Description of fossil muskoxen and relative abundance of Pleistocene megafauna in central Alberta

Description of fossil muskoxen and relativeabundance of Pleistocene megafauna in centralAlberta

Christopher N. Jass, James A. Burns, and Peter J. Milot

Abstract: Significant work has gone into describing Ice Age faunas from Alberta, but relatively little work has been dedi-cated to understanding the actual structure of Quaternary faunal assemblages in the province. Development of such a dataset is necessary to fully understand differences in faunal assemblages that existed before and after the last glacial maximum,and may eventually provide an important historical perspective for understanding the impact of large-scale ecosystem dis-turbance. Muskoxen fossils from central Alberta were examined to differentiate specimens of Bootherium and Ovibos. Thoseremains, along with other fossils of Pleistocene megafauna collected from gravel deposits near Edmonton, were used to ex-amine patterns of relative abundance from both pre- and postglacial maximum time periods. Relative abundance for generaof Pleistocene megafauna was calculated using the number of individual specimens (NISP) from 11 individual localities(i.e., gravel pits) in central Alberta. Preglacial localities with statistically significant numbers of specimens (n ≥ 30) aredominated by horse (Equus). Mammoth (Mammuthus) and bison (Bison) are common, but other megafauna, such asJefferson’s Ground Sloth (Megalonyx jeffersoni) and Yesterday’s Camel (Camelops hesternus), are comparatively rare.Current data for the postglacial fauna indicate a shift in which Bison becomes the most abundant large herbivore onthe landscape, a pattern observed in other parts of North America.

Résumé : Si de nombreuses études se sont penchées sur la description de faunes de l’ère glaciaire en Alberta, relativementpeu de travaux ont tenté de comprendre la structure des assemblages fauniques quaternaires dans cette province. Pour biencomprendre les différences entre les assemblages fauniques présents avant et après le dernier maximum glaciaire, l’établisse-ment de tels ensembles de données est nécessaire. Cela pourrait en outre constituer une importante base d’information per-mettant de mieux comprendre l’incidence des perturbations des écosystèmes à grande échelle. Des fossiles de bœufsmusqués provenant du centre de l’Alberta ont été examinés dans le but de distinguer les spécimens de Bootherium et d’Ovi-bos. Ces restes, ainsi que d’autres fossiles de grands animaux pléistocènes prélevés dans des dépôts de gravier près d’Ed-monton, ont été utilisés pour étudier la distribution de leurs abondances relatives avant et après le maximum glaciaire.L’abondance relative des genres de grands animaux pléistocènes a été calculée à partir du nombre de spécimens individuels(NISP) dans onze localités (c.-à-d. gravières) différentes du centre de l’Alberta. Dans les localités préglaciaires présentant unnombre significatif de spécimens (n ≥ 30), les chevaux (Equus) constituent le genre dominant. Les mammouths (Mammu-thus) et bisons (Bison) sont également répandus, alors que d’autres grands animaux, tels que le paresseux terrestre de Jeffer-son (Megalonyx jeffersoni) et le chameau occidental (Camelops hesternus) sont relativement rares. Les données actuellementdisponibles sur la faune postglaciaire indiquent une transition selon laquelle Bison devient le grand herbivore le plus abon-dant dans le paysage, cette transition étant également observée dans d’autres régions de l’Amérique du Nord.

[Traduit par la Rédaction]

IntroductionDuring the late Pleistocene, coalescence of the Laurentide

ice sheet with Cordilleran glaciers likely resulted in the extir-pation of most plant and animal life throughout the provinceof Alberta, Canada (Young et al. 1994; Burns 1996). There

are currently many conservation concerns regarding the im-pacts of ecosystem disturbance on plants and animals, and re-search on Pleistocene and Holocene ecosystems offers thepotential for providing a unique historical perspective on thisissue (Hadly and Barnosky 2009). Alberta’s Ice Age historypreserves a recent geologic record of the ultimate ecosystemdisturbance — a total loss of plant and animal life — acrossa broad geographic gradient, and a record of subsequent re-population. Therefore, Alberta’s Quaternary faunal recordhas the potential for providing an important perspective onhow animals respond once ecologically disturbed regions arere-opened for colonization. Significant work has gone intodescribing the Ice Age fauna from Alberta, but as of yet, rel-atively little work has been dedicated to understanding theactual structure of Quaternary faunal assemblages in theprovince. Development of such a data set is necessary to ex-amine differences or similarities in pre- and post-Wisconsin

Received 3 August 2010. Accepted 15 November 2010.Published at www.nrcresearchpress.com/cjes on 2 May 2011.

Paper handled by Associate Editor Hans-Dieter Sues.

C.N. Jass and P.J. Milot. Royal Alberta Museum, 12845 - 102Avenue, Edmonton, AB T5N 0M6, Canada.J.A. Burns. Curator Emeritus, Royal Alberta Museum,Edmonton, AB T5N 0M6, Canada; Geology/Palaeontology, TheManitoba Museum, 190 Rupert Avenue, Winnipeg, MB R3B0N2, Canada.

Corresponding author: C.N. Jass (e-mail: [email protected]).

793

Can. J. Earth Sci. 48: 793–800 (2011) doi:10.1139/E10-096 Published by NRC Research Press

faunas in the province. Here we present new specimens offossil muskoxen from central Alberta, and discuss patterns ofrelative abundance of Pleistocene megafauna from gravel de-posits occurring near Edmonton.

Geological setting and contextFossiliferous gravels that occur widely throughout Alberta

are an important source of Pleistocene fossil materials (Lang-ston 1959) in the province. In the area surrounding Edmon-ton, Pleistocene deposits include both pre-late glacialmaximum (LGM; preglacial) gravels-and-sands formerlyknown as the Saskatchewan gravels and sands (now assignedto the Empress Formation), as well as post-LGM (postgla-cial) alluvium (Young et al. 1994; Hills and Wilson 2003).Quartzite and chert cobbles dominate the gravels of the Em-press Formation, and shield clasts are notably absent (Younget al. 1994; Hills and Wilson 2003). Conversely, shield clastsare common in postglacial alluvium preserved in terraces(Young et al. 1994; Hills and Wilson 2003). The pre- andpostglacial vertebrate record in central Alberta is separatedby a gap between 21 000 and 11 600 years BP (Burns 1996).During that timeframe, the effects of Laurentide ice likelyrendered the local landscape uninhabitable (Burns 1996; Sha-piro et al. 2004).Previous reports discuss individual vertebrate specimens or

groups of specimens recovered from gravel deposits near Ed-monton (e.g., Fuller and Bayrock 1965; Harington 1978;Burns and Young 1994; Hills and Wilson 2003, and others),but a significant number of specimens housed in the Quater-nary Palaeontology Collection at the Royal Alberta Museum(RAM) are currently unreported in the literature. The bulk ofknown Pleistocene vertebrate material from the Edmontonarea was collected through cooperative efforts of RAM staffand local aggregate companies. Previous collecting efforts in-cluded both passive collecting (e.g., specimens salvaged byemployees of aggregate companies) and systematic collectingwithin the framework of aggregate industry operations (e.g.,onsite monitoring and collecting as gravels are processed bymechanized equipment). As a result, the stratigraphic contextfor most Pleistocene specimens from central Alberta is broad,and positional relationships between individual fossils withinlocal sands and gravels are essentially unknown. In some in-stances, individual localities contain both preglacial and post-glacial fossils, a result likely owing to bulk collectingmethods or reworking of preglacial gravels into postglacialdeposits (Hills and Wilson 2003). While this situationpresents challenges for examining faunal dynamics at finechronologic intervals, radiocarbon data can be used tobracket general age ranges of different gravel deposit local-ities (see “Materials and methods”).

Materials and methodsFossils utilized for this study are derived from fluvial sand

and gravel deposits occurring northwest and northeast of Ed-monton, Alberta (Fig. 1). A systematic description of musk-oxen fossils from the Edmonton gravels was required todistinguish fossils of closely related genera for the relativeabundance analysis. Both Ovibos and Bootherium were previ-ously reported from Edmonton area gravels (Burns andYoung 1994). Specimens of muskoxen described in this pa-

per are housed in the Quaternary Palaeontology Collection atthe Royal Alberta Museum. Higher level taxonomy followsMcKenna and Bell (1997). Descriptions of specimens and as-sociated data are provided in the “Systematic paleontology”section. Measurements were taken using dial calipers. As-signment of specimen numbers followed protocols of theRAM and are also listed in the “Systematic paleontology”section.Relative abundance for genera of Pleistocene megafauna

was calculated using the number of individual specimens(NISP) from 11 individual localities (i.e., gravel pits). Thisapproach assumes that fossil data reflect general patterns ofabundance on the landscape in the past. Relative abundancepresented here was based on generic abundance rather thanspecies abundance because many specimens (e.g., probosci-deans) need further evaluation to establish the validity of spe-cies identifications. Taxa included were Alces, Arctodus,Bison, Bootherium, Camelops, Cervus, Equus, Mammut,Mammuthus, Megalonyx, Odocoileus, Ovibos, Ovis, Pan-thera, Rangifer, and Ursus. Raw data for calculating theNISP were taken from catalogued specimens in the Quater-nary Palaeontology Collection at the RAM. Given the time-transgressive nature of the deposits and the lack of detailedstratigraphic context for individual fossils, NISP seemed themost appropriate measure. Other methodologies for examin-ing abundance (e.g., minimum number of individuals (MNI))would assume a level of knowledge regarding the spatial re-lationships of fossils that is not available for these specimens.Six localities have associated radiocarbon ranges that pre-

cede the LGM (preglacial), one has associated ages that post-date the LGM (postglacial), and four have associated age datathat include both pre- and postglacial time (Table 1). Clearly,many of the localities represent the same depositional frame-work (i.e., Empress Formation), but consideration of local-ities on an individual basis provides a possible means forseparating pre- and postglacial remains and for identificationof potential taphonomic bias throughout different portions ofthe depositional framework. Although work at some of thelocalities is ongoing, the data for this project consisted ofmaterials collected through 2009.

Fig. 1. Geographic position of localities included in relative abun-dance analyses. Modified from Young et al. (1994).

794 Can. J. Earth Sci., Vol. 48, 2011

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Included data from individual sites varied considerablywith respect to both total NISP and 14C analyses. NISP val-ues for individual sites ranged from n = 11 (Horse Hills Pit)to n = 2585 (Pit 48). Numbers of radiocarbon dates rangedfrom n = 1 (Apex Galloway Pit) to n = 30 (Pit 48). Unfortu-nately, some of the well-sampled localities have associatedradiocarbon data that indicate the presence of both pre- andpostglacial materials (e.g., Pit 48, CloverBar Sand & GravelPit). Although these sites were useful for evaluating abun-dance for the late Pleistocene fauna as a whole, they wereproblematic when we tried to evaluate possible changethrough time for the late Pleistocene. Interpretation of certainsites (e.g., Pit 48) as predominantly representative of eitherpre- or postglacial time on the basis of the abundance of spe-cific taxa or percentage of 14C ages is tempting, since 29 of30 14C ages from Pit 48 are preglacial; however, to do sowould result in circular logic in the context of this study.Other sites (e.g., Apex Galloway Pit) are known to containpreglacial fossils, but occur in postglacial terrace settings.Sites with statistically low fossil sample sizes (i.e., n ≤ 30)and those known, or thought, to contain both pre- and post-glacial materials were excluded when considering changes inrelative abundance through time. Sites that were used in-cluded four of preglacial age and one of postglacial age.Institutional abbreviations are as follows: AECV, Alberta

Environmental Centre, Vegreville, Alberta; CMN, CanadianMuseum of Nature, Ottawa, Ontario; BETA, Beta Analytic,Inc., Miami, Florida, USA; BGS, Brock University Earth Sci-ences Radiocarbon Laboratory, St. Catharines, Ontario; OxA,

University of Oxford, Oxford, UK; UA, University of Alberta,Edmonton, Alberta.

Results

Systematic paleontologyMammalia Linnaeus, 1758Artiodactyla Owen, 1848Bovidae Gray, 1821

Bootherium Leidy, 1852Bootherium bombifrons (Harlan), 1825

REFERRED SPECIMENS: P89.13.20, partial skull and right horn core(Fig. 2A); P09.7.11, partial skull and right horn core(Fig. 2B); P98.5.250, partial cranium (Fig. 2C); P94.1.744,right frontal fragment with horn core base.LOCALITIES: Inland Aggregates Pit 48 (= Consolidated ConcretePit 48 of Burns and Young 1994) — P89.13.20, P98.5.250,P94.1.744; LaFarge Pit 542 — P09.7.11.DESCRIPTION: Cranial specimens were identified as B. bombifronson the basis of horn core structure and associated characteris-tics of the dorsal portion of the skull. Complete right horncores are preserved on two specimens (P89.13.20 andP09.7.11). Horn cores emanate laterally from the frontals,and descend ventrally and anterior relative to the base of thehorn core. The bases of both complete horn cores retain adistinct burr line and are round to oval in cross-section.Measurements taken on the horn cores were as follows: dia-meter at base of horn core (P89.13.20 = 73.2 mm; P09.7.11

Table 1. Summary age and sample data for localities considered in this paper.

Gravel pit Minimum age (years BP) Maximum age (years BP) nInland Aggregates Pit 45 27 730±1060a >41 800b 10Inland Aggregates Pit 46 31 520±450c 39 960±3950d 2CloverBar Sand & Gravel 11 090±55e >63 100f 13Twin Bridges Pit 4 10 730±160g 11 285±55h 2Riverview Pit 31 290±1930i >58 500j 7Apex Evergreen Pit 25 210±760k >59 900l 8Inland Aggregates Pit 48 11 065±55m >62 200n 30Twin Bridges Pit 1042 – LaFarge Pit 542 37 800±2060p >43 500this report 2Horse Hills Pit 4370±100q 26 050±880r 3Twin Bridges Pit 80 1850±100s >62 300t 13Apex Galloway Pit 40 700±3000u 40 700±3000u 1

Regional separation of west Edmonton and east Edmonton localities follows Young et al. (1994). n, number of 14C ages for locality. Footnotes includelaboratory number, sample information, d13C values (when available), or citation if age was previously reported.

aAECV-599C, bone collagen, d13C = –20.5.bAECV-1820C, bone collagen, d13C = –19.0.cYoung et al. (1994).dYoung et al. (1994).eOxA-14578, accelerator mass spectrometry (AMS) on bone collagen.fOxA-14274, AMS on bone collagen.gAECV-1111C, bone collagen, d13C = –19.4.hOxA-14573, AMS on bone collagen.iAECV-941C, bone collagen, d13C = –20.3, listed as 31 290±1960 in Young et al. (1994).jOxA-11619, AMS on bone collagen.kAECV-1201C, bone collagen, d13C = –19.1.lOxA-14269, AMS on bone collagen.mOxA-14579, AMS on bone collagen.nOxA-14275, AMS on bone collagen.pAECV-1465C, wood, d13C = –22.4.qAECV-611C, bone collagen.rYoung et al. (1994).sAECV-543C, wood, d13C = –25.0.tOxA-14276, AMS on bone collagen.uBGS 2107, bone collagen.

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= 73.65 mm), circumference at base of horn core (P89.13.20= 208 mm; P09.7.11 = 201 mm), and length of horn frombase to tip along the dorsal surface (P89.13.20 = 241 mm;P09.7.11 = 210+ mm).Neither specimen with an intact horn core exhibits pitting

or exostosis on the preserved portion of the frontals; there-fore, the specimens likely represent female B. bombifrons(Figs. 2A, 2B). Horn cores in female B. bombifrons typicallyretain a distinct burr line at the base of the horn core, arewidely spaced, and lack evidence of pitting or exostosis onthe frontals (McDonald and Ray 1989; Guthrie 1992).Conversely, the cranial specimen that lacks horn cores(P98.5.250) is likely from a male individual since it preservesexostosis extending across the top of the cranium to the pari-etal (Fig. 2C).DISCUSSION: Helmeted muskoxen were geographically widespreadin North America during the Pleistocene (McDonald and Ray1989), and were previously reported from Alberta (Churcher

1972, 1984; Harington 1975, 1978; Stalker and Churcher1982; Hills and Wilson 2003; McNeil et al. 2005). The speci-mens of B. bombifrons presented here add several additionalrecords to the literature. Direct radiocarbon ages forspecimens of B. bombifrons from central Alberta range from30 570 ± 250 years BP (Hills andWilson 2003) to > 43 500 yearsBP (BETA-270089; P09.7.11, this report)

cf. Bootherium bombifrons (Harlan), 1825

REFERRED SPECIMENS: P89.13.251, partial left dentary with p2–m2;P89.13.698, partial (proximal) right metatarsal; P89.13.140,partial axis; P96.9.81, cervical vertebra; P06.1.9, cervical ver-tebra; P94.1.850, cervical vertebra; P98.5.371, cervical verte-bra; P95.2.41, thoracic vertebra; P89.13.761, thoracicvertebra; P98.5.98, lumbar vertebra; P98.4.2, left, ventralportion of atlas; P95.1.21, basisphenoid and partial occipital;P94.1.934, basisphenoid and partial pterygoid; P94.1.186vertebra fragment.

Fig. 2. Fossil muskoxen from central Alberta. (A) Dorsal view of partial frontal and right horn core of Bootherium bombifrons (P89.13.20).(B) Dorsal view of partial skull with right horn core of B. bombifrons (P09.7.11). (C) Dorsal view of partial cranium of B. bombifrons(P98.5.250). (D) Dorsal view of partial cranium of Ovibos moschatus (P97.5.1). Scale bars = 1 cm.



LOCALITIES: Inland Aggregates Pit 48 — P89.13.698,P89.13.140, P06.1.9, P94.1.850, P98.5.371, P89.13.761,P98.5.98, P94.1.934; P94.1.186; Twin Bridges Gravel Pit4 — P96.9.81; Apex Evergreen Pit — P95.2.41; CloverBarSand & Gravel — P95.1.21; Alberta Concrete Product Ltd.locality — P98.4.2.DESCRIPTION: All specimens identified as cf. B. bombifrons likelybelong to that species. They are dissimilar to the skeletal ele-ments of other artiodactyls known from the Edmonton gravelpits (e.g., Bison, Camelops), but we cannot point to particularfeatures that permit a definitive species identification.The dentary identified as cf. B. bombifrons (P89.13.251)

retains teeth that are selenodont and hypsodont. The smallersize of the jaw, the lack of buccal stylids on m1–m2, the sim-ple uncrenulated molar fossettes, and the occlusal pattern onthe premolars distinguish it from Bison. The jaw and teethappear too large to be assigned to Ovibos. Measurementstaken include occlusal length of p2 (14.65 mm), p3(20.80 mm), p4 (25.05 mm), m1 (27.20 mm), and m2(36.25 mm). Currently, there are very few data available onthe dentition of B. bombifrons. Some mention of the upperdentition is found in prior reports (Semken et al. 1964;McDonald and Bartlett 1983; McDonald 1984; McDonaldand Ray 1989), but the lower dentition is almost completelyunknown or undescribed for the purposes of identification.Identified vertebrae conform to descriptions outlined by

McDonald and Bartlett (1983) and McDonald et al. (1987).Future comparisons with related taxa may further clarify theidentification of the vertebral elements reported here.DISCUSSION: Identification of specimens as cf. B. bombifrons re-presents an admittedly conservative approach to specimenidentification, but one that represents an appropriate taxo-nomic placement based on available data. Presentation of thespecimens will hopefully bring attention to areas of descrip-tive paleontological research that require further investigationand clarification, such as structure of the lower dentition inBootherium and variation in vertebral structure in medium-sized artiodactyls.

Ovibos de Blainville, 1816

Ovibos moschatus (Zimmerman), 1780REFERRED SPECIMENS: P94.1.568, partial right frontal and orbit;P97.5.1, cranium with horn core bases (Fig. 2D).LOCALITY: Inland Aggregates Pit 48 — P94.1.568, P97.5.1.DESCRIPTION: The cranium (P97.5.1) preserves strongly developedexostoses on the frontals. A well-defined medial groove sepa-rates the horn core bases, a character consistent with identifi-cation to a male individual (Harington 1970). The partialright frontal (P94.1.568) retains evidence of exostosis on thesurface, and was originally thought to represent B. bombi-frons. During examination of P97.5.1, it was determined thatP94.1.568 represents a broken portion of P97.5.1. This dis-covery was something of a surprise, since the specimenswere collected three years apart.DISCUSSION: Tundra muskoxen were previously reported fromcentral Alberta (Dawson 1901; Harington 2003), but like thehelmeted muskoxen, they are not common in the Pleistocenerecord of Alberta. Other records of Ovibos from Alberta in-clude a cranium from the Edmonton area (CMN-6765), askull fragment collected 4 miles west of Ponoka (CMN-

9816), a partial skull collected 20 miles west of Ponoka(UA-612), skull fragments (UA-843A, B) from gravel pitsnear Cold Lake, and postcranial remains from the easternPeace River District (Harington 1978; in litt. to J.A. Burns1997; Churcher and Wilson 1979). The only published radio-carbon data for Ovibos from Alberta are preglacial, rangingfrom 23 720 ± 80 years BP for CMN-9816 to 43 100 ±490 years BP for CMN-6765 (n = 2; Harington 2003).

Relative abundance analysisOnly a single site (Pit 48) produced remains of all taxa

considered here. Other sites contained only partial representa-tion of the megafauna known from central Alberta, and thereis some indication that greater sampling of individual siteshas some correlation to the number of known genera (r2 =0.74). Summaries of NISP and relative abundance of generaof megafauna at individual sites are presented by locality andage (i.e., preglacial, mixed pre- and postglacial, and postgla-cial) in Tables 2 and 3.Bison, Equus, and Mammuthus account for 97% of known

megafauna in central Alberta during the late Pleistocene.When considered as a whole, the late Pleistocene megafaunaof central Alberta is dominated by Equus (relative abundanceof all combined sites = 0.59). Bison is also a common com-ponent (relative abundance of all combined sites = 0.35). Noother taxon has a relative abundance greater than 0.03 (Mam-muthus). However, when considered in the context of chrono-logic brackets (preglacial, postglacial), an interestingdeviation from those results is observed.In preglacial localities, Equus has the highest relative

abundance (Table 2). Mammuthus or Bison has the next high-est relative abundance at preglacial localities, but sites whereMammuthus has the second highest abundance have lowersample sizes. This might reflect collecting bias towards largerspecimens at certain localities. Regardless, preglacial mega-faunal assemblages in central Alberta are dominated byhorse, followed by either bison or mammoth. Other taxa(e.g., sloth, mastodon, carnivorans) represent minor compo-nents of the preglacial fauna. The single postglacial site pre-serves bison, horse, and mammoth as the three mostcommon faunal components (Table 3). Unlike the preglaciallocalities, Bison is the most abundant taxon in the postgla-cial assemblage, suggesting a shift from an Equus-domi-nated landscape in central Alberta to one in which Bisonwas more prevalent.

DiscussionFor measures of relative abundance in the fossil record to

be meaningful, some recognition of spatial and chronologicconstraint is necessary. The assemblages considered here arethought to represent a restricted geographic distribution, butthey clearly encompass a broad time span on the scale ofthousands to tens of thousands of years. Similar scenariosare known for other Pleistocene deposits, and studies fromsites in southern California provided insight into the relativeabundance of megafauna from southwestern portions of theUnited States (e.g., Springer et al. 2010). For the DiamondValley Lake local fauna of southern California, a paucity oflarge carnivorans relative to herbivores was used to infer rep-resentative sampling of megafauna (Springer et al. 2010).

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Similarly, carnivorans are rare in the localities from centralAlberta, suggesting that the information presented here repre-sents a useful approximation for the structure of megafaunalassemblages in the region.Horses, bison, and mammoths dominate the pre- and post-

glacial faunas of central Alberta. These taxa were importantlate Pleistocene components of faunas both to the north andsouth of central Alberta (e.g., Guthrie 2003; Hills and Har-ington 2003; Shapiro et al. 2004; Springer et al. 2010); how-ever, some specific differences are evident. In Alaska,mammoths were more abundant relative to horses until theonset of the LGM (Guthrie 2003), whereas in central Alberta,Equus was the most abundant taxon until that same time.Other herbivores that were more common elsewhere in North

America represent only a minor component of the preglacialPleistocene landscape in central Alberta (e.g., Camelops; seeSpringer et al. 2010).A recent summary suggests that the local recession of the

Laurentide ice sheet took place between approximately 13 000and 11 000 years BP (Dyke 2005). Relative abundance dataand summary radiocarbon data presented here indicate thatBison replaced Equus as the most abundant large herbivorewhen megafauna re-appeared in the central Alberta recordduring the latter portion of that time frame (Tables 1–3). Thechange from horse-dominated assemblages to bison-domi-nated assemblages in central Alberta does not appear to co-incide with periods of population boom in some northernNorth American Bison (Shapiro et al. 2004), although a

Table 2. Relative abundance of megafauna from preglacial localities in central Alberta.

Preglacial

Genus Pit 45 Pit 46 Riverview Apex Evergreen Pit 1042/Pit 542 Apex GallowayAlces — — — — — —Arctodus 0.02 (1) — <0.01 (1) <0.01 (1) — —Bison 0.15 (10) 0.07 (3) 0.24 (51) 0.40 (84) 0.46 (11) 0.52 (12)Bootherium — — — <0.01 (1) 0.04 (1) —Camelops — — 0.01 (2) — 0.04 (1) —Cervus — — — <0.01 (1) — 0.39 (9)Equus 0.61 (40) 0.64 (27) 0.62 (130) 0.54 (113) 0.42 (10) 0.04 (1)Mammut 0.05 (3) 0.02 (1) — — — 0.04 (1)Mammuthus 0.17 (11) 0.26 (11) 0.12 (25) 0.02 (4) 0.04 (1) —Megalonyx — — — <0.01 (1) — —Odocoileus — — — — — —Ovibos — — — — — —Ovis — — — <0.01 (1) — —Panthera — — <0.01 (1) <0.01 (1) — —Rangifer 0.02 (1) — — 0.01 (2) — —Ursus — — — — —Total NISP (66) (42) (210) (209) (24) (23)

Numbers in parentheses denote NISP for locality.

Table 3. Relative abundance of megafauna from mixed-age and postglacial localities in central Alberta.

Mixed pre- and postglacial Postglacial

Genus CloverBar Pit 48 Horse Hills Pit 80 Pit 4Alces — <0.01 (1) — — —Arctodus <0.01 (1) <0.01 (2) — — —Bison 0.32 (146) 0.27 (686) 0.09 (1) 0.72 (385) 0.72(113)Bootherium — 0.01 (15) — — <0.01 (1)Camelops <0.01 (2) <0.01 (6) — — —Cervus — <0.01 (3) 0.09 (1) 0.03 (13) —Equus 0.65 (294) 0.67 (1739) 0.64 (7) 0.25 (135) 0.26 (41)Mammut — <0.01 (3) — — —Mammuthus 0.01 (3) 0.02 (49) 0.18 (2) <0.01 (1) 0.01 (2)Megalonyx <0.01 (1) <0.01 (3) — — —Odocoileus — <0.01 (1) — — —Ovibos — <0.01 (1) — — —Ovis — <0.01 (4) — — —Panthera — <0.01 (5) — — —Rangifer <0.01 (2) 0.02 (63) — — —Ursus <0.01 (1) <0.01 (3) — — —Total NISP (450) (2585) (11) (534) (157)

Numbers in parentheses denote NISP for locality.



subsequent study of the same data set suggested a reducedpopulation rebound near the end of the Pleistocene (Drum-mond et al. 2005). The pattern of change shown by datapresented here is congruent with observations made byScott (2010) and others (e.g., Wycoff and Dalquest 1997;Scott and Cox 2008) who report a predominance of Bisonin portions of North America during the terminal Pleisto-cene.The early postglacial dominance of Bison in the central Al-

berta megafauna may plausibly be explained by the inferencethat Bison recolonized the province from the south, a patterncurrently supported by palaeontological and genetic data (e.g., Wilson 1996; Shapiro et al. 2004; Wilson et al. 2008;Burns 2010). Abundance data presented here indicate thatthe postglacial population of Bison was able to thrive on thelocal landscape and possibly outcompete the once-predominantEquus for available resources. This suggestion is not novel,as Scott (2010) eloquently established an extinction modelfor the late Pleistocene, in which competitive success of Bi-son in the late Pleistocene, in conjunction with environmen-tal change, contributed to the loss of other megafauna.Currently, we have little direct evidence to suggest a cause

for the failure of horses to repopulate central Alberta as thepredominant herbivore following glacial recession. A loss ofoptimal food resources was cited as a possible cause of thedecline of horse populations elsewhere (Guthrie 2003); how-ever, there are currently scant vegetation data available forthe preglacial of central Alberta that would provide an envi-ronmental framework for this hypothesis. Mossy, blackspruce (Picea mariana) wetlands are inferred for central Al-berta on the basis of plant material known from pits 45 and48 (Burns and Young 1994; J.A. Burns, unpublished data),but very little is known otherwise.Horses are reported to be the most abundant taxon at the

postglacial Wally’s Beach site in southern Alberta (Kooymanet al. 2001), providing evidence that Equus successfully re-colonized southern portions of Alberta fairly rapidly follow-ing the recession of ice sheets. However, given the evidenceof human hunting of horses at Wally’s Beach, present com-parisons of abundance between that site and sites in centralAlberta are not analogous. More taphonomic research ongravel deposits in central Alberta is needed to explore poten-tial biases in the results presented here. However, the obser-vation that geographically spaced preglacial gravelsconsistently contain high abundances of Equus, Bison, andMammuthus suggests that local taphonomic effects are notimpacting the interpretations presented in this paper.One final cautionary note to the interpretations presented

here, well illustrated by the presentation of systematic de-scriptions of muskoxen fossils, relates to our initial assump-tion that some identifications of genera in the RAM databasewere correct. The specimens of cf. Bootherium bombifronspresented earlier in the text were identified as B. bombifronsin the RAM database and were incorporated into our relativeabundance study as such. In this case, the number of speci-mens was so low that including specimens we now regard ascf. Bootherium bombifrons in the generic-level analysis ofrelative abundance would have little impact on the results.However, this exemplifies the necessity for researchers to beexplicit about the assumptions that they are making whenthey incorporate undescribed fossil specimens from museum

collections, or even from faunal lists, for subsequent studiesof broad patterns in the Pleistocene record.In summary, the Pleistocene megafauna of central Alberta

was taxonomically diverse but was dominated by high abun-dances of Equus, Bison, and Mammuthus. Bison replacedEquus as the most abundant large herbivore after recessionof the Laurentide ice sheet, a shift observed elsewhere inNorth America. This is of special interest, because it suggeststhat aspects of the return of megafaunal assemblages to post-glacial Alberta reflected broader patterns of faunal dynamics.In other words, the changes impacting populations of Pleisto-cene species were not mitigated by the re-opening of ecolog-ically disturbed areas. Future work is needed to substantiatethe hypothesized local geographic origin of fossils depositedin gravels in central Alberta, to examine the chronologicranges of individual taxa, to further examine age data for thereported postglacial locality (Pit 4), and to examine the im-pacts of revised identifications on broad patterns of faunaldynamics.

AcknowledgementsThe authors thank LaFarge Aggregates and Inland Aggre-

gates for continued cooperation and for donations of speci-mens to the Quaternary Palaeontology Collection at theRoyal Alberta Museum. Gene Seal donated a significant col-lection of fossil material. Alwynne Beaudoin provided help-ful discussions regarding Pleistocene faunal and vegetationdynamics in Alberta. Several radiocarbon data presentedhere were provided by Alan Cooper (then of the Universityof Oxford, Oxford, UK) as part of previous collaborative re-search with J.A. Burns. Many others were made availablethrough Dr. Dave Arnold, formerly of the Alberta Environ-mental Centre in Vegreville, Alberta. Comments on early ver-sions of this manuscript were made by Renata Brunner Jass.Greg McDonald, Hans-Dieter Sues, and Eric Scott providedconstructive reviews that improved the manuscript.

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Description of fossil muskoxen and relative abundance of Pleistocene megafauna in central Alberta