4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



knowledge that at one time M. portoricensis and M. f rater were con- 

 temporaneous on Puerto Rico. Monophyllus portoricensis has a long 

 diastema (like other Greater Antillean forms) and M. frater has a 

 short one (like the Lesser Antillean assemblage). Thus, Puerto Rico 

 is interpreted as once having been inhabited by two stocks of Mono- 

 phyllus, one Greater Antillean and the other Lesser Antillean, of 

 which the latter is presumed presently to be extinct. 



Once this dichotomy is recognized, the two species can be shown 

 to differ in some average cranial measurements. Greatest length 

 of skull in Greater Antillean bats varies from 19.0 to 23.9, for example, 

 whereas that of Lesser Antillean bats ranges from 21.4 to 24.2. Post- 

 orbital constriction shows almost no overlap, with Greater Antillean 

 Monophyllus having measurements of 3.8 to 4.6 and Lesser Antillean 

 specimens having measurements of 4.5 to 5.0 Less trenchant differ- 

 ences include length of forearm (35.5 to 42.8 in Greater Antilles, 

 38.8 to 45.7 in Lesser Antilles). Although facial adornments have 

 been gainfully employed to distinguish between congeneric species 

 of other genera of phyllostomatids, the noseleaves and chin details 

 in all Monophyllus appear identical. It is possible that we are over- 

 emphasizing the single dental character between the two species 

 and that they are indeed preferably considered as conspecific, but 

 such an action tends to obscure the one major difference between the 

 two geographic segments of Monophyllus. It also poses the problem 

 of the relationships of M. frater, which would then have to be regarded 

 as a local derivative of M. portoricensis on Puerto Rico — a derivative 

 oddly like its Lesser Antillean congeners — or else double invasion 

 of the island by widely different stocks of the same species would 

 need to be postulated. We feel that our arrangement is defensible 

 zoogeographically as well as morphologically and provides a more 

 meaningful systematic arrangement than that currently in use. 



Monophyllus Leach 



Monophyllus Leach, 1821, p. 75. [Generotype: Monophyllus redmani Leach.] 

 Monophyllus redmani Leach 



Definition. — A species of Monophyllus characterized by a com- 

 bination of small to large size (total length 58-80), small hind foot 

 (9-14), small ear (ear from notch 9-14), short forearm (35.5-42.8), 

 small skull (greatest length 19.0-23.9), narrow postorbital constric- 

 tion (3.8-4.6), and the upper premolars separated by a disatema one- 

 half or more the length of the first premolar. The pelage is some 

 shade of brown, tending generally toward paler shades. 



