Abstract
Exosphaeroma amplicauda (Stimpson, 1857) from the west coast of North America is reviewed and redescribed and revealed to be a group of closely related species. A neotype is designated and the species redescribed based on the neotype and topotypic specimens. Exosphaeroma amplicauda is known only from the coast of California, at Marin, Sonoma and San Mateo Counties. Exosphaeroma aphrodita (Boone, 1923), type locality La Jolla, California and previously considered nomen dubium is taken out of synonymy and re-validated. A further three species: Exosphaeroma paydenae sp. n., Exosphaeroma russellhansoni sp. n., and Exosphaeroma pentcheffi sp. n. are described herein. Sphaeroma octonctum Richardson, 1899 is placed into junior synonymy with Exosphaeroma amplicauda. A key to the Pacific West Coast Exosphaeroma is provided.
Highlights
Exosphaeroma pentcheffi sp. n. unlike the other Exosphaeroma species in this ‘species flock’ lacks strong sexual dimorphism and is unique in that females shares the same dorsal ornamentation as males; males differ from females in having slightly stronger tubercles, longer pleotelson and longer uropods
E. pentcheffi sp. n. males can be identified by: pereonites 5 and 6 having 7 longitudinal rows of strong tubercles, pereonite 7 with a strong median process with 3 lateral tubercles; pleotelson dorsum with 3 strong medial tubercles on either side of the longitudinal axis, with 1 strong medial tubercle between the longitudinal axis and lateral margin, pleotelson covered with numerous, additional, small tubercles (Figures 13A, B; 24A, D, E, F)
N. Dean Pentcheff contributed to field collections from Washington to Pt. Fermin, and Todd Haney and Ernie Iverson contributed specimens from San Diego and several other locals
Summary
We redescribe Exosphaeroma amplicauda from the type locality Tomales Bay (central California coast) and E. aphrodita from San Diego, and describe three new closely related species: E. paydenae sp. Pleotelson length 2.6 width, dorsal surface with 2 medium tubercles on either side of longitudinal axis; posterior margin of pleotelson acuminate (Figure 21E, F).
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