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Home , Agriotherium, Ailuropoda, Amphicyon, Caniformia, Cave bear, Cephalogale

A REVIEWOF EVOLUTION

BRUCEMCLELLAN, Forest Sciences Research Branch,Revelstoke Forest District,RPO#3, Box 9158, Revelstoke, BC VOE3KO DAVIDC. REINER,U.S. Fish and WildlifeService, NS 312, Universityof Montana, Missoula, MT

Abstract. Ursidae is a young family, evolving from early canids during the late and early , about 20-25 million ago. The family has frequently been divided into subfamilies. Although debated, these often include: (1) , (2) Agriotheriinae, (3) ,(4) , and (5) Ailuropodidae. Based on scatteredliterature published over the past century, we trace the evolutionary lineage of the various genera and found in these subfamilies; most are extinct, 8 species remain. Many if not most of the relationships have been disputed for many years and we may be far from the definitive history. Speculatedcauses of usually involved climate change and competition. Primitive man may have been the major competitorof some extinct species and modem man is definitely a major influence on bear evolution today.

Int. Conf. Bear Res. and Manage.9(1):85-96

Members of the bear family, Ursidae, currently however, have separatedthese 2 families but frequently inhabit , , , and South disagree on where the line between canids and ursids, America. Using generic names suggested by Hall and many other taxonomic boundaries, should be (1981), Nowak and Paradiso (1983), Goldman et al. drawn. Recently, the families Ursidae and Otariidae (1989), and Wayne et al. (1989), species found in Asia have been placed in the superfamily Ursoidea. These include the ( arctos), Asiatic black 2 families have been joined with members of the bear (U. thibetanus), (U. malayanus), sloth Canoidea superfamily, , , bear (U. ursinus), and (U. maritimus). The ,and Phocidae, into the suborderCaniformia taxonomic status of the sixth Asian member, the giant (Wozencraft1989). panda ( melanoleuca), remains in question, The purpose of this paper is not to create another although most evidence suggests that it belongs to view of bear evolution and resultingtaxonomy. Rather, Ursidae. Brown and polar bears are found in it is to summarize for the interest of biologists who Europe and these 2 species plus the American black work with extant species the large body of knowledge bear (Ursus americanus) inhabit North America. The that has grown over the past century but is scatteredin ( ornatus) is the only journals and papers that many of us rarely encounter. member of Ursidae in . Ursidae are placed in the Carnivorabut, except for the largely carnivorous polar bear, bears are SUBFAMILIESOF URSIDAE omnivorous, feeding mostly on plant material, insects, Although 2 major contributorsto bear , fish, and . They are generally large, stocky, Simpson (1945) and Erdbrink (1953), did not favor and powerful . All bears are , subfamilydivisions as suggested by Kragavlich(1926), walking on their entire foot. The radius and ulna and most systematicians divide the bear family into 3 the tibia and fibula are separate,which enables bears to (Kragavlich 1926, Kurten 1966) or 4 (Pilgrim 1932, rotate their limbs, improving their ability to dig and Thenius 1959) subfamilies without including manipulate food, and facilitating climbing by some Ailuropodidae, the subfamily that includes the giant species. Bears' teeth reflect their omnivoroushabits by panda. These authors generally disagree over the lacking the common in other mammalian inclusion of the subfamily Hemicyoninae, or -like- and having flattened molars adapted to bears (or bear-like-), with either the canids or crushing and grinding vegetation. Bears' premolarsare ursids. Hendey (1980) splits the bears into 5 reduced in size and utility, creating a gap between subfamilies and 7 tribes; his groups include different incisors and molars similar to that found in many genera than other students. We will include the giant herbivorous mammals. panda as a bear and discuss 5 subfamilies (Fig. 1): Bears are a young family, evolving from early canids (1) Hemicyoninae,(2) Agriotheriinae,(3) Tremarctinae, during the late Oligocene and , about 20- (4) Ursinae, and (5) Ailuropodidae. 25 million years before present (MYBP). So recent is this divergence that some taxonomists believe that canids and ursids should be considered as one family SUBFAMILY HEMICYONINAE and dividing them is due to "custom of more than a It is believed that bears evolved from the canid line century" (Simpson 1945). The majority of students, during the late Oligocene and early Miocene (Kurten 86 Int. Conf.Bear Res. and Manage.9(1) 1994

Fig. 1. A tentative phylogeny of Ursidae subfamilies. and are base genera for these subfamilies.

1966). The change from canids to ursids left a fossil first bears. record relatively rich with intermediategenera and this Several students (Erdbrink 1953, Kurten 1966, has led to various opinions on where to differentiatethe Mitchell and Tedford 1973, Thenius 1979) suggested 2 families. Frick (1926) separatedsome intermediate that the evolutionary line between the canid subfamily forms from both the canids and ursids by creating the Amphicynodontinae and the ursid subfamily family Hemicyoninae, in which he included the genera Hemicyoninaewas throughthe genera Cephalogale and , , Hyaenarctos, and Ursavus (since Ursavus (Fig. 2). Matthew [1929] Hyaenarctos is considered to be Members of Hemicyoninae were relatively small ). Frick (1926) specifically refrainedfrom during their early history with Cephalogale being about including this new family in the Ursidae, although the size of a . As was often the trend with Mitchell and Tedford (1973) thought that he had Ursidae, however, they increased in size with time and presented enough evidence that suggested it did belong some became the size of the largest modem bears. with bears. Pilgrim (1932) placed Frick's family, Hemicyoninae were largely carnivorous, but it appears Hemicyoninae, plus earlier genera, Amphicyon and that Cephalogale became increasingomnivorous, which Cephalogale, into Ursidae. This general division is why it is considered to be the ancestor of all ursids. between canids and ursids was favored by many authors Cephalogale occurred in from the late (Thenius 1959, Hendey 1972, Mitchell and Tedford Oligocene and North America from the early Miocene 1973) although Kurten (1966) placed this group with (Tedford et al. 1987). The much larger Hemicyon was the canids and considers the Ursavus to be the confined to Eurasiaduring its early history but became BEAREVOLUTION * McLellan and Reiner 87

Period SUBFAMILY HEMICYONINAE North America Eurasia ? --

Pliocene

5 --x x x

10

Miocene

15 Hemicyon

/

20

Cephalogale

25

Fig. 2. A tentative phylogeny of the genera of the subfamily Hemicyoninae and approximate extinction dates. very successful and spread to North America in the SUBFAMILYAGRIOTHERIINAE mid-Miocene (Hendey 1972, Tedford et al. 1987). The ursid subfamily Agriotheriinaeas described by Scott (1937) believed the bear-dogs were the dominant Thenius (1959) and Kurten (1966) include the genera canid type in North America during the late Miocene Ursavus, , and Agriotherium. The genus and . The extinction of Hemicyoninae has Ursavus, which is believed to have evolved in Europe been related to the radiation of a more advanced from Cephalogale, appearsto have given rise to its own subfamily of bears, Agriotheriinae (Hendey 1972, subfamily Agriotheriinae plus the subfamilies Kurten 1971), or possibly due to competitionwith large Tremarctinae, Ursinae, and Ailuropodidae (Fig. 3). felids (Lydekker 1883, Frick 1926). Ursavuselmensis, which was about the size of a , is 88 Int. Conf.Bear Res. and Manage.9(1) 1994

Fig. 3. A tentative phylogeny of the subfamilyAgriotheriinae. thought to be the most primitive species of this genus primitive U. brevirhinus. Members of the genera (Crusafont and Kurten 1976). It existed during the Ursavus were found in Eurasia for over 10 million early Miocene, when the climate in Europe was years. It appears that Ursavus, perhaps the debated relatively stable and sub-tropical. species U. pawniensis, was also in North America from From the small, primitive U. elmensis, 2 larger the early to mid-Miocene (Tedford et al. 1987). species appear to have evolved, U. primaevus and U. Hendey (1980) suggests the genus Ursavus should be brevirhinus (Crusafont and Kurten 1976). Crusafont their own subfamily, Ursavinae. and Kurtenbelieve that these 2 species were sympatric The transitionfrom the genus Ursavus to Indarctos in Europe for a relatively long period and therefore during the early Pliocene appearsto follow an increase deserve specific distinction, which Stromer(1940) and in body size (Hendey 1972). Crusafont and Kurten Thenius (1949, cited from Crusafontand Kurten 1976) (1976) proposed that the relatively lightly built did not give them. From U. primaevus, Crusafontand Indarctos vireti was the most primitive species of this Kurten (1976) suggest that 2 larger species, U. genus. The various species of Indarctos generally ehrenbergi and U. depereti evolved. Thenius (1949) continued to increase in size and spread from Europe mentioned that U. ehrenbergi may have been close to and Asia to North America, where the remains of I. the line leading to the subfamily Ursinae, though oregonensis, a very large bear, was discovered in Crusafont and Kurten (1976) propose that the ursine Oregon (Merriamet al. 1916) and Nebraska(Shultz and bears probably arose from a line closer to the more Martin 1975). BEAREVOLUTION * McLellan and Reiner 89

in For many years there has been disagreementon the thibetanus have crossed captivity questions placing relationships of the third genus of the subfamily, Tremarctosin its own subfamily (Mondolfi 1983). is and was Agriotherium. Recently, Thenius (1959) and Hendey The earliest Tremarctinae (1972 and 1980) conclude that Agriotheriumevolved found in the upper Pliocene of (Frick 1926) from Indarctos and may even have been congeneric althoughearlier roots in Asia are suspected (Kurtenand of (Hendey 1980). Dalquest (1986), however, believes Anderson 1980). This genus is likely the ancestor that the 2 are not closely related. The long-standing the 2 other genera of the subfamily, Tremarctos and confusion over the evolutionary direction of the 2 Arctodus (Fig. 4). These 2 genera made their first South species may be due to Agriotherium being more appearance in the Pleistocene of North and carnivorousthan Indarctos, which is againstthe general America (Kurten 1966). trend of the Ursidae (Hendey 1980). The early history of both Arctodus and Tremarctosis Remains of Agriotheriumhave been found in many poorly recorded in the fossil record. Early students parts of the world including Europe, , , South such as Merriam et al. (1916) and Frick (1926) and , and North America (Hendey 1972). In North more recently Erdbrink (1953), believed Arctodus America, its known range extended from Californiato evolved from a line close to Indarctos. Thenius (1959) Florida and from Nebraska to southern Mexico and Kurten(1966), however, believe that Arctodus was (Dalquest 1986). In North America Agriotherium a Tremarctinae. became larger than any extant species of bear (Scott Of the 5 species of Arctodus, A. pristinus,and A. 1937, Shultz and Martin 1975). simus were in North America and A. bonariensis, A. The extinction of Agriotherium due to competition pamparus, and A. brasiliensis were found in South with early Ursinae, as was a probable cause of America. Kurten (1967) suggested A. pristinus may extinction for other genera of Agriotheriinae,appears represent a relatively primitive form. It was smaller, less plausible because Agriotheriumwas thought to be more lightly built, and probably less carnivorous than largely carnivorous. Competitionwith other carnivores the other species and so far has only been found in the may have been involved (Hendey 1972). Many southeasternportion of North America. carnivoreshad difficulties during the general extinction More is known of A. simus, the great short-faced of the late Hemphillian near the Miocene/Pliocene bear, than other Arctoidbears, because the fossil record boundary, when 60 mammalian genera disappeared is extensive in area, covering most of North America, from North America (Martin 1984). The last known and relatively complete. A. simus was a very large representativeof this subfamily,A. insigne, disappeared bear, with some individuals weighing at least 650 kg after the Villafranchianin Europe (Kurten 1968) as the (Emslie and Czaplewski 1985). This bear had long legs climatebegan gradualcooling and warmingoscillations, and stood about 2 m at the shoulder, which suggests an foreshadowing the ice age. adaptationfor fast movement. Kurten (1967) thought that A. simus was not truly a cursorial predator, but may have been capable of bursts of speed exceeding SUBFAMILY TREMARCTINAE those of U. arctos. Kurten (1967) suggested that its The subfamily Tremarctinae includes the genera short but wide jaws demonstratedconvergence with the Plionarctos, Arctodus, and Tremarctos(Thenius 1959, great and indicatedthat it was largely carnivorous. Kurten 1966). There is 1 extant species, Tremarctos According to Kurten's interpretation,A. simus was by ornatus of the South American . Although the far the most powerful predator during the Pleistocene fossil evidence leading to Tremarctinae is poor, and possibly preyed on contemporaryspecies of bison, paleontologists suggest that Ursavus is likely the , , and ground sloth. Stirling and Derocher ancestral genus (Thenius 1959, 1976; Kurten 1966). (1990) and McLellan(1993) suggested that co-existence Cytological and molecular methods indicate that with A. simus for or over 1 million years inflicted T. ornatus diverged from the genus Ursus 10.5-15 significant constraints on the evolution of Ursus MYBP (O'Brien et al. 1985, Goldman et al. 1989), americanus. when Ursavus sp. were common in Eurasia and Emslie and Czaplewski (1985) disagree with the apparentlypresent in North America. Although there conclusions of Kurten(1967). Based on characteristics are several morphological and biochemical differences of the skull, body size, and relative lengths of distal and between Tremarctinae and Ursidae, including a proximallimb segments, Emslie and Czaplewski (1985) different number of chromosomes (2n is 74 in Ursus suggest that A. simus was largely herbivorous. and 52 in Tremarctos), the fact that T. ornatus and U. A. simus disappeared at the end of the Wisconsin 90 Int. Conf.Bear Res. and Manage.9(1) 1994

Fig. 4. A tentative phylogeny of the subfamily Tremarctinae. glaciation,perhaps due to competitionwith Ursusarctos explaining the extinction, which (Kurtenand Anderson 1974). These 2 bears, however, perhaps led to the extinction of A. simus, are overkill apparently co-existed in Beringia for about 100,000 by Paleoindians of the Clovis culture, and climatic years, so if competition was the leading factor, other change that included a very dry period and a resulting conditions must have changed. The close proximity in reductionof habitatdiversity. time between the disappearanceof A. simus and the late Relatively little is known of Arctodus in South Pleistocene extinction, when 57 of the 79 species of America because few fossils have been found. A. large ( > 45 kg) in North Americadisappeared brasiliensis was the smallest of the 3 species and, as it ( 1984), suggests a correlation,particularly if A. more closely resembled the North American species, simus was largely carnivorous and much of its prey may have been an intermediate. A. pamparus was also disappeared. The peak of this extinction was about relativelysmall, whereasA. bonariensis was very large, 11,000 YBP (Martin 1984) whereas the last A. simus rivalingA. simus in size (Kurten1967). A. bonariensis remains to be dated were more than 1,000 years older. had large canines and carnassials but short posterior This date, however, was obtained on an Equus bone molars, suggesting a carnivorous diet. Based on the found at the deepest level of a (Kurten and structureof their molars, Kurten (1967) suggested the Anderson 1980) and the bear was likely younger, possibility of a mollusk-eating specialization for the perhaps near the 10,000 years ago suggested by other South American species. Harrington (1973). Two competing hypotheses The genus Tremarctos consists of 2 species, BEAREVOLUTION * McLellan and Reiner 91

Tremarctosfloridanus and the extantspectacled bear, Americaat least by the early Blancan,perhaps 3.5 T. ornatus. As was the case with Arctodus, the MYBP (Kurten and Anderson 1980). In North ancestral genus to Tremarctosis believed to be America,this species is calledU. abstrusus,but may be Plionarctos (Kurten 1966; Thenius 1959, 1976). conspecificwith U. minimus. This small early ursid Fossils of the North Americanspectacled bear have likely gave rise to the Asiatic and Americanblack been found most often in Florida and only rarely bears. The timingof the divergenceof U. americanus elsewhere(Kurten and Anderson1980). T. floridanus estimatedfrom fossils is similar to the 4.4 MYBP seems to have been a slow-moving,heavily built, derived through 2-dimensional electrophoresis medium-sizedbear with powerfulforelimbs. Kurten (Goldmanet al. 1989) and the 3.8 MYBP estimated (1966) suggestedthat T. floridanus filled a nichesimilar from mitochondrialDNA divergence (Shields and to thatof the Europeancave bear, Ursusspelaeus, as a Kocher1991). powerful,almost exclusively vegetarian bear. Reasons U. thibetanusranged into Europeduring in the mid- for the extinctionof T. floridanusin the last 8,000 Pleistocenewith remains being found in manycountries years are unclear, although competitionwith U. (Kurten1968). Why it was extirpatedfrom Europeis americanushas been suggested. These species, or at unknown,but competitionwith the largelyherbivorous least early versions, co-existedin NorthAmerica for cave bearsmay have been a factor. In NorthAmerica, about 3 million years, so if competitionwith U. blackbears are by far the mostcommon fossil bearsof americanuswas the cause of extinction,an additional the Pleistoceneand have been foundacross most of the change,such as climate,must have precipitated it. . As was the case with many species, late- Pleistoceneblack bears were muchlarger than they are today. Behavioraland morphologicalcharacteristics SUBFAMILYURSINAE imposedon black bears by other ursids have been The subfamilyUrsinae has been dividedinto many discussedby Herrero(1972), Stirlingand Derocher different phylogeneticgroups in the past. Until (1990), andMcLellan (1993). recently, 5 genera, Melursus(), Helarctos (sunbear), Thalarctos (polar bear), Selenarctos (Asiatic Cave Bears blackbear), and Ursus(brown bear and American black The small, primitive U. minimus gave rise to bear) were recognized. Molecularand cytological U. etruscus, which was also initially small but methods(O'Brien et al. 1985, Goldmanet al. 1989) continuedthe trendtowards a largerbody size. This plus successfulcrossing between several of the species speciesradiated across Eurasia. In Europe,it gave rise in captivity (C. Servheen, U.S. Fish and Wildlife to the cave bearsand in Asia it was ancestralto brown Service,pers. commun.)suggests that these bears are bears. congeneric. are a good environmentfor fossilization. The evolutionof Ursinaeover the past 5 million Bears, with large, stocky bones, are especiallywell years is well recordedin fossils of Europe. Early preserved.Thus cave bears, which often died in caves, Ursinae likely evolved from Ursavusof the Miocene, have one of the best fossil records. The evolutionary perhaps through the genus Protursusof the mid- lineageis so completethat delineating species has been Miocene(Thenius 1959, Crusafontand Kurten1976; difficult (Kurten 1968). In addition, the tens of Fig. 5). Climaticconditions in Europeduring the late thousandsof individualsrepresented (an estimated Miocene were and dry, savannahsand desertswere 30,000-50,000in 1 cave) has enabledthe typicalstudy common. Such conditionswere poor for bears, and of phylogenyand morphologyplus studiesof age and their fossils are scarce until the Pliocenebegan, 5-6 sex class structure,individual variation, and mortality MYBP. rates. Thenius(1959) recognizes 2 speciesof :U. Black Bears deningeriand U. spelaeus, the giant cave bear of Next to the Protursus, earliest member of the Europe. Kurten(1968) identifiesanother species, U. Ursinaeis believed to subfamily be , savini, betweenthe etruscanbear and U. deningeri. which has been found in many locationsin Europe Basedon fossils, U. spelaeusappears to have beena (Kurten1968). U. minimuswas a small, primitive large, stocky, mostly herbivorousbear. It had a that increasedin species, generally size during its relativelysmall geographicdistribution, being found existence. It appearsthat U. minimusor a species only in Europeand into the southwesterncorner of similarto it radiatedthrough Asia and was in North and the . Such a small distribution 92 Int. Conf.Bear Res. and Manage.9(1) 1994

Fig. 5. A tentative phylogeny of the subfamily Ursinae. suggests a dietary specialization or perhaps a Brown Bears dependence on caves or mountainous country where The brown bear is believed to have evolved from caves are found (Kurten 1976). Remains of U. U. etruscus in Asia. The oldest fossils were found in spelaeus have not been found where caves are from about 0.5 MYBP (Kurten 1968) and there uncommon. has been a continuousrecord of U. arctos in Asia since Many possible causes for the extinctionof cave bears then. U. arctos entered Europe about 0.25 MYBP and have been proposed. Kurten (1958) suggested that North Africa shortly after. Pleistocene remains of rapidly increasingnumbers of humansmay have settled U. arctos are common in and they may caves during summer dispersal periods and thus have contributed to the extirpation of the cave bear excluded bears returning to hibernate in the early there. winter. Extant brown and black bears often hibernate U. arctos apparentlyentered Alaska about 100,000 in caves much too small for occupation, so if YBP but did not move south until the late Wisconsin, this hypothesis is correct, then cave bears would have about 13,000 YBP. Kurten and Anderson (1980) had different requirementsthan the extant species, or suggest the possibility of 2 independent migrations; small caves were rare in their range. Competitionwith narrow-skulled bears from northern Siberia through increasing numbers of and brown bears for central Alaska to the rest of the continent becoming caves and other resourcesplus climate change appearto U. a. horribilis, and a southern migration of broad- be likely factors. skulled bears from Kamchatkato the Alaskan peninsula BEAREVOLUTION * McLellan and Reiner 93

becomingU. a. middendorffi.Fossils of brownbears bearsexploited new niches. in Ontario, Ohio, Kentucky (Guilday 1968), and Labrador(Spiess and Cox 1976) indicatethey were SUBFAMILYAILUROPODIDAE once found much farthereast than historicalrecords The phylogenyof the giantpanda has been disputed show. Guilday(1968) suggestedthat immediately after since 1870, when Milne-Edwardsplaced Ailuropoda the glacial retreat, a relatively boreal, parkland into the familyProcyonidae, while Davidhad calledit coniferousforest spread across the centraland southern an ursidthe previousyear (O'Brien et al. 1985). Some portionsof the continentand with it, severalwestern recentauthors (Tagle et al. 1986) linkedAiluropoda species, includingbrown bears. closerto the lesserpanda (Ailurus fulgens) thanto the bears,but therehas been an overwhelmingnumber of Polar Bear papersplacing Ailuropoda not close, butcloser to bears The Polar bear is a recentoffshoot of U. arctos. thanto the lesserpanda (Kurten 1985, O'Brienet al. Indicationsof a recentdivergence include the rarityof 1985, Mayr 1986, Ramsay and Dunbrack 1987, fully fossilized polar bear remains (Kurten 1964) Goldmanet al. 1989). Thesepapers were basedon 6 whereassubfossils are common,and that these species independentmolecular and genetic measures, fossil producefertile hybrids in captivity(Kowalska 1965). evidence, and reproductivecharacteristics. These MitochondrialDNA divergence(Shields and Kocher recentreports plus the comparativeanatomical work of 1991) and 2-dimensionalelectrophoresis (Goldman et Davis (1964), earlierprotein evolution work of Sarich al. 1989) also suggesta recentsplit. Polarbears are (1973), andthe synthesisof Thenius(1979) indicatethe repeatingthe trendthat was seenwith Agriotherium and giantpanda should be placedinto its own subfamily, Arctodusby becomingcarnivores; this time specializing Ailuropodidae,of the familyUrsidae. on marinemammals. The apparentmorphological and The earliestevidence of Ailuropodawas duringthe behavioraldifferences between polar bears and brown late Pliocene,about 3 MYBP (Schalleret al. 1985). bears indicatethat polar bears are rapidlyevolving as Wang (1974) divides Ailuropodainto 2 species: A. they exploita new niche. microtawas a smaller,primitive species that became extinctduring the mid-Pleistocene. A. melanoleucawas Sun and Sloth Bears once largerthan it is todayand then ranged south of the The fossil recordsof south Asian bears, the sun Yangtzeriver at least to Burma. The decreasein the (Ursus malayanus) and sloth bears (U. ursinus) are panda'srange has been attributedto climaticchanges poor, and theirorigins more speculativethan for other during the Pleistoceneand, like almost all extant species(Kurten 1966). U. malayanusis firstfound in species,man's activities during the postglacial(Schaller the late Pliocene and U. ursinus in the Pleistocene. et al. 1985). Thenius(1959) thoughtthey separatedfrom the other The fossil recordleading to Ailuropodais poor and Ursinaeeven before Protursus, whereas Hendey (1972) evolutionarylinks speculativeat best. Matthewand speculatedthat the splitwas afterProtursus but before Granger(1923), Davis (1964), Hendey (1972), and U. minimus. Electrophoreticanalysis indicates a more Wolff(1978) believed the panda evolved from Indarctos recentsplit, not significantlydifferent from that of other of the subfamily Agriotheriinae.Thenius (1979) extant membersof the subfamilyexcept the polarbear however, identifieda possible ancestor,Agriarctos, (Goldman et al. 1989). Recent analyses of fromthe late Miocene of ,and suggested it was mitochondrialDNA suggestthat the 6 ursine species a descendantof Ursavusfrom the mid-Miocene(Fig. originatedsequentially during the past 6 millionyears, 6). Afterre-evaluation, Hendey (1980) concludedthat beginningwith U. ursinusand endingwith the polar Ursavusdepereti was morelikely to be the ancestorof bear et al. (Waits unpubl. data, submitted). It is the pandas than was Indarctos. The divergence becoming increasingly evident that U. ursinus, betweenbears and the giantpanda has been estimated malayanus, thibetanus, americanus, and etruscus all to be 18-22 MYBP (Goldmanet al. 1989), and thus, branched from the primitive U. minimus or U. separationfrom an early Ursavus,either via Indarctos abstrusus that radiated through Eurasia near the or not, is possible. The pandahas a specializedniche Miocene/Pliocene boundaryand into North America and, like other species that diverged from the after. The shortly great morphologicaldifferences omnivoroustrend, likely went through a periodof rapid between U. malayanus, U. ursinus, and other bears is evolution,which accountsfor theirmorphological and likely due to recentadaptive change as the southAsian behavioraldifferences from other bears. 94 Int. Conf.Bear Res. and Manage.9(1) 1994

CL Period SUBFAMILY 0m AILUROPODIDAE2

Pleistocene A. melanoleuca I Alluropoda microta Pliocene

5

Agriarctos

10 U. depereti Miocene

15

Ursavus primaevus

2!0

Oligocene

2!5

Fig. 6. A tentative phylogeny of the subfamilyAiluropodidae.

CONCLUSIONS more specialized forms evolved. Several species, such The Ursidae is a young family consisting of 5 as Arctodus simus, Agriotherium insigne, and Ursus subfamilies: Ursinae, Tremarctinae, Agriotheriinae, maritimus, appear to have filled a more carnivorous Ailuropodidae,and Hemicyoninae. The distinctionand niche. Others, such as Ursus spelaeus, Tremarctos inclusion of the later 2 subfamilies in the family floridanus, and Ailuropodamelanoleuca, became more Ursidae is probably not settled. herbivorous. The importanceof climatic change and Patterns of extinction and evolution within the interspecific competition is repeated often by students Ursidae reflect some of the adaptive zones for who speculateon the causationof bear extinction. carnivores that disappear and then reappear (Martin Three species, U. thibetanus, U. americanus, and U. 1989). From the highly adaptableomnivorous base, arctos still have wide geographic ranges and exploit a BEAREVOLUTION * McLellan and Reiner 95

variety of niches from deserts to rain forests. These KURTEN,B. 1958. Life and deathof the Pleistocenecave species are likely candidates for future speciation of bear, Acta Zool. Fenn. 95:159. the family Ursinae. The recent explosion in human 1964. The evolution of the Polar bear, Ursus numbers and resulting selective pressures and genetic maritimusPhipps, Acta Zool. Fenn. 108:1-26. isolation is obviously driving bear evolution today. . 1966. Pleistocene bears of North America I, Genus Tremarctos,spectacled bears. Acta. Zool. Fenn. 115:1- 120. LITERATURECITED . 1967. Pleistocene bears of North America. II. Genus CRUSAFONT,M, ANDB. KURTEN. 1976. Bears and bear- Arctodus,Short-faced bears. Acta.Zool. Fenn. 117:1-60. dogs from the Vallesian of the Valles-Penedes basin, . 1968. Pleistocene mammals of Europe. Addine . Acta Zool. Fenn. 144:1-29. Publishing Co., Chicago, Ill. 317pp. DALQUEST.W.W. 1986. Lower jaw and of the . 1971. The age of mammals. Columbia University Hemphillianbear, Agriotherium(Ursidae), with the Press. New York, N.Y. 250pp. descriptionof a new species. J. Mamm.67:623-631. _ . 1976. The cave bear story: life and death of a DAVIS,D. 1964. The giantpanda: a morphologicalstudy of vanished . Columbia University Press, New York, evolutionarymechanisms. Fieldiana: Zool. Mem. 3:1-339. N.Y. 163pp. EMSLIE,S.D., ANDN.J. CZAPLEWSKI.1985. A new record .1985. A molecular solution to the riddle of the giant of giant short-facedbear, Arctodussimus, from western panda's phylogeny. Nature. Lond. 318:487. North America with a re-evaluation of its paleobiology. , ANDE. ANDERSON. 1974. Association of Ursus Nat. Hist. Mus. of Los Angeles County. Contrib. in Sci. arctosand Arctodus simus (Mammalia: Ursidae) in the late 371:1-12. Pleistoceneof Wyoming.Breviora 426:1-6. ERDBRINK,D.P. 1953. A review of fossil and recent bears ., ANDE. ANDERSON.1980. Pleistocene mammals of of the Old World. Deventer:Jan de Lange.2 Vol. NorthAmerica. ColumbiaUniversity Press, New York, FRICK,C. 1926. The Hemicyoninae and an American N.Y. 442pp. Tertiarybear. Bull. Amer. Mus. Nat. Hist. 56:1-119 LYDEKKER,R. 1883. Siwalik and Narbada . Pal. GOLDMAN,D., P.R. GIRI, AND S.J. O'BRIEN. 1989. Ind. 10:178-351. Molecular genetic-distanceestimates among the Ursidae as MARTIN,L.D. 1989. Fossil history of the terrestrial indicated by one- and two-dimensional protein Carnivora. Pages 536-568 in J.L. Gittleman, ed. electrophoresis.Evolution 43:282-295. Carnivorebehavior, ecology, and evolution. Comstock GUILDAY,J.E. 1968. Grizzly bears from eastern North Publ. Assoc. Ithaca,N.Y. America. Amer. Midl. Nat. 79:247-250. MARTIN,P.S. 1984. Catastrophicextinctions and late E.R. 1981. The mammalsof North HALL, America. 2nd ed. Pleistocene blitzkrieg: two radiocarbon tests. Pages 153- N.Y. Wiley, 189 in P.S. Martin and R.G. Klein, eds. Quaternary C.R. 1973. HARRINGTON, A short faced bear from ice age : a prehistoric revolution. Univ. Ariz. Press, deposits at Lebret, Sask. The Blue Jay 31:11-14. Tucson, Ariz. HENDEY. 1972. A Pliocene Ursid from Q.B. . MATTHEW,W.D. 1929. Critical observations upon Siwalik Ann. S. Afr. Mus. 59:115-133. mammals.Bull. Amer. Mus. Nat. Hist. 56:437-560. . 1980. Agriotherium (Mammalia, Ursidae) from , ANDW. GRANGER.1923. New fossil mammals from Langebaanweg,South Africa, and relationshipsof the thePliocene of Sze-Chuan,China. Bull.Amer. Mus. Nat. genus. Ann. S. Afr. Mus. 81:1-109. Hist. 48:563-598. HERRERO,S. 1972. of evolution and Aspects adaptationin MAYR,E. 1986. Uncertaintyin science: is the American black bears (Ursus americanus Pallas) and a bearor a raccoon? Nature.Lond. 323:769-771. brown and bears grizzly (U. arctos Linne.) of North MCLELLAN,B.N. 1993. Competition between black and America. Int. Conf. Bear. Res. and Manage. 2:221-231. grizzly bears as a naturalpopulation regulating factor. Z. KOWALSKA, 1965. Cross-breeding between a female Pages 111-116 in J.A. Keay, ed. Proc. of the Fourth Europeanbrown bear anda male (Ursusarctos) polarbear Western Black Bear Workshop. USDI Tech. Rep. (U. maritimus) in the Logzkim Zoo. Przegiad NPS/NRWR/nrtr-93/12. Zoologicznum.9:313-319. MERRIAM,J.C., C. STOCK,AND C.I. MOODY. 1916. An KRAGAVLICH,L. 1926. Los arctoterios norteamericanos American Pliocene bear. Univ. of Cal. Pub. in . (Tremarctotheriumn. gen.) en relacioncon los de Sud 10:87109. An. America, Mus. Nac. Hist. Nat. BuenosAires. 33:1- MITCHELL,E., AND R.H. TEDFORD. 1973. The 16. Elaliarctinae. A new group of extinct aquatic carnivora 96 Int. Conf. Bear Res. and Manage. 9(1) 1994

and a consideration of the origin of the Oteridae. Bull. HOFMANN, G. BRAUNITZER,R. GOLTENBOTH,AND J. Amer. Mus. Nat. Hist. 151:201-284. JALANKA.1986. Hemoglobin of pandas; phylogenetic MONDOLFI,E. 1983. The feet and of the relationships of carnivores as ascertained with protein spectacled bear, with comments on ursid phylogeny. J. sequence data. Naturwessenschaften73:512-514. Mamm. 64:307-310. TEDFORD,R.H., M.F. SKINNER,R.W. FIELDS, J.M. NOWAK,R.M., AND J.L. PARADISO. 1983. Walker's RENSBERGER,D.P. WHISTLER,T. GALUSHA, B.E. mammals of the world. 4th ed. Vol. 2. Johns Hopkins TAYLOR,J.R. MACDONALD,AND S.D. WEBB. 1987. Univ. Press., Baltimore, Md. Faunal succession and biochronology of the Arikareenan O'BRIEN,S.J., W.G. NASH,D.E. WILDT,M.E. BUSH,AND through Hemphillian interval (late Oligocene through R.E. BENVENISTE.1985. A molecular solution to the earliest Pliocene epochs) in North America. Pages 153- riddle of the giant panda's phylogeny. Nature. Lond. 210. in M.O. Woodburne, ed. Cenozoic mammals of 317:140-144. North America. Univ. Calif. Press, Berkeley, Calif. PILGRIM,G.E. 1932. The fossil carnivoraof India, Pal. Ind. THENIUS,E. 1949. Die carnivoren von Goriach 18:1-232. (Steiermark).Beitrage zur Kenntnis der Saugetierrestedes RAMSAY,M.A., ANDR.L. DUNBRACK.1987. Is the giant steirischnTertiars IV. Sitber. Akad. Wiss. Wien 158:695- panda a bear? Oikos 50:267. 762. SARICH,V. 1973. The giant panda is a bear. Nature. Lond. ___ . 1959. Ursidenphyloyenese und biostratigraphieZ. 245:218-220. Saugetierk. 24:78-84. SCHALLER,G.B., H. JINCHU,P. WENSHI,AND Z. JING. 1985. . 1976. Zur stammesgeschichtlichenHerkunft von The giant pandas of Wolong. Univ. Chicago Press, Tremarctos(Ursidae, Mammalia) Z. Saugetierk. 41:109- Chicago, Ill. 298pp. 114. SCOTT,W.B. 1937. A history of land mammals in the . 1979. Zur systematischem und phylogenetischen western hemisphere. Rev. ed. Macmillan, New York. Stellungdes bambusbaren:Ailuropoda melanoleuca David 786pp. (Carnivora, Mammalia) Z. Saugetierk. 441:286-305. SHIELDS,G.F., AND T.D. KOCHER.1991. Phylogenetic WAITS,L.P., S.J. O'BRIEN,AND R.H. WARD. 1994. Recent relationshipsof North American Ursids based on analysis paraphyletic evolution in bears suggested by multiple of mitochondrialDNA. Evolution 45:218-221. region mtDNA phylogeny. Nature:Submitted. SHULTZ,C.B., ANDL.D. MARTIN. 1975. Bears (Ursidae) WANG,T.K. 1974. On the taxonomic position of species, from the Late Cenozoic of Nebraska. Bull. Univ. geological distribution and evolutionary history of Nebraska State Mus. 10:47-54. Ailuropoda. Acta Zool. Sinca 20:191-201. SIMPSON,G.G. 1945. Principles of classification and a WAYNE,R.K., R.E. BENVENISTE,D.N. JANCZEWSKI,AND classification of mammals. Bull. Amer. Mus. Nat. Hist. S.J. O'BRIEN. 1989. Molecular and biochemical 85:1-350. evolution of the Carnivora. Pages 465-494 in J.L. SPIESSA., ANDS. Cox. 1976. Discovery of the skull of a Gittleman,ed. Carnivorebehavior, ecology, and evolution. in Labrador. Arctic 29:194-200. Comstock Publ. Assoc. Ithaca, N.Y. STIRLINGI., ANDA.E. DEROCHER.1990. Factors affecting WOLFF,R.G. 1978. Function and phylogenetic significance the evolution and behavioralecology of the modern bears. of cranial of an early bear (Indarctos) from Int. Conf. Bear. Res. and Manage. 8:189-204. Pliocene sediments of Florida. Carnivora 1:1-12. recent STROMER,E. 1940. Die jungtertiarefauna des flinzes und WOZENCRAFT,W.C. 1989. The phylogeny of the des Schweiss-Sandes von Munchen. Nachtrage und Carnivora. Pages 495-535 in J.L. Gittleman, ed. and evolution. Comstock Berichtigungen. Abh. Bayer. Akad. Wiss. n.s. 48:1-102. behavior, ecology, TAGLE, D.A., M.M. MIYAMOTO, M. GOODMAN, O. Publ. Assoc., Ithaca, N.Y.