Staurocladia, Hartlaub, 1917

Ahuatzin-Hernández, José María, Hernández-Solís, Pablo Alberto & León-Deniz, Lorena Violeta, 2024, First record of the genus Staurocladia (Hydrozoa: Cladonematidae) in the Gulf of Mexico with the description of Staurocladia dzilamensis sp. nov., a new species of crawling hydromedusa, European Journal of Taxonomy 921, pp. 251-275 : 259-260

Key for the nominal medusae of Staurocladia

1. Tentacles without nematocyst clusters on their proximal, unbranched portion................................. 2

– Tentacles with an occasional nematocyst cluster on their proximal, unbranched portion. One apical cluster, 2–3 aboral, and 1 oral, cnidome composed of stenoteles (23.00–25.00) × (17.00–19.00) μm and desmonemes (8.00 × 4.00) μm............................................................ S. haswelli ( Briggs, 1920)

2. Tentacles with lateral nematocyst clusters......................................................................................... 3

– Tentacles without lateral nematocyst clusters.................................................................................... 6

3. Tentacles with up to 6 lateral, alternating clusters per side, cnidome composed of stenoteles of four size classes: class one (28.00–30.50) × (20.00–21.00), class two (17.50–24.00) × (13.00–15.00), class three (9.50–14.50) × (7.00–9.50), class four (7.00–9.00) × (5.50–6.50) μm and desmonemes (10.50–14.50) × (4.00–6.00) μm......................................................... S. wellingtoni Schuchert, 1996

– Tentacles with 1 nematocyst cluster laterally placed slightly before the branching point or on the lateral side of the upper branch.......................................................................................................... 4

4. Tentacles with 2–5 aboral and 2–4 oral clusters. Medusa able to swim, cnidome composed of stenoteles of two size classes: class one (15.00 × 12.00), class two (25.00 × 21.00) μm and desmonemes (14.00– 16.00) × (4.00–7.00) μm................................................................... S. portmanni Brinckmann, 1964

– Tentacles with up to 2 aboral clusters................................................................................................ 5

5. Tentacles with 2 aboral and 1 oral clusters alternately placed, 11–25 tentacles. Umbrella pearl-white (reflected light), brown (transmitted light), cnidome composed of stenoteles of two size classes: class one (24.90 × 17.30), class two (14.30 × 9.50) μm and desmonemes (9.70 × 4.80) μm ............. ......................................................................................................... S. acuminata (Edmonson, 1930)

– Tentacles with 1 single nematocyst cluster on the aboral side, up to 12 tentacles. Umbrella brown coloured ............................................................................................ S. bilateralis (Edmonson, 1930)

6. Tentacles with clusters restricted to the aboral side........................................................................... 7

– Tentacles with clusters present on both aboral and oral sides ......................................................... 10

7. Tentacles with clusters alternating left and right along a median line............................................... 8

– Tentacles with clusters in a single row .............................................................................................. 9

8. Bell flattened, 0.8 mm wide, with densely granulate, central area, clear at periphery, up to 13 tentacles, upper branch with 6 alternating clusters along a median, aboral line...... S. alternata (Edmonson, 1930)

– Bell nearly hemispherical, up to 8 mm wide, manubrium, endoderm of ring canal and tentacles orange, up to 65 tentacles, upper branch with 32 alternating clusters along a median, aboral line..... .................................................................................................................... S. charcoti ( Bedot, 1908)

9. Bell 0.5 mm wide, brown or reddish brown, up to 20 tentacles, upper branch longer than lower one, with 2 aboral clusters, cnidome apparently composed of a single type of stenoteles.......................... .......................................................................................................... S. oahuensis (Edmonson, 1930)

– Bell 0.7–1.2 mm wide, mostly transparent, 16–30 tentacles, upper branch shorter than lower one, 3–4 aboral, collinear clusters, cnidome composed of stenoteles of two size classes: class one (18.60 × 12.60), class two (10.80 × 6.60) μm and desmonemes (9.60 × 4.20) μm.................. S. schizogena Bouillon, 1978

10. Bell 0.25–0.60 mm wide, up to 11 (usually 8) tentacles, upper branch shorter than lower one, clusters alternately placed, 1 aboral and 1 oral, cnidome composed of stenoteles of two size classes: class one (15.00–17.50) × (12.50–15.00), class two (10.00 × 7.50) μm and desmonemes (7.50 × 5.00) μm .... ......................................................................................................................... S. dzilamensis sp. nov.

– Tentacles with upper branch longer than lower one .........................................................................11

11. Bell 0.2–0.8 mm wide, up to 16 tentacles, upper branch with 2–3 aboral and 1–2 oral clusters, cnidome composed of stenoteles of two size classes: class one (20.00 × 16.00), class two (12.00 × 8.50) μm and desmonemes (8.00 × 2.00) μm................................................ S. ulvae Bouillon, 1978

– Bell up to 3 mm wide, up to 42 tentacles, upper branch with up to 4 aboral and up to 3 oral clusters, cnidome composed of stenoteles of three size classes: class one (19.00–25.00) × (12.00–16.00), class two (14.00–15.50) × (8.50–10.50), class three (11.00–13.00) × (7.00–9.00) μm and desmonemes (10.00–11.00) × (4.50–5.50) μm............................................................ S. vallentini ( Browne, 1902)