A Generic Revision of the Stylasterina (Coelenterata: Hydrozoa).

Part 1. Description of the Genera

Prior to a phylogenetic analysis of the Stylasterina, the 23 genera and one subgenus in the order are redescribed with special emphasis on scanning electron microscopy of the skeleton, histology of soft parts, and variation within each genus. Two new genera are described. The type-species of each genus is also redescribed and figured by scanning electron micrographs. Tissue of 21 of the 23 Recent genera and subgenera was examined by histological serial sections; 18 of these 21 were type-species of genera. The first three-dimensional (SEM) photographs of stylasterine nematocysts are provided. Much of the terminology used to describe stylasterines is reviewed and some new terms introduced.

A critical checklist of all stylasterine taxa is given, which includes 23 genera, 1 subgenus, 184 valid species, 7 subspecies, 11 formae or facies, and 42 synonyms. Numerous new synonyms and new combinations are made in this checklist, many of the latter caused by the synonymy of Allopora with Stylaster.