Mammalia, Multituberculata) from Near Calgary, Southwestern Alberta, Canada

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Canadian Journal of Earth Sciences

First mammal from the Willow Creek Formation: a new, early Paleocene ptilodontid (Mammalia, Multituberculata) from near Calgary, southwestern Alberta, Canada

Journal: Canadian Journal of Earth Sciences

Manuscript ID cjes-2020-0151.R2

Manuscript Type: Article

Date Submitted by the 26-Jan-2021 Author:

Complete List of Authors: Scott, Craig S.; Royal Tyrrell Museum of Palaeontology, Preservation and Research Keyword: Multituberculate,Draft Paleocene, Puercan, Alberta, Willow Creek Formation Is the invited manuscript for consideration in a Special Not applicable (regular submission) Issue? :

1 First mammal from the Willow Creek Formation: a new, early Paleocene ptilodontid

2 (Mammalia, Multituberculata) from near Calgary, southwestern Alberta, Canada

4 Craig S. Scott

6 Royal Tyrrell Museum of Palaeontology, P. O. Box 7500, Drumheller, Alberta, T0J 0Y0,

7 CANADA

8 Ph: 403-820-6219

9 Fax: 403-823-7131

10 [email protected]

11 Draft

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24 First mammal from the Willow Creek Formation: a new, early Paleocene ptilodontid

25 (Mammalia, Multituberculata) from near Calgary, southwestern Alberta, Canada

27 Craig S. Scott

29 Abstract:

30 Although multituberculates are among the best-represented mammals of the Late Cretaceous and

31 early Paleogene in North America, their evolution during the first several tens to hundreds of

32 thousands of years following the Cretaceous-Paleogene (K-Pg) impact event is largely obscure.

33 A better understanding of the early Paleogene record of multituberculates is crucial, for their

34 dominance in early Paleocene mammalianDraft faunas is unquestionably a result of rapid evolution

35 during the immediate post-impact interval, and they accordingly played an important role in the

36 evolution of mammalian communities more generally. I report on a new multituberculate from

37 the early Paleocene of southwestern Alberta, in rocks of the Willow Creek Formation, the first

38 such occurrence in this otherwise poorly known unit. The new multituberculate, Aenigmamys

39 aries, most closely resembles the ptilodontid Kimbetohia campi in comparable parts of the

40 dentition, and sheds light on the early evolution of Ptilodontidae, one of the major cimolodontan

41 families that diversified during the Paleocene. The presence of Aenigmamys in mammalian

42 faunas that lived soon after the K-Pg boundary implies a still-deeper evolutionary history for

43 Ptilodontidae that may have extended into the Late Cretaceous. Aenigmamys is part of a new

44 mammalian fauna from southwestern Alberta, the taxonomic composition of which includes a

45 diversity of multituberculates, cimolestans, primates, and condylarths. The fauna correlates with

46 those of middle Puercan age from other parts of the Western Interior of North America, and its

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47 high taxonomic diversity further corroborates previous hypotheses that multituberculate

48 recovery–and mammalian recovery more generally–occurred relatively quickly after the K-Pg

49 extinction event.

51 Keywords: Multituberculata, Ptilodontidae, Puercan, Paleocene, Alberta

53 Résumé:

56 Introduction

57 The fossilized remains of mammals thatDraft lived during the first several hundred thousand years

58 after the Cretaceous-Paleogene (K-Pg) impact event, during the Puercan North American Land

59 Mammal Age (NALMA), are known almost exclusively from localities in the Western Interior of

60 North America (Cifelli et al. 2004; Lofgren et al. 2004). While this record is the most nearly

61 complete of anywhere in the world, much of what is known about mammalian faunal recovery

62 following the extinction event comes from but a handful of key localities, and although the

63 number and quality of localities have improved considerably in recent years (e.g., Fox et al.

64 2014; Dahlberg et al. 2016; Fuentes et al. 2019; Lyson et al. 2019;), the record overall remains

65 poor when compared to those from the preceding Lancian and succeeding Torrejonian

66 NALMAs. A better understanding of this record is important, as the K-Pg mass extinction

67 induced both a reorganization of terrestrial ecosystems and significant biotic turnover, and set the

68 stage for adaptive radiations in several major vertebrate clades. Although debate continues over

69 the timing and tempo of their diversification after the extinction event, there is little argument

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70 that among the beneficiaries of the selective nature of extinctions at the K-Pg boundary were

71 early Paleocene mammals (see, e.g., dos Reis et al. 2012; O’Leary et al. 2013; Beck and Lee

72 2014; Halliday et al. 2016, 2017; Fuentes et al. 2019). The demise of all non-avian dinosaurs

73 opened a significant number of previously occupied ecological niches, allowing mammals to

74 flourish during the Cenozoic (Archibald 1982; Archibald and Lofgren 1990; Lofgren 1995;

75 Clemens 2002; Archibald and Rose 2005; Wilson 2014; Sprain et al. 2015; Smith et al. 2018).

76 Of the mammals that survived the extinction, multituberculates are among the best

77 represented and best studied. Estimates of extinction and origination rates prior to and after the

78 impact vary (e.g., Archibald and Lofgren 1990; Wilson et al. 2012; Wilson 2014; Pires et al.

79 2018), but multituberculates generally achieved a modest level of taxonomic diversity during the

80 later parts of the Cretaceous, experiencedDraft reduced origination and diversification at the

81 extinction event (and the elimination of several higher-level taxa), and briefly radiated during the

82 early Paleogene before finally going extinct in the late Eocene (Krause 1986: fig. 1; Weil and

83 Krause 2008; Pires et al. 2018). Multituberculate survival across the K-Pg boundary–inferred

84 primarily from well-sampled, fossiliferous sections in northeastern Montana and southwestern

85 Saskatchewan–appears to have been restricted primarily to species of Mesodma Jepsen, 1940 and

86 Cimexomys Sloan and Van Valen 1965, and at least two additional neoplagiaulacids

87 (Parectypodus Jepsen, 1930 and Neoplagiaulax Lemoine, 1882 have been identified from a few

88 Lancian localities; Archibald 1982; Storer 1994). These Late Cretaceous survivors co-occur in

89 the early Puercan with several supposed immigrant multituberculates in local faunas (e.g., the

90 eucosmodontid Stygimys Sloan and Van Valen, 1965 and the taeniolabidoid Valenopsalis

91 Williamson et al., 2016). Because of the density of their fossil record, multituberculates have

92 figured importantly in understanding mammalian evolution during the first several hundred

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93 thousand years following the K-Pg extinction (e.g., Wilson et al. 2012; Wilson 2014; Pires et al.

94 2018).

95 I report herein on a new multituberculate from the Willow Creek Formation of

96 southwestern Alberta, a rock unit that has until relatively recently been regarded as poorly

97 fossiliferous, particularly the upper, Paleocene part. The new multituberculate, Aenigmamys

98 aries gen. et sp. nov., sheds light on the early evolution of Ptilodontidae, one of the major

99 cimolodontan families that diversified during the Paleocene (Weil and Krause 2008). The

100 specimens are noteworthy for their excellent preservation, with much of the dentition known

101 from articulated remains. Aenigmamys is part of a newly discovered mammalian local fauna that

102 existed in southwestern Alberta during the Puercan NALMA; this fauna is taxonomically

103 diverse, further corroborating previous hypothesesDraft that multituberculate recovery–and

104 mammalian recovery more generally–occurred relatively quickly after the K-Pg extinction event

105 (e.g., Archibald 1982; Johnston and Fox 1984; O’Leary et al. 2013; Wilson 2013, 2014; Halliday

106 et al. 2016; Pires et al. 2018).

107

108 Geological setting and locality

109 Geological Setting and Formational Nomenclature: Specimens described in this paper were

110 collected at outcrops of the Willow Creek Formation south of Calgary and east of Okotoks in

111 southwestern Alberta (Fig. 1). The formation, together with the laterally equivalent Scollard and

112 Coalspur formations of the central Plains and central Foothills, respectively, forms the upper

113 parts of an eastward-thinning clastic wedge of primarily fluvial sediments that were deposited in

114 the foreland basin during the latest parts of the Cretaceous and early parts of the Paleocene

115 (Jerzykiewicz 1997: figs. 1, 2; Hamblin 2010: fig. 1). The Willow Creek Formation was first

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116 described by Dawson (1883) for rocks exposed on Willow Creek south of Calgary; Williams and

117 Dyer (1930) defined the type section based on exposures at the mouth of the creek east of Fort

118 McLeod. The formation forms a strongly asymmetrical wedge that becomes thicker westwards,

119 from approximately 320 m in the plains to in excess of 1000 m in the southwestern corner of the

120 province (Jerzykiewicz 1997). The upper and lower contacts are unconformable, and the

121 formation is divided into lower and upper members by the Cretaceous-Paleogene boundary,

122 identified on the basis of palynomorphs, as the boundary coal and claystone are not developed

123 (Jerzykiewicz and Sweet 1988). Douglas (1950) divided the formation into five distinct units,

124 with the K-Pg boundary occurring in unit d.

125 The most characteristic features of the Willow Creek Formation are the presence of

126 “…alternating varicoloured claystone andDraft lesser soft grey calcareous sandstone, characterized by

127 brilliant colour banding which fades to the north…” (Hamblin 2010: 11, and references therein),

128 the development of extensive layers of caliche paleosols and hardpan, and the rarity of coal

129 (Jerzykiewicz 1997). These features are found exclusively in the lower, unnamed Cretaceous

130 member. The development of calcareous red beds and pedogenic caliche has been interpreted as

131 representing deposition in a warm, semi-arid environment (Jerzykiewicz and Sweet 1988;

132 Jerzykiewicz 1997). In contrast, the upper, Paleocene member is characterized primarily by dark

133 grey mudstone and fine-grained siltstones and sandstones that occur low in the member; cross-

134 bedded sandstone becomes more prominent towards the top of the member, nearer the contact

135 with the overlying Porcupine Hills Formation. Caliche facies occur in the upper part of the

136 formation (albeit significantly less frequently), suggesting a persistence of dry conditions into the

137 Paleocene, but a concomitant increase in angiosperm palynomorph diversity indicates that the

138 environment was less xeric than during the preceding Cretaceous. (Jerzykiewicz and Sweet

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139 1988: fig. 2; Jerzykiewicz and Sweet 1986; Jerzykiewicz and Norris 1992; Sweet and Braman

140 1992; Jerzykiewicz 1997; Hamblin 2010).

141 Although characterized as generally unfossiliferous, the Cretaceous part of the Willow

142 Creek Formation has produced fossils in the past (e.g., Russell and Landes 1940; Tozer 1956;

143 Braman and Sweet 1990), and is notable for being the source of a partly articulated specimen of

144 the theropod Tyrannosaurus rex (Currie 2003; Eberth et al. 2013). More recent work has

145 revealed a diversity of ootaxa from the Cretaceous part of the formation, with most of these

146 being referable to the ornithopod ootaxon Spheroolithus (Zelenitsky et al. 2017).

147 Locality: The Sheep Ahoy! locality was discovered by field parties from the Royal

148 Tyrrell Museum of Palaeontology (RTMP) in 2008 during a prospecting trip east of Okotoks

149 along Sheep River. The fossilized remainsDraft of trionychid turtles had been reported from

150 Highwood River near the mouth of Sheep River in the Aldersyde district in the late 1920s

151 (Russell 1930; Brinkman 2013), but no follow up prospecting had occurred since that time. The

152 first specimen to be discovered at Sheep Ahoy!, an upper molar of a condylarth, was found in

153 rocks exposed on the south side of Sheep River near the confluence with Highwood River (Fig.

154 1). In the ensuing field seasons, hundreds of specimens have been recovered from the locality,

155 making Sheep Ahoy! one of the most productive early Paleocene vertebrate localities in western

156 Canada. Significant prospecting of the Sheep River-Highwood River area occurred during the

157 2014–2017 field seasons by technicians from the RTMP as part of a Government of Alberta

158 initiative called the Southern Alberta Flood Mitigation Project (SAFMP). The SAFMP sought to

159 examine areas along river systems in southern Alberta that were affected by the severe flooding

160 of 2013, to identify fossil localities along these rivers that were newly exposed, and to mitigate

161 new and existing fossil localities that were deemed at imminent risk of being lost through

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162 erosion. These efforts resulted in the discovery of dozens of fossil localities that extend from

163 Sheep River west of Okotoks and Highwood River near High River, northeast to Bow River near

164 the mouth of Highwood River.

165 The Sheep Ahoy! locality occurs near the confluence of the Sheep and Highwood rivers,

166 east of the town of Okotoks and Alberta Provincial Highway 2. Rocks exposed in this area were

167 originally referred to the Paskapoo Formation (Russell 1930), but were subsequently referred to

168 the upper part of the Scollard Formation (e.g., Jerzykiewicz 1997), correlative with the upper

169 parts of the Coalspur Formation of the central Foothills and Willow Creek Formation of south-

170 western Alberta. The results of more recent work in the area by the RTMP suggest that the

171 lithology of the exposures at Sheep Ahoy! and vicinity is more consistent with that of the upper,

172 or Paleocene, part of the Willow Creek DraftFormation, and this interpretation is followed here.

173 The fossiliferous horizon occurs approximately 3 m above normal river level, in pale grey

174 to light green strata; massive, blocky sandstones occur above the horizon, and the area is capped

175 by Quaternary gravels. The fossiliferous horizon consists primarily of lenses of soft coquina,

176 consisting of nearly complete-to-badly fragmented shells of gastropods; the coquina rests on a

177 very fine-grained siltstone, in which occasional stringers of densely packed, hashed molluscan

178 shell can occur. The coquina grades upwards into a coarser siltstone containing the fossilized

179 shells of bivalves and gastropods, as well as the remains of small vertebrates, plant debris, and

180 occasional lignite. The coquina beds can be thick, particularly towards the mouth of Sheep River,

181 where they often exceed one metre, although vertebrate fossils appear to be less abundant in

182 these beds. The mammalian fossils occur along with those of actinopterygians (primarily amiids

183 and gar), amphibians, turtles, champsosaurs, crocodilians, and lizards, and an incomplete skull of

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184 a champsosaur was found during the initial discovery of the locality in 2008, in a dissociated

185 siltstone block on Highwood River at the confluence with Sheep River.

186

187 Methods, terminology, and abbreviations

188 Terminology and Measurements: Multituberculate dental terminology follows that of Krause

189 (1977, 1987, 1992). Upper fourth premolar cusp row homologies and cusp counts follow Krause

190 (1977, 1982). Measurements follow Krause (1987) and Scott (2003). “Incipient serration”

191 [=“pseudoserration” of Krause (1982) and Hunter et al. (1997)] refers to a serrate projection on

192 the anterior margin of the apical crest of multituberculate p4s; incipient serrations lack labial

193 ridges and are excluded from serration counts (Johnston and Fox 1984). “Exodaenodont lobe”

194 (the “triangular lobe” of Kielan-JaworoskaDraft et al. 2004) refers to the ventral projection of enamel

195 on the labial side of the anterior root on the p4 of many multituberculates. Outline drawings of

196 lower fourth premolars were made with the aid of a camera lucida following the methodology of

197 Jepsen (1940) and Krause (1977). Baseline of standard measurement refers to a line that extends

198 from the apex of the anterobasal concavity posteriorly to the point where the posterolabial shelf

199 intersects the posterior margin of the crown. All measurements are in millimeters, and were

200 taken using digital calipers and the aid of a microscope.

201 Institutional Abbreviations: ANMH, American Museum of Natural History, New York,

202 U.S.A.; TMP, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada; UALVP,

203 Laboratory for Vertebrate Paleontology, University of Alberta, Edmonton, Alberta, Canada;

204 UCMP, University of California Museum of Paleontology, Berkeley, California, U.S.A.

205 Dental Abbreviations: i, lower incisor; M/m, upper and lower molar, respectively; P/p,

206 upper and lower premolar, respectively.

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207 Other Abbreviations: “Lancian”, “Puercan”, “Torrejonian”, “Tiffanian”, and

208 “Clarkforkian” refer to several of the North American Land Mammal Ages (NALMA) of the

209 Late Cretaceous and Paleogene; NALMAs are biochrons, units of relative time defined by

210 mammalian taxa that lived during those intervals (Woodburne 2004).

211

212 Systematic paleontology

213 Class Mammalia Linnaeus, 1758

214 Subclass Allotheria Marsh, 1880

215 Order Multituberculata Cope, 1884b

216 Suborder Cimolodonta McKenna, 1975

217 Superfamily Ptilodontoidea SloanDraft and Van Valen, 1965

218 Family Ptilodontidae Cope, 1887

219 Genus Aenigmamys gen. nov.

220 DIAGNOSIS: As for the type and only species.

221 ETYMOLOGY: Aenigma, Latin noun, mystery; mys, Greek noun, mouse. In reference to the initial

222 difficulties in determining the taxonomic position of this multituberculate.

223

224 Aenigmamys aries sp. nov.

225 (Figs. 2–5)

226 DIAGNOSIS: Differs from Kimbetohia Simpson, 1936b in having significantly less robust,

227 narrower, and higher-crowned P4, and more smoothly arcuate p4 with steeper and more convex

228 anterior margin. Differs further from Kimbetohia in having a double-rooted P2. Differs from

229 Baiotomeus Krause, 1987 in having a higher-crowned P4 with a shorter labial cusp row, and

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230 lower-crowned and less symmetrical p4 generally bearing fewer incipient serrations. Differs

231 further from Baiotomeus in p4 being long relative to height. Differs from Ptilodus Cope, 1881 in

232 having a higher-crowned P4 with a generally weaker anterolabial bulge, and a less symmetrical

233 p4 with a lower first serration. Differs further from Ptilodus in having a three-cusped P2 and

234 lower molars that are longer relative to width. Differs from Prochetodon Jepsen, 1930 in having

235 relatively shorter and more robust P4 with significantly shorter labial cusp row, and p4 with

236 much steeper anterior margin and less obliquely directed labial and lingual ridges. Differs further

237 from Prochetodon in having a four-cusped P3.

238 HOLOTYPE AND LOCALITY: TMP 2011.096.0771, incomplete right dentary with p3–4, m1–2 (Fig.

239 3A–C). Sheep Ahoy! locality, Willow Creek Formation of Alberta, early Paleocene (middle

240 Puercan, Pu2), Ectoconus/Taeniolabis taoensisDraft Interval Zone of Lofgren et al. (2004).

241 REFERRED SPECIMENS: Upper dentition: TMP 2008.088.0749, incomplete right maxilla with P1–

242 4; 2013.032.0308, incomplete left maxilla with P1–3; 2008.088.0283, incomplete right maxilla

243 with P3–4; 2013.032.0020, incomplete left maxilla with P4; 2012.035.0427, incomplete right

244 maxilla with P4, M1–2; 2008.088.0287, 2008.088.0370, 2008.088.0384, 2008.088.0407,

245 2011.096.0151, 2011.096.0286, 2011.096.0479, 2011.096.0501, 2011.096.0556, 2012.035.0202,

246 2012.035.0214, 2012.035.0285, 2012.035.0459; 2012.035.0482, 2012.035.0576, 2013.032.0156,

247 2013.032.0277, 2013.032.0585, 2013.032.0616, P4; 2008.088.0337, 2008.088.0339,

248 2009.132.0049, 2009.132.0063, 2011.096.0138, 2013.032.0495, incomplete P4; 2008.088.0265,

249 2008.088.0438, 2008.088.0467, 2009.132.0099, 2009.132.0303, 2009.132.0368, 2011.096.0595,

250 2012.035.0249, 2013.032.0314, M1; 2008.088.0423, incomplete M1.

251 Lower dentition: TMP 2008.088.0462, 2011.096.0403, 2012.035.0033, 2012.035.0082,

252 2012.035.0095, M2; 2013.032.0158, incomplete right dentary with i1, p3–4; 2008.088.0355,

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253 incomplete left dentary with p4; 2012.035.0391, incomplete right dentary with p4;

254 2008.088.0475, 2008.088.0526, 2012.035.0563, incomplete left dentary with p4; 2008.088.0431,

255 incomplete right dentary with p4, m1; 2013.032.0439, incomplete left dentary with p4, m1;

256 2010.113.0227, incomplete left dentary with p3–4, m1; 2011.096.0141, incomplete right dentary

257 with p4, m1–2; 2008.088.0365, 2008.088.0516, 2008.088.0531, 2008.088.0536, 2009.132.0150,

258 2009.132.0365, 2010.113.0019, 2011.096.0306, 2011.096.0376, 2011.096.0485, 2011.096.0588,

259 2012.035.0418, 2012.035.0461, 2012.035.0479, 2012.035.0709, 2013.032.0170, 2015.066.0163,

260 2015.066.0164, p4; 2008.088.0425, 2008.088.0447, 2008.088.0524, 2011.096.0610,

261 2012.035.0146, incomplete p4; 2008.088.0305, 2008.088.0315, 2008.088.0422, 2009.132.0078,

262 2009.132.0263, 2011.096.0329, 2012.035.0066, 2013.032.0167, 2013.032.0479, 2013.032.0508,

263 m1; 2008.088.0328, 2011.096.0045, 2012.035.0279,Draft m2.

264 ETYMOLOGY: Aries, Latin noun, ram. In reference to Sheep River.

265 DESCRIPTION: The specimens from Sheep Ahoy! document nearly the entire dentition of

266 Aenigmamys, in addition to parts of the maxilla, including the facial and palatal processes,

267 anterior part of the zygomatic arch, and infraorbital canal.

268 Maxilla: The maxilla of Aenigmamys closely resembles that of other ptilodontoids (see,

269 e.g., Gidley 1909; Broom 1914; Simpson 1937; Sloan 1981; Kielan-Jaworowska and Hurum

270 2001; Fox 2005; Scott 2005). The facial process is best preserved in TMP 2008.088.0749 (Fig.

271 2D): it is robust and deep, especially at the level of P1 and P2, and its anterior edge is smoothly

272 finished for articulation with the posterior parts of the premaxilla. The maxilla widens slightly at

273 the level of P4, where the maxillary root of the zygomatic arch originates, but does not abruptly

274 flare laterally as in, e.g., taeniolabidids and lambdopsalids (e.g., Granger and Simpson 1929;

275 Kielan-Jaworowska 1970; Miao 1988; Kielan-Jaworowska and Hurum 1997; Fox 2005). The

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276 maxillary process of the zygomatic arch, best preserved in TMP 2008.088.0749 (Fig. 2F), is

277 stout at the base but tapers posteriorly. The posteriormost part of the base (see Rougier et al.

278 1997) arises near the level of the posteriormost cusp on P4, and extends posterolaterally at an

279 angle of about 160 degrees from the anteroposterior axis. The maxillary-squamosal suture is not

280 preserved in TMP 2008.088.0749, nor is there evidence on the parts preserved of a medially

281 positioned jugal (Hopson et al. 1989). The anterior zygomatic ridge (Gambaryan and Kielan-

282 Jaworowska 1995) is not developed in Aenigmamys, with the maxillary process instead being

283 divided into lateral and ventral parts by a prominent crest; the absence of the anterior zygomatic

284 ridge is consistent with that seen in other ptilodontids, and ptilodontoids more generally (Fox

285 2005) . The presence of intermediate and posterior zygomatic ridges, if these were present in life,

286 cannot be determined. A single, subcircularDraft infraorbital foramen is preserved in TMP

287 2008.088.0749 and TMP 2008.088.0283 (Figs. 2D, F, J): it is positioned dorsal to the anterior

288 part of P4, slightly posterior to that reported for Ptilodus montanus Douglass, 1908 (see Simpson

289 1937), and opens anteriorly and slightly ventrally. There is no evidence of a shallow, rounded

290 excavation on the maxilla anterior to the infraorbital foramen, as reported by Fox (2005) for

291 Microcosmodon conus Jepsen, 1930 and Scott (2005) for Neoplagiaulax cimolodontoides Scott,

292 2005. Although parts of the palatal process of the maxilla are preserved on TMP 2013.032.0308

293 and TMP 2008.088.0749 (2C, F), little can be said of its anatomy. The process is best seen in

294 TMP 2013.032.0308 (Fig. 2C), where it is preserved medial to the anterior premolars. An area of

295 smoothly finished bone medial to P2 and P3 marks the anterolabial margin of a large palatal

296 vacuity, similar to that reported for other ptilodontoids (e.g., Gidley 1909; Broom 1914; Simpson

297 1937; Fox 2005; Scott 2005), and a patch of small nutritive foramina occurs just medial to P2.

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298 P1–3: P1–3 are known from two specimens (TMP 2013.032.0308, TMP 2008.088.0749;

299 Fig. 2A–E), both preserving P1–3 in articulation; TMP 2008.088.0749 is particularly important

300 as it documents P1–3 in articulation with the P4. The anterior premolars closely resemble those

301 of most ptilodontids in their features, with the subconical cusps being large and coarse, and the

302 enamel bearing heavy vertical striations. The P1 supports three cusps arranged in a near-

303 equilateral triangle. The anterior cusp is smaller and lower than the two posterior cusps, and is

304 positioned somewhat closer to the lingual cusp; the lingual cusp occurs directly lingual to the

305 labial cusp. A prominent crest extends posterolabially from the apex of the anterior cusp, joining

306 with a similar crest running anterolingually from the labial cusp. The valley-facing sides of the

307 anterior and lingual cusps are slightly inflated, whereas that of the labial cusp is flat; the enamel

308 on the valley-facing sides of the cusps isDraft largely devoid of striations. The posterolingual part of

309 the crown is slightly extended posteriorly, and is positioned dorsal to the anterior margin of P2.

310 The crown of P2 is subtriangular in occlusal outline and largely resembles P1 in its

311 features, but is shorter relative to width. The crown bears three cusps, with the anteriormost cusp

312 positioned farther lingually than in P1; as a result, the anterior and lingual cusps on P1, and the

313 two lingual cusps on P2, are largely in line, forming a shallow arc. As in P1, the posterolingual

314 margin of the crown is slightly extended posteriorly and is dorsal to the anterior margin of P3.

315 The P3 is smaller and considerably lower crowned than P1 or P2, and the cusps are

316 smaller. The four cusps are arranged in two longitudinal rows on the subovate or subrectangular

317 crown, and the rows align with the labial and lingual rows on P2. As with P1 and P2, the

318 posterolingual part of P3 occurs dorsal to the anterior margin of P4 (Figs. 2D–E, G–H. This

319 arrangement–with the posterolingual part of the premolar crown positioned dorsal to the anterior

320 margin of the next posterior tooth–provides further confirming evidence that the replacement

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321 sequence of P1–3 proceeded posteroanteriorly in ptilodontoids (Clemens 1964; Fox 2005; Scott

322 2005).

323 P4: Cusp formula (0–1)2–4:9–10:0 [mode=(0)3:9:0; N=21]. The P4 is long and low, with

324 the cutting edge straight to slightly convex in lateral view, and with a modest increase in cusp

325 height posteriorly (best seen in Figs. 2N–O, Q–R). The crown is narrow posteriorly, but widens

326 anteriorly, where a moderately to strongly bulging anterolabial lobe is developed. The crown

327 supports two subparallel rows of cusps, with a single cusp occasionally developed on the

328 anterolabial lobe. The external row is variable in length, but extends posteriorly to at least the

329 fifth cusp of the middle row in all specimens at hand. The external row is convex labially,

330 forming a shallow arc, with the cusps increasing in size and height to the third cusp, which is the

331 largest on the crown. The cusps of the externalDraft row are subconical, being flatter labially and

332 convex lingually; short, low crests can connect the first two or three cusps anteriorly and

333 posteriorly. The cusps of the middle row are arranged in a straight to faintly curved line; they are

334 subequal in size, but become slightly taller posteriorly, and are connected to one another by high

335 crests. On unworn specimens, the posteriormost three or four cusps are highest above the base of

336 the enamel. The posterior slope is short, shallow, and usually faintly concave, and small cuspules

337 can be developed posterolingually, enclosing a small pocket. The enamel is wrinkled and forms

338 prominent ridges and grooves on the labial and lingual surfaces of cusps of the middle and

339 external rows.

340 M1: Cusp formula 8:8–10:5–7 (mode=8:10:5–6; N=8). The crown of M1 resembles that

341 of other ptilodontoids: it is teardrop shaped in occlusal outline, with three subparallel cusp rows,

342 and the occlusal surface is slightly concave in medial or lateral view. The cusps of the external

343 row are subconical anteriorly, but become increasingly pyramidal posteriorly, with square bases

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344 and four distinct surfaces; they are somewhat anteroposteriorly compressed towards their apices.

345 The middle cusp row is the longest on the crown, extending farther anteriorly than the external

346 row, and the cusps lean anteriorly; an obliquely directed crest connects the first cusp of the

347 external and middle rows, closing off the intercusp valley. The bases of the cusps of the middle

348 row are wide and subrectangular, and the cusps are weakly crescentic, particularly more

349 posteriorly in the row, where the anterior surfaces are faintly concave; cusp interlock is not

350 developed (Scott et al. 2018). The ultimate cusp in the middle row is the largest and tallest on the

351 crown. The internal cusp row begins at the level of the fourth, fifth, or sixth cusp of the middle

352 row, but a low, papillate ridge can extend anteriorly from the first cusp towards the anterior

353 margin of the crown. The cusps of the internal row are subpyramidal, with square bases and four

354 sides; like those of the external row, theDraft cusps of the internal row are slightly compressed

355 towards their apices. The valley-facing surfaces of the cusps are pitted and grooved, and the

356 enamel on the lingual side of the internal cusps, and the labial side of the external cusps, is

357 weakly wrinkled.

358 M2: Cusp formula 3:2:0 (mode=3:2:0; N=6). As with those of other ptilodontoids, the

359 crown of M2 is subtrapezoidal in occlusal outline, with transverse anterior and smoothly rounded

360 posterior sides. The external cusp row consists of a robust crest connecting the apices of the first

361 and last cusps of the middle row; the crest can bear irregular cuspules, but fully differentiated

362 cusps are not present. The two cusps of the middle row are large and stout, anteriorly leaning,

363 subcrescentic in cross section, and subequal in size and height. The cusps of the internal row are

364 lower and smaller than those of the middle row, are subpyramidal, and decrease in size and

365 height posteriorly. A prominent crest extends labially from the apex of the first cusp of the

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366 internal row to join the ridge-like crest of the external row. Deep, vertical grooves are present on

367 the valley-facing sides of the middle and external rows.

368 Dentary: The dentary of Aenigmamys resembles that of other ptilodontoids (Simpson

369 1937; Jepsen 1940; Fox 2005; Scott 2005). The alveolar process for i1 is short, robust, and deep,

370 contrasting with that in the neoplagiaulacids Neoplagiaulax hunteri (Simpson, 1936a) and N.

371 serrator, and the diastema is accordingly short. The unfused symphyseal surface is

372 anteroposteriorly short and comma shaped, and the bone smoothly finished, suggesting a

373 considerable degree of movement between the opposing dentaries was possible. The dorsal

374 margin of the alveolar process between i1 and p4 is smoothly rounded, and does not form a low

375 keel (Jepsen 1940; Scott 2005). As in other cimolodontans, the incisor alveolar process is

376 directed medially relative to the horizontalDraft ramus, with the two parts of the dentary forming an

377 angle of about 160º at their union. The coronoid process is best preserved in the holotype (TMP

378 2011.096.0771; Fig. 3A–B), where the robust base originates lateral to the anteroposterior

379 midpoint of m1, and although the ascending anterior part of the process is incompletely

380 preserved, the parts that remain indicate that the apex occurred well above the level of p4. The

381 lateral surface of the coronoid process is well excavated for insertion of the mandibular

382 adductors; the masseteric fossa is deeply excavated and extends anteriorly as a shallow

383 depression to the level of the posterior root of p4. The pterygoid shelf is robust, and forms the

384 floor of a deeply excavated pterygoid fossa, the area of attachment for the pterygoideus

385 musculature. The fossa extends anteriorly to the level of the posterior root of m2, and terminates

386 at a large, subovate mandibular foramen. The condyle and its associated process are preserved in

387 TMP 2008.088.0355 (Fig. 3F–G): posterior to the coronoid process, the ascending ramus

388 narrows and forms a short but robust condylar process that supports a low, broad condyle. As in

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389 other ptilodontoids, the anteroposterior axis of the condyle in TMP 2008.088.0355 is oriented

390 parallel to the cheek teeth, and the articulating surface is tilted slightly posteriorly (Scott 2005).

391 The condyle is imperfectly preserved in TMP 2008.088.0355, but its articulating surface was

392 clearly broad relative to length, and shallowly convex mediolaterally. A heavy, posteriorly

393 convex ridge connects the condylar process to the pterygoid shelf. A single mental foramen

394 occurs anteroventral to p3 on the alveolar process for i1.

395 i1: In contrast to that of several other ptilodontoids (e.g., Ptilodus montanus and Ptilodus

396 wyomingensis; see Gidley 1909: pl. 70; Simpson 1937: fig. 4; Jepsen 1940: pl. II, fig. 1a;

397 Neoplagiaulax serrator; see Scott 2005: fig. 4), the crown of i1 is relatively short and robust, and

398 is less procumbent, instead being directed more dorsally (Fig. 3D–E). In cross section, the crown

399 is convex laterally and flat medially. A medialDraft ridge extends posteroventrally from the apex of

400 the incisor, becoming more prominent posteriorly. Enamel covers the tip in its entirety, and there

401 is no indication that the enamel is significantly thicker labially or ventrally, as is the case in

402 several other multituberculate groups (e.g., Djadochtatherioidea or Taeniolabidoidea; Granger

403 and Simpson 1929; Kielan-Jaworowska 1970; Kielan-Jaworowska and Hurum 2001; Williamson

404 et al. 2016).

405 p3: The crown of p3 is bulbous and peg-like, and can support an anteriorly positioned

406 apical cuspule. As in other ptilodontoids, the crown of p3 occupies the anterobasal concavity of

407 the p4.

408 p4: The crown of p4 is long and low, with a slightly asymmetrically curved serrate crest

409 bearing 12, 13, or 14 serrations (mode=13, N=19). The labial surface of the crown is flat,

410 whereas the lingual surface is more convex, especially near the base of the crown. The leading

411 edge of the serrate crest is weakly convex in profile; it is slightly reclined, similar to p4 of

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412 Kimbetohia, but more nearly vertical than that of most species of Ptilodus, and considerably

413 steeper than that of Prochetodon. When the dentary is held in a horizontal plane, the apogee of

414 the serrate crest occurs at the third through fourth, fifth, or sixth serrations. Posterior to the

415 apogee, the serrate crest begins to descend posteroventrally at an angle of about 40 degrees from

416 horizontal. As is the case with most other ptilodontoids, the serrations become larger and coarser

417 posteriorly, with the last four or five being stout and nearly conical. Well-defined ridges occur

418 labially and lingually below the serrations, and become increasingly coarser and farther apart

419 posteriorly; the terminal one, two, or three serrations lack both labial and lingual ridges. The

420 labial and lingual ridges associated with the anterior serrations are variable in their development

421 and trajectory. In all specimens, the first serration supports a sharp crest that extends

422 anteroventrally and slightly labially, delimitingDraft the labial margin of the broad anterior face of the

423 crown; on some specimens (e.g., TMP 2008.088.0365, 2015.066.0163), one or two weak

424 incipient serrations are developed on this crest. The crest can be joined by a labial ridge from the

425 second serration (e.g., TMP 2012.035.0146) or the two can remain separate (e.g., TMP

426 2013.032.0439, 2013.032.0170), and on one specimen (TMP 2008.088.0475), a second labial

427 ridge descends ventrally from the first serration, joining with the second ridge. The labial ridges

428 posterior to the second ridge become farther apart and more nearly vertical in their orientation.

429 On most specimens, a short lingual ridge extends anteroventrally from the first serration, joining

430 the ridge from the second serration; on a few specimens (e.g., TMP 2009.132.0365), the first

431 lingual ridge is longer, and the ridge from the second serration joins it posteriorly. Like those on

432 the labial side of the crown, the lingual ridges posterior to the second serration become farther

433 apart, but their orientation is more nearly horizontal. The crown juts anteriorly at the union of the

434 serrate crest and exodaenodont lobe just dorsal to the anterobasal concavity, which is deep and

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435 peaked for reception of p3. The slightly inflated exodaenodont lobe is long, extending for more

436 than half the length of the crown on some specimens (e.g., Fig. 3F, H), and can be smoothly

437 rounded, or more often sharply pointed. The posterolabial shelf is prominent, laterally

438 protruding, and often heavily worn.

439 m1: Cusp formula 6–8:4–5 (mode=6:5; N=14). The m1 of Aenigmamys is similar to that

440 of most other ptilodontids in having labial and lingual cusp rows with large, massive cusps; in

441 several specimens a weak constriction occurs near the anteroposterior midpoint of the crown.

442 The anteriormost cusp of the external row is small, swollen, and subconical. The second, third,

443 and fourth cusps are pyramidal, with four distinct sides, whereas the remaining cusps are

444 subcrescentic and weakly interlocking (Scott et al. 2018), the fifth cusp being the widest in the

445 external row. The ultimate and penultimateDraft cusps in some specimens are fused. Prominent

446 vertical grooves occur on the valley-facing sides of the external cusps, becoming deeper towards

447 the posterior part of the row. The cusps of the internal row are slightly taller than those of the

448 external row. The anteriormost internal cusp is short and subconical, whereas the remaining

449 cusps are pyramidal, with swollen lingual sides. The third cusp of the internal row is usually the

450 tallest on the crown, and the terminal two cusps are sometimes fused. As with the external row,

451 vertical grooves occur on the valley-facing side of the internal row.

452 m2: Cusp formula 4:2 (mode=4:2; N=4). The cusps of the external row on m2 are

453 subcrescentic, with the first two or three cusps being subequal in size and height. The ultimate

454 cusp on the external row is longer than the first two or three and can be joined with the preceding

455 cusp. The two internal cusps are massive and swollen at their bases, with the more anterior of the

456 two the larger and taller; both cusps are subcrescentic in cross section. As with m1, deep grooves

457 are developed on the valley-facing side of the internal cusps.

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458

459 Discussion

460 THE SYSTEMATIC POSITION OF AENIGMAMYS

461 The enlarged and robust, heavily striated upper premolars, the low-crowned P4 supporting a

462 prominent anterolabial bulge, and the enlarged, near-symmetrical p4 seen in Aenigmamys is a

463 combination of dental characters seen, among ptilodontoids, in members of the Ptilodontidae

464 (Weil and Krause 2008), a family that first appears in the early Puercan (Lofgren et al. 2004;

465 Weil and Krause 2008). Further, the p4/m1 ratio for Aenigmamys is 1.83, falling within the range

466 that characterizes ptilodontids (1.7 to 2.4; Weil and Krause 2008), and the upper and lower

467 molars closely resemble those of other ptilodontids. Compared to neoplagiaulacid

468 multituberculates having broadly similarDraft p4s, that of Aenigmamys is more evenly arcuate and

469 less trapezoidal in lateral profile than those of most species of Neoplagiaulax, exhibiting a

470 shallower break in the trajectory of the cutting edge posterior to the apogee (compare, e.g., the p4

471 profiles of Aenigmamys with those of species of Neoplagiaulax in Krause 1977 and Scott 2005).

472 The p4 of Aenigmamys is more symmetrical in profile than that of either Mimetodon Jepsen,

473 1940 or Mesodma (see, e.g., Jepsen 1930, 1940), and is significantly lower crowned than that of

474 Ectypodus Matthew and Granger, 1921 and Parectypodus. While these characters point to

475 affinities with the Ptilodontidae, several features suggest that Aenigmamys may be a basal

476 member of the family, resembling those seen in other ptilodontoids, and in Kimbetohia,

477 considered to be the most basal ptilodontoid so far discovered (Krause 1982, and see below). For

478 example, although the P4 of Aenigmamys is low crowned, with the middle cusp row becoming

479 only slightly higher posteriorly, it nonetheless differs from that of most other ptilodontids in

480 which the middle cusp row is essentially horizontal, with little or no increase in height

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481 posteriorly (Krause 1982), and although the lateral profile of p4 is arcuate, forming a near-

482 symmetrical arc, it is less symmetrical when compared with that of most ptilodontids (Fig. 4).

483 The dentition of Aenigmamys most closely resembles that of Kimbetohia among currently

484 recognized ptilodontid genera. Kimbetohia is known primarily from the holotype (UCMP

485 31305), a skull fragment containing P1–4 collected from the Betonnie-Tsosie Arroyo, in the San

486 Juan Basin of New Mexico (Simpson 1936a), although scant records of the genus have since

487 been discovered in deposits from the North Horn Formation of Utah and the Fort Union

488 Formation of south central Wyoming (Lofgren et al. 2012; Lofgren et al. 2017); Sloan (1981)

489 referred several p4s to K. campi Simpson, 1936a, and although these were not found in

490 association with diagnostic upper premolars, they have been largely accepted as pertaining to the

491 genus (Krause 1992; Weil and Krause 2008),Draft and this opinion is followed here. Aenigmamys

492 differs from Kimbetohia primarily in having a narrower and higher crowned P4 and a more

493 evenly arcuate p4 (Figs. 4–5). Both genera have three cusps on P2 (one labially and two

494 lingually), a feature shared uniquely by these genera among ptilodontids, although this character

495 is likely primitive, occurring in various non-ptilodontid ptilodontoids (e.g., Scott 2005, 2008).

496 The P2 of Kimbetohia bears one root, in contrast to the two-rooted P2 of Aenigmamys and other

497 ptilodontids (this feature has been interpreted as a fusion of two roots, and likely a derived

498 character; Clemens 1964). The P4 of Kimbetohia is significantly wider than that of Aenigmamys,

499 and lower crowned, with the middle cusp row increasing in height only slightly towards the

500 posterior end of the crown. The P4 of Kimbetohia is notably more constricted lingually near the

501 anteroposterior midpoint, and has a greater number of cusps in the external row (1–4 as opposed

502 to 0–1 in Aenigmamys) (Lofgren et al. 2012) (Fig. 5F). The p4 of Aenigmamys is more evenly

503 arcuate than that of Kimbetohia, although both p4s exhibit a straighter posterior slope than that of

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504 either Ptilodus or Baiotomeus (Krause 1982, 1987; Fig. 4); the p4 is somewhat lower crowned

505 than that of most species of Ptilodus (e.g., Ptilodus mediaevus, Swain Quarry, early Paleocene,

506 Wyoming; Rigby 1980; Krause 1982) and more closely resembles Kimbetohia in that regard.

507 Other minor differences distinguish the p4s: the anterior margin is somewhat convex in

508 Aenigmamys, as opposed to the more nearly straight and reclined anterior margin in Kimbetohia,

509 although a few individual variants of Aenigmamys more closely resemble Kimbetohia in this

510 regard (e.g., TMP 2011.096.0306, 2011.096.0588); the p4 of Aenigmamys is shorter relative to

511 its height, and has a higher first serration; and the p4 of Aenigmamys has a shorter and somewhat

512 shallower exodaenodont lobe. The upper and lower molars of Kimbetohia are known from

513 several specimens questionably referred to a second species of Kimbetohia, K.? mziae Middleton

514 and Dewar, 2004, from the early PuercanDraft of Colorado (the diagnostic P4 has yet to be discovered

515 for K.? mziae, and Middleton and Dewar (2004) noted several features that might suggest equally

516 plausible, alternative taxonomic referrals). The p4 of K.? mziae differs from that of Kimbetohia

517 and Aenigmamys in having a steeper anterior margin and in being relatively higher crowned,

518 features that would seem to preclude a referral to either of the latter genera; given these

519 observations, and the ongoing uncertainties surrounding the taxonomic identity of K.? mziae, the

520 species is not considered any further here.

521 In addition to its occurrence at Sheep Ahoy!, Aenigmamys is tentatively identified as

522 occurring at the middle Puercan (Pu2) Schowalter locality of southern Alberta (pers. obs.;

523 locality information in Fox 1990 and Fox et al. 2014), and from Croc Pot and Rav W-1, two

524 middle Puercan localities in southwestern Saskatchewan (pers. obs.; locality information in Fox

525 1990 and Redman et al. 2015).

526

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527 AGE OF THE SHEEP AHOY! MAMMALIAN FAUNA

528 The age of the rocks in the vicinity of Sheep Ahoy! was initially thought to be middle or perhaps

529 late Paleocene, an estimate based primarily on the trionychid fossils found in the area and on the

530 assumption that the rocks represented the Paskapoo Formation, which in the Calgary and

531 Cochrane areas documents fossil mammals of what were then thought to be of Tiffanian or even

532 Clarkforkian age (Russell 1926, 1929, 1930, 1958). A better understanding of the age came with

533 recognition that strata south and east of Okotoks were more likely referable to the Upper

534 Cretaceous/lower Paleocene Scollard and Willow Creek formations, rather than the Paskapoo

535 Formation, and the identification of the K-Pg boundary within these formations (Sweet and Hills

536 1984; Lerbekmo and St. Louis 1986; Lerbekmo et al. 1979; Lerbekmo et al. 1987; Jerzykiewicz

537 and Sweet 1988; Sweet et al. 1990). Draft

538 The mammalian fauna at Sheep Ahoy! is Puercan in age, a conclusion based on the

539 occurrences of several taxa that are otherwise restricted to this Land Mammal Age (Appendix 2),

540 including the cimolestid Procerberus Sloan and Van Valen, 1965, the purgatoriid Purgatorius

541 Van Valen and Sloan, 1965, and several condylarths, including Protungulatum Sloan and Van

542 Valen, 1965, Oxyprimus Van Valen, 1978, and Baioconodon Gazin, 1941 (Lofgren et al. 2004).

543 Given the well-documented difficulties correlating Puercan mammalian faunas from the more

544 northern parts of the Western Interior with those from ostensibly coeval beds in the San Juan

545 Basin to the south (Lofgren et al. 2004; Fox and Scott 2011; Fuentes et al. 2019), a more

546 constrained age within the Puercan NALMA for the Sheep Ahoy! fauna is challenging,

547 particularly given that several of the mammalian taxa in the fauna are new (at both the genus and

548 species level) or are only tentatively identified, and there is presently little in the way of

549 chronostratigraphic control for the locality. Overall, the mammalian fauna at Sheep Ahoy!

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550 resembles those from Pu2 localities from other areas of the northern part of the Western Interior.

551 Although there are no taxa at Sheep Ahoy! that are restricted to the Pu2 interval zone, at least

552 seven genera that make their first appearance during Pu2 have been confidently identified

553 (Xyronomys Rigby, 1980, Ectypodus, Microcosmodon, Ursolestes Fox, Scott, and Buckley,

554 2015, Loxolophus Cope, 1885, Carcinodon Scott, 1892, Bubogonia Johnston and Fox, 1984),

555 and potentially 13 genera that are characteristic of the Pu2 interval zone more generally (Lofgren

556 et al. 2004). In contrast, none of the genera at Sheep Ahoy! is considered an index of Pu3, nor

557 are there any taxa that are thought to have made their first appearance during that interval zone

558 (Lofgren et al. 2004); there are possibly seven genera that are characteristic of the Pu3 interval

559 zone, but all but one of these (Microcosmodon) are also considered characteristic of Pu2, or even

560 Pu1. Of potential interest is the presenceDraft of three condylarths: Oxyprimus, considered an index

561 taxon for Pu1, and Protungulatum sp., cf. P. donnae and Baioconodon sp., cf. B. nordicum,

562 species that are known primarily from Pu1 localities (e.g., Jepsen 1930; Sloan and Van Valen

563 1965; Van Valen 1978; Archibald 1982; Fox 1989; Lofgren 1995; Eberle and Lillegraven 1998);

564 their presence at Sheep Ahoy! may be the youngest occurrences of these taxa, and accordingly

565 would represent temporal range extensions for each. Overall, the mammalian fauna at Sheep

566 Ahoy! is most similar in taxonomic composition to those from Rav W-1, Ravenscrag Formation

567 of southwestern Saskatchewan, and Simpson Quarry, Bear Member of the Fort Union Formation,

568 Montana, both considered Pu2 in age (Johnston and Fox 1984; Buckley 1994; Fox and Scott

569 2011; Buckley 2018). The Sheep Ahoy! fauna includes several genera in common with the Rav

570 W-1 and Simpson Quarry faunas (e.g., Mesodma, Parectypodus, Stygimys, Procerberus,

571 Purgatorius, Oxyclaenus Cope, 1884a, Carcinodon, Bubogonia), and although many of these are

572 stratigraphically long ranging or otherwise occur at other Puercan localities (e.g., Garbani

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573 Quarry, Pu3; Wilson 2014), their combined occurrence at these localities argues for closeness in

574 relative age. The mammalian faunas at Sheep Ahoy! and Simpson Quarry additionally share two

575 taxa that are presently known only from these localities: the purgatoriid Ursolestes, and a new

576 periptychid with a dentition resembling that of Conacodon Matthew, 1897 (Buckley 1994; Fox et

577 al. 2015).

578 Although independent chronostratigraphic data are not yet available for Sheep Ahoy!, the

579 magnetic polarity of the rocks can be estimated by reference to a regional magneto- and

580 biostratigraphic framework proposed by Lerbekmo and Sweet (2000, figs. 19–21) for the area.

581 Sheep Ahoy! is higher in elevation than the lowest parts of the section at Nature’s Hideaway, a

582 locality some 5 km to the northeast, at a large cutbank on Highwood River (Fig. 1). Lerbekmo

583 and Sweet (2000) determined the age ofDraft the rocks at Nature’s Hideaway to be earliest Paleocene,

584 with the lowest 8 m being in reversed polarity, and the uppermost 5 m being in normal polarity.

585 Based on the magnetostratigraphy and the palynological assemblages recovered in the lower 8 m,

586 Lerbekmo and Sweet (2000) suggested that the lower part of the section falls within the

587 Paleocene part of magnetochron 29r, while the uppermost 5 m falls within magnetochron 29n,

588 and further postulated that the K-Pg boundary likely occurs at or just below river level. Sheep

589 Ahoy! occurs approximately 980 m above sea level, some 25 m higher than Nature’s Hideaway;

590 the locality likely occurs in sediments of normal polarity, correlative with magnetochron 29n

591 and, accordingly, with mammalian faunas of Pu2 and Pu3 age from other parts of the Western

592 Interior of North America (Lofgren et al. 2004). Corroboration of this working hypothesis must

593 obviously await magnetostratigraphic analysis of the sediments at Sheep Ahoy!

594

595 Conclusion

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596 The enlarged, robust upper premolars, the low-crowned P4, and the enlarged, near-symmetrical

597 p4 suggest that Aenigmamys is best referred to the Ptilodontidae, with closest similarity to

598 comparable parts of the dentition of Kimbetohia. Aenigmamys, like Kimbetohia, represents a

599 basal ptilodontid, exhibiting a mosaic of primitive ptilodontoid and derived ptilodontid

600 characters. The earliest ptilodontids occur in middle Puercan mammalian faunas, although the

601 possible presence of Aenigmamys (and Ptilodus tsosiensis Sloan, 1981) at Rav W-1 in

602 southwestern Saskatchewan, a locality that occurs in sediments correlated with magnetochron

603 29r (Johnston and Fox 1984; Lerbekmo 1985; Fox 1989), suggest that the family may have first

604 appeared not long after the K-Pg event. The proposed Pu2 age for the Sheep Ahoy! mammalian

605 fauna is coeval with those from the Betonnie-Tsosie wash (Williamson 1996; Lofgren et al.

606 2004), the area in the San Juan Basin ofDraft New Mexico where the majority of specimens of

607 Kimbetohia have been collected, indicating that ptilodontids achieved a wide geographic

608 distribution early in the Paleocene. The occurrence of Aenigmamys, along with Kimbetohia and

609 Ptilodus, in middle Puercan deposits further suggests that the evolutionary history of the family

610 likely extends back to Pu1, or possibly into the latest part of the Cretaceous.

611

612 Acknowledgements

613 I extend thanks to the Hamer family for access to the Sheep Ahoy! locality, and for their many

614 hospitalities. Personnel from the Royal Tyrrell Museum of Palaeontology were instrumental in

615 collecting microfossils from Sheep Ahoy!, as well as the processing and sorting of bulk matrix.

616 Special recognition is given to J. Sanchez for his expert preparation of several of the specimens

617 included in this paper. Thanks are extended to M. Caldwell and R. Fox, UALVP, and J. Meng

618 and A. Gishlick, AMNH, for access to specimens in their care. Discussions with R. Fox D.

27 © The Author(s) or their Institution(s) Classification: Protected A Canadian Journal of Earth Sciences Page 28 of 58

619 Krause, and A. Weil, and comments by D. Krause and A. Averianov greatly improved the

620 quality of the manuscript.

621

622 References

623 Archibald, J. D. 1982. A study of Mammalia and geology across the Cretaceous-Tertiary

624 boundary in Garfield County, Montana. University of California Publications in

625 Geological Science, 122: 11–286.

626 Archibald, J.D. and D. L. Lofgren. 1990. Mammalian zonation near the Cretaceous-Tertiary

627 boundary. In Dawn of the Age of Mammals in the Northern Part of the Rocky Mountain

628 Interior, North America. Edited by T. M. Bown and K. D. Rose. Geological Society of

629 America Special Paper, 243: 31–50.Draft

630 Beck, R. M. and M. S. Lee. 2014. Ancient dates or accelerated rates? Morphological clocks and

631 the antiquity of placental mammals. Proceedings of the Royal Society B: Biological

632 Sciences, 281: 20141278.

633 Braman, D. R., and A. R. Sweet. 1990. Overview of Campanian to Paleocene stratigraphy,

634 southern Alberta Foothills. In Field guide to Uppermost Cretaceous Strata in Southern

635 Saskatchewan and Alberta. Edited by D. R. Braman and A. R. Sweet, Canadian Society

636 of Petroleum Geologists Annual Convention Fieldtrip Guide, pp. 66–70.

637 Brinkman, D. B. 2013. Non-trionychid turtles from the Paleocene of Alberta, Canada. Canadian

638 Journal of Earth Sciences, 50: 282–293.

639 Broom, R. 1914. On the structure and affinities of the Multituberculata. Bulletin of the American

640 Museum of Natural History, 33: 115–134.Buckley, G. A. 1994. Paleontology, geology,

641 and chronostratigraphy of Simpson Quarry (early Paleocene), Bear Formation, Crazy

28 © The Author(s) or their Institution(s) Classification: Protected A Page 29 of 58 Canadian Journal of Earth Sciences

642 Mountains Basin, south-central Montana. Unpublished PhD thesis, Rutgers, The State

643 University of New Jersey, New Brunswick, NJ, 375 pp.

644 Buckley, G.A. 2018. Magnetostratigraphy of Upper Cretaceous (Lancian) to Middle Paleocene

645 (Tiffanian) strata in the northeastern Crazy Mountains Basin, Montana, USA. Rocky

646 Mountain Geology, 53: 59–74.

647 Cifelli, R. L., J. J. Eberle, D. L. Lofgren, J. A. Lillegraven, and W. A. Clemens. 2004.

648 Mammalian biochronology of the latest Cretaceous. In Late Cretaceous and Cenozoic

649 mammals of North America: biostratigraphy and geochronology. Edited by M. O.

650 Woodburne. Columbia University Press, New York, pp. 21–42.

651 Clemens, W. A. 1964. Fossil mammals of the type Lance Formation, Wyoming: Part I.

652 Introduction and Multituberculata.Draft University of California Publications in Geological

653 Sciences, 48: 1–105.

654 Clemens, W. A. 2002. Evolution of the mammalian fauna across the Cretaceous-Tertiary

655 boundary in northeastern Montana and other areas of the Western Interior. In The Hell

656 Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains.

657 Edited by J. H. Hartman, K. R. Johnson, and D. J. Nichols. Geological Society of

658 America Special Paper, 361: 217–245.

659 Cope, E. D. 1881. Eocene Plagiaulacidae. American Naturalist, 15: 921–922.

660 Cope, E. D. 1884a. Second addition to the knowledge of the Puerco epoch. Proceedings of the

661 American Philosophical Society, 21: 309–324.

662 Cope, E. D. 1884b. The Tertiary Marsupialia. American Naturalist, 18: 686–697.

663 Cope, E. D. 1885. The oldest Tertiary Mammalia. American Naturalist, 29: 385–387.

664 Cope, E. D. 1887. The marsupial genus Chirox. American Naturalist, 21: 566–567.

29 © The Author(s) or their Institution(s) Classification: Protected A Canadian Journal of Earth Sciences Page 30 of 58

665 Currie, P. J. 2003. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of

666 Alberta, Canada. Acta Palaeontologica Polonica, 48: 191–226.

667 Dahlberg, E. L., J. J. Eberle, J. J. Sertich, and I. M. Miller. 2016. A new earliest Paleocene

668 (Puercan) mammalian fauna from Colorado's Denver Basin, USA. Rocky Mountain

669 Geology, 51: 1–22.

670 Dawson, G. M. 1883. Preliminary report on the geology and the Bow and Belly River region,

671 Northwest Territory, with special reference to the coal deposits; Geological Survey of

672 Canada, Report of Progress, 1800–1882, pt. B: 1–23.

673 dos Reis, M., J. Inoue, M. Hasegawa, R. J. Asher, P. C. Donoghue, and Z. Yang. 2012.

674 Phylogenomic datasets provide both precision and accuracy in estimating the timescale of

675 placental mammal phylogeny. ProceedingsDraft of the Royal Society B: Biological Sciences,

676 279: 3491–3500.

677 Douglas, R. J. W. 1950. Callum Creek, Langford Creek, and Gap Map-areas, Alberta. Geological

678 Survey of Canada Memoir, 255: 1–124.

679 Douglass, E. 1908. Vertebrate fossils from the Fort Union beds. Annals of Carnegie Museum, 3:

680 11–26.

681 Eberle, J. J., and J. A. Lillegraven. 1998. A new important record of earliest Cenozoic

682 mammalian history: Eutheria and paleogeographic/biostratigraphic summaries. Rocky

683 Mountain Geology, 33: 49–117.

684 Eberth, D. A., D. C. Evans, D. B. Brinkman, F. Therrien, D. H. Tanke, and L. S. Russell. 2013.

685 Dinosaur biostratigraphy of the Edmonton Group (Upper Cretaceous), Alberta, Canada:

686 evidence for climate influence. Canadian Journal of Earth Sciences, 50: 701–726.

30 © The Author(s) or their Institution(s) Classification: Protected A Page 31 of 58 Canadian Journal of Earth Sciences

687 Fox, R. C. 1989. The Wounded Knee local fauna and mammalian evolution near the Cretaceous-

688 Tertiary boundary, Saskatchewan, Canada. Palaeontographica Abteilung A, 208: 11–59.

689 Fox, R. C. 1990. The succession of Paleocene mammals in western Canada. In Dawn of the Age

690 of Mammals in the Northern Part of the Rocky Mountain Interior, North America. Edited

691 by T. M. Bown and K. D. Rose. Geological Society of America Special Paper, 243: 51–

692 70.

693 Fox, R. C. 2005. Microcosmodontid multituberculates (Allotheria, Mammalia) from the

694 Paleocene and Late Cretaceous of western Canada. Palaeontographica Canadiana, 23: 1–

695 109.

696 Fox, R. C. and C. S. Scott. 2011. A new, early Puercan (earliest Paleocene) species of

697 Purgatorius (Plesiadapiformes, Primates)Draft from Saskatchewan, Canada. Journal of

698 Paleontology, 85: 537–548.

699 Fox, R. C., B. D. Rankin, C. S. Scott, and A. R. Sweet. 2014. Second known occurrence of the

700 early Paleocene plesiadapiform Pandemonium (Mammalia: Primates), with description of

701 a new species. Canadian Journal of Earth Sciences, 51: 1059–1066.

702 Fox, R. C., C. S. Scott, and G. A. Buckley. 2015. A ‘giant’ purgatoriid (Plesiadapiformes) from

703 the Paleocene of Montana, USA: mosaic evolution in the earliest primates.

704 Palaeontology, 58: 277–291.

705 Fuentes, A. J., W. C. Clyde, K. Weissenburger, A. Bercovici, T. R. Lyson, I. M. Miller, et al.

706 2019. Constructing a time scale of biotic recovery across the Cretaceous–Paleogene

707 boundary, Corral Bluffs, Denver Basin, Colorado, USA. Rocky Mountain Geology, 54:

708 133–153.

31 © The Author(s) or their Institution(s) Classification: Protected A Canadian Journal of Earth Sciences Page 32 of 58

709 Gambaryan, P. P. and Z. Kielan-Jaworowska. 1995. Masticatory musculature of Asian

710 taeniolabidoid multituberculate mammals. Acta Palaeontologica Polonica, 40: 45–108.

711 Gazin, C. L. 1941. The mammalian faunas of the Paleocene of central Utah, with notes on the

712 geology. Proceedings of the United States National Museum, 91: 1–53.

713 Gidley, J. W. 1909. Notes on the fossil mammalian genus Ptilodus with descriptions of new

714 species. Proceedings of the U. S. National Museum, 36: 611–626.Granger, W. and G. G.

715 Simpson. 1929. A revision of the Tertiary Multituberculata. Bulletin of the American

716 Museum of Natural History, 56: 601–676.

717 Halliday, T. J. D., P. Upchurch, and A. Goswami. 2016. Eutherians experienced elevated

718 evolutionary rates in the immediate aftermath of the Cretaceous–Palaeogene mass

719 extinction. Proceedings of the RoyalDraft Society B: Biological Sciences, 283: 20153026.

720 Halliday, T. J. D., P. Upchurch, and A. Goswami. 2017. Resolving the relationships of Paleocene

721 placental mammals. Biological Reviews, 92: 521–550.

722 Hamblin, A. P. 2010. Scollard/Willow Creek/Coalspur formations: summary of literature and

723 concepts. Geological Survey of Canada, Open File 6555.

724 Hopson, J. A., Z. Kielan-Jaworowska, and E. F. Allin. 1989. The cryptic jugal of

725 multituberculates. Journal of Vertebrate Paleontology, 9: 201–209.

726 Hunter, J. P., J. H. Hartman, and D. W. Krause. 1997. Mammals and mollusks across the

727 Cretaceous-Tertiary boundary from Makoshika State Park and vicinity (Williston Basin),

728 Montana: University of Wyoming Contributions to Geology, 32: 61–114.

729 Jepsen, G. L. 1930. New vertebrate fossils from the lower Eocene of the Bighorn Basin,

730 Wyoming. Proceedings of the American Philosophical Society, 69: 117–131.

32 © The Author(s) or their Institution(s) Classification: Protected A Page 33 of 58 Canadian Journal of Earth Sciences

731 Jepsen, G. L. 1940. Paleocene faunas of the Polecat Bench Formation, Park County, Wyoming:

732 Part I. Proceedings of the American Philosophical Society, 83: 217–340.

733 Jerzykiewicz, T. 1997. Stratigraphic framework of the uppermost Cretaceous and Paleocene

734 strata of the Alberta basin. Geological Survey of Canada, Bulletin, 510: 1–121.

735 Jerzykiewicz, T. and A. R. Sweet. 1986. Caliche and associated impoverished palynological

736 assemblages: an innovative line of paleoclimatic research into the uppermost Cretaceous

737 and Paleocene of southern Alberta. Geological Survey of Canada Paper, 86-1B: 653–663.

738 Jerzykiewicz, T. and A. R. Sweet. 1988. Sedimentological and palynological evidence of

739 regional climatic changes in the Campanian to Paleocene sediments of the Rocky

740 Mountain Foothills, Canada. Sedimentary Geology, 59: 29–76.

741 Johnston, P. A., and R. C. Fox. 1984. PaleoceneDraft and Late Cretaceous mammals from

742 Saskatchewan, Canada. Palaeontographica A, 186: 163–222.

743 Kielan-Jaworowska, Z., 1970. New Upper Cretaceous multituberculate genera from Bayn Dzak,

744 Gobi Desert. Palaeontologia Polonica, 21: 35-49.

745 Kielan‐Jaworowska, Z., and J. H. Hurum. 2001. Phylogeny and systematics of multituberculate

746 mammals. Palaeontology, 44: 389–429.

747 Kielan-Jaworowska, Z., R. L. Cifelli, and Z.-X. Luo. 2005. Mammals from the age of dinosaurs:

748 origins, evolution, and structure. Columbia University Press.

749 Krause, D.W. 1977. Paleocene multituberculates (Mammalia) of the Roche Percée local fauna,

750 Ravenscrag Formation, Saskatchewan, Canada. Palaeontographica Abt. A, 159: 1–36.

751 Krause, D. W. 1982. Evolutionary history and paleobiology early Cenozoic Multituberculata.

752 Unpublished Ph.D. thesis, University of Michigan, Ann Arbor.

33 © The Author(s) or their Institution(s) Classification: Protected A Canadian Journal of Earth Sciences Page 34 of 58

753 Krause, D. W. 1986. Competitive exclusion and taxonomic displacement in the fossil record; the

754 case of rodents and multituberculates in North America. Rocky Mountain Geology, 24

755 (special paper 3): 95–117.

756 Krause, D. W. 1987. Baiotomeus, a new ptilodontid multituberculate (Mammalia) from the

757 middle Paleocene of western North America. Journal of Paleontology, 61: 595–603.

758 Krause, D. W. 1992. Clemensodon megaloba, a new genus and species of Multituberculata

759 (Mammalia) from the Upper Cretaceous type Lance Formation, Powder River Basin,

760 Wyoming. PaleoBios, 14: 1–8.

761 Lemoine, V. 1882. Sur deux Plagiaulax tertiaires, recueillis aux environs de Reims. Comptes

762 Rendus de l’Academie des Sciences, Paris, 95: 1009–1011.

763 Lerbekmo, J. F. 1985. MagnetostratigraphicDraft and biostratigraphic correlations of Maastrichtian to

764 early Paleocene strata between southcentral Alberta and southwestern Saskatchewan.

765 Bulletin of Canadian Petroleum Geology, 33: 213–226.

766 Lerbekmo, J. F., and R. M. St. Louis. 1986. The terminal Cretaceous iridium anomaly in the Red

767 Deer Valley, Alberta, Canada. Canadian Journal of Earth Sciences, 23: 120–124.

768 Lerbekmo, J. F., and A. R. Sweet. 2000. Magnetostratigraphy and biostratigraphy of the

769 continental Paleocene in the Calgary area, southwestern Alberta. Bulletin of Canadian

770 Petroleum Geology, 48: 285–306.

771 Lerbekmo, J. F., M. E. Evans, and H. Baadsgaard. 1979. Magnetostratigraphy, biostratigraphy

772 and geochronology of Cretaceous-Tertiary boundary sediments, Red Deer Valley. Nature,

773 279: 26.

774 Lerbekmo, J. F., A. R. Sweet, and R. M. St. Louis. 1987. The relationship between the iridium

775 anomaly and palynological floral events at three Cretaceous-Tertiary boundary localities

776 in western Canada. Geological Society of America Bulletin, 99: 325–330.

777 Linnaeus, C. 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera,

778 species cum characteribus, differentiis, synomymis, locis. Editio decima, reformata, I:

779 Regnum animale. Laurentii Salvii, Stockholm, 824 pp.

780 Lofgren, D. L. 1995. The Bug Creek problem and the Cretaceous-Tertiary transition at McGuire

781 Creek, Montana. University of California Publications in Geological Science, 140: 1–

782 200.

783 Lofgren, D. L., J. A. Lillegraven, W. A. Clemens, P. D. Gingerich, and T. E. Williamson. 2004.

784 Paleocene biochronology: the PuercanDraft through Clarkforkian land mammal ages. In Late

785 Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and

786 Geochronology. Edited by M.O. Woodburne. Columbia University Press, New York, pp.

787 43–105.

788 Lofgren, D. L., B. M. Gaytan, M. Pastrano, J. E. Rice, and R. L. Zheng. 2012. First Record of

789 Kimbetohia campi (Mammalia, Multituberculata) from the Paleocene Part of the North

790 Horn Formation, Utah. Journal of Vertebrate Paleontology, 32: 1214–1217.

791 Lofgren, D. L., G. Gosney, C. Soltis, K. Oney, and L. West. 2017. New records of Kimbetohia

792 campi and Xanclomys mcgrewi (Mammalia, Multituberculata) from the Fort Union

793 Formation of the Great Divide Basin, Wyoming. Paludicola, 11: 43–50.

794 Lyson, T. R., I. M. Miller, A. D. Bercovici, K. Weissenburger, A. J. Fuentes, W. C. Clyde, et al.

795 2019. Exceptional continental record of biotic recovery after the Cretaceous–Paleogene

796 mass extinction. Science, 366: 977–983.

797 Marsh, O. C. 1880. Notice of Jurassic mammals representing two new orders. American Journal

798 of Science, 11: 425–428.

799 Matthew, W. D. 1897. A revision of the Puerco fauna. American Museum of Natural History

800 Bulletin, 9: 1–66.

801 Matthew, W. D., and W. Granger. 1921. New genera of Paleocene mammals. American Museum

802 Novitates, 13: 1–7.

803 McKenna, M. C. 1975. Toward a phylogenetic classification of the Mammalia. In Phylogeny of

804 the Primates. Edited by W. P. Luckett and F. S. Szalay, Plenum Publishing Corporation,

805 New York, pp. 21–46.

806 Miao, D. 1988. Skull morphology of Lambdopsalis bulla (Mammalia, Multituberculata) and its

807 implications to mammalian evolution.Draft Contributions to Geology, University of Wyoming,

808 Special Papers, 4: 1–104.

809 Middleton, M. D. and E. W. Dewar. 2004. New mammals from the early Paleocene Littleton

810 fauna (Denver Formation, Colorado). In Paleogene Mammals. Edited by S. G. Lucas, K.

811 E. Zeigler, and P. E. Kondrashov. New Mexico Museum of Natural History and Science

812 Bulletin, 26: 59–80.

813 O'Leary, M. A., J. I. Bloch, J. J. Flynn, T. J. Gaudin, A. Giallombardo, N. P. Giannini, et al.

814 2013. The placental mammal ancestor and the post–K-Pg radiation of placentals. Science,

815 339: 662–667.

816 Pires, M. M., B. D. Rankin, D. Silvestro, and T. B. Quental. 2018. Diversification dynamics of

817 mammalian clades during the K–Pg mass extinction. Biology Letters, 14: 20180458.

818 Redman, C. M., J. D. Gardner, C. S. Scott, and D. R. Braman. 2015. Geological setting of

819 vertebrate microfossil localities across the Cretaceous-Paleogene boundary in

820 southwestern Saskatchewan, Canada. Canadian Journal of Earth Sciences, 52: 846-862.

821 Rigby Jr, J. K. 1980. Swain Quarry of the Fort Union Formation, middle Paleocene

822 (Torrejonian), Carbon County, Wyoming: geological setting and mammalian fauna.

823 Evolutionary Monographs, 3: 1–179.

824 Rougier, G. W., M. J. Novacek, and D. Dashzeveg. 1997. A new multituberculate from the Late

825 Cretaceous locality Ukhaa Tolgod, Mongolia: Considerations on multituberculate

826 interrelationships. American Museum Novitates, 3191: 1–26.

827 Russell, L. S. 1926. A new species of the genus Catopsalis Cope from the Paskapoo Formation

828 of Alberta. American Journal of DraftScience, 12: 230–234.

829 Russell, L. S. 1929. Paleocene vertebrates from Alberta. American Journal of Science, 17: 162–

830 178.

831 Russell, L. S. 1930. A new species of Aspideretes from the Paskapoo Formation of Alberta.

832 American Journal of Science, 1930: 27–32.

833 Russell, L. S. 1958. Paleocene mammal teeth from Alberta. National Museum of Canada

834 Bulletin, 147: 96–103.

835 Russell, L. S. and R. W. Landes. 1940. Geology of the southern Alberta Plains. Geological

836 Survey of Canada, Memoir, 221: 1–223.

837 Scott, C. S. 2003. Late Torrejonian (middle Paleocene) mammals from south central Alberta,

838 Canada. Journal of Paleontology, 77: 745–768.

839 Scott, C. S. 2005. New neoplagiaulacid multituberculates (Mammalia: Allotheria) from the

840 Paleocene of Alberta, Canada. Journal of Paleontology, 79: 1189–1213.

841 Scott, C. S., A. Weil, and J. M. Theodor. 2018. A new, diminutive species of Catopsalis

842 (Mammalia, Multituberculata, Taeniolabidoidea) from the early Paleocene of

843 southwestern Alberta, Canada. Journal of Paleontology, 92: 1–15.

844 Scott, W. B. 1892. A revision of the North American Creodonta with notes on some genera

845 which have been referred to that group. Proceedings of the Academy of Natural Sciences

846 of Philadelphia, 44: 291–323.

847 Simpson, G. G. 1936a. Additions to the Puerco fauna, lower Paleocene. American Museum

848 Novitates, 849: 1–11.

849 Simpson, G. G. 1936b. A new fauna from the Fort Union of Montana. American Museum

850 Novitates, 873: 1–27.

851 Simpson, G. G. 1937. Skull structure ofDraft the Multituberculata. Bulletin of the American Museum

852 of Natural History, 73: 727–763.

853 Sloan, R. E. 1981. Systematics of Paleocene multituberculates from the San Juan Basin, New

854 Mexico. In Advances in San Juan Basin Paleontology. Edited by S. G. Lucas, J. K.

855 Rigby, Jr., and B. S. Kues. University of New Mexico Press, Albuquerque, pp.127–160.

856 Sloan, R. E. and L. Van Valen. 1965. Cretaceous mammals from Montana. Science, 148: 220–

857 227.

858 Smith, S. M., C. J. Sprain, W. A. Clemens, D. L. Lofgren, P. R. Renne, and G. P. Wilson. 2018.

859 Early mammalian recovery after the end-Cretaceous mass extinction: A high-resolution

860 view from McGuire Creek area, Montana, USA. Geological Society of America Bulletin,

861 130: 2000–2014.

862 Sprain, C. J., P. R. Renne, G. P. Wilson, and W. A. Clemens. 2015. High-resolution

863 chronostratigraphy of the terrestrial Cretaceous-Paleogene transition and recovery

864 interval in the Hell Creek region, Montana. Geological Society of America Bulletin, 127:

865 393–409.

866 Storer, J. E. 1991. The mammals of the Gryde Local Fauna, Frenchman Formation

867 (Maastrichtian: Lancian), Saskatchewan. Journal of Vertebrate Paleontology, 11: 350–

868 369.

869 Sweet, A. R., and L. V. Hills. 1984. A palynological and sedimentological analysis of the

870 Cretaceous-Tertiary boundary, Red Deer River valley, Alberta, Canada. Proceedings of

871 the Sixth International Palynological Conference, Calgary, Alberta: 160A.

872 Sweet, A.R. and D. R. Braman. 1992. The KT boundary and contiguous strata in western

873 Canada: interactions between paleoenvironments and palynological assemblages.

874 Cretaceous Research, 13: 31–79.Draft

875 Sweet, A.R., D. R. Braman, and J. F. Lerbekmo. 1990. Palynofloral response to K/T boundary

876 events; A transitory interruption within a dynamic system. In Global Catastrophes in

877 Earth History; An Interdisciplinary Conference on Impacts, Volcanism and Mass

878 Mortality. Edited by V. L. Sharpton and P. D. Ward. Geological Society of America

879 Special Paper, 247: 457–469.

880 Tozer, E. T. 1956 Uppermost Cretaceous and Paleocene non marine molluscan faunas of

881 Western Alberta. Geological Survey of Canada, Memoir, 280: 1–125.

882 Van Valen, L. 1978. The beginning of the age of mammals. Evolutionary Theory, 4: 46–80.

883 Van Valen, L. and R. E. Sloan. 1965. The earliest primates. Science, 150: 743–745.

884 Weil, A., and D. W. Krause. 2008. Multituberculata. In Evolution of Tertiary Mammals of North

885 America, Volume 2. Edited by C. M. Janis, G. F. Gunnell, and M. D. Uhen. Cambridge

886 University Press, Cambridge, U.K., pp. 19–38.

887 Williams, M. Y. and W. S. Dyer. 1930. Geology of southern Alberta and southwestern

888 Saskatchewan. Geological Survey of Canada Memoir, 163: 1-160.

889 Williamson, T. E. 1996. The Beginning of the Age of Mammals in the San Juan Basin, New

890 Mexico: Biostratigraphy and evolution of Paleocene mammals of the Nacimiento

891 Formation. New Mexico Museum of Natural History and Science Bulletin, 8: 1–141.

892 Williamson, T. E., S. L. Brusatte, R. Secord, and S. Shelley. 2016. A new taeniolabidoid

893 multituberculate (Mammalia) from the middle Puercan of the Nacimiento Formation,

894 New Mexico, and a revision of taeniolabidoid systematics and phylogeny. Zoological

895 Journal of the Linnean Society, 177: 183–208.

896 Wilson, G. P. 2013. Mammals across the K/Pg boundary in northeastern Montana, USA: dental

897 morphology and body-size patternsDraft reveal extinction selectivity and immigrant-fueled

898 ecospace filling. Paleobiology, 39: 429–469.

899 Wilson, G. P. 2014. Mammalian extinction, survival, and recovery dynamics across the

900 Cretaceous-Paleogene boundary in northeastern Montana, USA. In Through the End of

901 the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and

902 Adjacent Areas. Edited by G. P. Wilson, W. A. Clemens, J. R. Horner, and J. H.

903 Hartman. Geological Society of America Special Paper, 503: 365–392.

904 Wilson G. P., A. R. Evans, I. J. Corfe, P. D. Smits, M. Fortelius, and J. Jernvall. 2012. Adaptive

905 radiation of multituberculate mammals before the extinction of dinosaurs. Nature, 483:

906 457–460.

907 Woodburne, M.O. (ed.) 2004. Late Cretaceous and Cenozoic Mammals of North America.

908 University of California Press, Berkeley, USA, 391 pp.

909 Zelenitsky, D. K., F. Therrien, K. Tanaka, Y. Kobayashi, and C. L. DeBuhr. 2017. Dinosaur

910 eggshells from the Santonian Milk River Formation of Alberta, Canada. Cretaceous

911 Research, 74: 181–187.

912 913

Draft

914

915 Table 1.—Measurements and descriptive statistics for the upper dentition of Aenigmamys aries

916 gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern

917 Alberta, Canada. Lg, anteroposterior length; M, upper molar; P, upper premolar; W, maximum

918 crown width.

919

Element P N OR M SD CV

P1 Lg 2 1.70 — — — W 2 1.50–1.58 — — — P2 Lg 2 1.52–1.55 — — — W 2 Draft1.53 — — — P3 Lg 2 1.61–1.67 — — — W 2 1.21–1.22 — — — P4 Lg 21 3.82–4.60 4.18 0.18 0.043 W 21 1.39–2.05 1.69 0.14 0.085 M1 Lg 9 3.90–4.31 4.09 0.11 0.028 W 9 1.78–1.90 1.84 0.041 0.022 M2 Lg 7 1.61–2.01 1.79 0.15 0.086 W 7 1.67–1.90 1.78 0.082 0.046 920

921

922

923 Table 2.—Measurements and descriptive statistics for the lower dentition of Aenigmamys aries

924 gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern

925 Alberta, Canada. H, height, the distance between the first serration and the baseline used to

926 measure length; Lg, anteroposterior length; L1, the distance between the anterior “beak” and the

927 point where the lines used to measure length and height intersect at right angles; m, lower molar;

928 p, lower premolar.

929

Element P N OR M SD CV

p4 Lg 22 5.34–6.17 5.77 0.25 0.043 L1 18 Draft1.08–1.62 1.35 0.16 0.12 H 18 1.98–2.34 2.09 0.090 0.043 m1 Lg 15 2.97–3.36 3.20 0.12 0.037 W 15 1.34–1.45 1.41 0.036 0.026 m2 Lg 4 1.79–2.17 1.95 0.17 0.089 W 4 1.51–1.67 1.56 0.075 0.048 930

931

932

933 Appendices

934 Appendix 1.—Specimens used in generating p4 lateral profile diagrams (Figure 4).

935

936 Ptilodus sp. “C”: UALVP 46290, incomplete skull with left P3–4, M1–2, right P1–4, M1–2,

937 incomplete left dentary with i1, p3–4, m1–2, incomplete right dentary with i1, p3–4, m1–2;

938 UALVP 40454, incomplete left dentary with i1, p3–4; UALVP 40465, incomplete right dentary

939 with i1, p3–4, m1–2; UALVP 46344, incomplete left dentary with p3–4; UALVP 46318,

940 incomplete right dentary with p4, m1; UALVP 40461, 46322, 46323, 46324, p4. All specimens

941 from the DW-2 locality, late Paleocene (Ti3), south central Alberta, Canada (Fox 1990; Scott

942 2008). Draft

943

944 Kimbetohia campi: The figured profile diagram was modified from Krause (1982: fig. 11A).

945 Krause (1982) did not identify the individual specimens of K. campi used in generating the

946 lateral profile diagram, but indicated that they had been collected from the Betonnie-Tsosie

947 wash, early Paleocene (Pu2), New Mexico, USA; these likely included some or all of AMNH

948 26363, 58392, 58499, 58659, 59940, UCMP 36496.

949

950 Aenigmamys aries: TMP 2012.035.0709, 2011.096.0771, 2011.096.0376, 2008.088.0526,

951 2008.088.0365, 2011.096.0485, 2011.096.0588, 2009.132.0365, 2008.088.0355, 2008.088.0475,

952 2013.032.0439, 2010.095.0019, 2011.096.0306, 2009.132.0150, 20080.088.0531,

953 2011.096.0141, 2013.032.0170. All specimens from the Sheep Ahoy! locality, early Paleocene

954 (Pu2), southwestern Alberta, Canada.

955

956 Appendix 2.—Preliminary list of mammalian taxa from the Sheep Ahoy! locality, early

957 Paleocene (Pu2), southwestern Alberta, Canada.

958

959 Order Multituberculata

960 Cimexomys minor, Cimexomys sp., cf. C. gratus, Mesodma formosa, Xyronomys sp. 1

961 (equivalent to that at Rav W-1; Johnston and Fox 1984); Xyronomys sp. 2, cf. Ectypodus sp.,

962 Parectypodus sp., cf. P. armstrongi, Parectypodus sp., Neoplagiaulax sp., cf. N. kremnus,

963 Neoplagiaulacidae gen. et. sp. unidentified, Aenigmamys aries, Stygimys sp., Microcosmodon

964 arcuatus

965 Draft

966 Order Cimolesta

967 Procerberus sp., cf. P. formicarum, Procerberus sp., cf. P. grandis, Cimolestes sp., Cimolestidae

968 unidentified genus and species 1–3

969

970 Order Lipotyphla

971 Lipotyphla new genus and species

972

973 Order Primates

974 Purgatorius sp. nov., cf. P. unio, Ursolestes perpetior

975

976 “Condylarthra”

977 Protungulatum sp., cf. P. donnae, Oxyprimus sp., cf. O. galadrielae, Oxyclaenus sp., cf. O.

978 corax, cf. Loxolophus schizophrenus, Carcinodon aquilonius, Baioconodon sp., cf. B. nordicum,

979 Chriacidae unidentified genus and species 1–2, Eoconodon sp., cf. E. nidhoggi, Bubogonia

980 saskia, cf. Oxyacodon sp. 1–2, Periptychidae gen. et sp. nov.

981

982 Figure Captions

983

984 Fig. 1. Map of southern Alberta showing the locations of the (1) Sheep Ahoy! and (2) Nature’s

985 Hideaway localities. Locality data from the current study. Base maps courtesy of d-maps.com

986 (https://d-maps.com/carte.php?num_car=213970&lang=en).

987 Draft

988 Fig. 2. Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek

989 Formation, southwestern Alberta, Canada. TMP 2013.032.0308, incomplete left maxilla with

990 P1–3 in (A) labial, (B) lingual, and (C) occlusal views. TMP 2008.088.0749, incomplete right

991 maxilla with P1–4 in (D) labial, (E) lingual, and (F) occlusal views; TMP 2008.088.0283,

992 incomplete right maxilla with incomplete P3, P4 in (G) labial, (H) lingual, (I) occlusal, and (J)

993 anterior views. TMP 2013.032.0158, incomplete right maxilla with P4, M1–2 in (K) labial, (L)

994 lingual, and (M) occlusal views. TMP 2011.096.0479, RP4 in (N) labial, (O) lingual, and (P)

995 occlusal views. TMP 2011.096.0501, LP4 in (Q) labial, (R) lingual, and (S) occlusal views. TMP

996 2008.088.0265, LM1 in (T) labial, (U) lingual, and (V) occlusal views. TMP 2009.132.0126,

997 RM1 in (W) labial, (X) lingual, and (Y) occlusal views. TMP 2012.035.0082, RM2 in (Z) labial,

998 (AA) lingual, and (BB) occlusal views. iof = infraorbital foramen. Scale bars = 2 mm.

999

1000 Fig. 3. Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek

1001 Formation, southwestern Alberta, Canada. TMP 2011.096.0771, holotype, incomplete right

1002 dentary with p3–4, m1–2 in (A) labial, (B) lingual, and (C) occlusal views. TMP 2012.035.0427,

1003 incomplete right dentary with i1, p3–4 in (D) labial and (E) lingual views. TMP 2008.088.0355,

1004 incomplete left dentary with p4 in (F) labial and (G) lingual views. TMP 2008.088.0475,

1005 incomplete left dentary with p4, m1 in (H) labial, (I) lingual, and (J) occlusal views. TMP

1006 2011.096.0141, incomplete right dentary with p4, m1–2 in (K) labial, (L) lingual, and (M)

1007 occlusal views. TMP 2009.132.0239, Rm1 in (N) labial, (O) lingual, and (P) occlusal views.

1008 TMP 2008.088.0328, Rm2 in (Q) labial, (R) lingual, and (S) occlusal views. con = condyle; cor

1009 = coronoid process; maf = mandibular foramen; pts = pterygoid shelf. Scale bars = 2 mm.

1010 Draft

1011 Fig. 4. Camera lucida outlines of p4s of (A) Ptilodus sp. “C”, from the Blindman River localities,

1012 Paskapoo Formation, south central Alberta (Fox 1990; Scott 2008), (B) Kimbetohia campi from

1013 the Nacimiento Formation, Betonnie-Tsosie Arroyo area, New Mexico (modified from Krause

1014 1982), and (C) Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow

1015 Creek Formation, southwestern Alberta. The p4s are oriented along a line passing through the

1016 peak of the anterobasal concavity and the base of the posterolabial shelf, and registered at a point

1017 midway along the baseline (see Krause, 1982). Scale bars = 2 mm. The p4s were scaled to

1018 approximately the same size, and those from the right side were reversed, for ease of

1019 comparison. Specimens listed in Appendix 1.

1020

1021 Fig. 5. Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek

1022 Formation, southwestern Alberta, and Kimbetohia campi from the Nacimiento Formation,

1023 Betonnie-Tsosie Arroyo area, New Mexico. Aenigmamys aries, TMP 2011.096.0479, RP4 in (A)

1024 labial, (B) lingual, and (C) occlusal views. Kimbetohia campi, AMNH 59789, LP4 (reversed

1025 from original) in (D) labial, (E) lingual, and (F) occlusal views. Aenigmamys aries, TMP

1026 2008.088.0475, incomplete left dentary with p4, m1 in (G) labial and (H) lingual views.

1027 Kimbetohia campi, AMNH 58392, Lp4 in (I) labial and (J) lingual views. Scale bar = 2 mm.

1028 Specimens were scaled to approximately the same size for ease of comparison.

Draft

Table 1.—Measurements and descriptive statistics for the upper dentition of Aenigmamys aries

gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern

Alberta, Canada. Lg, anteroposterior length; M, upper molar; P, upper premolar; W, maximum

crown width.

Element P N OR M SD CV

P1 Lg 2 1.70 — — — W 2 1.50–1.58 — — — P2 Lg 2 1.52–1.55 — — — W 2 1.53 — — — P3 Lg 2 Draft1.61–1.67 — — — W 2 1.21–1.22 — — — P4 Lg 21 3.82–4.60 4.18 0.18 0.043 W 21 1.39–2.05 1.69 0.14 0.085 M1 Lg 9 3.90–4.31 4.09 0.11 0.028 W 9 1.78–1.90 1.84 0.041 0.022 M2 Lg 7 1.61–2.01 1.79 0.15 0.086 W 7 1.67–1.90 1.78 0.082 0.046

Table 2.—Measurements and descriptive statistics for the lower dentition of Aenigmamys aries

gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern

Alberta, Canada. H, height, the distance between the first serration and the baseline used to

measure length; Lg, anteroposterior length; L1, the distance between the anterior “beak” and the

point where the lines used to measure length and height intersect at right angles; m, lower molar;

p, lower premolar.

Element P N OR M SD CV

Draft

Fig. 1. Map of southern Alberta showing the locations of the (1) Sheep Ahoy! and (2) Nature’s Hideaway localities. Locality data from the current study. Base maps courtesy of d-maps.com (https://d- maps.com/carte.php?num_car=213970&lang=en).

155x117mm (300 x 300 DPI)

Draft

Fig. 2. Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern Alberta, Canada. TMP 2013.032.0308, incomplete left maxilla with P1–3 in (A) labial, (B) lingual, and (C) occlusal views. TMP 2008.088.0749, incomplete right maxilla with P1–4 in (D) labial, (E) lingual, and (F) occlusal views; TMP 2008.088.0283, incomplete right maxilla with incomplete P3, P4 in (G) labial, (H) lingual, (I) occlusal, and (J) anterior views. TMP 2013.032.0158, incomplete right maxilla with P4, M1–2 in (K) labial, (L) lingual, and (M) occlusal views. TMP 2011.096.0479, RP4 in (N) labial, (O) lingual, and (P) occlusal views. TMP 2011.096.0501, LP4 in (Q) labial, (R) lingual, and (S) occlusal views. TMP 2008.088.0265, LM1 in (T) labial, (U) lingual, and (V) occlusal views. TMP 2009.132.0126, RM1 in (W) labial, (X) lingual, and (Y) occlusal views. TMP 2012.035.0082, RM2 in (Z) labial, (AA) lingual, and (BB) occlusal views. iof = infraorbital foramen. Scale bars = 2 mm.

180x279mm (300 x 300 DPI)

Draft

Fig. 3. Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern Alberta, Canada. TMP 2011.096.0771, holotype, incomplete right dentary with p3–4, m1–2 in (A) labial, (B) lingual, and (C) occlusal views. TMP 2012.035.0427, incomplete right dentary with i1, p3–4 in (D) labial and (E) lingual views. TMP 2008.088.0355, incomplete left dentary with p4 in (F) labial and (G) lingual views. TMP 2008.088.0475, incomplete left dentary with p4, m1 in (H) labial, (I) lingual, and (J) occlusal views. TMP 2011.096.0141, incomplete right dentary with p4, m1–2 in (K) labial, (L) lingual, and (M) occlusal views. TMP 2009.132.0239, Rm1 in (N) labial, (O) lingual, and (P) occlusal views. TMP 2008.088.0328, Rm2 in (Q) labial, (R) lingual, and (S) occlusal views. con = condyle; cor = coronoid process; maf = mandibular foramen; pts = pterygoid shelf. Scale bars = 2 mm.

180x279mm (300 x 300 DPI)

Draft Fig. 4. Camera lucida outlines of p4s of (A) Ptilodus sp. “C”, from the Blindman River localities, Paskapoo Formation, south central Alberta (Fox 1990; Scott 2008), (B) Kimbetohia campi from the Nacimiento Formation, Betonnie-Tsosie Arroyo area, New Mexico (modified from Krause 1982), and (C) Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern Alberta. The p4s are oriented along a line passing through the peak of the anterobasal concavity and the base of the posterolabial shelf, and registered at a point midway along the baseline (see Krause, 1982). Scale bars = 2 mm. The p4s were scaled to approximately the same size, and those from the right side were reversed, for ease of comparison. Specimens listed in Appendix 1.

215x139mm (300 x 300 DPI)

Draft

Fig. 5. Aenigmamys aries gen. et sp. nov. from the Sheep Ahoy! locality, Upper Willow Creek Formation, southwestern Alberta, and Kimbetohia campi from the Nacimiento Formation, Betonnie-Tsosie Arroyo area, New Mexico. Aenigmamys aries, TMP 2011.096.0479, RP4 in (A) labial, (B) lingual, and (C) occlusal views. Kimbetohia campi, AMNH 59789, LP4 (reversed from original) in (D) labial, (E) lingual, and (F) occlusal views. Aenigmamys aries, TMP 2008.088.0475, incomplete left dentary with p4, m1 in (G) labial and (H) lingual views. Kimbetohia campi, AMNH 58392, Lp4 in (I) labial and (J) lingual views. Scale bar = 2 mm. Specimens were scaled to approximately the same size for ease of comparison.

177x139mm (300 x 300 DPI)

Appendix 1.—Specimens used in generating p4 lateral profile diagrams (Figure 4).

Ptilodus sp. “C”: UALVP 46290, incomplete skull with left P3–4, M1–2, right P1–4, M1–2,

incomplete left dentary with i1, p3–4, m1–2, incomplete right dentary with i1, p3–4, m1–2;

UALVP 40454, incomplete left dentary with i1, p3–4; UALVP 40465, incomplete right dentary

with i1, p3–4, m1–2; UALVP 46344, incomplete left dentary with p3–4; UALVP 46318,

incomplete right dentary with p4, m1; UALVP 40461, 46322, 46323, 46324, p4. All specimens

from the DW-2 locality, late Paleocene (Ti3), south central Alberta, Canada (Fox 1990; Scott

2008).

Kimbetohia campi: The figured profile diagramDraft was modified from Krause (1982: fig. 11A).

Krause (1982) did not identify the individual specimens of K. campi used in generating the

lateral profile diagram, but indicated them having been collected from the Betonnie-Tsosie wash,

early Paleocene (Pu2), New Mexico, USA; these likely included some or all of AMNH 26363,

58392, 58499, 58659, 59940, UCMP 36496.

Aenigmamys aries: TMP 2012.035.0709, 2011.096.0771, 2011.096.0376, 2008.088.0526,

2008.088.0365, 2011.096.0485, 2011.096.0588, 2009.132.0365, 2008.088.0355, 2008.088.0475,

2013.032.0439, 2010.095.0019, 2011.096.0306, 2009.132.0150, 20080.088.0531,

2011.096.0141, 2013.032.0170. All specimens from the Sheep Ahoy! locality, early Paleocene

(Pu2), southwestern Alberta, Canada.

Appendix 2.—Preliminary list of mammalian taxa from the Sheep Ahoy! locality, early

Paleocene (Pu2), southwestern Alberta, Canada.

Order Multituberculata

Cimexomys minor, Cimexomys sp., cf. C. gratus, Mesodma formosa, Xyronomys sp. 1

(equivalent to that at Rav W-1; Johnston and Fox 1984); Xyronomys sp. 2, cf. Ectypodus sp.,

Parectypodus sp., cf. P. armstrongi, Parectypodus sp., Neoplagiaulax sp., cf. N. kremnus,

Neoplagiaulacidae gen. et. sp. unidentified, Aenigmamys aries, Stygimys sp., Microcosmodon

arcuatus

Order Cimolesta Draft

Procerberus sp., cf. P. formicarum, Procerberus sp., cf. P. grandis, Cimolestes sp., Cimolestidae

unidentified genus and species 1–3

Order Lipotyphla

Lipotyphla new genus and species

Order Primates

Purgatorius sp. nov., cf. P. unio, Ursolestes perpetior

“Condylarthra”

Protungulatum sp., cf. P. donnae, Oxyprimus sp., cf. O. galadrielae, Oxyclaenus sp., cf. O.

corax, cf. Loxolophus schizophrenus, Carcinodon aquilonius, Baioconodon sp., cf. B. nordicum,

Chriacidae unidentified genus and species 1–2, Eoconodon sp., cf. E. nidhoggi, Bubogonia

saskia, cf. Oxyacodon sp. 1–2, Periptychidae gen. et sp. nov.

Draft