Two lineages are distinguished in the Cenozoic anascan family Bicorniferidae, in which groups of zooecia are arranged in internodes, presumably connected by uncalcified joints. The lineage of Bicornifera is represented in the Paleocene by a species with internodes composed of four zooecia. During subsequent evolution the number of zooecia per internode was reduced to three, and the shape of the unit became more and more compact. Possibly also the size of the whole zoarium underwent reduction; in the end-member of the lineage. Bifissurinella, it was represented by a single triangular unit of three zooecia. In the second lineage of Voorthuyseniella connections between zooecia of particular branches were very fragile; consequently only isolated zooecia are found in the fossil record.

Key words: Bryozoa, Cheilostomata, Anasca, Bicorniferidae, microproblematica, biology, evolution, Cenozoic.