Made available in DSpace on 2022-04-29T08:28:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01; Recent molecular clock studies place the origin of phylum Cnidaria within the Cryogenian Period (ca. 850-635 Ma), with the split between the two subphyla (Anthozoaria and Medusozoa) likewise occurring during this time interval. However, the oldest cnidarian macrofossils, all medusozoans, occur in rocks ...