Palaeictops matthewi Novacek, 1977

Velazco, Paúl M. & Novacek, Michael J., 2016, Systematics of the genus Palaeictops Matthew, 1899 (Mammalia: Leptictidae), with the description of two new species from the Middle Eocene of Utah and Wyoming, American Museum Novitates 2016 (3867), pp. 1-42 : 17

Palaeictops matthewi Novacek, 1977

Figure 8–10 , table 1

HOLOTYPE: FMNH P26904 (fig. 8A–B), consisting of a damaged skull that retains P2–P5 (broken), M1–M2 (roots), and M3 (broken) on the left side; the right side retains roots of C– P1, P2 (broken), P4–P5, and M1–M3. Right ramus with c–p1 (broken), p2–p5, m1–m2 (broken), and root of i2 (fig. 9). Left ramus with c (broken), p1, p2 (broken), p4–p5, m1–m3 (broken), and root of i2 (fig. 10). Partial skeleton including lumbar and caudal vertebrae, pelvis, femur, tibia, carpals, tarsals, and phalanges.

TYPE LOCALITY: Exposure near top of Buzzard Pass, Mesa Co., Colorado. De Beque Formation, Rifle Member, Lower Eocene (Wasatchian NALMA).

DIAGNOSIS (modified from Novacek, 1977): Similar to Palaeictops multicuspis in having tall, trenchant p4 but differs from P. multicuspis in slightly smaller size and in having a more slender ramus; p2 with only one main, trenchant cusp and a basal posterior cuspule; p4 with anterior main cusp larger than posterior main cusp and a short transverse ridge on the posterior heel separated from the rest of the crown by a transverse trough (figs. 9, 10). P4 trenchant tooth, taller than P5 with a very prominent paracone, smaller metacone and low protocone (fig. 8B). Species has postcranial features used to diagnose Palaeictops (see above diagnosis).

DISTRIBUTION: De Beque and Huerfano formations, Colorado, Lower Eocene (Wasatchian NALMA).

REFERRED SPECIMENS: AMNH 17555, skull fragment, partial lower jaws and partial skeleton. Garcia Canon region, Colorado. Lower beds of Huerfano Formation.

REMARKS: Bown and Schankler (1982: 11–12) stated that Palaeictops matthewi is probably conspecific with P. multicuspis , because differences in size and p2 morphology are trivial. Synonymy is, however, unwarranted. The jaw proportions and p2 and p 4 in these species are clearly distinct as described in the diagnosis of each species (this paper). Bown and Schankler (1982) maintained that such characters might be insignificant and subject to intraspecific variation. There is, however, no sample evidence supporting this assessment and, in absence of data to the contrary, P. matthewi is here recognized as diagnosed above.

Figures

FIG.8. The skull of Palaeictops matthewi FMNH P26904 (holotype), containing P2–P5 (broken), M1–M2 (roots), and M3 (broken) on the left side; the right side retains roots of C–P1, P2 (broken), P4–P5, and M1–M3.A, (opposite page) dorsal (top) and ventral (bottom) views and B, (above) right lateral (top) and left lateral (bottom) views.Scale bar = 1 cm.

FIG. 9. Right ramus of Palaeictops matthewi FMNH P26904 (holotype), containing c–p1 (broken), p2–p5, m1– m2 (broken), and root of i2, in (clockwise from upper left) medial, occlusal, and lateral views. Scale bar = 1 cm.

FIG. 10. Left ramus of Palaeictops matthewi FMNH P26904 (holotype), containing c (broken), p1, p2 (broken), p4–p5, m1–m3 (broken), and root of i2, in (clockwise from upper left) medial, occlusal, and lateral views. Scale bar = 1 cm.