Data from: United by chewing: Hunter-Schreger band-like pattern and wavy enamel in a fossil crocodile suggest functional convergence with mammals and dinosaurs

Tooth enamel of most mammals shows alternating light-dark bands, called
Hunter-Schreger bands (HSB), in longitudinal sections caused by a
decussating arrangement of bundles of prisms, the unit building blocks of
mammalian enamel. HSB is thought to increase resistance to abrasive food
and mitigate crack propagation and hence is considered a mammalian
adaptation to high-efficiency mastication. Here we report for the first
time the presence of HSB-like features in the tooth enamel of a
non-mammalian amniote, Iharkutosuchus, an extinct herbivorous crocodile
with strong heterodonty and a unique chewing mechanism. Lacking
mammal-like decussating prisms as revealed by traditional visualization
techniques, the enigmatic nature of this HSB-like enamel pattern in
Iharkutosuchus was only explainable using X-ray diffraction computed
tomography which showed its purely crystallographic origin. Wavy enamel, a
well-known structure in herbivorous ornithopod dinosaurs with
shearing-type mastication, is also demonstrated in Iharkutosuchus. The
unexpected finding of both enamel features in this herbivorous crocodile
speaks for their role in high-efficiency chewing. However, the profoundly
different structural background of mammalian and crocodilian HSB
demonstrated here and the phylogenetic distribution of both HSB and wavy
enamel imply nanostructure-scale convergences highlighting the importance
of mastication-related challenges in driving dentary evolution of
amniotes.