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The ear in mammal-like reptiles and early mammals

100%

Kermack K. A., Mussett F.

Acta Palaeontologica Polonica

1983

tom 28

nr 1-2

The early members of the Theropsida lacked a tympanic membrane. In the later theropsids, the Therapsida, a tympanic membrane developed from the skin on the lateral side of the lower jaw. The tympanum is not homologous in the Therapsida and the Sauropsida. The therapsid ear was a poor receiver of airborne sound, both in high frequency response and in the range of frequencies encompassed. With the radiation of the Sauropsida in the Triassic the large therapsids became extinct, the small therapsids evolved into the mammals and became nocturnal. High frequency hearing was essential for the nocturnal mode of life; quadrate and articular became dissociated from the jaw hinge to become the mammalian auditory ossicles. In the Theria the cochlea became coiled. The spiral cochlea could not have existed until there was a middle ear with the necessary high frequency response. This may not have been until the Cretaceous.

Ograniczanie wyników

1 Acta Palaeontologica Polonica

1 Kermack K. A.

1 Mussett F.

1 1983

Wyniki wyszukiwania

The ear in mammal-like reptiles and early mammals