PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 108(2):338-369. 1995. Systematic studies of oryzomyine rodents (Muridae: Sigmodontinae): definition and distribution of Oligoryzomys vegetus (Bangs, 1902) Michael D. Carleton and Guy G. Musser (MDC) Divison of Mammals, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, U.S.A.; (GGM) Department of Mammalogy, American Museum of Natural History, New York City, New York 10024, U.S.A. Abstract. —Morphologicsil and distributional evidence is presented to doc-ument the specific stature of Oligoryzomys vegetus (Bangs, 1 902) and to clarify its identification with respect to Central American populations of O.fulvescens. The geographic range of O. vegetus covers not only the mountains of western Panama but also the Cordilleras de Tilaran, Central, and Talamanca of Costa Rica, generally above 1000 meters elevation and within lower montane and montane biotic zones. Within southern Central America, populations of O. fulvescens usually occur from sea level to 1000 meters in wet tropical and subtropical associations, but numerous instances of sympatry with O. vegetus are recorded in the 1000-1500 meter zone. Two species-group taxa, both de-scribed from Costa Rica, are allocated to subjective junior synonymy under O. vegetus, namely Oryzomys fulvescens creper GoodWin, 1945 and Oryzomys fulvescens reventazoni Goodwin, 1945. With improved understanding of its taxonomy and geographic range, Oligoryzomys vegetus emerges as another species of small terrestrial mammal restricted to the highlands of Costa Rica and western Panama, a region which has formed a modest center for mam-malian endemism in southern Central America. In 1902, Outram Bangs reported two spe-Two years later, Allen (1904a) examined cies of Oligoryzomys occurring together at seven additional specimens from Boquete, Boquete and its vicinity, on the southeast-collected by J. H. Batty in 1901, and com-em slopes of Volcan de Chiriqui between pared them with Bang's original material. 3800 and 4800 ft in western Panama. Five Allen (1904a:69) at first did not appreciate specimens, ranging in age from young to old the distinctions between the forms Bangs adults, were identified as Allen's (1893) hdid id^nXifiQd 2iS costaricensis dind vegetus: Oryzomys costaricensis; 1 3 others, howev-"The type and 1 2 topotypes of O. vegetus, er, about the same in age span, were larger-kindly sent me for examination by Mr. bodied with darker fur, bigger hindfeet, and Bangs, do not differ appreciably from the longer, monocolored tails. The latter Bangs type, 3 topotypes, and additional Costa Rica (1902) described as a new species, Oryzo-specimens of O. costaricensis. They also mys (Oligoryzomys) vegetus. To Bangs, the agree with the 7 Boquete specimens col-collection of Oligoryzomys from Volcan de lected by Mr. Batty, which I unhesitatingly Chiriqui was clearly separable into two spe-refer to O. costaricensis.'^ In a brief com-cies, and the comparative data he listed sup-mentary on previously described forms of port this view. Oligoryzomys, Allen later stated (191 6:526):
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