Ben Creisler
Some recent non-dino papers with free pdfs:
Free pdf:
Serjoscha W. Evers, ÂJames M. Neenan, ÂGabriel S. Ferreira, ÂIngmar Werneburg, ÂPaul M. Barrett & ÂRoger B. J. Benson (2019)
Neurovascular anatomy of the protostegid turtle Rhinochelys pulchriceps and comparisons of membranous and endosseous labyrinth shape in an extant turtle.
Zoological Journal of the Linnean Society, zlz063
doi:
https://doi.org/10.1093/zoolinnean/zlz063https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlz063/5552592?searchresult=1Chelonioid turtles are the only surviving group of reptiles that secondarily evolved marine lifestyles during the Mesozoic Early chelonioid evolution is documented by fossils of their stem group, such as protostegids, which yield insights into the evolution of marine adaptation. Neuroanatomical features are commonly used to infer palaeoecology owing to the functional adaptation of the senses of an organism to its environment. We investigated the neuroanatomy and carotid circulation of the early Late Cretaceous protostegid Rhinochelys pulchriceps based on micro-computed tomography data. We show that the trigeminal foramen of turtles is not homologous to that of other reptiles. The endosseous labyrinth of R. pulchriceps has thick semicircular canals and a high aspect ratio. Comparisons among turtles and other reptiles show that the endosseous labyrinth aspect ratio is not a reliable predictor of the degree of aquatic adaptation, contradicting previous hypotheses. We provide the first models of neuroanatomical soft tissues of an extant turtle. Turtle brain morphology is not reflected by the brain cavity, and the endosseous labyrinth provides an incomplete reflection of membranous semicircular duct morphology. Membranous labyrinth geometry is conserved across gnathostomes, which allows approximate reconstruction of the total membranous labyrinth morphology from the endosseous labyrinth despite their poor reflection of duct morphology.
===
Free pdf:
Muofhe Tshibalanganda, ÂAnton du Plessis, ÂStephan G. Le Roux, Wendy L. Taylor, Roger M. H. Smith & Claire Browning (2019)
Systematic experiments to quantitatively assess image quality for CT scans of a Karoo tetrapod fossil.
Palaeontologia Africana 54: 1-13
URI:
https://hdl.handle.net/10539/27891http://wiredspace.wits.ac.za/handle/10539/27891Over the past decade non-destructive, three-dimensional visualization and analysis of fossils using X-ray tomography has greatly Âadvanced palaeontological studies worldwide. Micro-computed tomography (microCT) is now accepted as best practice in Âpalaeontological studies to augment the anatomical description of newly discovered fossils. Despite advances in laboratory microCT Âhardware, software and skills of users, there is a lack of clear methodologies for scanning and analysing fossils. Here we report on a Âsystematic and detailed study of the quantitative effects of the variation of different microCT scanning parameters on the image quality Âof an unprepared fossilized Karoo tetrapod skull and parts of the postcrania. Results indicate that voltage variations do not increase the Âcontrast for the bone as one would expect, and the best image quality solution is found using high frame averaging and high X-ray flux Â(current). Although this study was limited to one specimen, the results may find a practical use for future studies involving similar Âfossils.
===========
Free pdf:
We here describe the first fossil remains of a green lizard of the Lacerta group from the late Miocene (MN 13) of the Solnechnodolsk locality in southern European Russia. This region of Europe is crucial for our understanding of the paleobiogeography and evolution of these middle-sized lizards. Although this clade has a broad geographical distribution across the continent today, its presence in the fossil record has only rarely been reported. In contrast to that, the material described here is abundant, consists of a premaxilla, maxillae, frontals, parietals, jugals, quadrate, pterygoids, dentaries and vertebrae. The comparison of these elements to all extant green lizard species shows that these fossils are indistinguishable from Lacerta trilineata. Thus, they form the first potential evidence of the occurrence of this species in the Miocene. This may be also used as a potential calibration point for further studies. Together with other lizard fossils, Solnechnodolsk shows an interesting combination of survivors and the dawn of modern species. This locality provides important evidence for the transition of an archaic Miocene world to the modern diversity of lizards in Europe. In addition, this article represents a contribution to the knowledge of the comparative osteological anatomy of the selected cranial elements in lacertids. This study gives special emphasis to the green lizards, but new data are also presented for related taxa, e.g., Timon lepidus, Podarcis muralis or Zootoca vivipara. Although the green lizards include several cryptic species for which determination based on isolated osteological material would be expected to be difficult, our comparisons show several important morphological differences, although a high degree of variability is present.