14 magg 460000000 anni a. C. - Bony and cartilaginous fish diverge

Descrizione:

Jawed fish split two ways, into the armoured placoderms, and the ancestor of bony fish and acanthodians. Acanthodians possess characteristics of both bony and cartilagionous fish, and constitute an intermediate form of sorts. They were originally small, shark-like, and having fixed spines to support their fins and protect themselves against larger predators.

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