The Beryciforms are an order of very primitive fishes (there are fossil records of species that lived during the Upper Cretaceous) and generally little known that inhabit tropical seas and great depths. Within this order we find species such as alfonsinos, squirrelfishes, flashlight fishes, fangtooth fishes, spinyfins, pineconefishes, redfishes, roughies, and slimeheads.
As a characteristic feature of the Beryciforms, it is worth mentioning some spines of considerable robustness in their fins. The caudal fin of these species has between 18 and 19 rays. They are also characterized by depressions near the operculum, which in certain species may present chemiluminescent bacterial growths. The body is laterally compressed, and generally has large eyes that allow them to see in low light conditions such as caves, at night or at great depths, as well as a relatively large mouth.
As for the size of the species that make up this order, we find from species that barely reach 8 cm in total length, to species that can reach sizes of up to 60 cm in length.
The diet of these species is usually carnivorous, feeding on small fish and invertebrates, especially crustaceans.
Beryciforms are mostly nocturnal species, and some species can be found at a depth of 2,000 meters, while others approach the surface during the night. During daylight hours, and in those species located in shallower waters, Beryciforms can be found sheltering in caves or crevices in the rocks.
A total of 104 species of Beryciforms are currently known, divided into 2 suborders (Stephanoberycoidei, Berycoidei), 8 families, 24 genera.