SESPEDECTINAE Novacek, 1985

Murphey, Paul C. & Kelly, Thomas S., 2017, Mammals from the earliest Uintan (middle Eocene) Turtle Bluff Member, Bridger Formation, southwestern Wyoming, USA, Part 2: Apatotheria, Lipotyphla, Carnivoramorpha, Condylartha, Dinocerata, Perissodactyla and Artiodactyla, Palaeontologia Electronica (Cambridge, England: 2003) 20 (2), pp. 1-51 : 10-11

Subfamily SESPEDECTINAE Novacek, 1985 Sespedectinae, genus undetermined

Figure 3.12-13 , Table 2

Referred specimen. From SDSNH Locality 5841, partial Lm1 or 2, SDSNH 110343.

Description. The partial m1 or 2 is broken with the posterolingual corner of the tooth missing, so the development of the entoconid or hypoconulid cannot be determined. However, even in its broken state, the following characters can still be discerned. The trigonid is robust, anteroposteriorly compressed, about one-half the height of the talonid and projects slightly anteriorly. The protoconid and metaconid are bunodont, about equal in size and height, and connected by a relatively tall postprotocristid. The paracristid is a short shelf, slightly lower in height than the postprotocristid, that extends from the anterior base of the protoconid to terminate near the anterior base of the metaconid, resulting in the trigonid being almost closed off lingually. A parastylid is lacking at the lingual terminus of the paracristid. Although the entoconid is missing, the entocristid is moderately tall and extends anteriorly from the posterolingual broken edge of the tooth to terminate on the posterior wall of the metaconid, resulting in a talonid that is blocked off lingually. The hypoconid is bunodont and well developed with the cristid obliqua extending anteriorly from its apex to terminate at the posterior wall of the trigonid, at a point below the protoconid apex. The anterior cingulid is very weak, extending only a short distance labially from the anterolabial base of the protoconid as a slight ridge on the enamel surface that fades out about halfway across the middle of the anterior face of the protoconid. Labial and posterior cingulids are lacking.

Remarks. The partial m1 or 2 (SDSNH 110343) from the TBM exhibits an occlusal morphology that is most similar to those of the Sespedectidae , including the following: 1) an anteriorly inclined and anteroposteriorly compressed trigonid, about half the height of the talonid; 2) a blade-like paracristid terminating close to the metaconid and lacking a distinct paraconid at its lingual terminus; and 3) relatively connate (bunodont) primary cusps. However, SDSNH 110343 also exhibits certain differences from all known sespedectid genera. It can be easily distinguished from Scenopagus by the following: 1) a much more weakly developed metaconid and protoconid; 2) a weaker paracristid positioned slightly higher on the crown with its lingual terminus positioned slightly higher and closer to the metaconid, almost closing off the trigonid lingually; 3) a more anteroposteriorly expanded hypoconid; 4) a taller cristid obliqua, terminating anteriorly slightly more labially and higher on the posterior wall of the protoconid; and 5) a much weaker anterior cingulid. SDSNH 110343 is significantly smaller than Proterixoides davisi Stock, 1935 , larger than Sespedectes davisi Stock, 1935 , and similar in size to Sespedectes stocki Novacek, 1985 . It differs from the m1-2 of Proterixoides and Sespedectes by the following: 1) higher crowned; 2) a more anteroposteriorly compressed trigonid with its height taller relative to the talonid height; 3) a more weakly developed paracristid; 4) much less bulbous (swollen) primary cusps; and 5) less exodaenodont. It differs from Patriolestes novaceki Walsh, 1998 , by the following: 1) much smaller size; 2) a more anteroposteriorly compressed trigonid; 3) a paracristid positioned relatively higher on the crown; 4) a taller postprotocristid with a much shallower central notch; and 5) a taller and more robust cristid obliqua. It differs from the putative sespedectid Macrocranion Weitzel, 1949 , by the following: 1) trigonid more anteriorly inclined and anteroposteriorly compressed with the trigonid significantly taller relative to the trigonid height; 2) a relatively taller postprotocristd with a much shallower central notch; 3) a taller cristid obliqua; 4) a taller, more distinct entocristid, closing off the talonid lingually; and 5) a weaker anterior cingulid. Of all sespedectid taxa, SDSNH 110343 is most similar in size and occlusal morphology to the m1-2 of Crypholestes vaughni ( Novacek, 1976; see also Novacek, 1980) from early Uintan faunas (Murray Canyon and Mesa Drive local faunas, and Poway Fauna) of southern California ( Novacek, 1976; Walsh, 1996b), but differs by the following: 1) a relatively higher positioned paracristid on the crown; 2) a slightly more anteroposteriorly compressed trigonid; 3) a slightly taller and more robust entocristid; and 4) a much weaker anterior cingulid.

SDSNH110343 appears to represent a previously unknown sespedectid species, and probably also a new genus most closely related to the early Uintan Crypholestes , but until additional material of this taxon becomes available to better characterize it, we refer it to an undetermined genus of the Sespedectinae .

Figures

FIGURE 3. Sespedectidae from TBM. 1-8, Scenopagus curtidens: LM1 (UCM 68966) in occlusal view (1); Ldp4 (UCM 110344) in occlusal (2) and labial (3) views; Lm1 or 2 (UCM 95685) in occlusal (4) and labial (5) views; Rm1 or 2 (UCM 95684) in occlusal (6) and labial (7) views; partial Rm3 (UCM 68968) in occlusal view (8). 9-11, Scenopagus priscus: Rm1 or 2 (UCM 95683) in occlusal (9) and labial (10) views; Rm3 (SDSNH 110345) in occlusal view (11). 12- 13, Sespedectidae, genus undetermined, partial Lm1 or 2 (SDSNH 110343) in labial (12) and occlusal (13) views. Scale bar equals 1 mm.

FIGURE 4. Entomolestes westgatei new species from TBM. 1-2, partial dentary with Lp4-m1 (UCM 95687, holotype) in labial (1) and occlusal (2) views. 3-5, partial dentary with partial Rm1 and m2-3 (UCM 67884) in occlusal (3), labial (4), and lingual (5) views. Scale bar equals 1 mm.

FIGURE 5. Entomolestes westgatei new species from TBM. Specimens showing position of mental foramen (MF) and alveoli for antemolars anterior of p4. See text for proposed alveolar homologies. 1-2, partial dentary with Lp4-m1 (UCM 95686, m1 not shown) in occlusal (1) and labial (2) views. 3-4, partial dentary with Lp4-m1 (UCM 95687, holotype, m1 not shown) in occlusal (3) and labial (4) views. Scale bar equals 1 mm.

FIGURE 6. Geolabididae from TBM. 1-4, Centetodon bembicophagus: LP4 (UCM 68681) in occlusal view (1); partial Lm1 or 2 (UCM 68899) in occlusal view (2); Lm1 or 2 (DMNH 75256) in occlusal view (3); Lm3 (DMNH 75257) in occlusal view (4). 5-10, Centetodon pulcher: partial dentary with Lp4-m1 (UCM 95767) in occlusal (5) and labial (6) views; Rm1 or 2 (UCM 95768) in occlusal view (7); partial dentary with Lp1 and p4-m3 (UCM 68963) in occlusal (8), labial (9), and lingual (10) views. Scale bar equals 1 mm.

FIGURE 7. Nyctitherium gunnelli new species from TBM, associated Lp4-m2 (SDSNH 110393, holotype): Lp4 in occlusal (1), labial (4), and lingual (7) views; Lm1 in occlusal (2), labial (5), and lingual (8) views; Lm2 in occlusal (3), labial (6), and lingual (9) views. Scale bar equals 1 mm.

FIGURE 8. Nyctitheriidae from TBM. 1-6, Nyctitherium velox: RM2 (DMNH 75292) in occlusal view (1); RM2 (UCM 95771) in occlusal view (2); RM2 (UCM 68581) in occlusal view (3); RM3 (DMNH 75291) in occlusal view (4); partial Lm2 (DMNH 75317) in occlusal view (5); partial Lm2 (SDSNH 110409) in occlusal view (6). (7), Pontifactor bestiola, RM1 (UCM 71129) in occlusal view. 8-10, Nyctitherium gunnelli new species, LP4 (UCM 95769) in occlusal (8), labial (9), and lingual (10) views. Scale bar equals 1 mm.

FIGURE 9. Chart comparing m1-2 anteroposterior length (ap) versus m1-2 talonid width (trp) in mm of specimens of Nyctitherium velox (including two referred specimens from TBM, SDSNH 110409 and UCM 68967) and holotype m1- 2 (SDSNH 110393) of Nyctitherium gunnelli new species. Black solid filled squares/circles are m1s and white filled squares/circles are m2s. Except for SDSNH 110409 and UCM 68967, measurements of other specimens of N. velox from Robinson (1968a) and Krishtalka (1976b).

FIGURE 10. Oligoryctidae and unnamed lipotyphlan from TBM. 1-4, unnamed apternodontid sp.: partial LM1 or 2 (SDSNH 110348) in occlusal (1) and anterior (2) views; partial Rm1 or 2 (SDSNH 110349) in occlusal (3) and labial (4) views. 5-6, unnamed lipotyphlan sp., partial dentary with Rp4 (DMNH 75258) in occlusal (5) and labial (6) views. Scale bars equals 1 mm.

FIGURE 11. Carnivoramorpha and Condylartha from TBM. 1, Viverravus gracilis, LM2 (UCM 95809). 2-3, Hyposodus lepidus: RM1 or 2, UCM 67958 (2); Rm1 or 2, UCM 67956 (3). All occlusal views. Scale bar = 1 mm.

FIGURE 12. Dinocerata and Perissodactyla from TBM. 1-3, Uintatherium anceps: Lp2, (DMNH 75310) in occlusal view (1); RP3 or 4 (DMNH 75308) in occlusal view (2); Lm2 (DMNH 75309) in occlusal view (3). 4-10, Wickia sp., cf. W. brevirhinus: LC (DMNH 75306) in labial view (4); RI3 (DMNH 75312) in lingual view (5); RP2 (DMNH 75311) in occlusal view (6); LM1 (DMNH 75305) in occlusal view (7); RM3 (DMNH 75304) in occlusal view (8); partial Lp4? (DMNH 75314) in occlusal view (9); Lm1 (DMNH 75307) in occlusal view (10). Scale bar equals 10 mm.

FIGURE 13. Perissodactyla from TBM. 1-4, Triplopus sp., cf. T. obliquidens, partial left dentary with alveolus for p1, p2, partial p3, p4 and partial m1 (UCM 69053 with 1, 3-4 original specimen, 2 cast showing detail better) in occlusal (1- 2), labial (3) and lingual (4) views. 5-6, Epihippus sp., cf. E. gracilis, Rp3 (SDSNH 110408) in occlusal (5) and lingual (6) views. Scale bars for 1-2 and 3-4 equals 5 mm. Scale bar for 5-6 equals 1 mm.