Velcí draví dinosauři, jako je T. rex, si vyvinuli různé tvary očních důlků, aby umožnily silnější kousnutí.

Podle nových výzkumů velcí draví dinosauři jako např Tyrannosaurus rex Pro lepší zvládnutí vyšších kousacích sil byly vyvinuty různé formy očních dutin.

Zatímco u mnoha zvířat, včetně většiny dinosaurů, je oční důlek kruhový otvor v lebce, který obsahuje oční bulvu, u velkých masožravců je to zcela odlišné.

Nová studie odhalila, jak se neobvyklé oválné nebo oválné oční důlky nalezené v lebkách těchto predátorů mohly vyvinout, aby pomohly lebce absorbovat šok, když se vrhne na kořist. Tento výzkum vědců v University of Birminghamzveřejněné dnes (11. srpna 2022) v Komunikační biologie.

Rekonstrukce lebky a život u Tyrannosaura Rex pomocí původní oční objímky a oka (vlevo) a virtuální rekonstrukce pomocí kruhové oční objímky a oční hypertrofie (vpravo). Kredit: Dr. Stefan Lautschlager, University of Birmingham

Dr. Stefan Luttenschlager, docent v paleobiologii ve společnosti[{“ 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