Key to known species of Prionospio with five pairs of branchiae

(Modified from Delgado-Blas 2014)

1. Dorsal crests or folds on several postbranchial chaetigers..................................................... 2

- Dorsal crests or folds absent............................................................................. 4

2. Prostomium triangular-shaped; anterior neuropodial prechaetal lamellae large............ P. heterobranchia Moore, 1907

- Prostomium bottle-shaped; anterior neuropodial prechaetal lamellae very small.................................... 3

3. Prostomium with small medial peak in dorsal region, neuropodial postchaetal lamellae of chaetiger 1 very small, much smaller than 1/3 the size of the notopodial lamella; branchial pairs 2 and 3 cirriform; low dorsal ridges across the dorsum on chaetigers 8–29; sabre chaetae in neuropodia from chaetigers 12–13……………….......................... P. gabriellae sp. nov.

- Prostomium without small medial peak in dorsal region, neuropodial postchaetal lamellae of chaetiger 1 large, almost the same size as the notopodial lamellae; branchial pairs 2 and 3 triangular; low dorsal ridges across the dorsum on chaetigers 7–15; sabre chaetae in neuropodia from chaetigers 14–15..................................... P. caribensis Delgado-Blas, 2014

4. Neuropodial postchaetal lamellae on chaetiger 2 rounded, square or rhomboid; anterior notopodial and neuropodial lamellae overlapping or touching................................................................................ 5

- Neuropodial postchaetal lamellae on chaetiger 2 subrectangular, with dorsally directed process, the lower corners rounded; anterior notopodial and neuropodial lamellae separate............................... P. rosariae Delgado-Blas, 2014

5. Prostomium with a small medial peak on anterior margin; neuropodial lamellae on chaetiger 3 subtriangular; anterior neuropodial prechaetal lamellae large; ventral and dorsal edges of the notopodial and neuropodial lamellae overlapping on chaetigers 2–8; hooks without secondary hoods.................................................... P. newportensis Reish, 1959

- Prostomium without small medial peak; neuropodial lamellae on chaetiger 3 rounded or square; anterior neuropodial prechaetal lamellae short; ventral and dorsal edges of the notopodial and neuropodial lamellae overlapping or touching on chaetigers 2–4; hooks with secondary hoods. …………………………………………...………….. 6

6. Prostomium anteriorly rounded; peristomium long; neuropodial lamellae on chaetiger 2 square or rhomboid; anterior notopodial chaetae not granulated; hooded hooks with 2–3 pairs of teeth................................................... 7

- Prostomium anteriorly truncated; peristomium short; neuropodial lamellae on chaetigers 2–3 rounded; anterior notopodial chaetae granulated; hooded hooks with 4 pairs of teeth.................................... P. texana Hartman, 1951

7. Neuropodial lamellae rhomboid on chaetiger 2 and rounded on chaetiger 3; sabre chaetae without sheaths; hooded hooks with 2–3 pairs of teeth...................................................... P. spongicola Wesenburg-Lund, 1958

- Neuropodial lamellae on chaetigers 2–3 square; sabre chaetae with sheaths; hooded hooks with 3 pairs of teeth................................................................................... P. jamaicensis Delgado-Blas, 2014