Microsyops annectans ( 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 : 8

Microsyops annectans ( Marsh, 1872)

Figure 3.5-7 , Table 1

Referred specimens. From UCM Locality 92189: m1, UCM 67984; partial dentary with m2, UCM 70315.

Description. The partial dentary is missing the ascending ramus and the portion of the horizontal ramus anterior of the p2 alveolus. Its morphology is typical of that of Microsyops , being relatively deep (depth of ramus below m2 = 5.50 mm) and with the mental foramen positioned below the posterior root of p3. The m1 differs from the m2 by being narrower relative to its length and by having the paracristid slightly less robust. Otherwise the m1 and m2 are very similar. The metaconid, protoconid, and hypoconid are robust and bulbous, whereas the paraconid is reduced to a small, but distinct cusp. The trigonid is narrower than the talonid and compressed anteroposteriorly with the paraconid positioned relatively close to the metaconid. The talonid basin is relatively deep with the cristid obliqua extending anterolingually from the hypoconid to join the posterior wall of the trigonid, lingual of the protoconid apex. The hypoconulid is smaller than the entoconid and positioned relatively close to it, giving these cusps a somewhat twinned appearance.

Remarks. The TBM Microsyops specimens agree well in size and molar occlusal morphology to those of Microsyops annectans (e.g., Marsh, 1872; Wortman, 1903; Szalay, 1969a; Silcox and Gunnell, 2008) and are referred to the species.

Figures

FIGURE 3. Microsyopidae from TBM. 1-4, Uintasorex parvulus: 1, RM1 or 2, SDSNH 110359; 2-3, Rdp4, SDSNH 110358; 4, Lm2, DMNH 75287. 5-7, Microsyops annectans: 5, Rm1, UCM 68541; 6-7, partial dentary with Rm2, UCM 70315. 1-2, 4-6, occlusal views. 3 and 7, labial views. Scale bars equal 1 mm for 1-6 and scale bar for 7 equals 5 mm.

FIGURE 4. Primates from TBM. 1-3, Notharctus robustior: 1, RM1, DMNH 75300; partial RM1 or 2, UCM 78457; 3, partial RM3, UCM 69054. 4-5, Trogolemur myodes: 4, Rm2, UCM 78097; 5, Rm3, UCM 67883. 6, Washakius insignis, LM1 or 2, UCM 68541. 7-9, Omomys carteri: 7, LM3, 110357; 8, Lm1, SDSNH 110355; 9, Rm3, DMNH 75326. All occlusal views. Scale bar equals 1 mm.

FIGURE 5. Microparamys from TBM. 1-5, Microparamys minutus: 1, LdP4, UCM 66310; 2, LP4, UCM 95695; 3, LM1 or 2, UCM 95697; 4, Rp4, SDSNH 110374; 5, Lm1 or 2, DMNH 74140. 6-9, Microparamys sp.: 6, LdP4, SDSNH 110395; 7, Lp4, SDSNH 110360; 8, Lm1, SDSNH 110361; 9, Lm2, SDSNH 110362. All occlusal views. Scale bar equals 1 mm.

FIGURE 6. Thisbemys and Rodentia, family undetermined from TBM. 1, Thisbemys corrugatus, Rm1, UCM 70671. 2-3, Rodentia, family undetermined, Rm1 or 2, UCM 95700. 1-2, occlusal views. 3, oblique labial view. Scale bar equals 1 mm.

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.