title: Fossil evidence of avian crops from the Early Cretaceous of China.
abstract: The crop is characteristic of seed-eating birds today, yet little is known about its early history despite remarkable discoveries of many Mesozoic seed-eating birds in the past decade. Here we report the discovery of some early fossil evidence for the presence of a crop in birds. Two Early Cretaceous birds, the basal ornithurine Hongshanornis and a basal avian Sapeornis, demonstrate that an essentially modern avian digestive system formed early in avian evolution. The discovery of a crop in two phylogenetically remote lineages of Early Cretaceous birds and its absence in most intervening forms indicates that it was independently acquired as a specialized seed-eating adaptation. Finally, the reduction or loss of teeth in the forms showing seed-filled crops suggests that granivory was possibly one of the factors that resulted in the reduction of teeth in early birds.
authors: Institute of Geology and Paleontology, Linyi University, Linyi, Shandong 276000, China.
authors: Xiaoting
authors: X
authors: Zheng
authors: Larry D
authors: LD
authors: Martin
authors: Zhonghe
authors: Z
authors: Zhou
authors: David A
authors: DA
authors: Burnham
authors: Fucheng
authors: F
authors: Zhang
authors: Desui
authors: D
authors: Miao
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000033:anatomy & histology* / Q000145:classification / Q000502:physiology; D001842:Bone and Bones / Q000033:anatomy & histology; D002681:China; D003426:Crop, Avian / Q000033:anatomy & histology* / Q000502:physiology; D004032:Diet; D005580:Fossils; D012639:Seeds; D013045:Species Specificity