Ben Creisler
Some recent non-dino papers:
Neusticemys neuquina (FernÃndez and de la Fuente, 1988) is a turtle from the Upper Jurassic of the NeuquÃn Basin, Patagonia, Argentina. Here we describe in detail a new skull, lower jaw, and a vertebra, utilizing both traditional anatomical description and computed tomography (CT). New diagnostic cranial characters of Neusticemys neuquina are: a round depression on the ventral surface of the basisphenoid, a relatively larger oval foramen nervi trigemini, and reduced and steepened triturating surfaces on both the maxilla and dentary. The new morphological information presented in this study was included in a phylogenetic analysis, the primary result of which was recovery of Neusticemys neuquina within Thalassochelydia. Characters recognized as synapomorphies of this clade include: (1) anterolateral recess of the anterior surface of the quadrate positioned lateral to the processus trochlearis oticum, (2) presence of a fossa on the supraoccipital-opisthotic-exoccipital contact area, (3) foramina anterius caroticus cerebralis located close together but independently perforating the basisphenoid, and (4) the presence of the splenial in the mandible. Two contrasting dispersal scenarios could explain how this species of Thalassochelydia can be found outside of Europe. The presence of Neusticemys neuquina in the NeuquÃn Basin could be the consequence of an early dispersion event, for which we lack intermediate forms, or it could be the result of a later event once the clade was already established in Europe.
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Robert L. Cieri Â& C.G. Farmer (2019)
Computational fluid dynamics reveals a unique net unidirectional pulmonary pattern of airflow in savannah monitor lizards (Varanus exanthematicus).
The Anatomical Record (advance online publication)
doi:
https://doi.org/10.1002/ar.24293https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24293This report models pulmonary airflow in the savannah monitor (Varanus exanthematicus) using computational fluid dynamics simulations, which are based on computed tomography data. Simulations were validated by visualizing the flow of aerosolized lipids in excised lungs with good but not perfect agreement. The lung of this lizard has numerous successive bronchi branching off a long intrapulmonary bronchus, which are interconnected by intercameral perforations. Unidirectional flow has been documented in the lateral secondary bronchi of the savannah monitor, but patterns of airflow in the rest of the lung remain unknown, hindering our understanding of the evolution of pulmonary patterns of airflow in tetrapods. These results indicate the lung contains a unique net unidirectional flow, where the overall flow scheme is similar during expiration and late inspiration, but dissimilar during early inspiration. Air is transported net caudad through the intrapulmonary bronchus and net craniad through secondary bronchi, much like the pattern of flow in birds. The simulations show that many chambers feature flow in multiple directions during parts of the respiratory cycle, but some regions also show robust unidirectional airflow. Air moves craniad through secondary bronchi and between adjacent secondary bronchi through intercameral perforations. The first secondary bronchus, the hilarâcranial bronchus, contains tidal flow that may improve ventilation of the central and dorsal lung parenchyma. These results expand our understanding of flow patterns in varanid lungs and suggest lungs with net unidirectional flow as an evolutionary pathway between tidal flow and complete unidirectional flow in multicameral lungs.
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A comprehensive qualitative and quantitative description of shell microanatomy of Testudinata is presented.
Data do not support a correlation between costal bone shell microstructure and habitats.
Paleoecological inferences based on bone microstructure must be taken very cautiously.
Abstract
Extant turtles exhibit a range of ecological adaptations to terrestrial and pelagic marine habitats. Bone shell microanatomy, and specifically, qualitative and quantitative approaches to shell bone porosity, have been used to infer palaeoecology and habitat. However, such inferences are hindered by the lack of a comprehensive sampling of testudine taxa and, in some instances, of long bones of vertebrates other than turtles. In this paper, we carry out an osteohistological analysis of Testudinata shell bones, including 31 different taxa, both extant and extinct, of known habitats. Costal and peripheral elements of published species and new data presented here are statistically analysed. Although, in some cases, values are congruent with those expected for a particular habitat (e.g. Hydromedusa casamayorensis), this is not true for all taxa examined. Moreover, microanatomical features of several taxa (e.g. Chelonia mydas) are inconsistent with habitat data. Results indicate that, although the microanatomical structure of the shell is related to habitat, this is not the only influence and indeed, in several cases, not the most important factor.