Order Spirophorida Bergquist & Hogg, 1969

Abstract

Spirophorida (Demospongiae) is a well-defined small group of non-lithistid tetractinomorph sponges characterized by sigmaspire microscleres (spined c-or s-shaped spicules of 10–40 μm length). Triaenes and tetractine spicules are shared with sponges of the order Astrophorida, but are absent in some taxa. Sigmaspires are shared with the lithistid family Scleritodermidae, which points to a probable close relationship with this family, once again demonstrating polyphyly of the ‘order Lithistida’. Spirophorida comprise three families, Samidae Sollas is monotypic, Spirasigmidae Hallmann with two genera, and Tetillidae Sollas has eight valid genera. Samidae are excavating sponges with amphitriaenes and lacking long-shafted triaenes and lacking oxeas; Spirasigmidae are encrusting to small conical sponges with only oxea megascleres, lacking triaenes, with a plumose skeleton fanning out towards the periphery, and one genus with a secondary skeleton of roughened ‘microxeas’; Tetillidae are globular sponges with protriaenes as the characteristic megascleres.