Coelacanth

Coelacanths ( /ˈsiːləkænθ/, adaptation of Modern Latin Cœlacanthus "hollow spine", from Greek κοῖλ-ος koilos "hollow" + ἄκανθ-α akantha "spine", referring to the hollow caudal fin rays of the first fossil specimen described and named by Louis Agassiz in 1839) are members of an order of fish that includes the oldest known living lineage of Sarcopterygii (lobe-finned fish and tetrapods).