On the evolution of the Hedbergellidae from the Praehedbergellidae

In order to establish the relationship between the smooth, microperforate p raehedbergellid forms of the genus Blefuscuiana with the younger, macroperf orate and muricate forms typical of Hedbergella, two similar taxa but with the different characters of the two genera, are studied here: Blefuscuiana praetrocoidea (Kretchmar & Gorbachik) and its descendant Hedbergella trocoi dea (Gandolfi), the type species of Hedbergella, and which typifies the Hed bergellidae. B. praetrocoidea was only found in the Early Aptian in the North Tethys. H. trocoidea ranges from the Late Aptian to Early Albian (?M. Albian) and is a cosmopolitan species. It evolves into Ticinella roberti (Gandolfi), a Lat e Aptian-Albian species with fused portici. The evolution of the Praehedber gellidae into the Hedbergellidae appears to be related to a relative sea-le vel rise in the Late Aptian and Albian (and the opening of the Proto-Atlant ic) which provided a number of deep-water niches which the Hedbergellidae o ccupied.