Fig. 2

Characteristics of the eggs and clutches of several nonavian maniraptorans support the inclusion of birds within these theropod dinosaurs. For example, the presence of at least two distinct crystalline layers in the eggshell and the existence of an asymmetric egg (less asymmetric among oviraptorids) can be traced back to as far as the maniraptoran divergence. The distribution of the eggs within a clutch in oviraptorids indicates that these dinosaurs laid their eggs sequentially (other evidence also indicates that, as in the case of birds, they also brooded their clutch)