Synthetic analysis of trophic diversity and evolution in Enantiornithes with new insights from Bohaiornithidae
Description
Version 1 accompanies the reviewed preprint of this work, Version 2 accompanies the revised work, Version 3 reflects changes made during the editorial process. Extended abstract: The “opposite birds” Enantiornithines were the dominant birds of the Mesozoic, but our understanding of their ecology is still tenuous. In particular, diets of enantiornithine species have remained speculative until recently. We introduce new data on the enantiornithine family Bohaiornithidae, famous for their large size and strong teeth and claws. Alongside previously-published data on the earlier-diverging pengornithids and later-diverging longipterygids, we comment on the breadth of enantiornithine ecology and potential patterns in which it evolved. Body mass, mechanical advantage, finite element analysis, and traditional morphometrics are compared between bohaiornithids and living birds. We find bohaiornithids ecologically diverse: Bohaiornis and Parabohaiornis resemble living plant-eating birds; Longusunguis resembles raptorial carnivores; Zhouornis resembles both fruit-eating birds and generalist feeders; and Shenqiornis and Sulcavis plausibly ate fish, plants, or a mix of both. This ecological diversity is wider than any other enantiornithine family studied previously. With these new data, there is support for enantiornithines inhabiting nearly every trophic level. We predict the ancestral enantiornithine bird to have been a generalist. This suggests the ecological diversity of enantiornithine birds represents specialisation in taking foods their ancestors were already eating, rather than many dramatic changes in diet. However, more quantitative data from across the enantiornithine tree is needed to refine this prediction. By the Early Cretaceous, enantiornithine birds had diversified into a variety of ecological niches in a similar way to crown birds after the K-Pg extinction, adding to the body of evidence that traits unique to crown birds cannot completely explain their ecological success.