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Both sexes of a new genus and species of Ancorabolidae are described from the San Diego Trough in the Northeastern Pacific. Arthuricornua nendopodia, new genus, new species, is placed in the newly defined Ceratonotus-group which includes the genera Ceratonotus Sars, Dorsiceratus Drzycimski, and Polyascophorus George. Members of this group are characterized by the cylindrical body shape, presence of dorsal processes on somites bearing P2-P4, rostral shape, proximal antennulary elongation, 3-segmented condition of d P3 endopod, and absorption of P5 endopodal lobe in both sexes. The major evolutionary transformations within the Ceratonotus-group are discussed and polarized by outgroup comparison with the Cletodidae. Parsimony analysis confirmed Dorsiceratus and Ceratonotus as monophyletic genera, but demonstrated the polyphyletic status of Polyascophorus. Polyascophorus schminkei George is identified as the earliest offshoot within the Ceratonotus-group and is transferred to a new genus Touphapleura. The common ancestry of Arthuricornua and Dorsiceratus, and the sistergroup relationship between Ceratonotus and Polyascophorus, are strongly supported. A basal dichotomy divides the genus Ceratonotus into two geographically separated clades. The genus Polyascophorus is redefined to include only P. martinezi George and P. gorbunovi (Smirnov). The harpacticoid family Ancorabolidae Sars comprises two subfamilies, the Ancorabolinae and the Laophontodinae (Lang, 1944), and currently contains 46 species and subspecies in 16 genera. In the visually striking Ancorabolinae, the number of species has almost quadrupled since Lang's (1948) review of the family, unveiling an unexpected wide distribution in both northern and southern hemispheres (see Conroy-Dalton and Huys, 2000). The majority inhabit the coastal zone and muddy sediments in the deep sea, with a few exceptions including reports from brackish waters (Kunz, 1935), sandy sediments (Drzycimski, 1969; Moore et al., 1987), and polar pack ice tow net samples (Brady, 1918). Recent discoveries include new taxa from the Arctic (George, 1998a) and (sub-) Antarctic waters (George, 1998b; George and Schminke, 1998) and the first record of the subfamily from a deep-sea hydrothermal vent in the northeastern Pacific Ocean (Conroy-Dalton and Huys, 2000). Although members of the Ancorabolinae are generally found in low numbers, with males typically scarcer than females, their previously accepted rarity and currently underestimated diversity can be regarded merely as a reflection of logistic problems related to sampling the deep sea and other remote environments. In the early 1970s the benthos of the San Diego Trough was extensively sampled during the Expedition Quagmire (Thiel and Hessler, 1974), an American integrated-sampling programme designed to investigate the entire benthic community at a single deep-sea locality. Thistle (1978) examined the harpacticoid fauna and identified a total of 140 putative harpacticoid species from these samples. Species were arbitrarily allocated to three functional groups according to presumed habitat utilization which he inferred from their basic morphology (Thistle, 1982). Species which typically had sediment particles attached to the dorsal surface of the body were assigned to the "sediment-covered" group and included the Argestidae, Ancorabolidae, and members of Malacopsyllus Sars (Ameiridae). Thistle (1982) discriminated four species of Ancorabolinae at the Quagmire site, belonging to the genera Dor-

Systematics and Phylogeny of the Ancorabolidae (Copepoda: Harpacticoida). II. Polyphyly of Polyascophorus and Description of Arthuricornua, New Genus