Archisenia gen. nov. is proposed to accommodate the sibirica-group of the genus Danielssenia Boeck, 1872. Re-examination of Alaskan material of D. stefanssoni Willey, 1920 has shown the latter species to be a junior synonym of D. sibirica Sars, 1898, the type and only species of the new genus. Danielssenia robusta Sars, 1921 and Fladenia intermedia (Wells, 1965) are synonymous and consequently F. robusta comb. nov. becomes the type species of the genus Fladenia Gee & Huys, 1990. Danielssenia similis Chislenko, 1971 is regarded as species inquirenda and the genus Danielssenia is redefined from the type species D. typica Boeck, 1872, and two other species (D. quadriseta Gee, 1988 and D. reducta Gee, 1988). The status of D. fusiformis (Brady, 1880) nec Sars (1910) is reconsidered and as a result the genus Sentirenia Huys & Gee, 1992 is relegated to a junior synonym of Jonesiella Brady, 1880 which is reinstated to accommodate J. fusiformis Brady, 1880 and J. eastwardae (Coull, 1971) comb. nov. Psammis borealis Klie, 1939 is removed from the genus Psammis Sars, 1910 but retained in the Paranannopidae as species incertae sedis. P. longifurca Bodin, 1968 is transferred from Psammis to Bathypsammis gen. nov. The genus Psammis is redefined on the basis of the type species P. longisetosa Sars, 1910, and P. longipes Becker, 1974. A detailed redescription of A. sibirica and new illustrations of D. typica, P. longisetosa, P. longipes and B. longifurca are provided. Intersexuality in copepods and the possible phylogenetic relationships of Danielssenia, Psammis, Fladenia, Archisenia gen. nov. and Bathypsammis gen. nov. are briefly discussed. A key to the genera of the Paranannopidae is presented.