MATERIALS AND METHODS

The original and early finds from Fiene were collected in situ by Robert L. Levin. Subsequently, we collected and gently washed approximately 400 pounds of matrix through a fine screen (0.7 mm mesh). The recovered arivicolines consisted primarily of isolated teeth. Four m1s are in mandibles. The specimens are housed at Fort Hays State University in the Sternberg Museum of Natural History, Section of Vertebrate Paleontology (FHSM VP), Hays, Kansas.

Measurements were taken on the lower first molar (m1) and the upper third molar (M3) to the nearest 0.01 mm using a Gaertner measuring microscope. Variables measured on m1 (Figure 2.3) were the same as taken by Pfaff (1990) with the addition of the width of the anterior cap (A–A’) from Repenning (1992). Terminology used when discussing the teeth is defined in Figure 3 and where first used in the text. Ratios for the variables measured on m1 were determined using the method proposed by Van der Meulen (1978). Variables measured on the M3 (Figure 2.4) were defined by Repenning (1992). Descriptive statistics were determined for each variable measured on m1 and M3. The mean values of the variables for each morphotype were compared using a Student's t test with P <0.05. Statistical analyses were performed using Micosoft Excel^©. Juvenile specimens and those etched or damaged so that none of the variables could be measured were not included in the analyses. Measurements of teeth from other sites were taken from the literature.