Pseudoderivations of Paracraticularia cylindrica (Michelin, 1840) (Porifera, Hexactinellida)

Abstract

The morphological diversity of diosculumic sponges, known as Paracraticularia cylindrical, results from the fact that many fossils assigned to this species prove to be fragments of the apical segments of internodes (branches) from major colonies that are rarely encountered as totally preserved fossils. The structures of the branch apical segments and the oscula outlines reflect various manifestations of hexactinellida synchronous division conductive to morphological diversity of the descendants, the succeeding complicatedly structured colonial sponges. Some morphs (parataxa) are considered to belong to the species which are mostly fragments of the apical segments from the braches of the Paracraticularia primary colonies.