Ben Creisler
Some recent papers:
Elena Previtera (2019)
Diagenetic characterization of dinosaur remains through histology in fluvial contexts from the Upper Cretaceous of the Loncoche Formation, Mendoza, Argentina
Ameghiniana (advance online publication)
doi:10.5710/AMGH.16.01.2019.3235
Histological and diagenetic features of sauropod and theropod bones from the late Cretaceous Loncoche Formation of southern Mendoza, Argentina were analyzed to elucidate the degree and type of taphonomic alteration in relation to their depositional environment. The histological thin sections reveal a predominance of fibrolamellar bone tissue in the sauropod suggesting an overall fast bone growth, contrary the presence of parallel-fibered bone tissue that suggests a slow-down growth in the theropod. However, the existence of lines of arrested growth (LAGs) indicates periodic interruptions of growth, and likely expressed their ability to respond to rapid environmental changes. The fossil bones show post-mortem modifications such as weathering, fragmentation, abrasion and hydraulic sorting during transport. Diagenetic processes include substitution, fracturing, plastic deformation due to lithostatic compression, and permineralization events. Petrographic and SEM-EDS analyses show the substitution of hydroxyapatite by fluorapatite in the bone microstructure. Permineralization stages include infilling of vascular canals, trabeculae and fractures with iron oxides and carbonate minerals during the burial history. This work provides an integral approach to the study of dinosaurs from the Loncoche Formation for assessing the diagenetic changes in the bone microstructure and its link with burial environments.
=====
Yet another theory on the extinction of dinosaurs--vitamin D deficiency...
Free pdf:
D. R. Fraser (2019)Â
Why did the dinosaurs become extinct? Could cholecalciferol (vitamin D3) deficiency be the answer?
Journal of Nutritional Science 8: d9: 1-5
Palaeontological deductions from the fossil remnants of extinct dinosaurs tell us much about their classification into species as well as about their physiological and behavioural characteristics. Geological evidence indicates that dinosaurs became extinct at the boundary between the Cretaceous and Paleogene eras, about 66 million years ago, at a time when there was worldwide environmental change resulting from the impact of a large celestial object with the Earth and/or from vast volcanic eruptions. However, apart from the presumption that climate change and interference with food supply contributed to their extinction, no biological mechanism has been suggested to explain why such a diverse range of terrestrial vertebrates ceased to exist. One of perhaps several contributing mechanisms comes by extrapolating from the physiology of the avian descendants of dinosaurs. This raises the possibility that cholecalciferol (vitamin D3) deficiency of developing embryos in dinosaur eggs could have caused their death before hatching, thus extinguishing the entire family of dinosaurs through failure to reproduce.
=====
Free pdf:
Martin QvarnstrÃm, Joel Vikberg WernstrÃm, RafaÅ Piechowski, Mateusz TaÅanda, Per E. Ahlberg and Grzegorz NiedÅwiedzki (2019)
Beetle-bearing coprolites possibly reveal the diet of a Late Triassic dinosauriform.
Royal Society Open Science. 6: 181042
Free pdf:
Diets of extinct animals can be difficult to analyse if no direct evidence, such as gut contents, is preserved in association with body fossils. Inclusions from coprolites (fossil faeces), however, may also reflect the diet of the host animal and become especially informative if the coprolite producer link can be established. Here we describe, based on propagation phase-contrast synchrotron microtomography (PPC-SRÎCT), the contents of five morphologically similar coprolites collected from two fossil-bearing intervals from the highly fossiliferous Upper Triassic locality at KrasiejÃw in Silesia, Poland. Beetle remains, mostly elytra, and unidentified exoskeleton fragments of arthropods are the most conspicuous inclusions found in the coprolites. The abundance of these inclusions suggests that the coprolite producer deliberately targeted beetles and similar small terrestrial invertebrates as prey, but the relatively large size of the coprolites shows that it was not itself a small animal. The best candidate from the body fossil record of the locality is the dinosauriform Silesaurus opolensis Dzik, 2003, which had an anatomy in several ways similar to those of bird-like neotheropod dinosaurs and modern birds. We hypothesize that the beak-like jaws of S. opolensis were used to efficiently peck small insects off the ground, a feeding behaviour analogous to some extant birds.