The taxonomy of schizasterid spatangoids is discussed and the term is restricted to include onlySchizaster-like echinoids. Within the genusSchizasterAgassiz the following morphological subgenera are recognized:ParasterPomel,DipneustesArnaud andOvaGray. Seven species are described from Palaeocene to Miocene rocks of Australia. New species areS. (Paraster) carinatus, S. (Paraster) tatei, S. (Schizaster) halliandS. (Dipneustes) fosteri. Schizasterand its various morphotypes are thought to have evolved from aLinthia-like root stock through progressive morphological changes in test shape, form of ambulacra and adoral test morphology. Such changes are interpreted as being adaptations which allowed the sea urchins to occupy various levels of substrate in different sediment types. Morphotypes appear to have evolved iteratively, perhaps due to variation in the onset of sexual maturity.