Tooth‐On‐Tooth Interlocking Occlusion Suggests Macrophagy in the Mesozoic Marine Crocodylomorph Dakosaurus

Abstract

Metriorhynchidae was a peculiar but long-lived group of marine Mesozoic crocodylomorphs adapted to a pelagic lifestyle. Recent discoveries show that metriorhynchids evolved a wide range of craniodental morphotypes and inferred feeding strategies. One genus, Dakosaurus, is arguably the most aberrant marine crocodylomorph due to its large, robust, ziphodont teeth; very low tooth count; and brevirostrine/oreinirostral snout. We here report an additional unusual feature of Dakosaurus that is unique among marine crocodylomorphs: tightly fitting tooth-totooth occlusion, whose inference is supported by reception pits along the upper and lower tooth rows, indicative of vertically orientated crowns that were in close contact during occlusion, and three distinct types of dental wear. These include irregular spalled surfaces near the apex (probably caused by tooth-food contact), semi-circular wear near the base, and elongate surfaces extending along the mesial and distal margins of the teeth, obliterating the carinae (including the denticles). Scanning electron micrographs show that these latter surfaces are marked by parallel apicobasal striations, which in extant mammals reflect tooth-tooth contact. As such, we interpret the carinal wear facets in Dakosaurus as being formed by repeated tooth-tooth contact

A small, exquisitely preserved specimen ofMosasaurus missouriensis(Squamata, Mosasauridae) from the upper Campanian of the Bearpaw Formation, western Canada, and the first stomach contents for the genus

“…Sediment was initially affixed to the broken surfaces, which were exposed carefully during preparation to identify areas with possible bite damage. The presumed bite damage on the vertebral centra suggests that the fish was broken apart by the mosasaur before being swallowed, a necessary mode of macrophagic feeding in aquatic amniotes to prevent asphyxiation (e.g., Young et al, 2012), with the notable exception of sea snakes and sea kraits (e.g., Greene, 1997).…”

Gene networks, occlusal clocks, and functional patches: new understanding of pattern and process in the evolution of the dentition

“…Wear striations on fossil teeth demonstrate that dental occlusion evolved independently in ten or more clades of amniote vertebrates, many of them are herbivores like the sail-backed synapsids of the Edaphosauridae [92][93][94][95][96]. Even conodonts, tiny jawless lamprey-like animals that were common in Paleozoic seas, have sophisticated tooth-on-tooth feeding movements [97,98].…”

Precise occlusion and trophic niche differentiation indicate specialized feeding in Early Devonian jawed vertebrates

“…5) suggest that it could have been an effective predator of large prey (relative to its body size), including soft-bodied animals. Tightly interlocking teeth have been suggested as an indicator of macrophagy in crocodylians (Young et al 2012), and the anterior and posterior flanges would have formed an almost continuous slicing or cutting surface. The teeth of E. rugosus also have longitudinal ridges (Blais et al 2015), which, in other taxa, have been suggested to indicate the presence of plicidentine (Meunier et al 2014).…”