FIGURE 1. Apatemyid localities in Sioux County, Nebraska. R: Raben Ranch locality of Ostrander (1980, 1987); A: Anthill locality of Hough and Alf (1956); T: Twin Buttes locality of Ostrander (1985); S: Sand Creek locality; O: Orella Road locality; W: Whitehead Creek locality.

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FIGURE 2. Apatemys specimens from the Whitehead Creek locality. 1, left M2 (UMPC 14190) and 2, left M3 (UMPC 14191). Teeth are shown in occlusal view. Scale is approximately 1 mm.

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FIGURE 3. Apatemyid first molars from Raben Ranch. 1 and 2, right m1s of Sinclairella dakotensis (SDSM 10241) and 3, right m1 of Apatemys sp. (SDSM 10242). Teeth are shown in occlusal view. Scale is approximately 1 mm.

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FIGURE 4. Plot of apatemyid M2 width x length. Circles indicate Sinclairella dakotensis specimens. Squares indicate Apatemys specimens. The open square indicates the Whitehead Creek specimen described in this study. Data for AMNH 56046 and YPM 15284 are from West and Atkins (1970). Data for (RSM) P2374.006 are from Meyer (2007). Sinclairella data come from Clemens (1964), Cavin and Samuels (2012), and this study.

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FIGURE 5. Plot of natural log width x length of M2, open symbols above diagonal, and m1, solid symbols below diagonal from different apatemyid species, the M2 from Whitehead Creek (UMPC 14190), and the m1 from Raben Ranch (SDSM 10242). Note the compatible size relationship between the specimens from the Chadronian of Sioux County, Nebraska (circles). Data are compiled from the following sources: Apatemys chardini (Gingerich, 1982; Ma, 1998), A. bellulus (Gazin, 1958; Ma, 1998), A. bellus (Gazin, 1958; West, 1973; Ma, 1998), Sinclairella dakotensis (Clemens, 1964; Ostrander, 1987; Cavin and Samuels, 2012; this study).

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FIGURE 6. Teeth of Sinclairella dakotensis from Sioux County, Nebraska. 1, right M1 (UMPC 14860); 2, right M3 (UMPC 14864); 3, left P4 (SDSM 10392); 4, left M1 (UMPC 13937); 5, left M2 (UMPC 14862); 6, right M3 (UMPC 14863) (reversed); 7, left p2 (SDSM 10244) (reversed); 8, right m1 (UMPC 14861); 9, left m2 (UMPC 14866) (reversed); 10, left m3 (SDSM 10245) (reversed); 11, right m1 (UMPC 13938) and 12, left m2 (UMPC 13869). Teeth are shown in occlusal view. Divisions in scale are approximately 1 mm.

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