TYPE GENUS. — Trichogypsia Carter, 1871 by original designation.
DIAGNOSIS. — Baeriida with a skeleton entirely formed by diactine spicules.
DESCRIPTION
We propose to put sponges that have affinities with the Baeriidae, but that have only diactine spicules in the family Trichogypsiidae. As discussed above, one of the characteristics of the Baeriida is the presence of small “mortar-shaped” diactines that make up either all of, or a large part of a specific portion of the skeleton. The Trichogypsiidae have large diactines, which are probably not homologous with “mortar-shaped” diactines. It is difficult to establish whether the absence of triactine spicules is a primitive condition or is a consequence of a secondary reduction of the skeleton. In the Leucosoleniida, diactines are the first spicules to be secreted, but it is not known if this is also true for the Baeriida. All the Trichogypsiidae are very poorly known, having been described in early studies from a small number of specimens; there are no recent studies that provide a detailed description of their cytology or biology. Up to now, the Trichogypsiidae have been only described from boreal or arctic regions.