Bubaridae Topsent 1894

Family Bubaridae Topsent, 1894

The tuberculated diactines that characterize family Bubaridae were found in my material. These very characteristic spicules may belong to the genus Monocrepidium Topsent, 1898 which is characterized by a basal skeleton that includes stout, smooth, tuberculate or annulate diactines (Alvarez & van Soest 2002). Such exact spicules have been found in the studied samples (Figs. 15 A–F, I). The genus Monocrepidium has been previously referred to various taxonomic groups [e.g., family Desmanthidae (Lithistida), Axinellidae (Halichondrida)] but now is assigned to the family Bubaridae. Bubarids are exclusively encrusting sponges with hispid surfaces that are restricted today to rather deep waters and recorded from the East Atlantic, Mediterranean, with only one species— Monocrepidium eruca (Carter, 1880) occurring today in the Indian Ocean (Alvarez & van Soest 2002; van Soest et al. 2013). The diactines described here most probably belong to this species.

The other similar but less tuberculated spicules that are sometimes only slightly curved (Figs. 15 H, J–L) are very similar to those of Bubaris Gray, 1867a (compare with Alvarez & van Soest 2002, figs. 1F, G), although they are also close morphologically to spicules of ancorinid Jaspis Gray, 1867a (order Astrophorida). Today, Bubaris, which is a rather deep water inhabitant, is recorded from the Arctic, Indian Ocean, Indonesia, Japan, New Zealand, and Antarctica, so the spicules found in the studied material may belong to one of the species noted in adjacent areas, or may be the relic of other species that inhabited this area in the Late Eocene.

The tuberculated diactines that may have belonged to the sponges of family Bubaridae have already been described from the fossil record by Schrammen as Scolioraphis cerebriformis (1924, pl. 7, figs. 2, 3) from the Cretaceous of NW Germany and Mostler (1986, pl. 6.6) described similar spicules from the Rhaetian of the Alps. Spicules belonging to this family were also noted by Łukowiak et al. (2014, figs. 5N, O) from the Miocene of central Paratethys.