Consumption of crustaceans by megaherbivorous dinosaurs: dietary flexibility and dinosaur life history strategies

Karen Chin,Jessica N Tashman,Rodney M Feldmann

doi:10.1038/s41598-017-11538-w

Karen Chin, Jessica N Tashman + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-11538-w

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Abstract

Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because their derived teeth and jaws were capable of processing fibrous plant foods. This inferred feeding behavior offers a generalized view of dinosaur food habits, but rare direct fossil evidence of diet provides more nuanced insights into feeding behavior. Here we describe fossilized feces (coprolites) that demonstrate recurring consumption of crustaceans and rotted wood by large Late Cretaceous dinosaurs. These multi-liter coprolites from the Kaiparowits Formation are primarily composed of comminuted conifer wood tissues that were fungally degraded before ingestion. Thick fragments of laminar crustacean cuticle are scattered within the coprolite contents and suggest that the dinosaurian defecators consumed sizeable crustaceans that sheltered in rotting logs. The diet of decayed wood and crustaceans offered a substantial supply of plant polysaccharides, with added dividends of animal protein and calcium. Nevertheless, it is unlikely that the fossilized fecal residues depict year-round feeding habits. It is more reasonable to infer that these coprolites reflected seasonal dietary shifts—possibly related to the dinosaurs’ oviparous breeding activities. This surprising fossil evidence challenges conventional notions of herbivorous dinosaur diets and reveals a degree of dietary flexibility that is consistent with that of extant herbivorous birds.

Highlights

Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because their derived teeth and jaws were capable of processing fibrous plant foods
A small number of cases of direct fossil evidence for diet allow us to test our inferences about the feeding behavior of large herbivorous dinosaurs
We report here the discovery of a new assemblage of wood-filled coprolites that indicates that wood consumption was far-ranging, but reveals another unexpected feeding habit of herbivorous dinosaurs—recurring ingestion of sizeable crustaceans

Summary

Introduction

Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because their derived teeth and jaws were capable of processing fibrous plant foods. The discoveries of reasonably well-substantiated gut contents within the articulated carcasses of an ankylosaur[13], a brachylophosaur[14], and a neornithischian[15] indicate that plant reproductive tissues and leafy browse were ingested by ornithischians Such dietary choices are comparable to the feeding habits of extant mammalian browsers. We report here the discovery of a new assemblage of wood-filled coprolites that indicates that wood consumption was far-ranging, but reveals another unexpected feeding habit of herbivorous dinosaurs—recurring ingestion of sizeable crustaceans. These specimens challenge us to reevaluate some of our preconceived perceptions of dinosaur feeding behavior. The specimens are identified as coprolites on the basis of their comminuted organic contents, paucity of clastic grains, pervasive backfilled burrows, sedimentological context, and similarity to 17 previously-described coprolite deposits from the Two Medicine Formation[16, 20]

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