Gyrinoformes

From Tlaquanaru

Gyrinoformes is one of two extant orders of Class Osteogyrinia. Members of the order resemble either a tadpole, or a very small hagfish. Most species are marine, with only a few (about 45 species) in freshwater habitats.

Gyrinophiidae

The gyrinophiids are slender, tadpole-like vertebrates that are inevitably found swimming in the water column, either within a few meters of the bottom, or within a few meters of the water's surface. While the largest species, Thunnugyrinos gargantua, is over 40 centimeters in length, the average length of gyrinophiids is around 2 to 5 centimeters. All species are considered to be planktivores, and feed by forcing water into their buccal cavities through constant extensions and contractions of their pharynx. However, many species have been observed feeding on zooplankters as large as themselves.

Mormophidae

Mormophids are hagfish-like gyrinids. The larger species (30 to 180 centimeters in length) burrow into mud of the abyssal plains, emerging only to hunt for prey. The smaller species (10 to 20 centimeters in length) are found in shallow marine environments, where they hunt small invertebrates.

The number of species is unknown, estimated at 4500.

Helminthichthidae

The helminthichthids are the ubiquitous, parasitic relatives of the mormophids. The helminthichthids are tiny (1 to 3 centimeter long), and inhabit the gills of bony fish.