Chirostyloidean squat lobsters (Crustacea: Decapoda: Anomura) from the Galapagos Islands.

Seven species of chirostyloidean squat lobsters are reported from the Galapagos Rift zone and Galapagos platform: Eumunida subsolanus n. sp. (Eumunididae), Heteroptychus galapagos n. sp., H. nautilus n. sp. (Chirostylidae), Uroptychus bellus Faxon, 1893, U. compressus n. sp., U. occidentalis Faxon, 1893 (Chirostylidae), and Sternostylus defensus (Benedict, 1902) (Sternostylidae). All new species are described and illustrated, and the two species previously known from the Galapagos Islands, Uroptychus bellus and U. occidentalis, are re-illustrated from respective lectotypes, herein designated, since both original descriptions were only brief. Both the species of Heteroptychus and Eumunida subsolanus are the first representatives of their respective genera in the eastern Pacific and the latter is also the first record for the family Eumunididae in the region.

Rediagnosis of the squat lobster genus Gastroptychus Caullery, 1896, with a new genus Sternostylus and a new family Sternostylidae (Crustacea: Decapoda: Anomura: Chirostyloidea).

The chirostyloidean squat lobster genus Gastroptychus Caullery, 1896 is revised and is split into two genera: Gastroptychus sensu stricto (type species, Ptychogaster spinifer A. Milne-Edwards, 1880) and Sternostylus new genus (type species, Ptychogaster formosus Filhol, 1884). Gastroptychus sensu stricto, is restricted to nine species with a sternal plastron, at sternite 3, abruptly demarcated from the preceding sternites (excavated sternum) by a distinct step forming a well-defined transverse or concave anterior margin at the articulation with maxillipeds 3, the maxillipeds 3 widely separated, with the distal parts accommodated in the excavated sternum between the left and right maxillipeds 3 when folded, and the P2-4 dactyli with the terminal spine demarcated by a suture. Sternostylus new genus, represented by 12 species, has the sternite 3 anteriorly bluntly produced medially and steeply sloping anterodorsally to the anterior sternite, with a pair of spines directly behind the anterior margin, the left and right maxillipeds 3 adjacent, and the P2-4 dactyli ending in an indistinctly demarcated corneous spine. The above-mentioned characters of Gastroptychus are consistent with Chirostylidae sensu stricto. Published molecular phylogenies indicate, however, that Sternostylus is the sister group to all the other Chirostylidae, and is designated the type genus of a new family, Sternostylidae.

Uroptychus atlanticus, a new species of squat lobster (Crustacea: Decapoda: Anomura: Chirostylidae) from the western Atlantic Ocean.

A new species of squat lobster, Uroptychus atlanticus, is described on the basis of a female specimen taken at a depth of 713-841 m in the southeastern Gulf of Mexico. The new species is readily distinguished from all known species of the genus from the western Atlantic by the very spinose carapace and pereopods, and a transverse row of spines on each of the abdominal tergites 1 and 2.

Uroptychus nitidus (A. Milne-Edwards, 1880) and related species (Crustacea: Decapoda: Anomura: Chirostylidae) from the western Atlantic.

Eight species of squat lobsters of the genus Uroptychus are reported from the western Atlantic based on the collections of the Museum of Comparative Zoology at Harvard, the Smithsonian Institution and Texas A&M University. Uroptychus nitidus (A. Milne-Edwards, 1880) is reviewed and redescribed, with a syntype taken at Blake Station 200 off Martinique designated as the lectotype. Uroptychus alphonsei n. sp. is named for U. nitidus variety C Chace, 1942, U. fenneri n. sp. for U. nitidus variety A Chace, 1942, and U. janiceae n. sp. for U. nitidus variety B Chace, 1942; U. lindae n. sp. is described on the basis of specimens collected by the Alaminos in the Caribbean Sea off northern Columbia; U. rafai n. sp. is described based on a sole specimen taken from the Straits of Florida; U. reedae n. sp. is described from among the syntypes of U. nitidus; and U. uncifer (A. Milne-Edwards, 1880) is redescribed to elaborate on its specific status, with the designation of lectotype from Blake Station 299 off the coast of Barbados. The number of species of Uroptychus from the western Atlantic now stands at 21. A key to these species is provided.

Uroptychus minutus Benedict, 1902 and a closely related new species (Crustacea: Anomura: Chirostylidae) from the western Atlantic Ocean.

A new squat lobster, Uroptychus marissae, is described based upon two specimens taken associated with the antipatharian Tanacetipathes sp. from the northern Gulf of Mexico, at a depth of about 90 m. It closely resembles U. minutus Benedict, 1902, known only from the type material from off Trinidad. The original description is so brief that an opportunity is taken here to redescribe it to help discriminate between the two species.