Persistence of Meckel's cartilage in sub-adult Struthio camelus and Dromaius novaehollandiae

This study describes the persistence of an embryonal structure through to sub-adulthood in the ostrich and emu. Mandibles from sub-adult ostrich and emu were subjected to special staining, light microscopy and dissected to reveal and describe Meckel's cartilage. Meckel's cartilage, composed of hyaline cartilage, was present within the neurovascular canal of both species. The persistence through to sub-adulthood of Meckel's cartilage in the ostrich and emu is a feature not previously reported in any other avian species. The proximal end of Meckel's cartilage was ossified in the region of the articular bone and the distal end was ossified in some specimens. Although this structure may ossify at a much later stage in life, the function in young and sub-adult birds may be to dampen shockwaves along the intramandibular nerve that result from the action of pecking. In the ostrich, the M. pseudotemporalis superficialis tendon inserted onto the supra-angular bone and Meckel's cartilage. In the emu, a small portion of the tendon was attached to the supra-angular bone and the main part to Meckel's cartilage. The persistence of Meckel's cartilage in adult lepidosaurs, crocodilians and ratites represents an unusual shared trait between the extant members of the above groups.