Tillomys senex Marsh, 1872

Kelly, Thomas S. & Murphey, Paul C., 2016, Mammals from the earliest Uintan (middle Eocene) Turtle Bluff Member, Bridger Formation, southwestern Wyoming, USA, Part 1: Primates and Rodentia, Palaeontologia Electronica 7 (8), pp. 1-55 : 21-24

Tillomys senex Marsh, 1872

Figure 7.5-7 , Table 4

Referred specimens. From SDSNH Locality 5841: m1 or 2, SDSNH 110363. From UCM Locality 92189: m1 or 2, UCM 95753, 78451. From DMNH Locality 4672: m1 or 2, DMNH 75279, 75328.

Description. The five m1 or 2s from the TBM are very similar in size and occlusal morphology. They have a relatively short anterior cingulid that extends lingually from the anterior edge of the protoconid to the anterolabial base of the metaconid. The primary cusps are robust with the hypoconid being the largest, the protoconid the second largest, and the metaconid and entoconid being about subequal in size. The metalophulid II (posterior arm of the protoconid) is incomplete, extending lingually from the apex of the protoconid to terminate near and slightly posterior to the posterolabial base tial).

of the metaconid. The entoconid is anteroposteriorly compressed with an incomplete hypolophid that extends posterolabially (obliquely) from the entoconid apex to terminate near the junction of the hypoconid and posterior cingulid. The mesoconid is transversely elongate and isolated from the protoconid and hypoconid. The posterior cingulid is robust, extending lingually from the hypoconid to terminate near the posterior base of the entoconid, where it is separated from the entoconid by a weak valley.

Remarks. Two species of Tillomys are recognized from the Bridger Formation, T. senex and T.? parvidens ( Troxell, 1923b; Wilson, 1938a, b; Walton and Porter, 2008). Both species are known only from lower dentitions. The five TBM lower molars are compatible in size and occlusal morphology to those of T. senex , including robust tall trigonids, moderately strong metastylid crests, and obliquely orientated hypolophids.

Figures

FIGURE 7. Larger Sciuravidae from TBM. 1, Sciuravus nitidus, RP4, UCM 68430. 2-4, Taxymys lucaris: 2, RM1 or 2, UCM 68307; 3, LM1 or 2, UCM 95762; 4, LM3, DMNH 75336. 5-7, Tillomys senex: 5, Lm1 or 2, DMNH 75328; 6, Rm1 or 2, DMNH 75279; 7, Rm1 or 2, SDSNH 110363. 8-9, Tillomys? parvidens: 8, Rm1 or 2, SDSNH 110379; 9, Lm3, DMNH 75288. All occlusal views. Scale bar equals 1 mm.