The first record of dinosaur eggshell from the Horseshoe Canyon Formation (Maastrichtian) of Alberta, Canada.

Eggs and eggshell are generally rare in the Upper Cretaceous rocks of Alberta, despite being relatively abundant nearby in Montana. Palaeontologists and other people have been prospecting the Horseshoe Canyon Formation for more than a 130 years, but eggshell fragments have only just been recovered. The fragments are unornamented with angusticanaliculate pores and three structural layers. Numerous features support their referral to Prismatoolithus levis, and they confirm the presence of a bird-like external layer in this ootaxon. The fragments, which likely belonged to Albertavenator curriei, are from a site with abundant troodontid teeth and perinate material from hadrosaurs, ceratopsians, and theropods. The discovery of eggshell challenges the notion that the Horseshoe Canyon Formation is too heavily sideritized to preserve eggshell. [ABSTRACT FROM AUTHOR]