New information on multispherulitic dinosaur eggs: Faveoloolithidae and Dendroolithidae

Abstract

ABSTRACT Dinosaurs produced a broad range of different types of eggs. Some of which have no analogue among those laid by living reptiles and birds. Eggs with shell units branching into an unusual labyrinth associated with a complicated pneumatic system were assigned to the parataxonomic oofamilies Faveoloolithidae and Dendroolithidae. While numerous new related ootaxa were described recently, many biological aspects as well as the identity of their producers have remained unknown or unresolved. Here, we provide the first experimental evidence that some mid-sized dendroolithid eggs were laid by a therizinosauroid theropod. We scanned and studied two faveoloolithid eggs. One of them contains putative embryonic remains that correspond to an articulated cranial skeleton exhibiting rather reduced antorbital region/opening similar to that in titanosaurian embryos. Another faveoloolithid egg exhibits unusual bending of the uninterrupted shell; we discuss three alternative interpretations: natural deformation, pathology and pliability, to explain this unusual phenomenon.