906


Journal of Paleontology 92(5):896–910


Table 2. Body mass estimates for North American taeniolabidoid multituberculates. Mass estimates based on mean length of lower tooth row (MLTR) were calcu- lated using the regressions of Freudenthal and Martin-Suarez (2013): ln (mass)=−0.447+2.723 (ln (MLTR)) (all rodents); ln (mass)=0.039+2.378 (ln (MLTR)) (rodents without premolars); ln (mass)=−0.381+2.747 (ln (MLTR)) (rodents with premolars). Correction factors (CF) were applied to each of the calculated body masses, where CF=antilog ((standard error of estimate2)/2). Mass estimates based on mean m1 occlusal area (LWm1) were calculated using the regressions of Legendre (1986): ln (mass)=2.172+(1.767 (ln (LWm1))) (rodents); ln (mass)=1.786+(1.621 (ln (LWm1))) (small mammals); ln (mass)=1.810+(1.827 (ln (LWm1))) (all mammals). Resultant values in grams were converted to kilograms. For references for measurement data, see Williamson et al. (2015); for measure- ments for Catopsalis johnstoni, see Fox (1989). *Values for p4 length, m1 width, and m2 length for C. foliatus follow the estimates of Williamson et al. (2015).


Taxon


Valenopsalis joyneri Catopsalis alexanderi Catopsalis foliatus


Catopsalis fissidens


Mean length tooth row (MLTR) (mm)


Catopsalis johnstoni —— — 19.5


15.4


Catopsalis waddleae —— — 15.9* 24.9


1.2208 2.3216 2.9526


Catopsalis calgariensis —— — Catopsalis kakwa n. sp. Taeniolabis taoensis Taeniolabis lamberti


11.9 40.5 34.7


4.5173 0.5365


16.9873 11.1517


Mass (MLTR, all rodents) (kg)


Mass (MLTR, rodents, no premolars) (kg)


0.7716 1.3527 1.6687


2.4191 0.4138


7.6916 5.3259


1987, and exhibits significant overlap with T. taoensis in both size and cusp number (Middleton, 1982; Simmons, 1987). Catopsalis is first known from Late Cretaceous deposits in southwestern Saskatchewan, at the Medicine Hat Brick and Tile Quarry Long Fall horizon in the Frenchman Formation (Johnston and Fox, 1984; Fox, 1989), although the age of this locality has been challenged and debate continues (Fox, 1990, and see Lofgren et al., 2004; Redman et al., 2015). The earliest uncontested record of Catopsalis is from the earliest part of the Paleocene at several localities in the Western Interior of North America, during the PuercanNorthAmericanLandMammalAge (NALMA),where three relatively poorly represented species have been identified (C. alexanderi, C. waddleae, and the genotypic speciesC. foliatus; and seeArchibald, 1982;Lofgren, 1995;Lucas et al., 1997). A denser record is known from slightly younger, Torrejonian age rocks in New Mexico, where a single species, C. fissidens, has been documented (Wilson, 1956;Williamson and Lucas, 1993; Williamson, 1996; Lucas et al., 1997). A final species, C. calgariensis, is known from the type locality at Calgary 2E in the upper part of the Scollard Formation in Alberta, and at the Shotgun locality in the Shotgun member of the Fort Union Formation in Wyoming, where its presence in the earliest Tiffanian represents the stratigraphically youngest occurrence of the genus (Russell, 1926; Middleton, 1982). The enlarged i1 having an anteriorly and laterally thickened


enamel band, the reduced p4, and the large upper and lower molars having stout, columnar cusps are features that in combination are otherwise restricted among multituberculates to the Taeniolabidoidea (as currently conceived; Weil and Krause, 2008;Williamson et al., 2015), leaving little question of the higher-level affinities of C. kakwa n. sp. Williamson et al. (2015) restricted the Taeniolabididae to Taeniolabis and Kimbetopsalis, and considered Catopsalis likely to be non- monophyletic (and see Simmons and Miao, 1986); given these results, we provisionally refer C. kakwa n. sp. only to the Taeniolabidoidea. Comparisons.—Among the taeniolabidoids so far dis-


covered, Catopsalis kakwa n. sp. most closely resembles species of Catopsalis in comparable parts of the dentition; referral to this genus rests principally on smaller size and the lower number of molar cusps when compared to species of Taeniolabis and


Mass (MLTR, rodents,


premolars) (kg) 1.3650


—


2.6106 —


3.3272 5.1095 —


0.6645


19.4402 12.7147


LxW m1 (LWm1) (mm)


21.1 48.9 41.8


152.5


139.7 15.9


205.9 128.0


53.6* 80.6


Mass (LWm1,


rodents) (kg) 1.9232


8.4964 6.4146


63.2741 9.9542


20.5193 54.2019 1.1710


107.5457 46.4224


Mass LWm1, small mammals) (kg)


0.8375 3.2725 2.5287


20.6454 3.7842 7.3480


17.9128 0.5313


33.5858 15.5395


Mass (LWm1, all mammals) (kg)


1.6080 7.4716 5.5873


59.5677 8.8007


18.5926 50.7595 0.9628


103.0861 43.2460


Kimbetopsalis (see Granger and Simpson, 1929; Weil and Krause, 2008; Williamson et al., 2015). The dentition of C. kakwa n. sp. differs from that of Valenopsalis and other species of Catopsalis most obviously in size, with upper and lower first molar lengths of C. kakwa n. sp. being significantly less than those of all other species of Catopsalis and being slightly smaller than those of V. joyneri. In addition to the dif- ference in size, the teeth of C. kakwa n. sp. differ further from Valenopsalis and other species of Catopsalis: these differences are discussed most economically through comparisons first with Valenopsalis and the Puercan species of Catopsalis— C. alexanderi, C. waddleae, and C. foliatus—and then with the younger species, C. fissidens and C. calgariensis. Despite being closest in size to Valenopsalis and


Catopsalis alexanderi, the dentition of C. kakwa n. sp. differs from those of the smaller Puercan taxa in significant ways, e.g., the ratio of M1 length to M2 length is higher in Valenopsalis (1.55, data from Sloan and Van Valen, 1965) and C. alexanderi (1.58, data from Middleton, 1982) when compared to that of C. kakwa n. sp. (1.29). The p4 in V. joyneri and C. alexanderi is anteroposteriorly long and relatively short, and the posterolabial shelf is robustly developed. In contrast, the p4 of C. kakwa n. sp. is tall relative to its length, and the posterolabial shelf is weakly developed, forming only a slight posterolabial bulge of enamel. Perhaps the most salient differences between C. kakwa n. sp. and Valenopsalis and C. alexanderi are in the upper and lower molars (Fig. 4). The M1 is broadly similar in all three species: the coronal outline is somewhat teardrop shaped, with the lingual cusp row extending to the anterior margin of the crown; the cusp formula is generally similar (7:7:8 in C. kakwa n. sp. and Valenopsalis, 7:7:9 in C. alexanderi), and the lingual cusp row is smoothly arcuate lingually, with cusp size decreasing relatively soon anterior to the anteroposterior midpoint. Despite these similarities, the M1 of C. kakwa n. sp. differs importantly from that in Valenopsalis and C. alexanderi in the shapes of the cusps. In M1of Valenopsalis and C. alexanderi, the cusps of the middle row are moderately to strongly crescentic, particularly the more posterior cusps. The anterior surface of each cusp is concave, and the posterior surface convex, with the convexity extending around to the lingual face; accordingly, the cusps of the middle row exhibit a weak to moderate overlap, or interlock,


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