plural noun
Tho·​ra·​cos·​tei | \ ˌthōrəˈkästēˌī, ˌthȯr-\

Definition of Thoracostei

in some classifications
: an order comprising fishes with the body more or less completely covered by bony plates and the pharyngeal bones and other structures about the head more or less undeveloped and including the sticklebacks, pipefishes, and sea horses

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History and Etymology for Thoracostei

New Latin, from thorac- + -ostei (from Greek osteon bone)

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