Os tímpanos de mamíferos, répteis e aves evoluíram independentemente

sexta-feira, maio 15, 2015

Developmental genetic bases behind the independent origin of the tympanic membrane in mammals and diapsids

Taro Kitazawa, Masaki Takechi, Tatsuya Hirasawa, Noritaka Adachi, Nicolas Narboux-Nême, Hideaki Kume, Kazuhiro Maeda, Tamami Hirai, Sachiko Miyagawa-Tomita, Yukiko Kurihara, Jiro Hitomi, Giovanni Levi, Shigeru Kuratani & Hiroki Kurihara

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Nature Communications 6, Article number: 6853 doi:10.1038/ncomms7853

Received 08 November 2014 Accepted 05 March 2015 Published 22 April 2015


The amniote middle ear is a classical example of the evolutionary novelty. Although paleontological evidence supports the view that mammals and diapsids (modern reptiles and birds) independently acquired the middle ear after divergence from their common ancestor, the developmental bases of these transformations remain unknown. Here we show that lower-to-upper jaw transformation induced by inactivation of the Endothelin1-Dlx5/6 cascade involving Goosecoid results in loss of the tympanic membrane in mouse, but causes duplication of the tympanic membrane in chicken. Detailed anatomical analysis indicates that the relative positions of the primary jaw joint and first pharyngeal pouch led to the coupling of tympanic membrane formation with the lower jaw in mammals, but with the upper jaw in diapsids. We propose that differences in connection and release by various pharyngeal skeletal elements resulted in structural diversity, leading to the acquisition of the tympanic membrane in two distinct manners during amniote evolution.

Subject terms: Biological sciences Developmental biology Evolution

FREE PDF GRATIS: Nature Communications

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E o que fazer daquela série de fósseis de ossos de mandíbulas de répteis que resultaram em ossos internos de ouvidos de mamíferos que argumentavam a favor de uma suposta evolução de mamíferos a partir de ancestrais reptilianos???