The Mesonychia is a group of archaic carnivorous mammals of uncertain phylogenetic affinities with a Holarctic distribution during the Paleogene. Intensive fossil collecting efforts in the Bighorn Basin, Wyoming, have resulted in recovery of the largest sample and most complete specimens yet known of the mesonychid Dissacus praenuntius from the second biozone of the Wasatchian North American Land Mammal Age (Wa-0). The Wa-0 biozone corresponds to the body of the Paleocene-Eocene Thermal Maximum (PETM), a brief but intense global warming event that occurred ~56 myr ago that significantly impacted terrestrial mammal faunas, including dwarfing in many mammal lineages. To evaluate the potential response of this lineage to climate change, we compared the PETM sample of D. praenuntius with those recovered from just before the PETM in the last biozone of the Clarkforkian North American Land Mammal Age (Cf-3) and just after the PETM in the Wa-1 biozone. While the sample size is still too small to say with certainty, tooth size (as a proxy for body weight) of D. praenuntius appears to be smaller during the late PETM than during either the pre-PETM Cf-3, or post-PETM Wa-1 biozones, suggesting the possibility of a muted dwarfing response to the PETM. However, the pattern observed for D. praenuntius differs from that of many other PETM mammals, as the shift to smaller body size is less pronounced and may have only occurred in late Wa-0.
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RBINS Staff Publications 2021
A description is provided of the crocodile remains that were found during an excavation carried out in 2019 at Qubbat al-Hawā (Aswan, Egypt). The material consists of five more or less complete bodies and five heads that were in varying states of preservation and completeness. The absence of resin, which was apparently not used during the preparation of the mummies, and the almost complete loss of linen bandages, due to insect damage, allowed a detailed morphological and osteometric description of the remains. Attention was focused on the general state of preservation of the crocodiles, the completeness of their skeletons and skulls, the presence of cut or other marks that could indicate the cause of death, and the processing of the carcasses. Moreover, the possible provenance of the crocodiles, the methods of capture and killing of the animals and their possible chronological attribution are discussed. It is concluded that the manner in which these specimens were prepared, as well as the variation observed in the type of ‘final product’, are unlike any other crocodile material described so far. The preparation method suggests a pre-Ptolemaic date for the deposit. The morphological and metrical features indicate that both Crocodylus niloticus and the recently resurrected species Crocodylus suchus are present among these individuals that range from 1.8 to 3.5 m in length.
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RBINS Staff Publications 2023
