delimitation in the Stenocereus griseus (Cactaceae) species complex reveals a new species, S. huastecorum
Electrocardiographic abnormalities in Chagas disease in the general population: A systematic review and meta-analysis
Biogeography of New World Tarantulas
Biogeography is a multidisciplinary field that is concerned with delimit- ing and explaining the geographic distributions of organisms in space and time. Due to their distribution patterns and interesting biology (e.g., ancient lineage with a nearly cosmopolitan distribution, sedentary lifestyle with limited dispersal capabili- ties), tarantulas are an appealing taxonomic group for addressing a variety of bio- geographic questions concerning the Earthâs history. In this chapter, we discuss some biogeographic basic concepts, delve into the distribution patterns of New World tarantulas, and explore some of the historical explanations that may have led to these distributions. We mostly review and highlight the results of recent studies but also include personal observations and unpublished data. The distributions of higher-level taxonomic groups (subfamilies and tribes) are described and we detail their latitudinal and elevational limits. We also review the distributions of groups with unique insular habitats such as those found on islands surrounded by seas, forested âislandsâ surrounded by âseasâ of deserts, and caves. Furthermore, we dis- cuss the distribution of some unique morphological characters of taxonomic impor- tance such as urticating setae. Finally, we review a handful of studies that have explicitly investigated the biogeography of New World tarantulas using a variety of different analytical methods.Fil: PerafĂĄn, Carlos. Universidad de la RepĂșblica. Facultad de Ciencias; UruguayFil: Ferretti, Nelson Edgardo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto de Ciencias BiolĂłgicas y BiomĂ©dicas del Sur. Universidad Nacional del Sur. Departamento de BiologĂa, BioquĂmica y Farmacia. Instituto de Ciencias BiolĂłgicas y BiomĂ©dicas del Sur; ArgentinaFil: Hendrixson, Brent E.. Millsaps College. Department Of Biology; Estados Unido