Bill depressed; scales absent in adult; pelvic fins and girdle absent; jaws toothless in adult; caudal peduncle in adult with single median keel on each side; 26 vertebrae.
Swordfish are a valuable commercial species. Length up to 4.5 m.
There is abundant evidence that the Xiphiidae and Istiophordae are sister groups. In addition to less visible characters, both groups share the following features: elongate premaxillary bill (rostrum) in adults; mouth inferior; fin-lets absent behind dorsal and anal fins; dorsal fin origin over back of head, first dorsal lacking true spines and with 37-55 rays; two anal fins; pectorals inserted low on body; pelvics reduced, one spine and two rays or absent; gill membranes free from isthmus; vertebrae 24 or 26. As the terminal groups of the scombroid clade, both could be recognized in the same family and were in Nelson (1994). However, such a synonymy is generally not followed (e.g., in Nelson et al., 2004) and I recognize both as separate families.
One species, Xiphias gladius (Swordfish).
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