Selon de nouvelles recherches, de grands dinosaures prédateurs tels que Tyrannosaure Rex Diverses formes de cavités oculaires ont été développées pour mieux gérer les forces de morsure plus élevées.

Alors que chez de nombreux animaux, y compris la plupart des dinosaures, l’orbite de l’œil est un trou circulaire dans le crâne qui contient le globe oculaire, c’est tout à fait différent chez les grands carnivores.

Une nouvelle étude a révélé comment les orbites ovales ou ovales inhabituelles trouvées dans les crânes de ces prédateurs peuvent avoir évolué pour aider le crâne à absorber les chocs lorsqu’il bondit sur une proie. Cette recherche menée par des scientifiques de Université de Birminghampublié aujourd’hui (11 août 2022) dans Biologie des communications.

Reconstruction du crâne et vie chez Tyrannosaurus Rex à l’aide de l’orbite et de l’œil d’origine (à gauche) et reconstruction virtuelle à l’aide d’une orbite circulaire et d’une hypertrophie oculaire (à droite). Crédit : Dr Stefan Lautschlager, Université de Birmingham

Dr. Stefan Luttenschlager, maître de conférences en paléobiologie à[{ » attribute= » »>University of Birmingham and author of the new study, analyzed the shape of the eye sockets of ca. 500 different dinosaurs and related species.

“The results show that only some dinosaurs had eye sockets that were elliptical or keyhole-shaped,” said Dr. Stephan Lautenschlager. “However, all of those were large, carnivorous dinosaurs with skull lengths of 1 m or more.”

Computer simulations of hypothetical dinosaur skulls. Colors indicate skull stress. High stresses occur in the skull with a round eye socket (top), lower stresses in a skull with a keyhole-shaped eye socket (bottom). Credit: Dr. Stephan Lautenschlager, University of Birmingham

Dr. Lautenschlager tested what purpose these unusual eye socket shapes could have by using computer simulations and stress analysis.

The results demonstrated that a skull with a circular eye socket was more prone to high stresses during biting. However, if these were replaced with other eye socket shapes stresses were significantly reduced. This allowed top predators, including Tyrannosaurus rex, to evolve high bite forces without compromising skull stability.

The study also showed that most plant-eating species and juvenile individuals retained a circular eye socket. Only large carnivores adopted other morphologies, such as elliptical, keyhole-shaped, or figure-of-eight-shaped eye sockets.

Skulls of different dinosaurs showing variation in eye socket shape (stippled outline). Credit: Dr. Stephan Lautenschlager, University of Birmingham

Dr. Lautenschlager added: “In these species, just the upper part of the eye socket was actually occupied by the eyeball. This also led to a relative reduction of eye size compared with skull size.”

The researchers also investigated what would have happened if eye size had increased at the same rate as skull length. In such a case, the eyes of Tyrannosaurus rex would have been up to 30 cm (12 inches) in diameter and weighed nearly 20 kg (44 pounds). This is instead of an estimated 13 cm (5 inches) and 2 kg (4.4 pounds).

Reference: “Functional and ecomorphological evolution of orbit shape in mesozoic archosaurs is driven by body size and diet” by Stephan Lautenschlager, 11 August 2022, Communications Biology.
DOI: 10.1038/s42003-022-03706-0