| The family Hyalellidae comprises eight genera according to Zeidler (1991) and Bousfield (1996). The composition of the family has been questioned (Barnard and Karaman, 1991, and Bellan-Santini, 1999), being reduced only to the freshwater genus Hyalella. Computer assisted cladistic analysis of morphological characters and DNA for some genera were undertaken, utilizing the program, PAUP. Morphological and DNA analysis shows that there is not enough evidence for Hyalellidae to remain a separated family, sensu Zeidler (1991) and Bousfield (1996). The genera of Hyalidae varied, clustering in different clades.; The work presented here focuses specifically on the genera Parhyalella and Hyalella. Sixteen redescriptions with new figures, ten provisionally new species, and 26 redescriptions with the original authors' figures are included.; Hyalella is known only from the Nearctic and Neotropical biogeographical areas. Nine new species are included. The species of Hyalella for the purpose of this work have been divided into several groups according to their morphological affinities, geographical distribution, or association with large river basins. The cladistic analysis of Hyalella produced clusters almost congruent with the geographical distribution of the species. The species of Lake Titicaca form two clades. The “patagonica complex” forms another clade. The species from North America and Central America, with the addition of the species from the Amazonian basin forms another clade. Species east and west of the Andes cluster together.; Parhyalella comprises only marine species, is morphologically close to Hyalella, and occurs on the coasts of every continent. One new provisional species is included in this work. Cladistic analysis indicates the genus could be divided into three groups. The Mediterranean species forms a clade by itself; there is a clade with the species from the Caribbean Sea, West Atlantic, East Atlantic and Pacific Ocean of the Americas, and a clade with the species from the Indo West Pacific area.; For purposes of zoological nomenclature, this work is not intended for public and permanent record. |
