Osteogyrinia

From Tlaquanaru

Osteogyrinia is a class of fish-like, jawless vertebrates, found primarily in aquatic habitats. There are 2 extant orders, Gyrinoformes, and Osteogyrinoformes. A third, extinct order, Gracilihelminthes†, provided it is a valid grouping, and not a "wastebasket" for obscure vertebrate fossils, is presumed to be the ancestral group. Pelagic species are planktivores, while the majority of benthic are detrius-feeders. Some species, particularly those in the family Helminthichthidae, are parasitic, feeding on blood and tissue (usually of other fish) much in the same manner as [lampreys] and [hagfish].

Extant Orders include

Gyrinoformes (2,067 species known)

Osteogyrinoformes (352 species known)