New species of lithistid sponges from the Paleogene of the Ukraine

Four new species of lithistid sponges, Lerouxia digitata n. sp., Theonella ukrainica n. sp. (Theonellidae, Tetracladina), Chenendopora piaskovskii n. sp. (Chenendoporidae, Tetracladina) and Plinthosella magna n. sp. (Plinthosellidae, suborder incertae sedis), are described from the Paleogene (most probably Oligocene) of the Ukraine. It is the largest lithistid fauna of that age known. In a preliminary report by Oakley (1942) these sponges were erroneously attributed to Corallistes (one species), Discodermia (three species) and Jereica clavaeformis Pomel. The species Lerouxia digitata n. sp., Chenedopora piaskovskii n. sp. and Plinthosella magna n. sp. represent genera which were known so far only from the Cretaceous. The species Theonella ukrainica n. sp. belongs to the still living genus. Such long stratigraphical ranges of the genera of the investigated sponges is more general feature known also among other lithistids. These sponges are extraordinarily preserved, showing even flexibility of the skeleton and have in most cases dermalia preserved in situ. A curious feature of this fauna is very heavy silification of most described sponges, unknown among Recent lithistids.