A North American freshwater sponge (Eospongilla morrisonensis new genus and species) from the Morrison Formation (Upper Jurassic), Colorado

Eospongilla morrisonensis n, gen, and sp., the oldest-described freshwater sponge (Demospongea: Spongillidae), is found in the Upper Jurassic (?Oxford ian/Kimmeridgian to Tithonian) Morrison Formation, east-central Colorado, U .S.A. Eospongilla morrisonensis occurs within the well-developed lacustrine carbonate succession of the Morrison Formation, and is represented by two micritic body fossils with calcite-replaced megascleres that range in lengt h from 180 to 300 mu m and in diameter from 20 to 35 mu m. Megascleres are simple oxeas and strongyles and lack apparent ornamentation, possibly due t o the diagenetic replacement. The oxeas are straight but the strongyles dis play a slight curvature. Microscleres are absent; gemmoscleres were not obs erved.