Geodiidae Gray, 1867a

Łukowiak, Magdalena, 2015, Late Eocene siliceous sponge fauna of southern Australia: reconstruction based on loose spicules record, Zootaxa 3917 (1), pp. 1-65 : 15-17

Family Geodiidae Gray, 1867a (Subfamily Geodiinae )

A great number of studied spicules belong to the astrophorid family Geodiidae . Their morphology is so characteristic that there are no doubts about their affinity. These are ovoid to subspherical cortical microscleres with short outgrowths with stellate tips, called sterrasters ( Figs. 4 A–I) that are diagnostic for this one astrophorid family. Their globular shape suggests that they do not belong to the subfamily Erylinae (because erylinids are characterised by having usually more or less flattened, disc-shaped spicules called aspidasters), but to the subfamily Geodiinae . At least two different morphological types of sterrasters have been found in the studied samples that may prove the presence of several different taxa. Their sculpture differs significantly—there are spicules with well developed, astrose or stellate outgrowths and others with nipple-shaped, densely packed and more numerous outgrowths (compare e.g., Figs. 4 A, B and Figs. 4 F, H), but that may be due also to the ontogenetic effect of changes during the development of a spicule. Although this differentiation in form of outgrowths may be an effect of the preservation as well as different stages of ontogenetic development, the presence of two different species of geodiids is here postulated. Unfortunately, more precise taxonomic assignment of the described spicules is not possible because today the taxonomical assignment of spicules of the family Geodiidae is based not only on the spicule morphology but chiefly on the arrangement of spicules within a sponge body ( Uriz 2002). The lack of articulated individuals precludes more precise attributions.

Today, geodiids are common and distributed worldwide ( Hooper & Wiedenmayer 1994), also along Australia, e.g., Geodia eosaster ( Sollas, 1888) , G. a re o l a t a Carter, 1880, G. berryi ( Sollas, 1888) , G. distincta Lindgren, 1897 , G. sphaeroides ( Kieschnick, 1896) , Geodia globostellifera Carter, 1880 , and G. punctata Hentschel, 1909 are recorded from the Australian waters (Atlas of Living Australia).

There was one microsclere noted ( Fig. 29 Q) that strongly resemble tylasters of Geodia globostellifera Carter, 1880 (compare with van Soest & Beglinger 2008, fig. 10F). It may prove that some of the studied sterrasters belong also to G. globostellifera as they are identical in morphology (compare Fig. 4 A with van Soest & Beglinger 2008, fig. 10C). But the studied sterrasters may belong to other species of Geodia as well. Generally, most species of the family Geodiidae have bathyal distribution and live predominantly on soft bottoms but some representatives occur in dark habitats in the littoral and shallow sublittoral zones, such as caves and overhangs ( Uriz 2002; Cárdenas 2011), which is clearly not the studied case.

It is worth mentioning that very similar (both, in morphology and size) microsclere spicules called selenasters occur in the hadromerid family Placospongiidae ( Placospongia Gray, 1867b ). However, in contrast to sterrasters, selenasters are characterized by short outgrows connected one to the other by ridges creating polygonal surface (see for example, Fig. 13 A), and are modified rhabds (see Vosmaer & Vernhout 1902, pl. 4, fig. 5).

Fossil sterrasters have been described so far in numerous papers from the Jurassic and Cretaceous deposits (for more detail see Wiedenmayer 1994), as well from the Miocene of Portugal ( Pisera et al. 2006), Slovakia ( Pisera & Hladilová 2003; Łukowiak et al. 2014, figs. 4M, N, Q), and the Central Atlantic ( Bukry 1978). They are also noted from the Paleocene of W Alabama, North America by Rigby & Smith (1992, figs. 4, 5), and the Late Cenozoic of New Zealand ( Rich 1958, fig. 1).

Figures

FIGURE 4. Spicules of sponges of the order Astrophorida; A – E—Sterraster microscleres of Geodia sp. 1, family Geodiidae; F – I—Sterraster microscleres of Geodia sp. 2, family Geodiidae; J – P—Different types of pynakids of the hypothetical species Dactylocalycites callodiscus, family? Geodiidae; Q – T—Spicules of the family Geodiidae; U – W—Triaenes of Penares cf. sclerobesa, family Geodiidae (subfamily Erylinae); X—Triaenes of Penares sp., family Geodiidae.

FIGURE 13. Spicules of sponges of the order Hadromerida; A – D—Different types of selenasters of Placospongia sp., family Placospongiidae; E—Micraster of the Tethya cf. omanensis, family Tethyidae; F – H—Oxyasters of the Tethyastra oxyaster, family Tethyidae.

FIGURE 29. Other demosponge spicules and their hypothetical assignment; A, B—Bold triods of unidentified sponge; C, D—Triods of unidentified sponge; E—Acanthotriod of Stelletta splendens - type, family Ancorinidae (order Astrophorida); F, G—Acanthocalthrops of unidentified sponge; H—Spicule of unidentified sponge; I— Crambe- like spicule, family Crambeidae (order Poecilosclerida); J—Spicule of unidentified sponge; K—Spicule of unidentified sponge; L—Spherical spicules of unidentified sponge / s; M—Spicule of unidentified sponge; N – Q—Different types of spined spicules of unidentified sponge / s.