T レックスなどの大型の肉食恐竜は、より強力な噛みつきを可能にするために、さまざまな眼窩の形状を進化させました。

新しい研究によると、 ティラノサウルス・レックス より高い咬合力をより適切に処理するために、さまざまな形態の眼腔が開発されています。

ほとんどの恐竜を含む多くの動物では、眼窩は眼球を含む頭蓋骨の円形の穴ですが、これは大きな肉食動物ではまったく異なります.

新しい研究は、これらの捕食者の頭蓋骨に見られる異常な楕円形または楕円形の眼窩がどのように進化して、頭蓋骨が獲物に襲われたときに衝撃を吸収するのを助けたのかを明らかにしました. の科学者によるこの研究 バーミンガム大学、本日（2022 年 8 月 11 日）に公開 コミュニケーション生物学。

元の眼窩と眼を使用したティラノサウルス レックスの頭蓋骨の再構築と生命 (左) と、円形の眼窩と眼肥大を使用した仮想再構築 (右)。 クレジット: Dr. Stefan Lautschlager、バーミンガム大学

Dr. Stefan Luttenschlager、古生物学上級講師[{” 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