Fossil eggshells from the Upper Cretaceous (Campanian) Fruitland Formation, New Mexico

Abstract

Approximately 1500 eggshell fragments were recovered from a vertebrate bonebed (NMMNH L-4010) in the late Campanian Fruitland Formation in northwestern New Mexico, a locality that represents one of the few southern occurrences of fossil eggshells in North America. Here, we present the first description of Campanian eggshells from New Mexico and identify six different eggshell types (Continuoolithus sp., Porituberoolithus sp., Testudoolithus sp., Prismatoolithus sp., krokolithid, indeterminate type) among the well-preserved fragments, which are attributable to dinosaurs, crocodilians and turtles. The taxonomic diversity of eggshells is comparable to the taxonomic diversity of animals represented by skeletal remains in the bonebed, which would have laid rigid-shelled eggs (i.e. dinosaurs, crocodilians and turtles). Eggshells of theropod dinosaurs are the most common and comprise approximately 85% of the eggshells, whereas those of crocodilians and turtles form the remaining 15%. Although bones of hadrosaurs and ceratopsians are well represented by skeletal remains at the locality, their eggshells have yet to be identified. The relative abundance of the taxa represented by eggshells at NMMNH L-4010, with those of theropods being by far the most common, is comparable to that observed in the more northern late Campanian microsites of Dinosaur Provincial Park, Alberta.