Journal of Paleontology; May 2005; v. 79; no. 3;
p. 460-468; DOI: 10.1666/0022-3360(2005)079<0460:SAAFFT>2.0.CO;2
© 2005 Paleontological Society
SPONGES AND ASSOCIATED FOSSILS FROM THE PENNSYLVANIAN CARBONDALE FORMATION OF NORTHWESTERN ILLINOIS
J. KEITH RIGBY1 and
PETER von BITTER1
1 Department of Geology, Room S389, Eyring Science Center, Brigham Young University, Provo, Utah 84602-4606, <rigbyjkeith{at}qwest.net> and Department of Palaeobiology, Royal Ontario Museum and Department of Geology, University of Toronto, 100 Queen's Park, Toronto M5S 2C6, Canada, <peter{at}rom.on.ca>
The two new sponges, Diagonodictya crusta n. gen. and sp., a small steeply obconical, dictyospongiid hexactinellid, and Pohlispongia monosphaera n. gen and sp., a spheroidal, single-chambered, monaxonid demospongealong with several isolated hexactinellid spiculesare described from low-energy, low pH, black shales within the Pennsylvanian Desmoinesian Carbondale Formation from northwestern Illinois, from the Illinois Basin. They are associated with a variety of small fossils, which range from radial and spheroidal to lobate obconical, here identified only as forms A and B, that are possible spore-bearing organs of plants. Some of these latter forms occur as core debris associated with fine hexactine-derived sponge spicules and bivalve? fragments in fecal pellets. The described assemblage may have lived as pelagic organisms in a protected environment and may have been deposited under swamp "flotants" in anoxic shallow water conditions. Alternatively, the assemblage may have lived as part of an open water pelagic biota, ending up in death in anoxic, deeper water environments.
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