Date of Award

Spring 6-7-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Karen Chin

Second Advisor

Garland Upchurch

Third Advisor

Joseph Sertich

Abstract

Although the ecological relationships between dinosaurs and angiosperms have long been debated, very little direct evidence of angiosperm consumption has been found to date. Two new coprolites discovered in the Campanian Kaiparowits Formation of southern Utah contain fragments of angiosperm wood. One of the angiosperm coprolites was discovered as a group of associated float fragments, the other was found in-situ and removed intact. Both coprolites were found near other herbivore coprolites that contain conifer, but not angiosperm, wood. Specimen inclusions and ground mass were characterized by visual examination of exposed surfaces and thin sections. Several lines of evidence support the conclusion that these specimens are coprolites, including: (1) the thoroughly disaggregated nature of the included plant cells suggesting feeding-induced comminution; (2) the paucity of detrital grains; (3) the sedimentological context; and (4) extensive bioturbation suggesting post-depositional reworking in a manner characteristic of coprophagous insects. The coprolites are at least 0.89 and 1.7 L in volume. Other than ornithischian dinosaurs, no other large-bodied plant eating animals have been found in the Kaiparowits Fm. assemblage to date that would have been capable of producing these coprolites.

Although the coprolites contain inclusions of mollusc shell, arthropod cuticle, and lizard bone, these may have been ingested incidentally while feeding on plant tissue. The wood fragments possibly indicate a diet of woody browse, and display taxonomically significant characteristics. The ground mass cells are poorly preserved, but may be brachysclereids, a type of cell found in many different plant tissues, but especially fruits.

Angiosperms first became common during the Early Cretaceous and diversified rapidly throughout the Late Cretaceous. This time period also had great dinosaur diversity, especially the Late Cretaceous Laramidian ecosystem represented by the Kaiparowits Fm. The coprolites described here reveal direct trophic interactions between angiosperms and dinosaurs in the ancient Kaiparowits ecosystem. Moreover, their co-occurrence with conifer-bearing coprolites may reflect seasonal dietary variance and/or ecological niche partitioning.

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