The genus
Styracaster is the greatest by the number of species and one of the most specialized genera in the family Porcellanasteridae. Fourteen species are known in the genus at present; a key for their identification is given. All known data on geographical and vertical distribution of the species have been summarized; in the majority of the species the former is limited by a single ocean or by a single zoogeographical region, and the range of the latter does not exceed 1000 or 2000 m. The greatest species diversity corresponds to the depths of 4500 down and 5000 m. On the basis of comparison of specimens of different ages in different species general generic trends of ontogenetic variability in a number of characters are outlined; in many cases the trends, apparently correspond to the development of the same characters in phylogenesis. A diagram of phylogenetic relationships between the species in the boundaries of the genera
Styracaster and
Eremicaster being descended, probabyl, from a common ancestor is proposed.
