Palaeontology: T. rex and relatives traded big eyes for bigger bites

In the case of Tyrannosaurus rex and similar large carnivorous dinosaurs (theropods), narrower orbits than their ancestors may have helped improve their bite force, a paper reports.Biology CommunicationsWill be published in.

Here, Stephan Lautenschlager compared the orbits of 2 fossil reptile specimens from the Mesozoic Era (5200 to 6600 million years ago).The fossil specimens included dinosaurs and their relatives, such as crocodilians.They found that the orbits of most reptile species (especially herbivores) are circular.In contrast, juveniles of large carnivores with skulls longer than 410 m tended to have circular orbits, whereas adults often had oval or keyhole-shaped orbits. .Ancient species were also more likely than newer species to have circular orbits, and large theropods were more likely to have keyhole-shaped orbits than ancestral species.This observation suggests that keyhole-shaped orbits evolved in large carnivorous species, but that this shape developed in adults rather than juveniles.

To investigate the effect of orbital shape on skull structure and function, Lautenschlager compared the forces experienced by a theoretical model of a reptilian skull with five different orbital shapes in occlusal simulations.Lautenschlager also compared the maximum eyeball size that the skulls of Tyrannosaurus models with circular and keyhole eye sockets could accommodate.Keyhole-shaped orbits deformed less during occlusion than circular orbits and helped reduce stress on the skull by distributing forces along the stronger part of the skull behind the orbit.In contrast, the Tyrannosaurus model with circular eye sockets accommodated a volume seven times larger than the model with keyhole-shaped eye sockets.

Lautenschlager believes that the evolution of narrow eye sockets reduced the space available for eyeballs in theropod skulls, while increasing the space available for jaw muscles, making the skull more robust. is shown.This may have helped increase bite force at the cost of having larger eyeballs.Previous studies have hypothesized that larger eyeballs lead to improved visual perception.Our findings shed light on the functional trade-offs that shaped dinosaur evolution.

doi: 10.1038 / s42003-022-03706-0
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Reprinted from: "Palaeontology: Tyrannosaurus rex and its relatives traded big eyes for strong bite force'

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