A new family of bathypelagic fishes, the Kasidoroidae, is described from the Atlantic Ocean from localities near Bermuda and northeast of the Bahamas. The family is based on Kasidoron edom, new genus and new species, a small, black species whose outstanding characteristic is
the development on the third ray of its abdominal pelvic fins of a spectacular arborescence whose terminal hollow sacs may possess a luminous substance. The familial relations seem closest to the Mirapinnidae and Eutnaeniophoridae, order Mirapinniformes, and this order is expanded to house
the Kasidoroidae. Placement of the order is itself uncertain but it is provisionally retained near the Myctophiformes and especially the Cetomimoidei. Kasidoron edom feeds on calanoid copepods. A possible use of its unusual pelvic tree is in mimicry of a siphonophore or a medusa,
the fish thus gaining some measure of predator immunity. The resemblance of the tree to the nectosome of a siphonophore engenders the common name siphonophore fish.
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