Fossil and Modern Sponge Fauna of Southern Australia and Adjacent Regions Compared

Contributions to Zoology, 85 (1) 13-35 (2016) Fossil and modern sponge fauna of southern Australia and adjacent regions compared: interpretation, evolutionary and biogeographic significance of the late Eocene ‘soft’ sponges Magdalena Łukowiak1, 2 1Institute of Paleobiology PAN, Twarda 51/55, 00-818 Warszawa, Poland 2E-mail: [email protected] Key words: Demospongiae, Homoscleromorpha, Porifera Abstract Discussion ........................................................................................ 27 Paleoecology and biogeography .......................................... 27 Comparison with Oamaru Diatomite sponge fauna The late Eocene ‘soft’ sponge fauna of southern Australia is ....... 28 Differences and similarities between Recent and fossil reconstructed based on disassociated spicules and is used to in- sponge faunas of Australia terpret the paleoecology and environmental context of shallow .................................................... 29 marine communities in this region. The reconstructed sponge Conclusions ...................................................................................... 30 association was compared with coeval sponge assemblages Acknowledgements ........................................................................ 30 from the Oamaru Diatomite, New Zealand, and with the mod- References ......................................................................................... 31 ern ‘soft’ sponge fauna of southern coastal of Australia. Based on the predominance of shallow- and moderately shallow-water species, the late Eocene assemblage is interpreted to have in- Introduction habited waters depths of about 100 m. This contrast with the spicule assemblage from New Zealand, which characterized deeper waters based on the presence of numerous strictly deep- Sponges are among the simplest metazoans and, thus, water sponge taxa, and the absence of spicules of shallow-water are crucial for understanding the origin of animals. demosponges represented in the Australian material. The Their fossil record dates back to the beginning of the southern Australian Eocene sponge assemblages have clear Paleozoic Era (e.g. Hamdi et al., 1989; Brasier, 1989; Tethyan affinities evidenced by the occurrence of sponges Kaesler et al., 2004). Some early Vendian fossils have known today from diverse regions. This distribution suggests much wider geographical ranges of some sponge taxa during been noted as sponges (Reitner and Mehl, 1995; Hooper the Eocene. Their present distributions may be relictual. The and van Soest, 2002), however, these findings were re- modern sponge fauna inhabiting southern Australian waters cently questioned (Antcliffe et al., 2014). Fossil sponges shows only moderate differences from these of the late Eocene. are cosmopolitan, preserved as both articulated bodies Differences are more pronounced at lower taxonomic levels and isolated spicules. The quality of the sponge fossil (family and genus). record varies through geological time, but some excep- tionally preserved and rich sponge (or spicule) associations may provide valuable information about the evo- Contents lution of the group. Fossil sponges and isolated spicules have been stud- Introduction ..................................................................................... 13 Material and methods .................................................................... 15 ied extensively since the nineteenth century (e.g. Gold- Geological context ................................................................... 15 fuss, 1826-33; Zittel, 1877; Roemer, 1860; Quenstedt, Results ............................................................................................... 15 1878; Hinde, 1883, 1893; Hinde and Holmes, 1892; Short ecological characteristic and biogeographic Rauff, 1893-95; and Hall and Clarke, 1899; Mostler, distribution of the recognized sponge taxa ........................ 15 Comparison of Australian Eocene spicule assemblage 1972, 1976, 1994; Pisera, 2006 and references therein). with reinterpreted Eocene sponge spicules from the The spicules were generally treated from the morpho- Oamaru Diatomite, New Zealand ........................................ 20 logical point of view, as separate disassociated ele- Comparison of the Australian late Eocene sponge ments, and rarely attributed to particular taxa. Conse- assemblage with the extant demosponge fauna of quently, there are very few papers describing ecologi- southern Australia ................................................................... 23 cal relationships of sponge associations and these deal Gulf Province (Spencer Gulf) vs. Blanche Point mostly with those associations from the northern part Formation sponge fauna ........................................................ 25 South Western Province vs. Western part of southern of the world (e.g., see Koltun, 1959, 1961; Pisera, 1997; Australia Eocene sponge fauna ............................................ 25 Pisera and Busquets, 2002; Pisera and Hladilová, 14 Łukowiak – Fossil and modern sponge fauna of southern Australia Fig. 1. A Triaene of Penares cf. sclerobesa; B Short-shafted triaene of Triptolemma cladosum; C Amphitriaene of Samus anonymus; D Spheraster of Chondrilla nucula; E-F Spherasters of Chondrilla secunda; G, H, J Anthasters of Diplastrella cf. megastellata; I Micraster of Tethya cf. omanensis; K, L Oxyasters of Tethyastra oxyaster (after Łukowiak, 2015, modified). 2003; Matteucci and Russo, 2005; Pisera et al., 2006; tailed study by Hinde and Holmes (1892) on the iso- Łukowiak et al., 2014; Frisone et al., 2014). The fossil lated sponge spicules from the Eocene of Oamaru Di- sponges from the Southern Hemisphere remained un- atomite (New Zealand). This study reconstructs the derstudied. There are a few exceptions such as the de- sponge assemblage and infers its bathymetry. Also, Contributions to Zoology, 85 (1) – 2016 15 Kelly and Buckeridge (2005) interpreted Early Paleo- tralia), through Norseman and Princess Royal in the gene sponge fauna from the New Zealand Chatham north (western Eucla Basin and associated palaeodrain- Island in terms of the environmental conditions and age channels), and Hamersley River and Doyle Road water depth. within the Fitzgerald River National Park in the west This approach – the biological interpretation of dis- (Bremer Basin of Western Australia). These sites are associated sponge spicules – was used to assess upper characterized by different geological histories and fa- Eocene spongiolites and spiculites exposed along the cies development. In the late Eocene, Australia was in southern coast of Australia. The reconstructed assem- its final stages of separation from Antarctica, after blage consisted of at least 42 species within 31 genera, which climatic cooling initiated due to inception of the 27 families, and 12 orders of ‘soft’ Demospongiae and Antarctic Circumpolar Current (for more details see Homoscleromorpha. Also, some lithistids and rare Exton et al., 2001; Barker et al., 2007; Quaglio et al., Hexactinellida were found in the assemblage. The 2007). spicules representing demosponge orders Poeciloscle- The megathermed to mesothermed climate of Aus- rida and Tetractinellida were the most diversified. The tralia, prior to the end of the Eocene was characterized rest of the ten orders (Chondrillida, Haplosclerida, Ax- in high climatic seasonality (McLoughlin and McNa- inellida, Bubarida, Agelasida, Polymastiida, Clionai- mara, 2001; Carpenter et al., 2014). Deep chemical da, Tethyida, Suberitida, and Homosclerophorida) weathering and the opal pulse that took place in the were less differentiated (for more details see Łukowiak, middle Eocene caused mobilization of silica and in- 2015). The taxonomical assignments in this paper creased levels of silica in the oceans (Diekmann et al., were updated basing on Morrow and Cárdenas (2015) 2004). new Demospongiae classification. The studied sponge spicules were obtained from In this paper, the reconstructed assemblage is inter- various upper Eocene units. Mainly muddy spiculites preted in a paleoecological and environmental context. and spongiolites were sampled from Doyle Road, Prin- Thanks to the comparisons with modern sponge com- cess Royal, and the Hamersley River glauconitic and munities of Australia, it was possible to establish the spiculitic marls and limestones and biosiliceous clays changes in the biota over the past 35 millions of years. were sampled at Blanche Point (for more details see Łukowiak, 2015). Material and methods Results The samples were collected in April-May 2004 by An- drzej Pisera (with the exception of core samples, do- Short ecological characteristic and biogeographic nated kindly by Paul Gammon, Canada). About 30 distribution of the recognized sponge taxa samples of spicule-rich clays, muddy spiculites, and spiculites were processed in the laboratory at the Insti- The diversity and excellent preservation of the sili- tute of Paleobiology, Polish Academy of Sciences, Po- ceous sponge spicules witness the presence of a very land. The samples were macerated using Glauber’s salt rich sponge fauna in southern Australia waters during (Na2SO4) or hydrogen peroxide (H2O2 30%) to remove the late Eocene. It is estimated that at least nine or- organic matter, and to clean and separate loose sponge ders, 27 families, 31 genera, and 42 species of ‘soft’ spicules (see Łukowiak, 2015 for additional prepara- (including the sponges of the class Homoscleromor- tion details). All the investigated

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