_________________________________________________________________________________________________________ Kölner Forum Geol. P<strong>al</strong>äont., 19 (2011) M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.) Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, <strong>Liège</strong>, August 19-29, 2011 _________________________________________________________________________________________________________ Caribbean reef recovery in the early Cenozoic - Mixed azooxanthellate and zooxanthellate faunas in the middle Eocene of Jamaica 166 Thomas A. STEMANN Department of Geography and Geology, The University of the West Indies, Mona, Kingston, 7 Jamaica; thomas.stemann@uwimona.edu.jm Reefs and cor<strong>al</strong>s in the Caribbean were severely affected by the biotic crisis at the termin<strong>al</strong> Cr<strong>et</strong>aceous. The diverse Caribbean cor<strong>al</strong> associations of the latest Cr<strong>et</strong>aceous left few <strong>de</strong>scen<strong>de</strong>nts in the P<strong>al</strong>eogene. Caribbean cor<strong>al</strong> faunas of the early Cenozoic are scarce and species poor (BUDD <strong>et</strong> <strong>al</strong>. 1992). No re<strong>al</strong> cor<strong>al</strong> buildups appear in the region until middle – late Eocene time and most faunas are comprised of only sm<strong>al</strong>l (
_________________________________________________________________________________________________________ Kölner Forum Geol. P<strong>al</strong>äont., 19 (2011) M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.) Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, <strong>Liège</strong>, August 19-29, 2011 _________________________________________________________________________________________________________ Biologic<strong>al</strong> spherulite: Record of physiologic<strong>al</strong> activity in stony cor<strong>al</strong> skel<strong>et</strong>on Jarosław STOLARSKI Institute of P<strong>al</strong>eobiology, Polish Aca<strong>de</strong>my of Sciences, Warsaw, Poland; stolacy@twarda.pan.pl The spherulitic mo<strong>de</strong>l of the skel<strong>et</strong>on growth (BRYAN & HILL 1943) was a breakthrough in providing a coherent mechanism of growth of the scleractinian skel<strong>et</strong>on and still remains an inspiration for some geochemic<strong>al</strong> mo<strong>de</strong>ls of skel<strong>et</strong>on formation (e.g., HOLCOMB <strong>et</strong> <strong>al</strong>. 2009). According to this mo<strong>de</strong>l, formation of the skel<strong>et</strong>on is explained in physico-chemic<strong>al</strong> categories, the same that apply to the abiotic growth of various spheroid<strong>al</strong> bodies consisting of radiating cryst<strong>al</strong>s. However, structur<strong>al</strong> and geochemic<strong>al</strong> similarity b<strong>et</strong>ween spherulites precipitated abiotic<strong>al</strong>ly and those formed by organisms (including cor<strong>al</strong>s) is not sufficient to invoke similar controlling mechanisms. Fish otoliths (spherulite-like c<strong>al</strong>cium carbonate structures involved in b<strong>al</strong>ance and hearing) provi<strong>de</strong> an extreme example for the failure of such reasoning: their radi<strong>al</strong>-concentric structure (or its lack) and selection of c<strong>al</strong>cium carbonate polymorph (aragonitic vs. c<strong>al</strong>citic) is controlled entirely by expression levels of the starmaker gene (SÖLLNER <strong>et</strong> <strong>al</strong>. 2003). Although, the role of distinct genes in the process of scleractinian cor<strong>al</strong> skel<strong>et</strong>ogenesis has not y<strong>et</strong> been precisely elucidated (preliminary hints e.g., REYES-BERMUDEZ <strong>et</strong> <strong>al</strong>. 2009) there is an increasing number of evi<strong>de</strong>nces suggesting the prevailing control of the structure and composition of the skel<strong>et</strong>on by the organism. Scleractinian skel<strong>et</strong>ons contain inclusions of organic macromolecules whose composition (acidic glycoproteins) and distribution pattern suggest their formative role during the skel<strong>et</strong>ogenesis rather than passive entrapment in cryst<strong>al</strong>s which cyclic precipitation is driven by c<strong>al</strong>cium carbonate saturation state. Similarly, concentrations and micro-sc<strong>al</strong>e patterns of some trace elements (e.g., Mg) differ essenti<strong>al</strong>ly from those in miner<strong>al</strong>s formed in equilibrium with the sea-water geochemistry (e.g., MEIBOM <strong>et</strong> <strong>al</strong>. 2008). Histologic<strong>al</strong> observations of intact tissue-skel<strong>et</strong>on interface (e.g., TAMBUTTÉ <strong>et</strong> <strong>al</strong>. 2007) c<strong>al</strong>l into question the presence of an Extracellular C<strong>al</strong>cifying Fluid (ECF) zone as postulated by some geochemic<strong>al</strong> mo<strong>de</strong>ls. In addition to the diversity in distribution patterns of Rapid Accr<strong>et</strong>ion Deposits („centers of c<strong>al</strong>cification”) which tradition<strong>al</strong>ly was consi<strong>de</strong>red as an evi<strong>de</strong>nce of limited organism<strong>al</strong> control on miner<strong>al</strong>ization, there is <strong>al</strong>so large diversity in Thickening Deposits („fibers”) organization. Their distinct patterns are closely associated with members of molecularly distinguished cla<strong>de</strong>s (e.g., KITAHARA <strong>et</strong> <strong>al</strong>. 2010; JANISZEWSKA <strong>et</strong> <strong>al</strong>. 2011). Such precise biologic<strong>al</strong> control of formation of the thickening <strong>de</strong>posits and lack of ECF space is <strong>al</strong>so suggested by skel<strong>et</strong>on isotope labeling experiments (HOULBREQUE <strong>et</strong> <strong>al</strong>. 2009). Many of the above mentioned skel<strong>et</strong><strong>al</strong> features that seems strongly biologic<strong>al</strong>ly-influenced are evi<strong>de</strong>nt <strong>al</strong>so in cor<strong>al</strong>la of the azooxanthellate genus Desmophyllum which otherwise can be consi<strong>de</strong>red as perfect mo<strong>de</strong>l of “spherulitic” organization (Fig. 1). The go<strong>al</strong> of this presentation is to provi<strong>de</strong> an overview of the most comprehensive up to date structur<strong>al</strong> and biogeochemic<strong>al</strong> an<strong>al</strong>ysis of the skel<strong>et</strong>on of Desmophyllum and di<strong>al</strong>ectic<strong>al</strong>ly confront comp<strong>et</strong>ing arguments regarding the role of “biologic<strong>al</strong>” vs. “geologic<strong>al</strong>” factors in the growth of the skel<strong>et</strong>on of this cor<strong>al</strong>. BRYAN, W.H & HILL, D. (1942): Spherulitic cryst<strong>al</strong>lization as a mechanism of skel<strong>et</strong><strong>al</strong> growth in the Hexacor<strong>al</strong>s. - Proceedings of the Roy<strong>al</strong> Soci<strong>et</strong>y of Queensland, 52: 78-91. HOLCOMB, M., COHEN, A.L., GABITOV, R.I. & HUTTER, J.L. (2009): Composition<strong>al</strong> and morphologic<strong>al</strong> features of aragonite precipitated experiment<strong>al</strong>ly from seawater and biogenic<strong>al</strong>ly by cor<strong>al</strong>s. - Geochimica <strong>et</strong> Cosmochimica Acta, 73: 4166-4179. HOULBREQUE, F., MEIBOM, A., CUIF, J.P., STOLARSKI, J., MARROCCHI, Y., FERRIER-PAGÉS, C., DOMART-COULON, I. & DUNBAR, R.B. (2009): Strontium-86 labeling experiments show spati<strong>al</strong>ly h<strong>et</strong>erogeneous skel<strong>et</strong><strong>al</strong> formation in the scleractinian cor<strong>al</strong> Porites porites. - Geophysic<strong>al</strong> Research L<strong>et</strong>ters, 36: L04604, doi:10.1029/2008GL036782. JANISZEWSKA, K., STOLARSKI, J., BENZERARA, K., MEIBOM, A., MAZUR, M., KITAHARA, M. & CAIRNS, S.D. (2011): A unique skel<strong>et</strong><strong>al</strong> microstructure of the <strong>de</strong>ep-sea micrabaciid scleractinian cor<strong>al</strong>s. - Journ<strong>al</strong> of Morphology, 272: 191-203, doi:10.1002/jmor.10906. 167
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