Cutlassfish

The cutlassfishes are about 45 species of predatory ray-finned fish in the family Trichiuridae of the order Scombriformes found in seas throughout the world. Fish of this family are long, slender, and generally steely blue or silver in colour, giving rise to their name. They have reduced or absent pelvic and caudal fins, giving them an eel-like appearance, and large fang-like teeth. Some of the species are known as scabbardfishes or hairtails; others are called frostfishes because they appear in late autumn and early winter, around the time of the first frosts. The earliest known remains of cutlassfish are isolated teeth assigned to Eutrichiurides from the Early Paleocene of Morocco, the United States, and Angola, although their affinities are subject to question. The earliest known body fossil of a cutlassfish is Exeomastix from the Early Eocene of Italy.