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Crocodyliforms with heterodont dentition, evolution and dental function

From: Ben Creisler

A new online paper:

Attila Ősia (2013)
The evolution of jaw mechanism and dental function in heterodont crocodyliforms.
Historical Biology (advance online publication)

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.
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