NO. 3 THE RELATIONSHIPS OF QUEMISIA GRAVIS — RAY 9 



nouncements on the detailed affinities of Clidomys must await careful 

 study of specimens already available and the collection of supplemen- 

 tary material, there can be no doubt that, even if Clidomys should 

 prove to be a heptaxodontid, its relationships to the eastern Carib- 

 bean forms are remote. Thus, the Heptaxodontinae at present in- 

 clude with certainty only Amblyrhiza on Anguilla and St. Martin, 

 and Elasmodontomys s on Puerto Rico. 



If Quemisia is not a heptaxodontine, then the only remaining 

 probable relatives among Antillean caviomorphs are the capromyids. 

 Of course, it is possible that Quemisia represents a separate invasion 

 from the mainland and thus has no close Antillean relatives. This 

 alternative is in my opinion the more radical and is unsupportable 

 on the basis of present, admittedly meager, evidence. Prior to X- 

 raying the mandible of Quemisia, I had confidently placed the genus 

 in the family Capromyidae, comparing it most closely with Plagio- 

 dontia. Discovery of diphyodonty at the P 4 locus in the specimen 

 makes this assignment untenable at present, but evolutionary much 

 more interesting if correct. The transfer of Quemisia to the 

 Capromyidae would disrupt not only the concept of that family but 

 current superfamilial groupings as well (cf. Schaub, 1953, pp. 396- 

 397 ; Wood, 1955, pp. 181-182 ; Wood and Patterson, 1959, pp. 323- 

 327), which is not warranted on the basis of inadequate knowledge 

 of a single genus. Pending discovery of more material, Quemisia 

 may be retained, incertae sedis, in the Heptaxodontidae, recognizing 

 that this is a temporary expedient. 



Considering Quemisia for the moment as a capromyid, the impres- 

 sion is strengthened that Hispaniola has been an important center of 

 capromyid radiation in the Antilles, in terms of both number of 

 forms (five genera and nine species on Hispaniola) and breadth of 

 diversification. The history of Antillean capromyid evolution as- 

 suredly is not a simple one of differentiation on and dispersal from 

 Hispaniola or any one island, but Plagiodontia, Isolobodon, and 

 Aphaetreus (with Quemisia?) do seem to constitute a natural as- 

 semblage (the Plagiodontia group), accounting for four genera and 

 eight species on Hispaniola. The importance of this group in the 

 Quaternary fauna of Hispaniola at least suggests origin of Isolobodon 

 on that island, followed by eastward dispersal by natural means or 

 human transport (or both) through Mona, Puerto Rico, St. Thomas, 

 and St. Croix. The Capromys group (including Capromys, Geo- 



" Heptaxodon is based on juvenile individuals of Elasmodontomys and is the 

 junior synonym (Ray, 1964b). 



