Cladoselachiformes
Encyclopedia
Cladoselachidae is an extinct family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of cartilaginous fishes and among the earliest predecessors of modern shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s. They are the only members of the order Cladoselachiformes and were characterized by having an elongated body with a spine in each of the two dorsal fins.
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