Confuciusornis, the "Confucius Bird," is a well-documented genus of animals from the Yixian and Jiufotang Formations in China. With a length of fifty centimeters and a wingspan of seventy centimeters, the Confuciusornis was not very different from modern birds. It was  one of the earliest birds known to  have a toothless beak, despite not being closely related to modern  birds. The beak therefore developed  through convergent evolution, which  is the evolution of similar features  in unrelated animals. Fossils of its  wings include many melanosomes  (cells that contain pigment), allow- ing us to learn that it was colored grey, red/brown, and black. The  wings were probably white, with the  long tail feathers being dark along  their entire length.   Confuciusornis was a piscivore,  catching and feeding upon small  Cretaceous fish with its beak. This diet is demonstrated in a fossil  specimen preserved with its last  meal in its belly, similar to the famous Compsognathus fossils. As a whole, Confuciusornis fossils are  intriguing because some have the  long tail feathers but others do  not, and some are much larger than others. The best explanation for  this variability is sexual dimorph- ism: the leading hypothesis states  that the larger ones are the  females, and both sexes lost the  feathers during molting season.