COMPARISON OF SOME GENERA AND SPECIES OF BOX CRABS 



(BRACHYURA: CALAPPIDAE), SOUTHWESTERN NORTH ATLANTIC, 



WITH DESCRIPTION OF A NEW GENUS AND SPECIES 



Austin B. Williams' and C. Allan Child^ 



ABSTRACT 



Five species of calappid crabs from the southwestern Atlantic that belong to the genera Calappa, Cydozo- 

 dion new genus, and Paracyclois are analyzed on the basis of morphology, morphometries, geographic, 

 and bathymetric range. Calappa tortugae, new rank, known in the past as C. angusta in the broad sense, 

 is restricted and compared with its eastern Pacific twin species, C. satissurei. Two small species placed 

 in Cyclozodion were until now unrecognized and partly included in Calappa angusta, broad sense. Cyclozo- 

 ditm angnstum. a relatively smooth form, is the tj-pe species of the new genus, and C. tuheratum, a rough 

 form superficially resembling Calappa tortugae, is described as new. Species of both Paracyclois and 

 the Early Tertiary genus Calappilia in which it was subsumed are reviewed, the former is revalidated, 

 and its only two species, western Atlantic P. atlantis and western Indo-Pacific P. milneedwardsii, are 

 rediagnosed. Diagnoses and discriminations are accompanied by illustrations. Keys to caJappid genera 

 in the Western Atlantic, and for identification of Cyclozodion and Paracyclois species are given. 



Holthuis (1958) revised five species of West Indian 

 box crabs, Calappa cinerea Holthuis 1958, C.flam- 

 mea (Herbst 1794), C. nitida Holthuis 1958, C. 

 ocellata Holthuis 1958, and C. sulcata. Rathbun 1898, 

 but a species from that region known until now as 

 C. angusta A. Milne Edwards 1880 was not included 

 in his paper because the collection he studied in- 

 cluded no representatives of that form. We find that 

 this latter species is not at all well defined, and the 

 purpose of this paper is to clarify its status and that 

 of similar species in related genera. 



Samples of decapod crustaceans from exploratory 

 trawling by the Bureau of Commercial Fisheries RV 

 Pelican, U.S. Fish and Wildlife Service RV Combat, 

 National Marine Fisheries Service RV Silver Bay, 

 RV Oregon, and RV Oregoji II deposited in the 

 crustacean collection of the National Museum of 

 Natural History (USNM), Smithsonian Institution, 

 contain specimens of a seldom reported calappid 

 crab, Paracyclois atlantis Chace 1939, 1940 from 

 the Caribbean region of the western North Atlan- 

 tic, and representatives of a genus not previously 

 recognized. Two small calappid species in the cata- 

 logued USNM crustacean collection have been at- 

 tributed to Calappa angusta A. Milne Edwards 1880 

 by Rathbun (1937) and other authors (see Williams 



'Systematics Laboratory, National Marine Fisheries Service, 

 NOAA, National Museum of Natural History, Washington, DC 

 20560. 



^Department of Invertebrate Zoology, National Museum of 

 Natural History, Washington, DC 20560. 



Manuscript accepted August 1988. 

 Fishery Bulletin, U.S. 87:105-121. 



1984) on the basis of what were thought to be juve- 

 nile characters exhibited by the carapace of that 

 species. Review of the material in the USNM shows 

 this concept to be in error. Moreover, representa- 

 tives of the extant type series of C. angusta in the 

 Museum of Comparative Zoology (MCZ), Harvard 

 University, consist of very small juveniles, a holo- 

 type and four paratypes in which definitive char- 

 acters are poorly developed, that surprisingly belong 

 not to one but three calappid species. "Calappa 

 angusta" as presently understood is in reality a com- 

 plex of species belonging in Calappa Weber 1895 

 and the previously unrecognized genus. 



Only two species of Paracyclois Miers 1886 

 have been described, the above mentioned, and the 

 type species, P. milneedwardsii Miers 1886, from 

 the western Indo-Pacific. Glaessner (1969) synon- 

 ymized Paraclyclois with Calappilia A. Milne 

 Edwards 1873, considered until that time to in- 

 clude only species of Middle Eocene to Upper 

 Oligocene ages in North America, Europe, and the 

 East Indian region, but did not discuss reasons for 

 his action. Because our determinations involved 

 generic placement of material from trawl samples, 

 we reviewed literature concerned with both of 

 these genera and studied specimens of selected 

 species of Calappilia in the fossil crustacean 

 collection of the USNM. Austin B. Williams devel- 

 oped the text, C. Allan Child rendered the draw- 

 ings, and both of us identified and cross-checked 

 material. 



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