Subgenus Hystricochaetonotus Schwank, 1990

Schwank, P. 1990, Gastrotricha. In: Brauer A. (Ed) Süsswasserfauna von Mitteleuropa. Bd. 3/ 1: 1–252. G. Fischer Verlag, Stuttgart, p. 217.

Type species: Chaetonotus hystrix Metschnikoff, 1865; designation by Schwank (1990)

The subgenus Hystricochaetonotus was established by Schwank (1990) for the Chaetonotus species previously included in the ‘group’ spinulosus by Remane (1936). The subgenus has been subsequently accepted by Kisielewski (1997) in its revision of the subgeneric division of the genus Chaetonotus. The diagnostic features of the subgenus are: a cuticular covering made of three-lobed scales with thick spines, a varying number of which form a dorsal group that can be generally recognized for the considerable length.

However, the great intraspecific morphological variability of most species, and the existence of species with intermediate features and thus difficult to be clearly assigned to this subgenus rather than to the subgenus C haetonotus s.s., make this character not reliable for diagnostic purpose, even for the type-species (C. hystrix). It seems that there is a continuum of the morphological characters putatively fixing the distinction between the subgenera Hystricochaetonotus and C haetonotus s.s., which seem actually to form a single natural group. Thus Chaetonotus (Hystricochaetonotus) is synonimized with Chaetonotus (Chaetonotus s.s.) (syn. nov.) and all the species currently included into it are moved to the latter:

Chaetonotus (Chaetonotus) hystrix Metchnikoff, 1865 (type species); C.(C.) acanthophorus Stokes, 1887; C.(C.) aemilianus Balsamo, 1978; C.(C.) anomalus Brunson, 1950; C.(C.) balsamoae Kisielewski, 1997; C.(C.) decemsetosus Marcolongo, 1910; C.(C.) enormis Stokes, 1887; C.(C.) euhystrix Schwank, 1990; C.(C.) ferrarius Schwank, 1990; C.(C.) italicus Balsamo & Todaro, 1995; C.(C.) longispinosus Stokes, 1887; C.(C.) lucksi Voigt, 1958; C.(C.) macrochaetus Zelinka, 1889; C.(C.) murrayi Remane, 1929; C.(C.) novenarius Greuter, 1917; C.(C.) octonarius Stokes, 1887; C.(C.) paucisetosus Marcolongo, 1910; C.(C.) persetosus Zelinka, 1889; C.(C.) polychaetus Daday, 1906; C.(C.) pungens Balsamo, 1990; C.(C.) quintospinosus Greuter, 1917; C.(C.) schlitzensis Schwank, 1990; C.(C.) spinifer Stokes, 1887; C.(C.) spinulosus Stokes, 1887; C. trichodrymodes Brunson, 1950; C.(C.) trilineatus Valkanov, 1937; C.(C.) trispinosus Balsamo, 1990; C.(C.) vargai Rudescu, 1967, and ten additional marine species.

Following the inclusion of the subgenus Hystricochaetonotus in the subgenus Chaetonotus sensu stricto, the original diagnosis of the latter (Kisielewski 1997, p. 148) is emended as follows: