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Temporal range: Early Silurian - Permian
Mesacanthus Parexus Ischnacanthus.JPG
Different extinct fishes of Early Devonian
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
(unranked): Teleostomi
Class: 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).