Protoschmidtia expansa var. aruensis Hentschel, 1912

Protoschmidtia expansa var. aruensis Hentschel, 1912: 408 (no illustrations).

Petrosia expansa var. aruensis; Hooper et al. 2000: 173 (listed only).

The variety was erected by Hentschel from three localities in the Aru Islands, approximate coordinates 5.7– 6.5°S 134.0– 134.7°E, depths 10–40 m (syntype specimens are registered in the Senckenberg Museum SMF 591, 1614 and 1638, cf. Barnich & Janussen 2006: 129–130 for detailed locality data). The differences with the typical variety described by Thiele (1903: 939, fig. 4, from Ternate, Halmahera, Moluccas region, approximate coordinates 0.7606°N 127.3767°E, with type material consisting of three syntypes, registered in the Senckenberg Museum, SMF 684, 1665 and ZMB 3139, cf. Barnich & Janussen 2006: 133 for detailed locality data) are the oxea lengths, which are 280–424 µm in var. aruensis, and only up to 250 µm in the typical variety. Variability in spicule lengths is commonly found in Petrosia species, and in view of the relatively close distance and similarity in shape I propose to merge the variety into a single somewhat variable species to be called Petrosia (Petrosia) expansa (Thiele, 1903) until a close comparison of the specimens has been completed. De Voogd & Van Soest (2002: 203) transferred Protoschmidtia expansa to the genus Xestospongia De Laubenfels, 1932, but here I assign it for the time being to Petrosia (Petrosia) based on the more dense skeleton and the variability of the spicule lengths.

The combinations Petrosia truncata var. aruensis (cf. above) and Petrosia expansa var. aruensis are secondary homonyms, but the junior homonym is here proposed to be merged with the nominotypical variety, which effectively removes the homonymy.