Heterodont dentition sometimes including multicuspid crowns appeared in numerous fossil
forms through all main lineages of the Crocodyliformes. Teeth in these complex dentitions
frequently bear wear facets that are exclusive indicators of tooth-tooth occlusion.
Besides, dental features, specialisations of the jaw apparatus, jaw adductors and
mandibular movement can be recognised, all reflecting a high variability of jaw mechanism
and of intraoral food processing. Comparative study of these features revealed four
main types of jaw mechanism, some of which evolved independently in several lineages
of Crocodyliformes. Isognathous orthal jaw closure (precise jaw joint, rough wear
facets) is characteristic for heterodont protosuchians and all forms possessing crushing
posterior teeth. Proal movement (protractive powerstroke) occurred independently in
Malawisuchus and Chimaerasuchus is supported by the antagonistic, vertically oriented
carinae. Developed external adductors are the main indicators of palinal movement
(retractive powerstroke) that evolved at least two times in various South American
taxa. The fourth type (in Iharkutosuchus) is characterised by lateromedial mandibular
rotation supported by extensive horizontal wear facets. This evolutionary scenario
resembles that of the masticatory system of mammals and suggests that the ecological
roles of some mammalian groups in North America and Asia were occupied in Western
Gondwana by highly specialised crocodyliforms. http://www.zoobank.org/urn:lsid:zoobank.org:pub:D6CE962F-2B38-47F8-BD4B-B9E035917F20
