Chondrillidae Gray, 1872

Łukowiak, Magdalena, 2015, Late Eocene siliceous sponge fauna of southern Australia: reconstruction based on loose spicules record, Zootaxa 3917 (1), pp. 1-65 : 40

Family Chondrillidae Gray, 1872

Among numerous spherical microsclere spicules observed in the studied samples there are some that clearly resemble those of the Recent chondrosid genus Chondrilla Schmidt, 1862 . These are spherical microscleres (80–200 µm in diameter) with randomly, densely arranged, short to moderately long conical rays/projections ( Figs. 24 A–L). The most probable assumption is that these spicules belong to the ancestor of one of the species of Chondrilla that currently inhabits Australian waters— Chondrilla australensis Carter, 1873 , Chondrilla secunda Lendenfeld, 1885 , Chondrilla mixta Schulze, 1877 , or Chondrilla linnaei Fromont, Usher, Sutton, Toze & Kuo, 2008 (Atlas of Living Australia). The spicules ( Figs. 24 B–L) resemble spicules of Chondrilla secunda the most (compare with Fig. 26 B) but as in other cases described above the spicules of Recent Chondrilla secunda are much smaller (15–100 µm) than the Eocene ones.

There are also spicules that clearly resemble those of the Recent Chondrilla nucula Schmidt, 1862 ( Fig. 24 A). However, the ones reported from the Eocene are about 80 µm in diameter and are bigger than the spicules of Ch. nucula . Today, Chondrilla nucula inhabits tropical and subtropical coasts of the Atlantic and the Mediterranean Sea (van Soest et al. 2013). However, there is a record of Chondrilla nucula from New Zealand ( Burton 1934). Also Bergquist (1968) suspects the presence of C. nucula in this region as she has noted that “chondrillid spicules occur in keratose sponges in northern waters (of New Zealand)” ( Bergquist 1968, p. 63). Also spicules of Ch. sacciformis Carter, 1879b , which is known from the neritic zone of the Indian Ocean and Indo-Malayan region (Wiedenmayer 1994; Dendy 1917, pl. 48, fig. 8A), and Ch. linnaei are somewhat similar but those described here are still, in my opinion, the most similar to those of Ch. nucula . Generally, chondrillids are cosmopolitan and live in tropical, subtropical, and temperate zones ( Boury-Esnault 2002).

There are some records of pycnasters from the geological record, for instance from the Middle Oligocene Deep Sea Drilling Project cores from around Tasmania, that clearly resemble those described here (see Kennet et al. 1975, pl. 2, fig. 2). Pycnaster-like spicules (oxyspearasters) are also reported by Mostler (1990, pl. 5, figs. 12, 13) from the Jurassic of the Alps.

Figures

FIGURE 24. Spicules of sponges of the order Chondrosida and unassigned spherical / astrose micorscleres; A— Chondrilla nucula, family Chondrillidae; B – L— Chondrilla secunda, family Chondrillidae; M – Q—Different types of other spherical microscleres; R – U—Different types of oxyspherasters.

FIGURE 26. Spicules of recent sponges; A—Spicules of Chondrilla nucula (from Rützler et al. 2007); B—Spicules of Chondrilla secunda (from Fromont et al. 2008); C, D—Amphiclads of Samus anonymus (from van Soest & Hooper 2002 a).