Acanthodii

Acanthodii (sometimes called spiny sharks) is a class of extinct fishes, having features of both bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes). They appeared in the early Silurian (430 mya) and lasted until the late Permian (250 mya). The earliest ancanthodians were marine, but during the Devonian, freshwater species became predominant. They are distinguished in two respects: they were the first known jawed vertebrates, and they had stout spines supporting their fins, fixed in place and non-movable (like a shark's dorsal fin).

Acanthodii Temporal range: Early Silurian - Permian
Different extinct fishes of Early Devonian
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Infraphylum:	Gnathostomata
(unranked):	Teleostomi
Class:	Acanthodii
Orders
Climatiiformes Ischnacanthiformes Acanthodiformes

Acanthodii Media

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  Three acanthodians from the Early Devonian of Great Britain: Mesacanthus (an acanthodiform), Parexus (a "climatiiform"), and Ischnacanthus (an ischnacanthiform)

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  Impression fossil of the diplacanthid Rhadinacanthus longispinus, at the Museum für Naturkunde, Berlin

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  Various acanthodians, from top left clockwise: Cheiracanthus, Acanthodes, Climatius, Ischnacanthus, Parexus, Gyracanthus. center: Diplacanthus.

Other websites

Media related to Acanthodii at Wikimedia Commons
Data related to Acanthodii at Wikispecies