Alleurythoe, Sun, Yue & Li, Xinzheng, 2017

Sun, Yue & Li, Xinzheng, 2017, A new genus and species of bristle worm from Beibu Gulf, South China Sea (Annelida, Polychaeta, Amphinomidae), ZooKeys 708, pp. 1-10 : 2-3

Genus Alleurythoe gen. n.

Type species.

Alleurythoe tenuichaeta sp. n.

Diagnosis.

Body elongate, quadrangular. Caruncle trilobed, attached to and confluent with posterior prostomial lobe, free from body wall, median lobe broadly sinusoidal, each lateral lobe with 6-7 folds, supported by a basal plate. Branchiae present from chaetiger 4, dendritically branched. Bifurcate neurochaetae capillary. Both noto- and neuropodial aciculae spinose.

Etymology.

The generic name is a combination of the prefix allo- (meaning “other” or “alternative” in Greek) and the generic name Eurythoe . The new genus is assigned to the subfamily Amphinominae and most similar to Eurythoe in morphology. Gender: feminine.

Remarks.

Alleurythoe gen. n. is assigned to the subfamily Amphinominae Lamarck, 1818 because of the absence of accessory dorsal cirri, and justified as a new genus by the nature of its caruncle ( Yáñez-Rivera 2011). The new genus is anatomically similar to Notopygos Grube, 1855 and Chloeia Lamarck, 1818 in the shape of caruncle which is trilobed and essentially supported by a basal plate. However, in contrast to Alleurythoe gen. n., the caruncle in the latter two genera has an elevated median keel with several bilateral folds, and it is usually fused to the body wall on chaetigers 1-2 and free thereafter. In the new genus, median keel of caruncle is broadly sinusoidal, thickened, lacks bilateral folds, and is attached to, and confluent with the posterior prostomial lobe, and free from the body wall. In addition, Alleurythoe differs from most other amphinomids in having spinous rather than hastate aciculae, bifurcate neurochaetae capillary, while other amphinomids with heftier bifurcate neurochaetae.

Alleurythoe gen. n. is superficially similar to Eurythoe Kinberg, 1857 in the shape of caruncle, which in both genera consists of a flattened, pronounced median keel and folded lateral lobes; however, the caruncle of Eurythoe Kinberg, 1857 is fused to the body wall for most of its length, the median keel overlaps the lateral lobes, which are scalloped on each side and lack a basal plate ( Bindra 1927; Borda 2012; Day 1967). Further, in the new genus, the neurochaetae are capillary (non-spurred or spurred), while the short, thick bifurcate neurochaetae, typical of Eurythoe Kinberg, 1857, are absent. An identification key to the genera of Amphinominae modified from Borda (2012) is provided below.