New Palaeogene sponges from the Red Bluff Tuff, Chatham Island, New Zealand

A horizon with well-preserved sponge body fossils occurs in the late Palaeocene-early Eocene Red Bluff Tuff of Chatham Island, located some 850 km east of mainland New Zealand. The body fossils are glass' and lithistid' sponges in which most of the original silica has been replaced by calcite during diagenesis, strewn in approximate growth position around the same horizon. We describe two new species, a lyssacinosidan (non-rigid) glass sponge Rossella cylindrica sp. nov. (Class Hexactinellida, Order Lyssacinosida, Family Rossellidae), significant as it provides only the second species in the fossil record of the genus Rossella, and a very large, foliose, tretodictyid (rigid) glass sponge, Anomochone chathamensis sp. nov. (Class Hexactinellida, Order Hexactinosida, Family Tretodictyidae). A large, nodulose lithistid sponge attributed to the Family Corallistidae, but not identifiable to genus, is also described. This material provides a window into the early Tertiary palaeoenvironment of what is now the southern Pacific Ocean.