Review of Oweniidae Rioja, 1917 (Annelida, Palaeoannelida) from Malaysia, with a description of two new species and a key to South China Sea species

Several species of the family Oweniidae Rioja, 1917 (Annelida) are believed to be responsible for sediment stabilisation, therefore the taxonomic identification and description of species from this family is crucial. Nevertheless, few oweniids have been identified in the South China Sea (SCS), whereas none were reported from the east coast of Peninsular Malaysia. Two new oweniid species are described here: Galathowenia minuta n. sp. and Owenia unipinnata n. sp., both stemming from the coastal defense structure area of Kuala Nerus, Terengganu, east coast of Peninsular Malaysia. These two species represent the smallest one ever recorded in their genera; G. minuta n. sp. is unique among all species of Galathowenia Kirkegaard, 1959 because of the following combination of features: brownish eyespots at head, first and second segments twice as long as the third, pigmentation encircling the fourth segment, seventh segment longest, and two blunt pygidial lobes. Conversely, O. unipinnata n. sp. is different from its congeners because of the presence of three pairs of tentacles on the branchial crown with three minor and simple ramifications, one of the pairs located solitary at the midventral side. Detailed descriptions and illustrations, as well as several comments on the biological and ecological traits of these two new species are included. Furthermore, identification keys to the species of oweniids recorded in the South China Sea (SCS) region are also provided.