LELAPIIDAE Dendy & Row, 1913

Borojevic, Radovan, Boury-Esnault, Nicole & Vacelet, Jean, 2000, A revision of the supraspecific classification of the subclass Calcaronea (Porifera, class Calcarea), Zoosystema 22 (2), pp. 203-263 : 241-242

Family LELAPIIDAE Dendy & Row, 1913

TYPE GENUS. — Lelapia Gray, 1867 by original designation.

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DIAGNOSIS.— Leucosoleniida with a syconoid, sylleibid or leuconoid organization. The choanoskeleton contains typical subatrial spicules in the proximal region, associated with spicular tracts, consisting of modified triactines arranged in parallel, which traverse either radially or obliquely the choanosome. The cortex contains tangential triactines and occasionally large longitudinal diactines and/or small perpendicular diactines.

DESCRIPTION

The family Lelapiidae is characterized by spicular fibres or tracts, that are not found in other Leucosoleniida . These tracts contain triactines with reduced paired actines (nail-spicules) or diapasons (tuning-fork spicules), which replace the typical choanoskeleton.This feature attracted a lot of attention in the past, since it is similar to the type of skeleton found in “the Pharetronida ”, and was understood to be an indication of the relationship between the Lelapiidae and the fossil Calcarea. Two lines of evolution can be distinguished in this family. In the Grantiopsis-Kebira line the fibres are formed by the “nail-spicules”, while in the Paralelapia-Lelapia line they are formed by diapasons. In both lines, the simplest sponges are quite reminiscent of the Grantiidae , while in the most complex ones the cortical skele-

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ton participates progressively in the reinforcement of the choanoskeleton, replacing the typical meshwork of choanosomal triactine spicules. The two types of modifications of the typical tangential triactines that participate in the spicule tracts are apparently related to the mechanical and spatial constraints of these linear structures. Similar modifications are found in the genus Guancha in the Calcinea, where the same constraints inside the peduncle induce either the reduction of the paired actines or their curvature into the diapason form (Borojevic et al. 1990). Consequently, we consider that the Lelapiidae belong to the Leucosoleniida , where they represent a rather specialized and well-delimited family, but that they do not have a close relationship with other calcareous sponges related to the fossil groups, such as the Lithonida and Murrayonida , which have diapasons. The Lelapiidae are characteristic of the Indo-Pacific region.