Contributions from the museum of Paleontology the university of miChigan Vol. 31, no. 10, pp. 211-243 December 15, 2006 MULTITUBERCULATES (MAMMALIA, ALLOTHERIA) FROM THE EARLIEST TIFFANIAN (LATE PALEOCENE) DOUGLASS QUARRY, EASTERN CRAZY MOUNTAINS BASIN, MONTANA by Craig s. sCott and DaviD W. Krause museum of Paleontology the university of miChigan ann arbor Contributions from the museum of Paleontology Philip D. gingerich, Director this series of contributions from the museum of Paleontology is a medium for publication of papers based chiefly on collections in the museum. When the number of pages issued is sufficient to make a volume, a title page plus a table of contents will be sent to libraries on the museum’s mailing list. this will be sent to individuals on request. a list of separate issues may also be obtained by request. Cor- respondence should be directed to the Publications secretary, museum of Paleontology, the university of michigan, 1109 geddes road, ann arbor, michigan 48109-1079 ([email protected]). vols. 1-31: Parts of volumes may be obtained if available. Price lists are available upon inquiry. see also: www.paleontology.lsa.umich.edu/Publications/publicationintro.html Publications of the museum of Paleontology are accessible online at: http://deepblue.lib.umich.edu/handle/2027.42/41251 text and illustrations ©2006 by the museum of Paleontology, university of michigan MULTITUBERCULATES (MAMMALIA, ALLOTHERIA) FROM THE EARLIEST TIFFANIAN (LATE PALEOCENE) DOUGLASS QUARRY, EASTERN CRAZY MOUNTAINS BASIN, MONTANA by Craig s. sCott1 and DaviD W. Krause2 Abstract—highly fossiliferous sequences from the eastern Crazy mountains ba- sin, south-central Montana, have figured importantly in current understanding of mammalian evolution during the middle and late parts of the Paleocene epoch in the Western interior of north america, and are crucial for intra- and interba- sinal biostratigraphic correlation, particularly those localities of early tiffanian (late Paleocene) age. one of these localities, Douglass Quarry, documents mam- mals of earliest tiffanian age, an important but poorly represented interval in mammalian evolution. notable among the specimens from Douglass Quarry are well-preserved teeth of multituberculates, a long-lived group of herbivorous or omnivorous mammals. neoplagiaulacidae are particularly abundant, and are represented by species of Mesodma, Ectypodus, and two species of Neopla- giaulax, one of which, Neoplagiaulax donaldorum, is new. two species of the cimolodontid Anconodon are identified, with Anconodon cochranensis being the most abundant multituberculate in the local fauna. the Douglass Quarry multi- tuberculate fauna closely resembles that from the Cochrane 2 locality, Paskapoo formation, alberta, also of earliest tiffanian age. multituberculate evolution in the Western interior of north america during the early part of the tiffanian is characterized by higher taxonomic diversity among neoplagiaulacids and, es- pecially, ptilodontids when compared with localities from the late torrejonian, and increased generic and specific diversity toward more northerly latitudes. introDuCtion multituberculata were a geologically long-ranging, primarily laurasian group of mammals with an abundance and diversity that peaked during the Paleocene, but declined thereafter until their extinction in the late eocene (Krause, 1986). multituberculates were common members of 1 laboratory for vertebrate Paleontology, Department of biological sciences, university of alberta, edmonton t6g 2e9, Canada ([email protected].) 2 Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York 11794-8081, USA (dkrause@ notes.cc.sunysb.edu.) 211 212 C. s. sCott and D. W. Krause north american early tertiary terrestrial vertebrate communities, and may have been among the first mammals to enter an herbivorous (Fox, 1971; Novacek and Clemens, 1977), or at least om- nivorous (Krause, 1982c), adaptive zone. the multituberculate record from the Western interior of North America is among the best known and densest stratigraphically in the world, with a temporal range spanning the middle? or late Jurassic to the late eocene, and geographically from southern Texas to Ellesmere Island (see summaries in Weil, 1999; Kielan-Jaworowska et al., 2004). the tiffanian record (the term “tiffanian” refers to a north american land mammal age or NALMA that is approximately equivalent to the early late Paleocene; see Lofgren et al., 2004) of multituberculates in the northern part of the Western interior of north america is especially rich, with numerous localities preserving multituberculate fossils (e.g., Granger and Simpson, 1929; Simpson, 1937a-b; Jepsen, 1930, 1940; Gazin, 1956; Holtzman and Wolberg, 1977; Krause, 1977, 1982a; Rose, 1981; Sloan, 1987; Fox, 1990a, 2005; Lofgren et al., 2002; Higgins, 2003a-b; Scott, 2003a-b; Kihm et al., 2004; and summaries in Archibald et al., 1987 and Lofgren et al., 2004). the earliest tiffanian biochron (ti-1) is a particularly important interval in that it represents a period of significant faunal turnover and possibly climatic change in North America, in addition to documenting the earliest occurrences of a number of higher-level mammalian taxa, including Phenacodus-Ectocion phenacodontid condylarths, apheliscine apheliscid condylarths, and titanoi- deid pantodonts (e.g., Rose, 1981; Archibald et al., 1987; Krause and Maas, 1990; Secord, 1998; Higgins, 2003a; Zack et al., 2005). Although the mammalian fossil record documenting the latest Torrejonian (To-3) in the Western Interior of North America is rich (e.g., Simpson, 1936, 1937a; Rose, 1981), the earliest Tiffanian is comparatively poorly known, with the majority of Ti-1-aged local faunas represented by only a few specimens, or remaining undescribed (see lofgren et al., 2004 for summary). multituberculates are taxonomically diverse and abundant during the torrejonian, and remain so through the early part of the middle Tiffanian (Ti-3; e.g., Scott, 2003b, 2005), yet their record during the earliest Tiffanian, like those of other contemporaneous mammals, remains obscure. the largest and potentially most informative local faunas of earliest tiffanian age are from the Co- chrane 2 locality of south central Alberta, Canada (Cochrane II of Russell, 1932; see Fox, 1990a; Scott et al., 2002), the Keefer Hill/Twin Buttes (“Shotgun”) locality of Wyoming, and the Breaks localities of south central Wyoming (Youzwyshyn, 1988; Gunnell, 1989; Fox, 1990a; Scott et al., 2002; Higgins, 2003a), but the bulk of these local faunas remains undescribed. studies on fossil mammals from an important series of localities in the eastern Crazy moun- tains Basin, Montana, have contributed to knowledge of Paleocene mammalian evolution and biochronology in the Western Interior of North America (see, e.g., Simpson, 1935, 1936, 1937a-b; Rose, 1981; Krause, 1982a, 2004; Krause and Gingerich, 1983; Archibald et al., 1987 and refer- ences therein; Krause and Maas, 1990; Hartman and Krause, 1993; Silcox et al., 2001; Lofgren et al., 2004 and references therein; Zack et al., 2005), with the ages of these local faunas being further refined by ongoing magnetostratigraphic work (see, e.g., Butler et al., 1987; Boyer et al., 2004a). the Crazy mountains basin localities preserve a succession of mammalian faunas span- ning middle/late torrejonian (to-2) through the early part of middle tiffanian (ti-3) time, with the three principal localities (gidley, silberling, and scarritt quarries) and their associated mammalian faunas having been thoroughly described by simpson (1935, 1936, 1937a-b). Douglass Quarry (locality 63 of simpson, 1937a), a fourth locality in the eastern part of the Crazy mountains basin, is one of the few localities in the region that documents mammals of earliest tiffanian age. two other localities, bingo Quarry in the eastern part of the basin and bangtail Quarry in the western part, have yielded exceptionally well-preserved specimens that are briefly discussed elsewhere (see, e.g., Gingerich et al., 1983; Boyer, 2003; Boyer et al., 2004b). It was discovered in 1902 by field parties from Princeton University, and was quarried for fossil vertebrates in 1940 primarily by John bell, for a senior thesis project at Princeton university, and albert C. silberling, a local fossil collector. these collections, now housed at yale university, as well as a small sample collected during a reconnaissance expedition from Stony Brook University in 1982, were described by Krause and gingerich (1983). intensive collecting from Douglass PaleoCene multituberCulates from Douglass Quarry 213 Quarry by field parties from Stony Brook University was initiated in 1983 and continued into the early 1990s. this effort augmented the earlier collections by an order of magnitude, substantially increased the number of taxa known from the locality, and further clarified Paleocene mammalian diversity near the beginning of the tiffanian nalma in the Western interior. a preliminary fau- nal list was presented by Krause and maas (1990: table 3). included among the new specimens from Douglass Quarry are numerous isolated teeth and jaw fragments of multituberculates, together representing a diverse assemblage of cimolodontan, microcosmodontid, and eucosmodontid taxa. our objectives here are to report on new and pre- viously undescribed multituberculate specimens, focusing on the non-ptilodontids; compare the multituberculate fauna from Douglass Quarry with those from other penecontemporaneous lo- calities in the Western Interior of North America; and comment briefly on larger-scale patterns of multituberculate evolution that occurred during the late torrejonian and early tiffanian in north america. the ptilodontids from Douglass Quarry and other localities of Paleocene age are under study by Krause (2004, in prep.). geologiCal setting Douglass Quarry is located in the eastern Crazy mountains basin, south-central montana, on the east side of us highway 191. it is in north-facing exposures of a south-to-north tributary of Sadie Creek in the NW¼ of Section 18, Township 5 North, Range 15 East, Sweetgrass County (see location maps in Simpson, 1937a, locality 63, plate 1; and Hartman and Krause, 1993, fig. 1; and photographs in Krause and Gingerich, 1983, fig. 1). Douglass Quarry occurs approximately 400 m above the base of the melville formation, fort union group (hartman and Krause, 1993). the melville formation, named for exposures near the town of melville (located west of us 191 roughly halfway between harlowton to the north and big timber to the south), is approximately 1500 m thick and consists primarily of “a basal, yellow to off-white sandstone overlain by olive- green shales and sandstones” (hartman and Krause, 1993, p. 76). the two dominant lithologies in the quarry were described by Krause and gingerich (1983, p. 158) as (1) an indurated, green- ish-grey, fine-grained quartz sandstone, and (2) a mottled orange/brown/green conglomerate with a fine-grained quartz sand matrix and angular to rounded, dark, greenish-grey mudstone clasts.” the vast majority of fossil mammal specimens, as well as a small molluscan assemblage (hartman and Krause, 1993), were recovered from the conglomeratic beds. Douglass Quarry is the type locality for the plesiadapiform primate Plesiadapis praecursor, an index fossil that characterizes the Plesiadapis praecursor Range Zone (earliest Tiffanian biochron ti-1) of gingerich (1975), more recently called the Plesiadapis praecursor/Plesiadapis anceps Lineage Zone (Archibald et al., 1987; Lofgren et al., 2004). Douglass Quarry lies stratigraphi- cally below scarritt Quarry (ti-2) and above bingo and glennie quarries (ti-1), all in the melville formation, and above gidley and silberling quarries (to-2), in the lebo formation (hartman and Krause, 1993, table 2). Paleomagnetic samples collected from Douglass Quarry by butler et al. (1987), as well as from bingo Quarry (boyer et al., 2004a), have been correlated to chron 26r. the age of Douglass Quarry, based on current litho-, bio-, and magnetostratigraphic evidence, is estimated to be between 60 and 60.5 million years (lofgren et al., 2004). samPle ComPosition, terminology, measurements, anD abbreviations Sample.— the sample analyzed in this report consists of non-ptilodontid multituberculates, primarily neoplagiaulacids and cimolodontids; the ptilodontid fraction is under study by one of us (DWK) and will be published elsewhere. the non-ptilodontid multituberculate assemblage from Douglass Quarry reported upon here consists of 89 specimens, of which almost all are isolated upper and lower fourth premolars. a single dentulous jaw containing P4, m1-2 of a neoplagiaulacid comprises the only articulated specimen in the sample. Of the 89 specimens, 82 were identifiable 214 C. s. sCott and D. W. Krause to at least family level. Taxa were identified on the basis of the morphology of complete or nearly complete upper and lower fourth premolars, the teeth most often used in previous diagnoses of multituberculate taxa, or incisors and molars where these teeth are diagnostic (e.g., microcosmo- dontids, eucosmodontids). the incisors, anterior premolars, and molars of neoplagiaulacids and cimolodontids are often closely similar between taxa and were not identified. Multituberculate classification follows Kielan-Jaworowska and Hurum (2001). Dental terminology.— Dental terminology follows that of Krause (1977, 1982a, 1987). fol- lowing the results of Hahn (1987), we consider the enlarged, blade-like tooth in the lower dental row to be the lower fourth premolar (P4) rather than the “molar blade” (“mb”; contra Schiebout, 1974; Sloan, 1981, 1987; Secord, 1998). Dental measurements follow Krause (1987) and scott (2003a); width of P4 was not measured (Krause, 1977, following the rationale of Ramaekers, 1975). “exodaenodont lobe” refers to the ventral projection of enamel on the labial side of the anterior root on the P4 of many multituberculates. outline drawings of lower fourth premolars were made with the aid of a camera lucida following the methodology of Jepsen (1940) and Krause (1977). baseline of standard measurement refers to a line that extends from the apex of the anterobasal concavity posteriorly to the point where the posterolabial shelf intersects the posterior margin of the crown (see Krause, 1982a for details). Tooth positions.— incisor, premolar, and molar tooth positions are abbreviated i, P, and m, respectively, with superscript numerals indicating particular upper teeth and subscript numerals indicating particular lower teeth. Multituberculate cusp formulae.— Cusp number and their expression in formulae follow the methods and rationale of Krause (1977). P4 and upper molar cusp formulae of the form x:y:z designate cusps of the labial (x), middle (y), and lingual (z) rows, respectively. lower molar cusp formulae of the form x:y designate cusps of the labial (x) and lingual (y) rows, respectively. Measurements and statistical abbreviations.— C, cusp formula; S, serration count; L, length of tooth; W, width of tooth; D, depth of incisor; M, mean; OR, observed range; SD, standard devia- tion; CV, coefficient of variation; N, number. An asterisk (*) indicates the measurement or count is an estimate. all measurements are in millimeters (mm). North American Land-Mammal Ages (NALMAs).— Pu, Puercan, subdivided into early, Pu-1; middle, Pu-2; and late, Pu-3 biochrons. To, torrejonian, subdivided into early, To-1; middle, To-2; and late, To-3 biochrons. Ti, tiffanian, subdivided into earliest, Ti-1; early, Ti-2; early middle, Ti-3; late middle, Ti-4; late, Ti-5; and latest, Ti-6 biochrons. institutional abbreviations amnh — American Museum of Natural History, New York MCZ — Museum of Comparative Zoology, Harvard University, Cambridge, Massachu- setts ualvP — laboratory for vertebrate Paleontology, university of alberta, edmonton um — museum of Paleontology, the university of michigan, ann arbor usnm — united states national museum of natural history, Washington, D. C. systematiC Paleontology Class mammalia linnaeus, 1758 subclass allotheria marsh, 1880 order multituberCulata Cope, 1884 suborder CimoloDonta mcKenna, 1975 superfamily PtiloDontoiDea (sloan and van valen, 1965) family neoPlagiaulaCiDae ameghino, 1890 PaleoCene multituberCulates from Douglass Quarry 215 A B C D E F G H I J K fig. 1 — multituberculates from the earliest tiffanian (ti-1, late Paleocene) Douglass Quarry, eastern Crazy mountains basin, montana. a-g are Mesodma pygmaea sloan, 1987, and h-K are Ectypodus sp. . a-C, left P4, UM 84196, in labial (A), lingual (B), and occlusal (C) views; D and E, right P4, um 84194, in labial (D) and lingual (E) views; F and G, left P4, um 84195, in labial (f) and lingual (g) views. h and i, left P4, um 84198, in labial (H) and lingual (I) views; J and K, left P4, um 84197, in labial (J) and lingual (K) views. scale = 2 mm. genus Mesodma Jepsen, 1940 Mesodma Jepsen, 1940, p. 267. Type species.— Mesodma ambigua Jepsen, 1940. Type locality.— mantua lentil locality (early Puercan, Pu-1, lofgren et al., 2004), fort union ( = Polecat bench) formation, bighorn basin, Wyoming, usa. Mesodma pygmaea sloan, 1987 figure 1a-g Mesodma sp. P, Krishtalka, 1973, p. 15; Krause, 1977, p. 20; Holtzman, 1978, p. 25. Mesodma pygmaea sloan, 1987, p. 188. Holotype.— amnh 35298, incomplete left dentary with P4, m1-2 (Sloan, 1987, p. 188, fig 10). Type locality.— gidley Quarry (middle torrejonian, to-2, lofgren et al., 2004), lebo forma- tion, eastern Crazy mountains basin, montana, usa. Referred specimens.— left P4: um 84196 (l = 2.0, W = 0.7). left P4: um 84195 (l = 2.6, s = 10). right P4: um 84194 (l = 2.7, s = 10). Description.— P4: Cusp formula ?2:6:0 (n = 1). P4 is short and low, with little elevation of the crown posteriorly. the crown is only slightly wider anteriorly than posteriorly, with the poorly developed anterolabial lobe supporting two cusps: a large conical cusp is developed adjacent to the second cusp of the middle row, while a second, smaller cusp is developed anterior and slightly lingual to the first; additional cusps may have been developed anterior to the second cusp, but the crown in this area is damaged. the cusps of the middle row are approximately equal to one an- other in size and height (as measured from cusp base to apex), and are arranged in a faintly arcuate line that is convex labially. the anterior slope is straight, with the ultimate and penultimate cusps 216 C. s. sCott and D. W. Krause together being highest above the base of the crown. the posterior slope is short, shallow, and slightly concave; a posterobasal cusp is not developed. P4: The profile of P4 is low and asymmetrical, with the anterior margin slightly convex, the dorsal crest smoothly arcuate, and the posterior slope virtually straight. Except for the weakly developed posterolabial shelf, the labial side of the crown is flat, and the faintly swollen exodae- nodont lobe is both narrow and deep. the anterobasal concavity is shallow, and the anterior root bears a vertical groove. The anterior margin of the crown inclines steeply to the low first serration, and when the tooth is held with the baseline of standard measurement in a horizontal position, the apogee of the dorsal crest occurs at the third serration, and the height of the first serration above the anterobasal concavity is approximately one-third the length of the crown. the cutting edge bears 10 serrations (N = 2), the first of which is set off anteriorly from the succeeding serrations; the apices of the remaining serrations are equidistant from one another, and their bases become stouter posteriorly. the crown below the serrations bears well-developed labial and lingual ridges that extend anteroventrally in a gentle arc; anteriorly the ridges are closely spaced and coarse, but become further separated from one another and weaker towards the posterior parts of the crown, disappearing below the last three serrations. Discussion.— the coronal features of the referred teeth are consistent with sloan’s (1987) diagnosis of the species and resemble teeth of Mesodma pygmaea from other localities in the Western interior of north america. the P4 of M. pygmaea from Douglass Quarry most closely resembles those referred to this species from the late torrejonian Who nose? locality and the earli- est Tiffanian Cochrane 2 locality, both known from southwestern Alberta, Canada (Youzwyshyn, 1988; Scott, 2003a), and differing from P4 of M. pygmaea from the late middle tiffanian roche Percée localities of Saskatchewan primarily in having a deeper and more swollen exodaenodont lobe (Krause, 1977). Mesodma pygmaea is a stratigraphically long-ranging taxon (late torrejonian through late tif- fanian) that appears to be restricted to the northern part of the Rocky Mountain Interior (Fig. 7) (the single record of M. pygmaea from the Black Peaks Formation, Texas, Schiebout, 1974, has been questioned; Krause, 1977). genus Ectypodus matthew and granger, 1921 Ectypodus matthew and granger, 1921, p. 1. Charlesmooria Kühne, 1969, p. 200. Type species.— Ectypodus musculus matthew and granger, 1921. Type locality.— Mason Pocket locality (late middle Tiffanian, Ti-4; Lofgren et al., 2004), Ani- mas formation, san Juan basin, Colorado, usa. Ectypodus sp. figure 1h-K Referred specimens.— left P4: um 84197 (l = 3.6, s = 11), um 84198 (l = 3.8, s = 10). Description.— P4: The lateral profile of UM 84197 and 84198 resembles that of P4 of Mesod- ma, Mimetodon, and other basal neoplagiaulacids in being asymmetrically arcuate, with a weakly convex to straight anterior margin and a long, straight posterior slope. the referred P4 differ from those of Neoplagiaulax in having a more arcuate profile (rather than more nearly trapezoidal), with a more convex anterior margin and more anteriorly positioned coronal apogee. the anterior margin of the crown does not project anteriorly as in P4 of more basal neoplagiaulacids (see, e.g., P4 of Mesodma thompsoni Clemens, 1964, or Mimetodon silberlingi (Simpson, 1936)); rather, the anterior edge forms a smooth arc extending from the base of the narrow and deep exodaenodont lobe to the high first serration, or to a slightly lower incipient serration (i.e., projection on the PaleoCene multituberCulates from Douglass Quarry 217 anterior margin of the apical crest and which lacks ridges; see Johnston and Fox, 1984). With the exception of the weakly developed posterolabial shelf, the labial side of the crown is virtually flat, while the lingual side is weakly convex. The cutting edge bears 11 or 12 serrations (N = 2), that become larger and more nearly conical posteriorly; the apogee of the crown is at the third or fourth serration. Obliquely oriented labial and lingual ridges are developed below the serrations; the ridges become weaker towards the posterior part of the crown, and are undeveloped below the penultimate and ultimate serrations. the anterobasal concavity is shallowly excavated for recep- tion of P3. Discussion.— um 84197 and 84198 resemble P4 of basal neoplagiaulacids in their asymmetri- cal profile, and in this regard are similar to P4 of Mesodma and particularly Mimetodon, the taxon to which these specimens were originally questionably referred (Krause and maas, 1990). the referred P4s differ from those of Mesodma and Mimetodon, however, in being higher-crowned, in having a more broadly arcuate anterior margin, and in having a relatively higher first serration, features more consistent with those on P4 of Ectypodus (e.g., relative height of P4 is approximately 50 percent standard length; Sloan, 1981). UM 84197 and 84198 resemble P4 of the late torre- jonian E. szalayi sloan, 1981 and especially the early middle tiffanian E. elaphus scott, 2005, differing from the latter only in their larger size and narrower exodaenodont lobe. While um 84197 and 84198 probably represent a new species of Ectypodus, we defer its formal naming and diagnosis, pending the discovery of additional, better-preserved material. Ectypodus sp. is also known from fragmentary specimens from the earliest Tiffanian Cochrane 2 and Aaron’s localities, Paskapoo Formation, Alberta (CSS, pers. obs.). genus Neoplagiaulax lemoine, 1882 Plagiaulax lemoine, 1880, p. 12. Neoplagiaulax lemoine, 1882, p. 1011. Type species.— Neoplagiaulax eocaenus (lemoine, 1880). Type locality.— Lemoine Quarry (Cernaysian, Savage and Russell, 1983; Lofgren et al., 2004), Cernay Conglomerate, northeastern Paris basin, france. Neoplagiaulax donaldorum n. sp. figure 2a-K; Tables 1, 2 Neoplagiaulax new species, Krause and maas, 1990, p. 84, table 3. Holotype.— um 84178, incomplete left dentary with P4, m1-2 (l P4 = 4.2, S = 12; L M1 = 2.6, W m1 = 1.2; L M2 = 1.6, W m2 = 1.4). Typodigm.— left P4: um 84192. right P4: um 84190-um 84191. left P4: um 84185-84189. right P4: um 84179-84184. Type locality.— Douglass Quarry, melville formation, eastern Crazy mountains basin, mon- tana, usa. Age and distribution.— earliest tiffanian (ti-1) of montana (type locality) and alberta (Co- chrane 2 locality, see Youzwyshyn, 1988; and Aaron’s locality, see Fox, 1990a). Diagnosis.— Differs from most other species of Neoplagiaulax in combining a short, rela- tively low crowned P4 with a more arcuate profile (i.e., the profile is more nearly circular than trapezoidal), and in having a more pronounced and projecting anterior margin; differs further in P4 having modally fewer cusps in the middle row. Differs from N. macintyrei sloan, 1981, ?N. burgessi archibald, 1982, and N. paskapooensis scott, 2005 in having a proportionately higher crowned and more arcuate P4. Differs from N. jepi sloan, 1987 in being proportionately lower crowned. Differs from N. kremnus Johnston and fox, 1984, N. hunteri (simpson, 1936), N. hazeni 218 C. s. sCott and D. W. Krause A B C D E F G H I J K L M N O P Q R S T U fig. 2 — multituberculates from the earliest tiffanian (ti1, late Paleocene) Douglass Quarry, eastern Crazy mountains basin, montana. a-K are Neoplagiaulax donaldorum n. sp, and l-u are Neoplagiaulax hunteri (simpson, 1936). a-C, right P4, UM 84190, in labial (A), lingual (B), and occlusal (C) views; D-F, right P4, UM 84191, in labial (D), lingual (E), and occlusal (F) views; G-I, incomplete left dentary with P4, m1-2, um 84178 (holotype), in labial (G), lingual (H), and occlusal (I) views; J and K, right P4, um 84182, in labial (J) and lingual (K) views. l-n, left P4, UM 84170, in labial (L), lingual (M), and occlusal (N) views; O-Q, right P4, UM 84173, in labial (O), lingual (P), and occlusal (Q) views; R and S, left P4, um 84157, in labial (R) and lingual (S) views; T and U, right P4, um 84166, in labial (t) and lingual (u) views. scale = 2 mm. (Jepsen, 1940), and N. mckennai sloan, 1987 in P4 and P4 being lower crowned and in P4 being less trapezoidal in profile. Differs from N. serrator scott, 2005 in having fewer serrations on P4, and fewer cusps on P4.