Three new species of Sternaspidae (Annelida: Sedentaria) from Thailand Author Plathong, Jintana 0000-0003-3473-1680 Marine Ecosearch Management Co., Ltd., 4 / 31 Moo 1, Namnoi, Hat Yai, Songkhla, 90110, Thailand. & Marine Science Learning Center, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand. sakanan 2004 @ yahoo. com; https: // orcid. org / 0000 - 0003 - 3473 - 1680 sakanan2004@yahoo.com Author Plathong, Sakanan 0000-0003-3473-1680 Marine Science Learning Center, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand. sakanan 2004 @ yahoo. com; https: // orcid. org / 0000 - 0003 - 3473 - 1680 sakanan2004@yahoo.com Author Salazar-Vallejo, Sergio I. 0000-0002-6931-0694 Depto. Sistemática y Ecología Acuática, El Colegio de la Frontera Sur, Chetumal, Quintana Roo, México. savs 551216 @ hotmail. com; https: // orcid. org / 0000 - 0002 - 6931 - 0694 savs551216@hotmail.com text Zootaxa 2021 2021-12-13 5081 3 373 388 journal article 2997 10.11646/zootaxa.5081.3.4 28190fde-35c3-4e10-b6a0-a45027518be0 1175-5326 5775763 241F3263-0DFB-4372-8CA8-1537BF9D0B91 Genus Petersenaspis Sendall & Salazar-Vallejo, 2013 Diagnosis (after Fiege 2019 ). Sternaspids with introvert hooks subdistally expanded. Preshield region with eight segments. Ventrocaudal shield stiff with poorly developed ribs and no concentric lines. Key to species of Petersenaspis Sendall & Salazar-Vallejo, 2013 (Modified after Salazar-Vallejo 2017 ) 1A. Shield orange or reddish, rarely purple.................................................................... 2 1B. Shield bluish, anterior margin projected forward; anterior segments with four bands of dark brown papillae............................................................................................. P. salazari Wu & Xu, 2017 ; South China Sea 2A. Shield with anterior margin truncate; fan with median notch only............................................... 3 2B. Shield with anterior margin projected forward............................................................... 4 3A. First-three chaetigers with about 10 introvert hooks per side............................... P. capillata Nonato, 1966 ; Central and Southern Brazil 3B. First three chaetigers with about 14–16 introvert hooks per side........................ P. deani Salazar-Vallejo, 2017 ; Costa Rica 4A. Radial ribs well defined; fan with a median and two lateral notches.............................................. 5 4B. Radial ribs barely defined; fan with median notch, no lateral notches................. P. harrisae Salazar–Vallejo, 2017 ; South Africa 5A. Anterior shield expanded and lateral shield strong curved..................................................... 6 5B. Anterior shield rounded, not expanded and lateral shield rounded......... P. palpallatoci Sendall & Salazar-Vallejo, 2013 ; off Kalibo, Philippines 6A. Shield with solid pigmentation, never banded............................................................... 7 6B. Shield with 2–3 concentric color bands, without ciliary clumps................................. P. narisarae sp. nov. ; Gulf of Thailand, Western Pacific 7A. Shield butterfly wing-shaped, dark reddish without ciliary clumps................................ P. apinyae sp. nov. ; Gulf of Thailand, Western Pacific 7B. Shield heart- or kidney-shaped, dark purple with ciliary clumps; posterior margin of fan strongly projected, and laterally expanded........................................................................... P. pakbaraensis sp. nov. ; Andaman Coast, Southern Thailand