Jaw mechanism in Archosaurs

Food processing and jaw mechanism in Mesozoic Archosaurian reptiles

In the vertebrate life of the Mesozoic there were several groups which either do not exist today (e.g. non-avian dinosaurs, pterosaurs), or only a few species are survived, or their lifestyle are markedly different from their ancestors (birds). An interesting question is related to the feeding habit and food preference of these extinct forms. Individual tooth morphology, architecture of the upper and lower dentition along with the reconstruction of the jaw adductors and the morphology of the jaw joint can provide significant information for the reconstruction of jaw mechanism and dental occlusion (figure 1).

This kind of studies have been fulfilled in case of crocodiles, pterosaurs and armored dinosaurs by Attila Ősi and colleagues. Research pointed out that various feeding related cranial features (e.g. special jaw movements, some specialized teeth) occured convergently several times during the evolution of these groups (figure 2).

For example, our studies along with those of other workers pointed out that crocodiles existing during the last 220 millio years were much more diverse during the Mesosoic than previously thought. Some of them were herbivores or omnivores, in some forms a burrowing life style has been suggested. Most of these specialized Mesozoic forms did not reach a body size longer than 70 cm (figure 3).

The evolution and diversity of complex jaw mechanisms and efficient food processing in crocodylians strongly resemble those of the chewing of mammals and suggest that the diverse ecological places filled in predominantly by mammals in North America and Asia were occupied in other Mesozoic ecosystems (e.g. in numerous habitats of South America and Africa, and on some islands of the European Cretaceous archipelago) by highly specialized crocodylians. One of thes crocodiles was Iharkutosuchus makadii from the Bakony Mountains.

figure 1. The reconstructed main jaw adductors in Iharkutosuchus and in the dinosaur Mochlodon.
figure 1. The reconstructed main jaw adductors in Iharkutosuchus and in the dinosaur Mochlodon.
figure 2. Dental occlusion and jaw mechanism in Iharkutosuchus.
figure 2. Dental occlusion and jaw mechanism in Iharkutosuchus.
figure 3. Skulls of some specialized crocodyliforms.
figure 3. Skulls of some specialized crocodyliforms.

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