Redescription of Cloeosiphon aspergillus (de Quatrefages 1866) (Sipuncula: Aspidosiphonidae) and description of a new species from the southern Mexican Pacific

A redescription of Cloeosiphon aspergillus is presented based on the type material and additional specimens from Madagascar, South Africa, and New Caledonia. Cloeosiphon aspergillus is characterized by its pineapple-shaped anal shield, bidentate hooks arranged in rings, and a continuous longitudinal muscle layer. Additionally, a new species, Cloeosiphon mexicanus sp. nov. is described from the southern Mexican Pacific. This new species differs from C. aspergillus by having an inconspicuous secondary tooth on posterior hooks and the absence of spherical units along the basal margin of the anal shield. Furthermore, a discussion on the synonyms of C. aspergillus is included. This study expands the taxonomic knowledge of the genus Cloeosiphon and highlights the importance of the detailed description for accurate species recognition.