Comment on Independent origins of middle ear bones in monotremes and therians?

GUILLERMO ROUGIER; ANALIA FORASIEPI; AGUSTIN MARTINELLI

SCIENCE

AMER ASSOC ADVANCEMENT SCIENCE

Año: 2005 vol. 309 p. 1492 - 1492

0036-8075

The malleus, incus, and stapes are the middle ear bones spanning from the eardrum externallyto the oval window in the inner ear. The malleus is formed in both groups of living mammals (monotremes and therians) from the embryonic prearticular and articular, which early in development are attached to the lower jaw (dentary). The prearticular and articular are also so attached as postdentary bones in fossil members of the mammalian lineage that show a progressive reduction in size and attachment. Rich et al. argue that the malleus has been independently freed from the dentary in monotremes and in therians and acknowledge that assertions of fundamental differences in development and morphology between monotreme and therian ears are no longer supported. Therefore, fossils likeTeinolophos, an extinct relative of Australia´s modern platypus, are the only potential sources of conflict. Our recent study of all available Teinolophos specimens suggests that the claim of Bindependent origins of middle ear bones in monotremes and therians is not supported.