PENIS MORPHOLOGY AS A DISTINCTIVE CHARACTER OF THE MURINE OPOSSUM GROUP (MARSUPIALIA DIDELPHIDAE) - A PRELIMINARY-REPORT

Penis morphology, associated with other features, has been suggested a s an identification trait and an additional variable useful for system atic arrangement of the murine opossum group. This is a numerically im portant group of American marsupials, with similar external characters but without yet a systematically arranged source list. The penis morp hology of four species, Micoureus cinereus, Gracilinanus agilis, Marmo sops incanus, and Marmosa murina is described. The internal anatomical aspects are similar in the four species. The main differences between the species are the form of the tip of the glans and the length of th e urethral grooves. The four species present distinctive external char acters of the penis that permit their identification in the field and could possibly be used as a taxonomic tool. Nevertheless, additional s tudies involving other species of the group are needed in order to det ermine the value of this feature in the systematics of the group as a whole.