Family Pachastrellidae Carter, 1875

Abstract

Pachastrellidae Carter (Demospongiae: Astrophorida), including Theneidae Carter, contains 12 valid genera and 2 subgenera. Most gen-era contain cup-like, massive, and submassive species and are distributed from tropical to high latitudes, mostly in epibathyal and bathyal habitats. A few genera also include encrusting or cavity-filling forms found predominantly in tropical or temperate shallow-water habitats. This astrophorid family is defined by the possession of tetraxons (calthrops, short-shafted triaenes, mesotriaene-derived desmas, or long-shafted triaenes) in combination with streptasters (never euasters) and in most cases by monaxonic microscleres (i.e., microxeas, microstyles and microstrongyles). The microscleres are densely packed at the ectosome forming a feltwork. The relationship between genera possessing a typical pachastrellid skeleton and some genera bearing tetraxial desmas other than mesotriaene-derived desmas (mesotriders), which have traditional been included in Lithistida, is still a matter of contention.