Marine Species Identification Portal : Order Verticillitida

Termier and Termier, 1977

Definition: Demospongiae with a solid aragonitic cortex producing a series of chambers on top of each other (Vaceletia).

Remarks: Living sphinctozoans lack free spicules. One fossil genus, previously associated with the 'sphinctozoa', has calcareous monaxon and triradiate spicules enclosed within the walls of the chambers. This late Mesozoic genus (Barroisia) bears monaxonid and triradiate calcareous spicules enclosed within the walls of the chambers, but its inclusion in this group is now debatable. Conversely, clues on the phylogeny of this group can be seen from the Recent genus Vaceletia, which lacks spicular elements in its skeleton but has cells and larvae that resemble those of the Demospongiae. The current, popular theory suggests that the "Sphinctozoa" probably represent independent but convergent lines of the two classes Calcarea and Demospongiae, for fossil and living species respectively. The alternative hypothesis, that all "Sphinctozoa" are Calcarea—with their identity revealed by the calcareous spicules of the genus Barroisia—whereby the line containing the Recent genus Vaceletia is merely convergent upon the Demosponges in cellular and developmental characters—is rejected, as is a third possibility is that the "Sphinctozoa" represent a completely independent class of sponges.
Only one extant order (Verticillitida) and a single family Cryptocoelidae Steinmann, 1982 (syn. Neocoelidae Hartman and Verticilitidae Senowbary) are recognized. The family is characterised by a skeleton bearing a prosiphonate lining of the atrial cavity (the lining of one chamber grows forward into the base of the next-younger chamber) and with numerous thin struts running from the floor to the roof of each chamber, the struts joined by more or less horizontal crossbars. The walls of the chambers as well as the atrial lining have trefoil or multifid perforations to allow for water intake through ostia and passage of exhalant water into the atrium. In mature specimens the seven or eight youngest chambers are filled with living tissue, while the basal seven or eight chambers are more or less filled in by secondary deposits of aragonite. The living tissue includes a cuticle and cells such as flattened endopinacocytes and spherule-bearing cells that are characteristic of demosponges (rather than calcareans). The choanocyte chambers are aphodal (with a small canal joining the chamber to the exhalant canal). The larvae are parenchymellae that
develop from a coeloblastula.
Only a single genus exists nowadays, but "Sphinctozoans" were the main reef constructors in the Middle Triassic, dating from the Middle Cambrian. (Vacelet,1979; Pickett (1982); Senowbari-Daryan (1990), Vacelet et al.1992.
Recent genus: Vaceletia Pickett, 1982 (type species: Neocoela crypta Vacelet, 1977—with a calcitic basal skeleton composed of an irregular arrangement of aragonitic crystals; no free spicules.

Source: Senowbari-Daryan, 1991; Vacelet, 2002.

Taxa represented in the area: None.

Order Verticillitida