XENACANTHIFORMESXENACANTHIFORMES
| Central Africa 2014 | Central Africa 2014 |
 |
 |
|---|---|
| Xenacanthus Xenacanthus sp. (Xenacanthidae) |
Orthacanthus Orthacanthus sp. (Orthacanthidae) |
The board gills subclass is the group of a shark and the ray where gills of several lines formed the side of the body and a line below. This friend appeared in the beginning in Devonian period in the Paleozoic era. The friend of another beginning shark which belonged to Xenacanthiformes appeared in Devonian period in the Paleozoic era. There was one thorny on the head, and a dorsal fin base was long, and there was copulation device in a male with two buttocks fin, and was different from Cladoselachiformes. Xenacanthiformes sustained itself in fresh water area after Cladoselachiformes was ruined, but a Triassic period began and has been ruined.
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