ASPECTS OF THE GENUS EUCHONE MALMGREN (SABELLIDAE: SABELLINAE) - A FALSE TAXON?
Cochrane, Sabine C.
Akvaplan-niva AS, 9005 Tromsø, Norway/ School of Environmental and Evolutionary Biology, University of St. Andrews, Fife, KY16 8LB, Scotland.
The genus Euchone Malmgren currently is separated from the related genus Chone Krøyer mainly by the presence of an anal funnel. The number of segments comprising the funnel varies between species, but is relatively constant within a given species. Transitional states of the anal funnel are discussed, together with other aspects, including the nature of the radiolar crown. Most Euchone species have few to many pairs of radioli, with numerous, tightly spaced, paired pinnules of equal length ('feather-like'). However, one group of species possesses three pairs of radioles with relatively few, widely spaced pinnules alternating along the length of the radiole. The mid-radiolar pinnules are longest, such that the majority terminate at the same height distally ('snowflake-like'). The species in this group also have only three segments comprising the anal funnel. Using phylogenetic analyses, the validity of the anal funnel as a generic characteristic is examined and a rediagnosis of the genus is suggested. An improved classification of those species with 'snowflake-like' radioles and three segments comprising the anal depression also is proposed.