Not all vegetarian dinosaurs chewed their food in the same way

SWhile studies have shown how different dinosaurs ate, little is known about the evolution of their preferred feeding styles. In a new study, researchers have discovered a surprising number of differences in how these extinct animals that ruled the planet ate a plant-based diet, filled out their jaw muscles and measured the bite force of dinosaurs.

Caption image: Reconstruction of the head and neck of the herbivorous dinosaur Heterodontosaurus tucki from the Lower Jurassic Upper Elliot and Clarence Formations of South Africa. (Tyler Keillor)

A group of researchers from the University of Bristol in Great Britain used scans of dinosaur skulls to trace the evolution of early herbivores. analyzed five dinosaur skulls from the group ornithistsincluding L’Heterodontosaurusthe Lesothosaurusthe ScelidosaurusI’Hypsilophodon and Psittacosaurus.

They are the earliest representatives of what would later become the largest group of herbivorous dinosaurs. Although they are all vegetarians, these five animals have evolved and adapted to eating plants in different ways. According to the researchers, this discovery could lead to a better understanding of how dinosaurs evolved to occupy certain ecological niches.

According to David Button, lead author of the study:

When we compared the functional performance of the skulls and teeth of these herbivorous dinosaurs, we found significant differences in relative jaw muscle sizes, bite forces, and jaw strength, indicating that they evolved different ways to approach their feeding.

After performing CT scans on the fossils, the researchers reconstructed the jaw muscles using data from living species such as birds and crocodiles to determine where the muscles would be located. They then performed “finite element analysis,” a numerical method that divides the surface into many small parts to predict how the model would respond to real-world forces, and calculated the bite force, muscles based on their size and arrangement.

CT reconstructions of the skull and jaws, as well as diagrams of jaw muscle placement in each dinosaur. The simplified family tree below shows how they are related to each other. (David Button/University of Bristol)

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During the simulations, the skulls bit down on an imaginary object so that the researchers could see how different elements reacted to the applied force. The heat maps showed which areas of the skull were very tense and which areas were tense. The results showed that all of the dinosaurs in the study ate plants, but each had their own way of doing it.

Here are some of the finite element models in the study comparing the bite performance of five ornithischian dinosaurs with different models showing different bite points. Cool colors (blue) indicate areas of low stress, while warm colors (red and pink) indicate areas of high stress. (David Button/University of Bristol)

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For example, Heterodontosaurus had large jaw muscles relative to its skull size, creating a high bite force ideal for eating tough vegetation. the Scelidosaurus had similar bite force but smaller jaw muscles. SkullHypsilophodonmeanwhile, it lacked large muscles, so it modified them to bite more efficiently with less muscle power.

According to study author Stephan Lautenschlager:

Some have compensated for poor eating performance with size, while others have developed larger jaw muscles, improved the efficiency of the jaw system, or a combination of these approaches. Although these animals look very similar, their individual solutions to the same problems illustrate the unpredictable nature of evolution.

Current Biology: Multiple Paths to Herbivory: ‘Vegetarian’ dinosaurs differed in how they ate their food, study reveals deep disagreements in ornithischian evolution, published on the University of Bristol website.

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