Prionospio dubia, Day, 1961

Delgado-Blas, Víctor Hugo & Peraza, Russell Giovanni Uc, 2024, Two new species of Prionospio (Annelida: Spionidae) from the Northwest and Northeast Atlantic, Zootaxa 5432 (1), pp. 69-82 : 79

Key to all similar species of P. dubia known worldwide

1 First pair of branchiae extending up to chaetigers 15–16; fourth branchial pair pinnate, shorter than the apinnate third pair................................................................................ P. anuncata Fauchald, 1972

- First pair of branchiae extending up to chaetigers 5–7; fourth branchial pair pinnate, equal to, or longer than the third apinnate pair................................................................................................. 2

2 Prostomium flask-shaped and anteriorly truncate; first pair of branchiae 3–4 times as long as the notopodial lamellae; middle chaetigers with very long notopodial capillaries, so long that they can appear coiled................. P. gayheadia sp. nov.

- Prostomium skittle-shaped and anteriorly rounded; first pair of branchiae 4–5 times as long as the notopodial lamellae; middle chaetigers with short or long notopodial capillaries, but never appear coiled....................................... 3

3 Eyes absent in specimens of all sizes; notopodial prechaetal lamellae well developed in branchial or postbranchial chaetigers.. 4

- Eyes present even if only in largest specimens; notopodial prechaetal lamellae low in branchial or postbranchial chaetigers... 5

4 Notopodial prechaetal lamellae slightly basally fused with the notopodial postchaetal lamellae in the branchial region; first pair of branchiae extending up to chaetiger 6 with a few pinnules along the outer lateral margin, and very long, naked distal tips; notopodial lamellae not extending slightly onto dorsum; neuropodial postchaetal lamellae of chaetigers 2–5 square; sabre chaetae from chaetigers 14–18; hooded hooks with 4 pairs of teeth...................... P. jonatani Delgado-Blas, 2015

- Notopodial prechaetal lamellae not fused in the postbranchial region; first pair of branchiae extending up to chaetiger 5 with many pinnules along the outer lateral margin, and very short, naked distal tips; notopodial lamellae extending slightly onto dorsum; neuropodial postchaetal lamellae of chaetiger 2 oval, chaetiger 3 subtriangular, chaetigers 4–5 rounded; sabre chaetae from chaetigers 19–24; hooded hooks with 3 pairs of teeth.................................... P. multisetosa sp. nov.

5 Sabre chaetae from chaetigers 12–14................................................... P. coorilla Wilson, 1990

- Sabre chaetae from chaetigers 15–20........................................................ P. dubia Day, 1961