AMPHINECTOMYS-SAVAMIS MALYGIN GEN-N ET SP -N, A NEW GENUS AND A NEW SPECIES OF WATER RAT (CRICETIDAE, RODENTIA) FROM PERUVIAN AMAZONIA

Comparative morphological, karyological and electrophoretic analyses o f 29 individuals of Nectomys squamipes from 4 different localities of Amazonia and an unsual specimen of water rat, captured on October 29, 1991 in primary rainforest, 7 km to the east of the village Henaro Err era on the right bank of the Ukayaly river, Requena province, Departme nt Loreto, Peru (04-degrees-55' SL and 73-degrees-45' WL) were carried out. The single specimen was defined as belonging to a new genus and a new species (holotype N S-155533, male, deposited in the collection of the Zoological Museum of Moscow State University), Amphinectomys sa vamis Malygin sp. n. The monotypical genus differs from the genus Nect omys s. 1. by several external characters (the webbing on hind feet ex tends over all digital phalanges up to the claws), the pattern of pela ge coloration, 8 quantitative and 10 qualitative cranial characters, k aryotype (2n = 52; NF = 66) and by the electrophoretic mobility of 5 o ut of 14 enzymes. A table containing morphometric data on 5 external a nd 14 cranial measurements as well as the values of parietal index and the weight of a specimen of A. savamis and 22 adult and subadult indi viduals of N. squamipes is given. The single specimen of A. savamis wa s trapped in primary rainforest, approximately 5 km to the North - Eas t of the spot, where 21 individuals of N. squamipes were caught. These two species inhabit different biotopes. The new species was found in the forest near a stream, whereas Nectomys spp. occur in open areas.