Eusyllinae, Exogoninae and Autolytinae (Syllidae: Polychaeta) from the Southern Mexican Pacific, with the description of three new species.

Previous studies have dealt recently with syllid polychaetes in soft sediments from Acapulco Bay (Southern Mexican Pacific) with new species and new records of the subfamily Syllinae published, but the remaining subfamilies found in the area had not been included. This study deals with syllids belonging to those subfamilies: Eusyllinae, Exogoninae and Autolytinae, since the Anoplosyllinae were not found. Three species are described as new: Odontosyllis septemdentata n. sp., characterized by having bidentate falcigers and a trepan with 7 teeth alternating in size; Sphaerosyllis tetralobata n. sp., which is characterized by having unidentate compound chaetae and segments divided in four annuli, and Prosphaerosyllis sotoi n. sp., characterized by having compound chaetae with short and hooked unidentate blades, and by being the only species of the genus that lacks dorsal cirri in the second parapodia. Additionally, Westheidesyllis gesae (Perkins 1981) is newly recorded for the Pacific Ocean, while Odontosyllis fulgurans (Audouin & Milne Edwards 1834), Erinaceusyllis bidentata (Hartmann-Schröder 1974) and Myrianida dentalia (Imajima 1966) are recorded for the first time from the Mexican Pacific coasts.

Description of two new species of Pisione (Polychaeta: Sigalionidae) and first record of Pisione galapagoensis Westheide in the Southern Mexican Pacific.

The genus Pisione Grube 1857 was composed up to now of 40 species and 4 subspecies. Although distributed worldwide, in the Mexican Pacific little is known about its taxonomy and distribution, and only two species of this genus have been recorded: Pisione longispinulata Aguado & San Martín, 2004 and Pisione remota (Southern, 1914), but the records of the latter remain questionable. For this study, 406 pisionids from soft sediments of Acapulco Bay, Southern Mexican Pacific, were examined. Two new species are described: Pisione hippocampus n. sp. characterized by having protruding notoaciculae in posterior chaetigers, the second dorsal cirrus elongated and copulatory organs resembling the body shape of a seahorse and Pisione sanmartini n. sp. characterized by having protruding notoaciculae from the first chaetiger, buccal aciculae with a distal crenulate plate resembling the edge of a shell, and prechaetal bifurcated lobes along the body. Pisione galapagoensis Westheide, 1974 is newly recorded for the Mexican Pacific, its known distribution being extended northward from the Galapagos Islands and Panama. A comparative table with the main diagnostic characters and the distribution of all the species so far described in the genus Pisione is included, as well as a key to the species of the Eastern Pacific.