Paul, G. S. | bioRxiv Science

bioRxiv2022

Restoring the True Form of the Gigantic Blue Whale for the First Time, and Mass Estimation

Using photographs of swimming blue whales and mounted skeletons, the body form of the largest known animal is correctly restored, no previous effort having been entirely accurate in part because of the absence of rigorous technical efforts prior to this study. The maximum total length/depth ratio is about 7.5-8.1, with the greatest depth in the chest forward of midlength. There is a subtle ventral concavity between the chest and abdomen. The chest is broader than deep, contradicting mounted skeletons in which the ribs are articulated too vertically so that the chest is falsely deeper than broad. The tip of the mandible is fairly blunt, although the throat pouch is streamlined when cruising, the head is very large. The result is an elongated, tear drop, hydrodynamically optimized shape. A volume based mass estimate based on the restoration is close to that observed in harvested blue whales relative to length, and indicates that the largest individuals reach ~200 tonnes.

zoology↗

bioRxiv2022

Observations on Paleospecies Determination, With Additional Data on Tyrannosaurus Including Its Highly Divergent Species Specific Supraorbital Display Ornaments That Give T. rex a New and Unique Life Appearance

Intrageneric dinosaur species have been being named for decades without either significant examination of the methods and standards used to do so, or widely publicized controversy over the results. The long standing assumption that all large known specimens of the iconic North American Tyrannosaurus consisted of just the one popular species T. rex was recently challenged with the first comprehensive test of the question. The result was the diagnosing and naming of two additional taxa, T. imperator and T. regina, based on a number of species levels characters regarding robustness and tooth proportions in the context of their stratigraphic distribution. In association a rare in-depth look was taken at the current state of naming vertebrate paleospecies, which it turns out are not highly rigorous because of inherent problems with the species concept and other matters. The results of the paper were severely criticized in in a manner never seen before for new dinosaur species even when based on less evidence. This study takes another look as the determination of paleospecies, and shows that many of the claims made in the criticisms regarding the Tyrannosaurus species work were inaccurate. New data on the proportions of strength bars in Tyrannosaurus skulls reinforces the basing of the three species in part on robustness factors, and allows all but one skull to be assigned to one of the species. These results allow the first detailed systematic examination of the supraorbital display bosses of the genus. They sort out as visually distinctive species specific ornaments based on both stratigraphic and taxonomic factors, strongly affirm that Tyrannosaurus was multispecific, and the species probably dimorphic. New skulls of T. rex show that the species sported - males probably -- striking display bosses not yet observed in other tyrannosaurids.

paleontology↗