Palaeictops borealis ( Russell, 1965 )

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 : 10-11

Palaeictops borealis ( Russell, 1965)

Figure 6 , table 1

Protictops? borealis Russell, 1965: 7–8 , pl. 1, figs. 1, 2.

Palaeictops borealis Storer, 1984: 22–26 : figs. 2A–B. First use of current name combination.

HOLOTYPE: ROM 1676 , right M1 (fig. 6B).

TYPE LOCALITY: Swift Current, Saskatchewan. Swift Current Creek Formation, Middle Eocene (Uintan NALMA) .

DIAGNOSIS: Palaeictops borealis can be easily distinguished from other species of the genus by its size (larger than P. altimontis , P. bicuspis , P. bridgeri , P. multicuspis , and P. matthewi, but smaller than P. robustus ). Like P. matthewi in having P5 with a more extensive precingulum in lingual region (less extensive precingulum present in P. altimontis and P. bicuspis ). Differs from P. altimontis , P. bicuspis , and P. matthewi in having the upper molars with a more extensive precingulum in lingual region. Like P. altimontis and P. bridgeri in having the lower molars with lower trigonids (higher trigonids present in P. bicuspis , P. matthewi , and P. multicuspis ).

DISTRIBUTION: Cypress Hills and Swift Current Creek Formations, Saskatchewan, Canada. Middle Eocene (Uintan–Duchesnean NALMAs).

REFERRED MATERIAL: RSM P1654.220, right DP5; RSM P1654.221–222, right P5; RSM P1654.226, right m1; ROM 23595, left m1; RSM P1654.225, right m2; ROM 1685, right m2; RSM P1654.223–224, left m1 or m2; Swift Current Creek Formation, Saskatchewan, Middle Eocene. RSM P1899.1472, right DP4; RSM P1899.1486, left M1 or M2; and P1899.1450, left m1 or m2; Cypress Hills Formation, Saskatchewan, Middle Eocene.

REMARKS: Russell (1965) could not assign with certainty the holotype of Palaeictops borealis to a specific locus (P5 or M1), but subsequently Storer (1984) considered the holotype to be an M1, an assignment with which we agree. Likewise, other teeth were not assigned to a specific locus by Russell (1965) and Storer (1984); ROM 1685, ROM 23595, and RSM P1654.223– 226 could not be assigned as either an m1 or m2. Based on our revision of all the Palaeictops material we were able to assign four of the six teeth to either m1 or m2 (see Referred Material), but we were not able to do this for RSM P1654.223 and RSM P1654.224 because of their poor preservation. We were not able to review the material from the Cypress Hill Formation (RSM P1899.1472, right DP4; RSM P1899.1486, left M1 or M2; and P1899.1450, left m1 or m2), but from the illustration it is clear that at least one specimen (RSM P1899.1450) belongs to P. borealis ( Storer, 1995: fig. 1a).

Figures

FIG. 6. Palaeictops borealis, occlusal (left), labial (center), and lingual (right) views of: A, right P5 (RSM P1654.221); B, right M1 (ROM 1676, holotype); C, left m1 (ROM 23595); D, right m2 (RSM P1654.225).