Ceratonotus pectinatus Sars, 1909, the type species of Ceratonotus Sars, 1909 (Copepoda: Harpacticoida: Ancorabolidae), is redescribed on the basis of females collected from southern Norway and by re-examination of extant material from the collections of Sars (Oslo, Norway), Lang (Stockholm, Sweden), and Drzycimski (Bergen, Norway). Some morphological characteristics of C. pectinatus males are provided from direct observations of the male copepodid V stage. Re-examination of Por's (1965) material from Raunefjord, Norway, did not provide any conclusive evidence to maintain C. pectinatus elaphus as a valid subspecies; it is considered here a junior subjective synonym of C. pectinatus. The validity of C. coineaui Soyer, 1964, is confirmed. Two new species of Ceratonotus are described, each based on a single sex, C. thistlei (♀) from the San Diego Trough (northeastern Pacific) and C. concavus (♂) from the eastern Mediterranean. An updated generic diagnosis for Ceratonotus is provided and intergeneric relationships discussed. Dendropsyllus thomasi, new genus, new species, is described from the San Diego Trough, northeastern Pacific. The new genus is characterised by the distinctive pattern of dendroid body processes (lacking on abdominal somites), lateroventral margins of cephalothorax with well-developed conical process, P1 exp-2 with 4 geniculate setae, P1 enp-2 with 1 apical seta, complete absence of P2 endopod, P3 exp-3 with 1 inner seta, and loss of the inner seta on P4 exp-3. Ceratonotus magellanicus and C. antarcticus, previously isolated as a distinct clade through parsimony analysis by Conroy-Dalton (2001), are both transferred to Dendropsyllus because they deviate significantly from the revised diagnosis for Ceratonotus. Ceratonotus and Dendropsyllus share a close sister-group relationship strongly supported by eight synapomorphies. The general phylogenetic relationships within the Ceratonotus-group are reinforced.