Abstract
BackgroundDinosaurs dominated terrestrial environments for over 100 million years due in part to innovative feeding strategies. Although a range of dental adaptations was present in Late Jurassic dinosaurs, it is unclear whether dinosaur ecosystems exhibited patterns of tooth disparity and dietary correlation similar to those of modern amniotes, in which carnivores possess simple teeth and herbivores exhibit complex dentitions. To investigate these patterns, we quantified dental shape in Late Jurassic dinosaurs to test relationships between diet and dental complexity.ResultsHere, we show that Late Jurassic dinosaurs exhibited a disparity of dental complexities on par with those of modern saurians. Theropods possess relatively simple teeth, in spite of the range of morphologies tested, and is consistent with their inferred carnivorous habits. Ornithischians, in contrast, have complex dentitions, corresponding to herbivorous habits. The dentitions of macronarian sauropods are similar to some ornithischians and living herbivorous squamates but slightly more complex than other sauropods. In particular, all diplodocoid sauropods investigated possess remarkably simple teeth. The existence of simple teeth in diplodocoids, however, contrasts with the pattern observed in nearly all known herbivores (living or extinct).ConclusionsSauropod dinosaurs exhibit a novel approach to herbivory not yet observed in other amniotes. We demonstrate that sauropod tooth complexity is related to tooth replacement rate rather than diet, which contrasts with the results from mammals and saurians. This relationship is unique to the sauropod clade, with ornithischians and theropods displaying the patterns observed in other groups. The decoupling of herbivory and tooth complexity paired with a correlation between complexity and replacement rate demonstrates a novel evolutionary strategy for plant consumption in sauropod dinosaurs.
Highlights
Dinosaurs dominated terrestrial environments for over 100 million years due in part to innovative feeding strategies
Dental complexity Late Jurassic dinosaurs exhibit a wide range of dental complexities (Fig. 1)
When the individual tooth complexities of macronarian and diplodocoid sauropods are analysed separately there is a significant difference between mean dental complexity of these groups (Student’s t-test: P < 0.01, t = 10.23, 9999 replicates)
Summary
Dinosaurs dominated terrestrial environments for over 100 million years due in part to innovative feeding strategies. Dental microwear analyses of sauropods strongly suggest that different clades employed differing feeding strategies, which may have permitted these large-bodied animals to live in the same environment [4, 16]. Another common quantitative dental assessment is the reconstruction of tooth replacement patterns and rates (all toothed dinosaurs exhibit polyphyodonty) [2, 17,18,19,20,21,22,23,24,25,26]. Histological investigations demonstrate that dental replacement rates vary substantially across the dinosaur clade, from every 777 days in the theropod Tyrannosaurus to 14 days in the sauropod Nigersaurus [2, 17, 19]
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