Dipolydora, Verrill, 1881

Radashevsky, Vasily I., 2022, Three new species of shell-boring Dipolydora (Annelida: Spionidae: Polydorini) from the South China Sea and the Gulf of Thailand, Vietnam, with comments on the modified spines in posterior notopodia and sperm morphology in polydorins, Zootaxa 5162 (2), pp. 101-119 : 115

Key to species of shell-boring Dipolydora from the South China Sea and the Gulf of Thailand

1 Posterior notopodia with only capillary chaetae. Pygidium trilobed, with one ventral lobe and two smaller dorsal lobes....................................................................................... D. vietnamita sp. nov.

- Posterior notopodia with awl-like spines in addition to capillary chaetae. Pygidium cup-shaped, with dorsal gap or incision, or bilobed, with dorsal and ventral incisions.................................................................. 2

2 Caruncle to end of chaetiger 2. Chaetiger 5 falcate spines with central main fang, large lateral tooth and apical structure appearing as wide cowling or third tooth on convex side of main fang; numerous fine bristles present on basis of teeth. Branchiae from chaetiger 7, up to seven pairs................................................................... D. armata

- Caruncle extending beyond chaetiger 2. Chaetiger 5 falcate spines without fine bristles on distal end. Branchiae from chaetigers 7−9, more than seven pairs............................................................................. 3

3 Caruncle to end of chaetiger 3. Occipital antenna absent. Chaetiger 5 falcate spines with thin collar on convex and lateral sides. Branchiae from chaetiger 7. Awl-like spines in posterior notopodia double-edged, with distal end slightly curved and basal end pointed, up to six in a tuft. Spermatids joined in tetrads....................................... D. echinata sp. nov.

- Caruncle to middle of chaetiger 5. Short occipital antenna present. Chaetiger 5 falcate spines with spoon-like hollow on concave side and narrow transverse shelf on convex side. Branchiae from chaetiger 8 (rarely chaetiger 9). Awl-like spines in posterior notopodia with basal end truncate, usually three in a tuft. Spermatids joined in octads........... D. spinosa sp. nov.