Old wife
Enoplosus armatus, commonly referred to as the old wife, is a species of centrarchiform ray-finned fish endemic to the temperate coastal waters of Australia. It is the only genus and species in the family Enoplosidae.
It has a deep and compressed body and concave forehead. These features are characteristic of typical butterflyfishes. However, the old wife is easily distinguished by its silver-and-black, vertical, zebra-striped coloration, and by its two prominent dorsal fins. The second dorsal fin is very long and sickle-shaped. The fish grows up to 50 cm long.
Its dorsal fins have bony, knife-like spines. These have no obvious venom groove nor gland. Nonetheless, the spines are widely considered to inflict a painful venom.
The name "old wife" refers to the sound it makes when caught, caused by it grinding its teeth. Other vernacular names have included "bastard dory", "zebra-fish", and "double scalare". It has a similar range and appearance to the Moonlighter.
History
The old wife was originally classified in the genus Chaetodon, but it is now classified as the sole modern species of its own family Enoplosidae and genus Enoplosus. Some fossils have also been added to the genus.File:Pungent chaetodon John White.jpg|thumb|right|The Pungent Chaetodon illustration accompanying the original 1790 description of Chaetodon ''armatus in John White's voyage journal. Attributed to convict artist Thomas Watling.
The first description of the species, one of the earliest for any Australian fish, was in 1790 by John White in his Journal of a Voyage to New South Wales though some sources give George [Shaw (biologist)|George Shaw] as the species authority. White originally named it the long-spined chaetodon and described it as follows:
The species was reclassified by Lacépède into its own genus, and was moved by Cuvier from Chaetodontidae into its own separate family within Percoidei.
In 1836, Agassiz identified closely related fossils at Monte Bolca as Enoplosus pygopterus. These exceptionally well-preserved fossils had a very similar body plan, and even a similar zebra pattern of colouring. However, more recent studies have recovered this species as actually being an early cardinalfish, moved to its own genus, Eosphaeramia''.