A new specimen of large-bodied basal enantiornithine Bohaiornis from the early Cretaceous of China and the inference of feeding ecology in Mesozoic birds

A new specimen of Bohaiornis guoi from the Jiufotang Formation, comprising a nearly complete skeleton, sheds light on enantiornithine morphological variation and ecological specialization. The new specimen was collected from near Lamadong Village in Liaoning Province, which is the same area where the sub-adult holotype specimen was reported. It provides new information on the cranial and pectoral girdle anatomy of the species, e.g., broad nasal, strikingly robust acromion, medially curved acrocoracoid process. In contrast to the holotype, the newly referred specimen has small rounded stones in the thoracic region that in other extinct taxa has been interpreted as direct evidence of diet. Direct evidence of diet is so far unknown in other Enantiornithes. Specifically the lack of “stomach stones” or gastroliths in enantiornithines despite their excellent fossil record has been proposed to be related to their insectivorous diet as well as to their arboreal ecology. We hypothesize that cran...