Thoosidae Cockerell, 1925

Łukowiak, Magdalena, 2015, Late Eocene siliceous sponge fauna of southern Australia: reconstruction based on loose spicules record, Zootaxa 3917 (1), pp. 1-65 : 21-23

Family Thoosidae Cockerell, 1925

Another very characteristic morphotype of the spicules found in the studied samples are tuberculated, about 500 Μm long, oxeas ( Figs. 7 J–N) that are similar to those of the Recent Alectona Carter, 1879a (family Thoosidae ). Sponges belonging to this family were assigned to the family Alectonidae and placed in the order Hadromerida but now thoosids are placed in the order Astrophorida (see van Soest et al. 2013; Borchiellini et al. 2004). These thoosids are characterized by the presence of oxeas, styles, or strongyles as macroscleres and microrhabs or amphiasters, or both, as microscleres ( Rützler 2002a). The spicules investigated here seem to be almost identical to those occurring in Alectona millari Carter, 1879a ( Fig. 8 A) and A. wallichii Carter, 1874 ( Fig. 8 B) described by Vacelet (1999). These thoosids are rare and small cryptic sponges excavating calcareous limestone substrata and live in burrows made in calcareous algae, scleractinian corallites, or the axial skeleton of octocorals ( Rützler 2002a). Whereas A. wallichii is recorded only from Africa and Hawaii, A. millari is widely distributed all around the world (e.g., the Azores, Mediterranean Sea), including Australia (van Soest et al. 2013) so the described spicules belong most probably to A. millari . Only the size (225–370 µm) of the tuberculated oxeas of A. millari is smaller ( Rützler 2002a) than of the studied oxeas.

The genus Alectona has already been described in the fossil record from the Miocene deposits of Portugal by Pisera et al. (2006, figs. 7O–R) and assigned to A. wallichii . Also Łukowiak et al. (2014) described tuberculated oxeas from Early Miocene of the Vienna Basin (central Paratethys, Slovakia; fig. 5G). There are also some aleconid-like spicules known from the Miocene of Bahamas (Burky 1978, pl. 11, figs. 15–18).

Other astrophorid spicules with generalized morphology. Besides the spicules described and attributed above, there are also numerous pro- ( Figs. 9 A–D, L, M), ortho- ( Figs. 9 E, F, J, K, N), and prodichotriaenes ( Figs. 9 G–I) found in the studied sample, as well as other, clearly astrophorid, spicules ( Fig. 5 K) that can be assigned only to the order level because they are too generalized morphologically. They may occur in a wide range of astrophorid families (e.g., Ancorinidae , Geodiidae ) and their more precise assignment is not possible.

Various long-shafted fossil triaenes were described from many localities and geological periods, starting from the Cambrian ( Kempen 1990, fig. 2). They were also noted in the Carboniferous of Scotland ( Hinde 1887, pl. 5, fig. 3), Jurassic of the Alps by Reif (1967, pl. 13, figs. 16–23), and from the Cretaceous ( Schrammen 1924, pl. 8.1–9; pl. 9.1, 2, 5–8). Such triaenes were also recorded from the Jurassic and Cretaceous of Poland by Moczydłowska & Paruch-Kulczycka (1978, pl. 3, figs. 9–15).

Figures

FIGURE 5. Spicules of sponges of the order Astrophorida; A—Mesodichotriaene, family Pachastrellidae; B—Dichotriaene, family Pachastrellidae; C – G—Mesotriaenes of Pachastrella - like sponge, family Pachastrellidae; H – J—Calthrops of Calthropella sp., family Calthropellidae; K—Spicule of the order Astrophorida; L—Triaene of Brachiaster cf. claudlevii, family Pachastrellidae; M—Triaene of Triptolemma cladosum, family Pachastrellidae; N – O—Calthrop and dichotriaene of Dercitus (Stoeba) - like sponge, family Ancorinidae.

FIGURE 7. Spicules of sponges of the order Astrophorida; A – E—Anatriaenes of Dercitus (Stoeba) - like sponge, family Ancorinidae; F – I—Different types of triaenes of Stelletta sp., family Ancorinidae; J – N—Different types of acanthoxeas of Alectona millari, family Thoosidae; O—Sanidaster-ataxaster of Dercitus (Stoeba) - like sponge, family Ancorinidae.

FIGURE 8. Acanthoxeas of recent Alectona species; A— Alectona millari (from Rützler 2002); B— Alectona wallichii (from Vacelet 1999).

FIGURE 9. Undetermined astrophorid triaenes; A – D, L, M—Protriaenes of order the Astrophorida; E, F, J, K, N—Orthotriaenes of the order Astrophorida; G – I—Prodichotriaenes of the order Astrophorida.