Family Euretidae Zittel, 1877

Abstract

Euretidae Zittel (Hexactinellida, Hexactinosida) contains a total of 45 extant species in 16 genera, including reinstatement of Pityrete Topsent pending future review of its relationship to other euretids. Subdivision of the family into two subfamilies, Euretinae and Chonelasmatinae, proposed by Reid (1958a) is accepted with slight modification of the basis and allocation of genera to the two groups. The family is distrib- uted world-wide between depths of 90–5600m, with few or no representatives from the North Pacific and South Atlantic basins. Body form is predominately tubular, often with extensive branching and anastomosing of components, but lamellar forms, compound cups and funnels with and without secondary lateral tubes also occur. Channelization of the dictyonal framework may be absent or consist of epirhyses with or without aporhyses, or amararhyses. The family is characterized by an euretoid dictyonal framework without diarhyses or schizorhyses and without regular alteration of epirhyses and aporhyses where these co-occur. Uncinates and scopules are characteristic free spicules in all but 2 of the 16 genera. Combinations of body form and spiculation are characters used to differentiate genera within the family. This large and diverse family deserves division at the family level, but presently available morphological data is inadequate to provide a division that is con- vincingly natural. This revision of the family also includes numerous lectotype and paralectotype designations.