期刊
EARTH AND ENVIRONMENTAL SCIENCE TRANSACTIONS OF THE ROYAL SOCIETY OF EDINBURGH
卷 104, 期 2, 页码 145-167出版社
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S1755691013000480
关键词
Branchial arches; fish-to-tetrapod transition; gills; gill skeleton; Lepospondyli; Mesozoic; Palaeozoic; stem-tetrapods; Temnospondyli
资金
- Deutsche Forschungsgemeinschaft (DFG)
The morphologies of the hyobranchial apparatus in early tetrapods are reviewed, based primarily on first-hand examination and supplemented by published descriptions. The basic arrangement of the aquatic hyobranchium, with four pairs of branchial arches and internal gills, was conserved to a remarkable degree across the fish-to-tetrapod transition and was retained in further evolution in adults of several tetrapod lineages. Thus, a fish-like hyobranchium in basal tetrapods does not necessarily represent a larval or paedomorphic character, respectively, as was often suggested in analogy to extant salamanders. Rather, it represents the plesiomorphic state of the adult hyobranchium in tetrapods. The changes in the hyobranchium during the fish-to-tetrapod transition include the reduction of the number of skeletal elements and their morphological simplification. In all three presently discussed scenarios of lissamphibian origin, the temnospondyl, lepospondyl and diphyly hypotheses, the internal gills were reduced independently within temnospondyls and on the amniote stem below seymouriamorphs. Evidence of remodelling into a true terrestrial hyobranchium, with reduction of the posterior branchial arches and modification to support terrestrial tongue feeding, is scarce in early tetrapods. It evolved within temnospondyls in zatracheids, amphibamids and lissamphibians, as well as once or several times in early amniotes or in their immediate stem-forms.
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