Dinosaurs Had Cheeks, Clues on Skull Bones

The snout of dinosaurs was probably different from what we have always imagined: some species may have had cheeks . This is evidenced by the presence on the skull bones of signs of insertion of a soft tissue , similar to a muscle or a ligament , located right between the cheekbone and the jaw . This anatomical structure, called exoparia , may have been crucial for chewing . This is suggested by the studypublished in the Journal of Anatomy by researchers at the University of Alberta in Canada.

Until now, paleontologists have been able to study the anatomy of dinosaurs starting from bone remains: to reconstruct the presence of soft tissues and muscles, degraded by time and therefore not preserved, they rely on a logic of ' phylogenetic kinship ' by making a comparison with the anatomy of their modern descendants , crocodiles and birds . A method that however has its limits. "What if dinosaurs had had their own muscles, which were not present in the dinosaurs that gave rise to birds, or that birds lost or adapted into something else?" Henry Sharpe, first author of the study, asked himself this when he discovered structural anomalies in the skull of an Edmontosaurus named Gary. "If this were a mammal skull, we would say it was a cheek muscle , but reptiles shouldn't have a cheek muscle. That got us thinking, what if there was something here that goes against the accepted model of dinosaur muscles?" To better understand this anatomy, Sharpe and his colleagues examined the same area of ​​the skull in other dinosaur species and found the same structure in all the specimens. "It was always in the same place, which was a pretty good indication to us that it was a muscle or a ligament ." To confirm this hypothesis, they analyzed thin sections of bone with polarized light microscopy, identifying the marks left by collagen fibers that anchored the soft tissue of the cheek.