Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology

Abstract

Large theropod dinosaurs are often reconstructed with their marginal dentition exposed because of the enormous size of their teeth and their phylogenetic association to crocodylians. We tested this hypothesis using a multiproxy approach. Regressions of skull length and tooth size for a range of theropods and extant varanid lizards confirm that complete coverage of theropod dinosaur teeth with extraoral tissues (gingiva and labial scales) is both plausible and consistent with patterns observed in living ziphodont amniotes. Analyses of dental histology from crocodylians and theropod dinosaurs, including Tyrannosaurus rex , further indicate that the most likely condition was complete coverage of the marginal dentition with extraoral tissue when the mouth was closed. This changes our perceptions about the appearance and oral configuration of these iconic predators and has broad implications for our interpretations of other terrestrial animals with large teeth.

The coevolution of rostral keratin and tooth distribution in dinosaurs

“…[ 42 ]. Rostral surfaces with only linearly aligned foramina along the jaw margin that are in low densities were also interpreted as surfaces without rostral keratinous cover since this has been associated with lipped jaws in modern squamates [ 43 ]. To infer toothrow distribution, we relied on in-place teeth and non-vestigial alveoli [ 5 ], which accounts for any teeth missing due to taphonomic filters or collection errors.…”

Animating fossilized invertebrates by motion reconstruction

“…In recent years, the advancements in 3D digital technologies using computational methods have provided paleontologists with an unprecedented opportunity to non-destructively investigate the dynamic characteristics and mechanical performance of extinct species [ 1 ]. Motion reconstruction of extinct species can provide tangible and vivid understandings of their evolutionary traces and bring disappeared ecological landscapes back into our view [ 2 , 3 ]. For example, a study based on well-preserved skeletal fossils has examined the movement pattern and its influence on the feeding ecology of an extinct shark [ 4 ].…”