Evolution of Avicularia in Cretaceous Cheilostome Bryozoan Wilbertopora

Cheilostome bryozoans are a diverse clade of colonial animals that first appeared during the Jurassic period. For the first 100 million years of their existence, colonies of cheilostomes were monomorphic, composed entirely of standard feeding individuals termed autozooids. Divergent body types, termed avicularia, first appeared in colonies in the early Cretaceous period, in the genus Wilbertopora. Over the course of its lifespan, Wilbertopora diversified into a total of 28 species, spanning the early Albian stage at least through the Maastrichtian. As avicularia are derived from autozooids, quantifying the patterns of divergence between autozooids and avicularia size and shape in Wilbertopora will help us to understand the evolutionary processes involved in the evolution of avicularia. In this study, we quantify autozooid and avicularia shape and size to evaluate how the morphological disparity of body types in colonies changes over the course of Wilbertopora diversification. By comparing changes in morphological disparity to changes in diversity we can assess the importance of functional and developmental evolution. If disparity increases more rapidly than diversity, then new species are exploring new ecologies by prioritizing the evolution of form. However, if diversity increases more rapidly than disparity new species are in a mode of ecological exploitation and increasing the frequencies of successful forms.