Cretaceous avian crops reveal dietary secrets and pose evolutionary questions.

A mong the most striking avian anatomical divergences from the typical tetrapod pattern is the reduction of the cephalic alimentary canal to a bare minimum required for food procurement, generally believed to be an adaptation for lightening the avian body for flight (1). Much of this anatomical modification involved jettisoning teeth concomitantly with the acquisition of a horny beak, the reduction of complex jaw musculature, great reduction of the tongue, and the development of a highly kinetic skull. The food processing normally accomplished by the teeth and masticatory apparatus was thus relegated to the lower digestive system, functioning in storage, disassembling, and digestion (2). Until now we knew virtually nothing of the timing of the origin of the anterior food canal, but in PNAS (3) Xiaoting Zheng of Linyi University in Shandong, China, and colleagues from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and the University of Kansas, reveal the discovery of avian crops in two distinctive lineages of Early Cretaceous birds, providing significant insight into this remarkably unique avian anatomical innovation, as well as early avian diet.