Leptalestes cooki ( Clemens, 1966 )

Brand, Nickolas A., Heckert, Andrew B., Sanchez, Israel, Foster, John R., Hunt-Foster, Rebecca K. & Eberle, Jaelyn J., 2022, New Late Cretaceous microvertebrate assemblage from the Campanian-Maastrichtian Williams Fork Formation, northwestern Colorado, USA, and its paleoenvironmental implications, Acta Palaeontologica Polonica 67 (3), pp. 579-600 : 593-594

? Leptalestes cooki ( Clemens, 1966)

Fig. 8D .

Material.— MWC 8859 , a left m2 or m3; from the Campanian–Maastrichtian , Williams Fork Formation, J &M site, northwest Colorado, USA .

Description.—MWC 8859, a left m2 or m3, is the only metatherian tooth thus far recovered from the J&M site ( Fig. 8D ). The protoconid is broken off, but the other cusps are intact. On MWC 8859, the cristid obliqua attaches to the posterior wall of the trigonid near the midline of the protoconid, as is diagnostic for pediomyoids ( Davis 2007). As is characteristic of? Leptalestes cooki (see Davis 2007; Clemens 1966), the metaconid is larger than the paraconid, and the talonid is wider than the trigonid. The entoconid and hypoconulid are twinned, and the posteriorly-projecting hypoconulid is the lowest cusp on the tooth. Anterolabial and posterolabial cingulids are present on MWC 8859, although they do not extend around the labial margins of the proto- and hypoconids, respectively.

Remarks.—MWC 8859 has a length of 2.36 mm, a trigonid width of 1.67 mm, and a talonid width of 1.75 mm. Its size is within the range of m3s of? Leptalestes cooki (= Pediomys cooki ) measured by Clemens (1966: table 22), and is 0.1 mm longer than UCM 57394, a right m2 or m3 of? Leptalestes cooki identified by Diem (1999) from the Williams Fork Formation.? Leptalestes cooki is known from Judithian– Lancian aged localities in the U.S. Western Interior and Alberta, Canada ( Davis 2007).

Figures

Fig. 8. Representative mammalian teeth from the J&M site, Colorado, USA, Williams Fork Formation, Campanian–Maastrichtian, Upper Cretaceous. A. Meniscoessus sp., MWC 8848, incisor crown in labial (A1) and lingual (A1) views. B. Multituberculata indet., MWC 8863, tooth crown in occlusal (B1), lingual (B2), and distal (B3) views. C. cf. Cimolodon nitidus Marsh, 1889, MWC 8860, left p4 tooth crown in occlusal (C1), labial (C2), and lingual (C3) views. D.?Leptalestes cooki (Clemens, 1966), MWC 8859, tooth crown in occlusal (D1), labial (D2), and lingual (D3) views.