Syllis alternata Moore, 1908: 323–325, text–fig. la–f.— San Martín & Viéitez, 1984: 153, figs 1, 2.
Syllis (Typosyllis) alternata Gardiner, 1976: 141, fig. 13b, c.— Uebelacker, 1984: 30–141, figs 30–136.
Typosyllis alternata. Imajima, 1966a: 273, fig. 58a–l.
Material examined. EAST TIMOR. East of Cape Fatucama, 300 m off Jesus Backside Beach, 08°31’16”S125°36’46”E, on Caulerpa geminata, 10.3 m depth, 19 Sep 2012, coll. L.E. Hughes, 1 spec. (AM W.45654).
Habitat. In seaweeds, concretions of calcareous algae and dead coral (San Martín 2003).
Distribution. Northeastern Pacific Ocean (from Alaska to California), Chukchi Sea, Japan, Caribbean Sea, Gulf of México, northeastern Atlantic, Mediterranean Sea, Indian Ocean, Indonesia, Arabian Sea (San Martín 1992; San Martín 2003; Aguado et al. 2008; Lucas et al. 2020). Apparently cosmopolitan, mainly in the northern hemisphere, but some of these records are probably the result of misidentifications, and S. alternata may be a species-complex (Lucas et al. 2020). First record for East Timor.