Peromyscus and Ochrotomys from the Pleistocene of Reddick, Florida

Abstract

Mandibles of 416 Peromyscus and Ochrotomys from the Pleistocene of Reddick, Florida, were examined. Molar width for m2 and m3, the alveolar length for the molar series, and the first two molars combined were measured. Code numbers were given to four qualitative categories of ml and m2. Six quantitative by quantitative, six qualitative by qualitative, and 16 qualitative by quantitative scatter diagrams were constructed by a computer. With the aid of these diagrams four species were segregated. Members of species A occupied a distinct cluster in the quantitative by quantitative diagrams. Members of species B occupied distinct sectors of the qualitative by qualitative diagrams. Members of species C and D were distinguished by utilizing the single observation formula to calculate the maximum and minimum likely value on the distribution of logarithms calculated from the values of the smallest and largest specimens, respectively, in each quantitative by quantitative diagram. Species A, B, C, and D are referable respectively to Peromyscus floridanus, Ochrotomys nuttalli, P. gossypinus and P. polionotus. Inasmuch as the Reddick site appears no younger than late Sangamon, speciation of these four species must have occurred at an earlier time.