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Mammoths, Bison and Time in North America
299
MAMMOTHS, BISON AND TIME IN NORTH AMERICA
C.R. HARI N G TON
ABSTRACT N o r t h American Land M a m m a l Ages a r e v a l u a b l e i n a p p r o x i m a t i n g geol o g i c a l t i m e i n t h e Q u a t e r n a r y , p a r t i c u l a r l y where o t h e r more p r e c i s e d a t i n g methods ( s u c h as r a d i o c a r b o n , t e p h r a and p a l e o m a g n e t i c ) a r e l a c k i n g . Mammoths and b i s o n a r e D a r t i c u l a r l y im-oortant f o s s i l i n d i c a t o r s , f o r t h e e a r l i e s t mammoth r e m a i n s i n N o r t h America m a r k t h e b e g i n n i n g of t h e I r v i n g t o n i a n Land M a m m a l Age ( a b o u t 1 . 8 m i l l i o n y e a r s a g o ) , and t h e e a r l i e s t b i s o n r e m a i n s m a r k t h e b e g i n n i n g of t h e Ranchola b r e a n Land M a m m a l Age ( a b o u t 1 . 2 m i l l i o n y e a r s a g o ) . I t i s w o r t h n o t i n g t h a t t h e R a n c h o l a b r e a n may h a v e o c c u r r e d e a r l i e r i n n o r t h e r n N o r t h America t h a n i n s o u t h e r n N o r t h America, b e c a u s e b i s o n seem t o have been d e l a y e d i n p e n e t r a t i n g t h e s o u t h e r n p l a i n s . The main m o r p h o l o g i c a l c h a n g e s s e e n i n mammoths and b i s o n as t i m e proceeded were, r e s p e c t i v e l y : ( a ) a n i n c r e a s e i n number and c o m p r e s s i o n of enamel p l a t e s , and a t h i n n i n g o f enamel i n m o l a r t e e t h ; and ( b ) a t l e a s t during t h e l a s t 1 2 , 0 0 0 y e a r s , a tendency t o p r o g r e s s i v e reduction i n s i z e of h o r n c o r e s .
More s p e c i f i c a l l y , s o u t h e r n a n d w o o l l y mammoths seem t o b e u s e f u l i n d i c a t o r s o f e a r l y ( N e b r a s k a n t o Kansan) and l a t e ( m a i n l y W i s c o n s i n ) Pleistocene deposits, respectively. Small-horned b i s o n a r e g e n e r a l l y u s e f u l time-guides f o r t h e l a s t 1 2 , 0 0 0 y e a r s , whereas s t e p p e b i s o n u s u a l l y i n d i c a t e d e p o s i t s o l d e r t h a n 1 2 , 0 0 0 BP. INTRODUCTION
Mammoths a n d b i s o n , two i m m i g r a n t s from E u r a s i a , a r e p a r t i c u l a r l y i m p o r t a n t b e c a u s e t h e y have b e e n u s e d b y Savage ( 1 9 5 1 ) i n e s t a b l i s h i n g I r v i n g t o n i a n and R a n c h o l a b r e a n N o r t h American Land M a m m a l Ages. T h i s i s a m a j o r d i v i s i o n of t h e Q u a t e r n a r y ( a p p r o x i m a t e l y t h e l a s t 2 m i l l i o n y e a r s o f g e o l o g i c a l t i m e ) b a s e d on f o s s i l v e r t e b r a t e a s s e m b l a g e s ( F i g u r e 1 ) . Savage e m p h a s i z e d t h a t t h e terms I r v i n g t o n i a n and R a n c h o l a b r e a n are b a s e d on f a u n a l names and o n a n i m a l s w i t h i n t h o s e f a u n a s from C a l i f o r n i a , and t h a t t h e y a r e e n t i r e l y s e p a r a t e from r o c k f o r m a t i o n a l names. Ke i n d i c a t e d t h a t t h e e a r l i e s t mammoth r e m a i n s mark t h e b e g i n n i n g o f t h e R a n c h o l a b r e a n . I r o n i c a l l y , t h e l a t t e r a g e a l m o s t came t o a n end a b o u t 1890 due t o human o v e r h u n t i n g of b i s o n ( R o e , 1 9 7 0 ; B a n f i e l d , 1 9 7 4 ) . The e x a c t t i m e d e m a r c a t i o n o f t h e s e a g e s m a y , p e r h a p s , o n l y b e e s t a b l i s h e d on a r e g i o n a l b a s i s and i n t h e f u t u r e , when t h e r e i s b e t t e r geochronological c o n t r o l over middle Pleistocene land mammal faunas. P r e s e n t l y , I s u g g e s t t h a t mammoths f i r s t e n t e r e d North America a b o u t 1 . 8 m i l l i o n y e a r s a g o d u r i n g t h e Nebraskan G l a c i a t i o n and a t t h e b e g i n n i n g o f t h e Q u a t e r n a r y , and t h a t b i s o n f i r s t e n t e r e d N o r t h America d u r i n g t h e Kansan G l a c i a t i o n a b o u t 1 . 2 m i l l i o n y e a r s a g o ( F i g u r e 1 ) . Of course, t h e e a r l i e s t t i m e s of e n t r y o f mammoths and b i s o n i n t o n o r t h e r n North America would p r e c e d e t h e t i m e s t h e y became e s t a b l i s h e d i n t h e s o u t h .
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F i g u r e 1 Suggested chronology and r e g i o n a l d i s t r i b u t i o n of Chronomammoths a n d b i s o n i n N o r t h A m e r i c a d u r i n g t h e q u a t e r n a r y . l o g i c a l d a t a i n t h r e e columns on l e f t are approximate, (modified from E r i c s o n a n d W o l l i n ( 1 9 6 8 ) , M a g l i o ( 1 9 7 3 ) a n d K u r t e n a n d A n d e r s o n (1980)), and p h y l o g e n i e s a r e h i g h l y s i m p l i f i e d . For example, I have n o t d e a l t w i t h t h e o r i g i n o f t h e d w a r f mammoths o f S a n t a R o s a I s l a n d , C a l i f o r n i a ( S t o c k and F u r l o n g 1 9 2 8 ) . Also, I have avoided t h e i s s u e of t h e pres e n c e o f s t e p p e - l i k e b i s o n o n t h e p l a i n s u n t i l m o r e i s known a b o u t t h e i r g e o l o g i c a l a g e and a f f i n i t i e s . P e r h a p s s t e p p e b i s o n ( e . g . Bison +rassicornis f r o m M a s s a c h u s e t t s r a d i o c a r b o n d a t e d a t a p p r o x i m a t e l y 2 1 , 2 0 0 BP ( R o m e r 1 9 5 1 ) ) p e n e t r a t e d t h e p l a i n s a s e c o n d t i m e before t h e p e a k of t h e l a s t g l a c i a t i o n . Some o f t h e s e s t e p p e - l i k e f o r m s may a l s o r e p r e s e n t smaller-horned d e r i v a t i v e s of g i a n t b i s o n s t o c k . ?fagnetic: Normal p o l a r i t y ( b l a c k ) from t o p t o b o t t o m Brunhes, Jaran i l l o , Olduvai; reversed p o l a r i t y (white). G l a c i a l s (black) and Interg l a c i a l ~ : N (Nebraskan); A (Aftonian); K (Kansan); Y (Yarmouth); I ( I l l i n o i a n ) ; S ( S a n g a m o n ) ; W ( W i s c o n s i n ) ; EI ( H o l o c e n e last 10,000 vears). N o t e b r e a k i n s c a l e a t GJ/H b o u n d a r y . E a c h o f t h e t w o c o l u m n s o n t h e r i g h t d e a l i n g w i t h mammoths a n d b i s o n a r e s u b d i v i d e d i n t o B e r i n g i a ("RER." - u n g l a c i a t e d p a r t s o f e a s t e r n S i b e r i a , B e r i n g I s t h m u s , A l a s k a a n d Yukon) on t h e l e f t , a n d P l a i n s ("PL." h e a r t l a n d o f t h e c o n t i n e n t ) on t h e r i g h t , i n o r d e r t o show p o s s i b l e r e l a t i o n s h i p s b e t w e e n p o p u l a t i o n s i n t h o s e r e g i o n s . Dashed l i n e s i n d i c a t e p o i n t s of Freatest u n c e r t a i n t y . Upright arrowh e a d s mark e v i d e n t times of e x t i n c t i o n s .
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MAMMOTES Mammoth remains. particularly complete molar teeth, are sometimes useful biostratigraphic indicators, for they are commonly widespread geographically and they tend to preserve well. The most primitive species known from North America, the southern mammoth (Mummuthus m e r i d i o n a l i s l probably entered this continent from Eurasia near the beginning of the Quaternary, when Repenning recognizes an invasion of rodents including P l i o m y s and S y n a p t o m y s (ReDenninp, 1980; Harington, 1980a). Severalmolars from the northern Yukon resemble those of the most advanced southern mammoth stock (Eacton Stage) or Eurasia, and I suspect that they represent the earliest North American mammoths (Harington 1977; Figure 2). This species also appears to be present in the Wellsch Valley fauna in Saskatchewan, where it may have lived Rearly 1.7 million years ago (A. PTacS. Stalker, .sers. commun., 1976), and at Bruneau, Idaho about 1.36 million years ago (Maglio, 1973). North American steppe mammoths (Mummuthus c o l u m b i and/or Mammuthus a r m e n i a c u s ) are the least valuable biostratigraphically and their origins present problems (Harington 1980b). It is now widely accepted that the Columbian mammoth (Mammuthus c o l u m b i , under which I include the imperial mammoth, Mammuthus i m p e r a t o r , following Kurtgn and Anderson 1980) arose from the southern mammoth in North America ( e . g . MagliO, 1973). As an alternative, I propose that steppe mammoths reached North America from Eurasia, replacing southern mammoths during the Kansan Glaciation about 1.2 million years ago. I think that they invaded with primitive muskoxen like S o e r g e l i a and E u c e r a t h e r i u m and perhaps Phenacomys, C J e t h r i o n o m y s , TJeodon and P i t y m y s (Repenning's (1980) "Irvingtonian II" microtines ) , From the evidence I have seen, I can only stress the similarities of Eurasian and North American steppe mammoths. Some specimens I have referred to Mammuthus c f . a r m e n i a c u s from the northern Yukon may record the earliest North American entry of steDpe mammoths from Eurasia (Harington, 1977). Also, Savage's (1951) description and measurements of Mammuthus c o l u m b i molars from Irvingtonian localities fit well with those of the Eurasian steppe mammoths now included in Mammuthus armeni a c u s . Further, Henry Fairfield Osborn (1942), a paleontologist with great experience in studying elephants, derived Columbian mammoths from Eurasian steppe mammoths now included in Mammuthus a r m e n i a c u s by Maglio (1973). If, indeed, Eurasian and North American steppe mammoths are not synonymous, we need a way of differentiating them -- preferably on molar characteristics. Although Maglio (1473) states that the North American lineage leading from southern to Columbian mammoths has broader molars, most steppe mammoth molars I have measured from the northern Yukon are slightly narrower than the average of a sample from Eurasia (Harington, 1977). Steppe mammoths (Figure 3) seem to have occupied North America for more than 1 million years. The most advanced type (sometimes considered as a separate species, Mammuthus j e f f e r s o n i i ) survived on the olains until about 11,000 years aqo (Kurtgn and Anderson, 1980). Evidently some steppe mammoths lived in eastern Ferinpia ?urine: the ?eak of the liisconsin Glaciation approximately 20,000 years ago (Harington, 1980b). Figure 1
Continued
Mammoths: s o u t h e r n (Mummuthus m e r i d i o n a l i s ) ; s t e p p e ( M , a r m e n i a c u s a n d / o r M . c o l u m b i ) ; w o o l l y IM. p r i m i g e n i u s i .
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steppe (earliest(?) Bison a l a s k e n s i s , a n d l a t e s t - B . c r a s s { c o r n i s : s o m e t i m e s t h e y a r e g r o u p r d u n d e r t h e name B . p r i s c u s ) ; g i a n t (B. l a t i f r o n s ) ; " o c c i d e n t a l i s - a n t i q u u s ~ o m p l e x ' ' I~B . b i s o n o c c i d e n t a l i s e v i d e n t l y d e r i v e d f r o m s t e p p e b i s o n s t o c k i n B e r i n g i a ; B . bison antiquus e v i d e n t l y derived from g i a n t bison s t o c k i n t h e p l a i n s ) ; wood (B. b i s o n a t h a b a s c a e - e v i d e n t l y d e r i v e d m a i n l y f r o m B . b i s o n o c c i d e n t a l i s s t o c k on t h e n o r t h e r n and w e s t e r n f l a n k s of t h e Canadian p l a i n s ) ; p l a i n s (B. b i s o n b i s o n - e v i d e n t l y d e r i v e d f r o m " o c c i d e n t a l i s antiquus" s t o c k on t h e p l a i n s ) . Bison:
302
Figure 2
llammoth t e e t h a r e o f t e n u s e f u l i n d i c a t o r s o f g e o l o g i c a l age and p a s t environment. The l o w e r t h i r d m o l a r o n t h e l e f t ( g r i n d i n g s u r f a c e shown w i t h e n a m e l p l a t e s i n b l a c k ) i s f r o m a s o u t h e r n mammoth (Mummuthus m e r i d i o n a l i s ) f r o n O l d Crow B a s i n , Yukon T e r r i t o r y , a n d s h o w s t h e " p r i m i t i v e " c o n d i t i o n of r e l a t i v e l y few, t h i c k , widely-spaced enamel plates. The l o w e r t h i r d m o l a r o n t h e r i g h t , from a w o o l l y mammoth (Mammuthus p r i m i g e n i u s ) f r o m t h e same r e g i o n o f t h e Y u k o n , s h o w s t h e " a d v a n c e d " c o n d i t i o n i n v o l v i n g more numerous, t h i n n e r , more compressed enamel p l a t e s . I n k s k e t c h by C h a r l e s Douglas.
However w o o l l y mammoths (Mammuthus p r i m i g e n i u s ) w e r e dominant t h e r e d u r i n g t h a t p e r i o d . C o n c e i v a b l y s t e p p e a n d w o o l l y mammoths may h a v e s h a r e d t h e i r r a n g e b o t h n o r t h and s o u t h o f t h e W i s c o n s i n i c e s h e e t s . Woolly mammoths ( F i g u r e 4 ) m i g r a t e d f r o m E u r a s i a t o N o r t h America i n l a t e I l l i n o i a n or e a r l y W i s c o n s i n t i m e ( H a r i n g t o n , 1 9 8 0 a ) . I n t h e s o u r c e a r e a , n o r t h e a s t e r n S i b e r i a , a n e a r l y tyDe o f w o o l l y mammoth i s known from t h e Utka Beds ( p r o b a b l y l a t e I l l i n o i a n ) , and t h e a d v a n c e d t y p e was e s t a b l i s h e d t h e r e by e a r l y W i s c o n s i n t i m e (Iedoma S u i t e ) ( S h e r , 1 9 7 1 ) . E v i d e n t l y w o o l l y mammoths f i r s t r e a c h e d t h e n o r t h e r n p l a i n s ( M e d i c i n e Hat, A l b e r t a ) d u r i n g t h e e a r l y W i s c o n s i n ( S t a l k e r and C h u r c h e r , 1 9 7 0 ) . The s p e c i e s s p r e a d t o e a s t e r n Canada d u r i n g t h e m i d W i s c o n s i n a b o u t 4 5 , 0 0 0 y e a r s a g o ( C h u r c h e r , 1 9 6 8 a ) . It seems t o h a v e occupied d i s c o n t i n u o u s t u n d r a - l i k e r a n g e s o u t h o f t h e Wisconsin i c e s h e e t , e x t e n d i n g from s o u t h e r n B r i t i s h Columbia t o s o u t h e r n O n t a r i o , a n d p e r h a p s f a r t h e r e a s t w a r d . S c a t t e r e d f o s s i l s of' o t h e r t u n d r a a d a p t e d m a m m a l s i n c l u d i n g lemmings, t u n d r a muskoxen and c a r i b o u a l s o o c c u r i n t h i s zone ( H a r i n g t o n a n d Ashworth, i n p r e p a r a t i o n ) . Woolly mammoths d i e d o u t i n N o r t h America a b o u t 1 3 , 0 0 0 y e a r s a g o . I c o n s i d e r t h i s s p e c i e s t o b e a n i n d i c a t o r of Wisconsin-age d e p o s i t s i n s o u t h e r n Canada and n o r t h e r n U n i t e d S t a t e s , a t l e a s t .
303
Figure 3
a N o r t h A m e r i c a n s t e p p e mammoth T h e y seem t o h a v e b e e n t h e m o s t common a n d w i d e s p r e a d o f N o r t h A m e r i c a n mammoths. I n k s k e t c h by C h a r l e s D o u g l a s .
Figure 4
R e s t o r a t i o n o f a w o o l l y mammoth (Mammuthus p r i m i g e n i u s ) . T h e y w e r e a d a p t e d t o t u n d r a - l i k e r a n g e and were w e l l a d a p t e d t o c o l d c o n d i t i o n s . I n k s k e t c h by Charles Douglas.
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(Marnrnuthus c o z u m b i ) .
304
BISON The s t u d y of N o r t h A m e r i c a n f o s s i l b i s o n i s f r a u g h t w i t h p r o b l e m s . E x p e r t s d i s a g r e e on many p o i n t s : n a m e l y , g e o l o g i c a l a g e b e y o n d 4 0 , 0 0 0 BP, phylogeny and d i s t r i b u t i o n a l h i s t o r y . I think that clarification o f many o f t h e s e p r o b l e m s d e p e n d s upon g a i n i n g a b e t t e r p e r s p e c t i v e on t h e h i s t o r y of E u r a s i a n f o s s i l b i s o n . To t h i s e n d , D . M . S h a c k l e t o n a n d M . L . W e s t o n , s p o n s o r e d by t h e N a t i o n a l Museum of N a t u r a l S c i e n c e s , b e g a n a s t u d y i n 1 9 7 9 . They a r e p r o c e s s i n g b i o s t r a t i g r a p h i c a n d n e t r i c d a t a on w e s t e r n E u r o p e a n f o s s i l s . Data f r o m 185 s k u l l s , 1 6 m a n d i b l e s a n d 1 6 8 p o s t c r a n i a l e l e m e n t s were c o l l e c t e d f r o m b i s o n f o s s i l s i n Soviet i n s t i t u t i o n s i n 1982.
B i s o n h a d e n t e r e d c e n t r a l A l a s k a by K a n s a n ( ? ) t i m e a c c o r d i n g t o r e m a i n s from t h e Fox G r a v e l u n i t n e a r F a i r b a n k s . The a g e e s t i m a t e r e s t s on P 6 w 6 ' s ( 1 9 7 5 a , b ) s t r a t i g r a p h i c i n t e r p r e t a t i o n of a n e x p o s u r e a t Eva C r e e k . O t h e r e a r l y s p e c i m e n s of b i s o n f r o m A l a s k a a r e f r o m d e p o s i t s of p o s s i b l e Yarmouth I n t e r g l a c i a l a g e n e a r B a l d w i n P e n i n s u l a ; I l l i n o i a n age n e a r F a i r b a n k s ( a f i s s i o n - t r a c k age of approximately 450,000 y e a r s f r o m t h e E a s t e r Ash Bed s u g g e s t s t h a t B i s o n r e m a i n s f r o m t h i s p a r t of t h e G o l d H i l l L o e s s may b e I l l i n o i a n i n a g e (T.L. P & w & , p e r s . commun., 1 9 8 2 ) ) ; a n d Sangamon I n t e r g l a c i a l a g e n e a r T o f t y . A s n o p u b l i s h e d d e s c r i p t i o n s of t h e s e f o s s i l s a r e a v a i l a b l e , i t i s d i f f i c u l t t o know w h e t h e r t h e y s h o u l d b e t r e a t e d m e r e l y a s B i s o n s p . , or w h e t h e r - a s seems l i k e l y - t h e y r e p r e s e n t s t e p p e b i s o n ( s e n s u Kurt6n and Anderson, 1980). I n t h e Yukon, I h a v e c o l l e c t e d s t e p p e b i s o n s p e c i m e n s w i t h unu s u a l l y l a r g e h o r n c o r e s ( B i s o n a t a s k e n s i s ) , one o f w h i c h y i e l d e d a r a d i o c a r b o n d a t e of >39,000 BP ( 1 - 5 4 0 5 ) . I c o n s i d e r i t t o be a s u i t a b l e a n c e s t o r for l a t e r , s m a l l e r - h o r n e d s t e p p e b i s o n ( B i s o n c r a s s i c o r n i s ) and t h e g i a n t b i s o n ( B i s o n Z a t i f r o n s ) of s o u t h e r n North America, and t o be c l o s e l y r e l a t e d t o , i f not.synonymous w i t h , Bison p r i s c u s gigas ( H a r i n g t o n a n d C l u l o w , 1 9 7 3 ; H a r i n g t o n , 1 9 8 0 a ) . The l a t t e r b i s o n was widespread i n E u r a s i a d u r i n g t h e middle P l e i s t o c e n e ( e q u i v a l e n t i n age f r o m Yarmouth t o Sangamon t i m e i n F l e r o v ' s ( 1 9 7 2 ) t e r m i n o l o g y ) . The e a r l i e s t o c c u r r e n c e s o f b i s o n on t h e p l a i n s a D p e a r t o be o f Yarmouth a g e i n C a n a d a ( S t a l k e r a n d C h u r c h e r , 1 9 7 0 ) a n d of p o s t - Kansan t o e a r l y I l l i n o i a n a g e i n t h e U n i t e d S t a t e s ( S c h u l t z and H i l l e r u d , 1977). Giant b i s o n are f i r s t d e f i n i t e l y r e c o r d e d there i n l a t e I l l i n o i a n time a n d seem t o h a v e s u r v i v e d u n t i l l a t e W i s c o n s i n t i m e ( K u r t 6 n a n d Anderson, 1980). N o r t h e r n s m a l l - h o r n e d b i s o n , or w e s t e r n b i s o n ( B i s o n b i s o n o c c i d e n t a Z i s ) e v i d e n t l y a r o s e from stepDe b i s o n ( B i s o n c r a s s i c o r n i s : F i g u r e 5 ) s t o c k i n B e r i n g i a t o w a r d t h e c l o s e of t h e l a s t g l a c i a t i o n . P r o b a b l y warmer, m o i s t e r c o n d i t i o n s o c c u r r i n g i n B e r i n g i a t h e n , a n d t h e r e s u l t i n g more h e a v i l y - w o o d e d t e r r a i n c o n t r i b u t e d t o t h e d e m i s e of s t e p p e b i s o n a n d t h e r i s e of w e s t e r n b i s o n ( H a r i n g t o n , 1 9 7 7 ) . T h e s e b i s o n s p r e a d r a p i d l y s o u t h w a r d , p o s s i b l y m i x i n g w i t h s o u t h e r n smallhorned b i s o n ( B i s o n b i s o n a n t i q u u s ) t h a t had evolved from l a r g e r - h o r n e d s t o c k s o u t h o f t h e W i s c o n s i n i c e s h e e t s ( G u t h r i e , 1 9 7 0 ) . It i s d i f f i c u l t t o u n t i e t h i s k n o t . For example, I have examined s k u l l s w i t h horncores t h a t r e p r e s e n t n e a r l y every p o s s i b l e combination of c h a r a c t e r s thought t o be d i a g n o s t i c of Bison b i s o n o c c i d e n t a Z i s and Bison b i s o n a n t i q u u s . For u t i l i t a r i a n r e a s o n s , I c a l l t h i s m o s a i c " t h e o c c i d e n t a l i s I n f a c t , such small-horned b i s o n a r e g e n e r a l l y usea n t i q u u s complex". f u l i n d i c a t o r s o f 1 2 , 0 0 0 - 6 , 0 0 0 BP d e p o s i t s . I t i s i n t e r e s t i n g t o s p e c u l a t e on t h e e v o l u t i o n o f modern b i s o n from t h e i r small-horned b i s o n a n c e s t o r s . A s a h y p o t h e s i s f o r t e s t i n g , I suggest t h a t t h e Hypsithermal (about 7,000-5,000 BP) p l a c e d r e l a t i v e l y g r e a t a n d s u d d e n s t r e s s o n s m a l l - h o r n e d b i s o n h e r d s t h a t were b e s t a d a p t e d t o w o o d l a n d o r p a r k l a n d c o n d i t i o n s , a n d t h a t some were a b l e t o a d a p t t o l i f e on t h e a r i d g r a s s l a n d s ( p l a i n s b i s o n , B i s o n b i s o n b i s o n ) w h i l e o t h e r s withdrew northward and westward f o l l o w i n g t h e r e t r e a t i n g m a r g i n s of t h e b o r e a l a n d s u b a l p i n e f o r e s t , o r r e m a i n e d i n s u c h a r e a s (wood b i s o n , B i s o n b i s o n a t h a b a s c a e ) . Adaptation of plains bison
305
Figure 5
R e s t o r a t i o n o f s t e p p e b i s o n (Bison crassicornis) bulls fighting. This species w a s most common in u n g l a c i a t e d a r e a s of A l a s k a and t h e Y u k o n d u r i n g the last glaciation. Based o n skeletal material from a late-Wisconsin site near Dawson, Yukon Territory. Ink sketch b y Bonnie Dalzell.
p r o b a b l y i n v o l v e d s u b s t a n t i 2 1 morDhologica1 and b e h a v i o u r a l c h a n g e s , w h e r e a s I s u s p e c t t h a t wood b i s o n d i f f e r l i t t l e ( e x c e p t f o r s m a l l e r h o r n s ) from B i s o n b i s o n o c e i d e n t a Z i s ( H a r i n g t o n , 1 9 7 7 ) . A b i s o n s k u l l from B a n f f , A l b e r t a y i e l d i n g a r a d i o c a r b o n d a t e of 3,240 5 90 B P (1-11654) i n d i c a t e s t h a t some w e s t e r n b i s o n s u r v i v e d t h i s p e r i o d o f c r i s i s i n i n t e r m o n t a n e p o c k e t s (Appendix; F i g u r e s 6 , 7 ) . T h i s i s i n c o n t r a s t t o l a r g e s a m p l e s o f s k u l l s b e s t r e f e r r e d t o modern b i s o n o f s i m i l a r g e o l o g i c a l a g e from s i t e s f a r t h e r e a s t n e a r F o r t S a s k a t c h e w a n , A l b e r t a , where I h a v e b e e n c o l l e c t i n g , and n e a r B o t t r e l l , A l b e r t a where L . V . H i l l s and M . Wilson ( p e r s . commun., 1 9 8 1 ) have b e e n collecting.
CONCLUSION I n summary, d i v i s i o n of t h e N o r t h American Q u a t e r n a r y i n t o I r v i n g t o n i a n and R a n c h o l a b r e a n Land M a m m a l Ages i s g e n e r a l l y u s e f u l n a r t i c u l a r l y where more p r e c i s e p h y s i c a l d a t i n g t e c h n i q u e s ( e . g . r a d i o c a r b o n , t e p h r a , p a l e o m a g n e t i c ) a r e n o t a p p l i c a b l e , and where m i c r o t i n e ( e . 9 . t h e O n d a t r a i d a h o e n s i s + a n n e e t e n s -+ n e b r a c e n s i s + z i b e t h i c u s l i n e a g e e x t e n d i n g from e a r l y I r v i n g t o n i a n t o Recent ( N e l s o n and Semken, 1 9 7 0 ) ) , and o t h e r u s e f u l i n d i c a t o r s , s u c h a s S o e r g e Z i a ( H a r i n g t o n , 1 9 7 7 ) , c o n s t i t u t e s u p p l e m e n t a r y f o s s i l e v i d e n c e o f g e o l o g i c a l a g e . Remains o f s o u t h e r n and w o o l l y mammoths seem to b e u s e f u l i n d i c a t o r s of e a r l y ( N e b r a s k a n t o Kansan) and l a t e ( m a i n l y W i s c o n s i n ) P l e i s t o c e n e d e p o s i t s , respectively. S t e p p e mammoth r e m a i n s , a l o n e , a r e n o t v e r y u s e f u l i n t h i s regard. Small-horned b i s o n a r e g e n e r a l l y u s e f u l time-guides f o r t h e l a s t 1 2 , 0 0 0 y e a r s , whereas s t e p p e b i s o n a r e i n d i c a t i v e o f d e p o s i t s o l d e r t h a n 1 2 , 0 0 0 B P . G f a m t b i s o n a r e n o t as u s e f u l i n t h i s r e s p e c t a s t h e y seemed t o b e a d e c a d e a g o , f o r t h e y e v i d e n t l y s u r v i v e d from t h e Yarmouth I n t e r g l a c i a l t o l a t e W i s c o n s i n t i m e . The main m o r p h o l o g i c a l c h a n g e s s e e n i n m o l a r s o f t h e r e l a t i v e l y " p r i m i t i v e " s o u t h e r n mammoth t o t h e r e l a t i v e l y "advanced" w o o l l y mammoth a r e : a n i n c r e a s e i n number and c o m p r e s s i o n of enamel p l a t e s ; and a t h i n n i n g of enamel a s t i m e p r o c e e d e d . I n bison, at l e a s t during the l a s t 1 2 , 0 0 0 y e a r s , t h e r e i s t e n d e n c y t o p r o g r e s s i v e r e d u c t i o n i n s i z e of horncores (Wilson, 1980).
306
F i n a l l y , I wish t o emphasize t h e p o s s i b i l i t y t h a t t h e Rancholabrean may h a v e o c c u r r e d e a r l i e r i n n o r t h e r n N o r t h A m e r i c a ( K a n s a n ? ) t h a n i n s o u t h e r n N o r t h A m e r i c a ( Y a r m o u t h ? ) , b e c a u s e b i s o n seem t o h a v e b e e n delayed i n penetrating the southern p l a i n s . ACKNOWLEDGEYENTS I a m g r a t e f u l t o : Edward J . Hart ( A r c h i v e s of t h e C a n a d i a n R o c k i e s ) f o r t h e l o a n of t h e b i s o n s k u l l from B a n f f , Alberta; Harry F o s t e r ( N a t i o n a l Museums o f C a n a d a ) f o r p h o t o g r a p h s o f t h a t s k u l l ; C h a r l e s H . D o u g l a s ( N a t i o n a l Museum o f N a t u r a l S c i e n c e s ) , a n d B o n n i e D a l z e l l for t h e i n k s k e t c h e s ; a n d Mrs. G a i l R i c e f o r t y p i n g t h e manuscript.
The B a n f f A r c h i v e s B i s o n I n t h e l a t e s u m m e r o f 1 9 6 7 , Mrs. C a t h a r i n e TAJhyte c o l l e c t e d a damaged p o s t e r i o r c r a n i a l f r a g m e n t of a n a d u l t b i s o n ( F i g u r e s 6 , 7) unc o v e r e d by a b u l l d o z e r o p e r a t o r e x c a v a t i n g t h e f o u n d a t i o n o f t h e Archives of t h e Canadian Rockies b u i l d i n g i n Banff, A l b e r t a . The s p e c i m e n c a m e f r o m a d e p t h o f a p p r o x i m a t e l y s e v e n f e e t ( 2 . 1 m) i n " g l a c i a l s i l t " ( b u f f sandy s i l t m a t r i x was found i n c a v i t i e s i n t h e c r a n i a l bone). R a d i o c a r b o n a n a l y s i s of bone c o l l a g e n from t h e b a s e of t h e c r a n i u m y i e l d e d a d a t e o f 3 , 2 4 0 ? 9 0 BP ( 1 - 1 1 6 3 8 ) , w h i c h a p p r o x i m a t e l y d a t e s t h e s t r e a m t e r r a c e f r o m w h i c h t h e s p e c i m e n was d e r i v e d . It i s noteworthy t h a t N. Rutter considered t h e t e r r a c e s i n t h i s a r e a u n l i k e l y t o b e o l d e r t h a n 3 , 5 0 0 BP ( W i l s o n , 1 9 7 5 ) , b e f o r e t h e s p e c i m e n was d a t e d . T h i s Banff t e r r a c e i s e v i d e n t l y c o r r e l a t i v e w i t h t h e l a t e T 2 t e r r a c e d e p o s i t s i n t h e Bow V a l l e y f a r t h e r e a s t ( M . W i l s o n , p e r s . commun., 1 9 8 1 ) .
On t h e b a s i s o f t h e r e l a t i v e l y l o n g ( c o m p a r e d t o m o d e r n b i s o n ) e s t i m a t e d s p r e a d o f t h e h o r n c o r e s ( a p p r o x i m a t e l y 7 8 0 mm), t h e r a t h e r n a r r o w ( c o m p a r e d t o Bison b i s o n a n t i q u u s ) f r o n t a l r e g i o n b e t w e e n h o r n c o r e s a n d o r b i t s ( 3 0 1 mm), a n d t h e b a c k s w e p t h o r n c o r e s ( F i g u r e 6 ; T a b l e l), I c o n s i d e r t h a t t h e s p e c i m e n i s b e s t r e f e r r e d t o t h e w e s t e r n bison (Bison bison occidentaZis). T h e r e f o r e , some b i s o n w i t h m a r k e d c h a r a c t e r i s t i c s of w e s t e r n b i s o n , s u r v i v e d i n a t l e a s t one p o c k e t n e a r t h e e a s t e r n f l a n k o f t h e Rocky M o u n t a i n s u n t i l a b o u t 3 , 0 0 0 y e a r s a g o , w h e r e a s c o n t e m p o r a n e o u s b i s o n f r o m two s i t e s f a r t h e r e a s t ( s e e t e x t ) i n A l b e r t a a r e b e s t r e f e r r e d t o modern b i s o n . S i n c e w e s t e r n b i s o n occ u r r e d n e a r C o c h r a n e a s e a r l y a s 1 1 , 0 0 0 BP ( C h u r c h e r , 1 9 6 8 b , 1 9 7 5 ) , t h e s p e c i e s o c c u p i e d t h i s p a r t o f w e s t e r n A l b e r t a f o r some 8 , 0 0 0 y e a r s . P e c u l i a r f e a t u r e s of t h e Banff specimen a r e t h e pronounced dep r e s s i o n s on t h e r i g h t ( m e d i a l t o t h e r i g h t o r b i t ) and l e f t ( m e d i a l t o t h e l e f t hornbase) f r o n t a l s : apparently t h e s e depressions are not due t o e r o s i o n d u r i n g t r a n s p o r t i n a stream b e d , b u t r e s u l t e d f r o m damage (by f i g h t i n g o r p o s s i b l y d i s e a s e ? ) i n l i f e .
***
307
Figure 6
Figure 7
Dorsal Q i e w of a bison s k u l l fragment from a l o w terrace a t Banff, Alberta. Bone f r o m t h i s s p e c i m e n h a s b e e n r a d i o c a r b o n d a t e d a t a b o u t 3 , 2 4 0 BP i n d i c a t i n g t h a t t h e r e were some l a t e - s u r v i v i n g w e s t e r n b i s o n ( B i s o n bison o c c i d e n t a z i s ) i n p o c k e t s n e a r t h e moutain Front.
P o s t e r i o r view of t h e western bison c r a n i a l fragment shown i n F i p u r e 6 .
308
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1 9 7 0 , The N o r t h A m e r i c a n B u f f a l o : a C r i t i c a l Study of t h e i n i t s Wild S t a t e , Second E d i t i o n : University of Toronto P r e s s , 991 ?. F.G.,
S pecies
Romer, A . S . , 1 9 5 1 , Bison erassfcornis i n t h e l a t e P l e i s t o c e n e o f N e w England: J o u r n a l o f Mammalogy, v . 3 2 , p . 2 3 0 - 2 3 1 . 1 9 5 1 , L a t e C e n o z o i c v e r t e b r a t e s o f t h e S a n F r a n c i s c o Bay Savage, D.E., region: U n i v e r s i t y of C a l i f o r n i a P u b l i c a t i o n s , B u l l e t i n Department of G e o l o g i c a l S c i e n c e s , v . 28, no. 1 0 , p . 215-314. S c h u l t z , C . B . and H i l l e r u d , J . M . , 1 9 7 7 , T h e a n t i q u i t y o f B i s o n latifrons ( H a r l a n ) i n t h e Great P l a i n s of N o r t h America: Trans. Nebraska Academy o f i e n c e s , v . 4, p . 103-116. Sher, A.V., 1971, M a m m a l s and S t r a t i g r a p h y of t h e P l e i s t o c e n e o f t h e Extreme N o r t h e a s t of t h e U.S.S.R. and PJorth America: Yoscow, Nauka. (English translation published i n the I n t e r n a t i o n a l Geology Review, v . 1 6 , p . 1 - 2 8 4 , 1 9 7 4 ) . S t a l k e r , A . MacS. a n d C h u r c h e r , C . S . , 1 9 7 0 , D e p o s i t s n e a r M e d i c i n e H a t , A l b e r t a , Canada: C h a r t p u b l i s h e d by t h e S u r v e y s and Mapping Branch, Department of Energy, Mines and R e s o u r c e s , O t t a w a . S t o c k , E . a n d F u r l o n g , E . L . , 1 9 2 8 , The P l e i s t o c e n e e l e p h a n t s o f Rosa I s l a n d , C a l i f o r n i a : S c i e n c e , (New S e r i e s ) , v . 5 8 , p .
Santa 140-141.
W i l s o n , M . , 1 9 7 5 , H o l o c e n e f o s s i l b i s o n f r o m Wyoming a n d a d j a c e n t a r e a s (M.A. T h e s i s ) : L a r a m i e , U n i v e r s i t y o f Wyoming, 276 p .
--
, 1980, Morphological d a t i n g of l a t e Quaternary bison on t h e northern plains: s a n a d i a n J o u r . A n t h r o p o l o g y , v . 1 , n o . 1, p . 81-85. T a b l e 1.
Specimen Banff Archives site, Alberta a
Measurements o f a p o s t g l a c i a l w e s t e r n b i s o n (Bison bison occidentalis) c r a n i a l fragment from Banff, Alberta
1 780b
2 800b
3
Measurements 4 5
265
380b
82b
(mm)a 6 85
7 260b
8
9
325
301
1. S p r e a d o f h o r n c o r e s ( t i p t o t i p ) , 2 . Greatest spread of horncores (on o u t s i d e c u r v e ) , 3. Horncore l e n g t h on upper c u r v e ( t i p t o b u r r ) , 4. Horncore l e n g t h on lower c u r v e ( t i p t o b u r r ) , 5. V e r t i c a l d i a m e t e r of horncore (at r i g h t a n g l e t o l o n g i t u d i n a l a x i s ) , 6 . T r a n s v e r s e d i ameter of h o r n c o r e ( a t r i g h t a n g l e t o l o n g i t u d i n a l a x i s ) , 7 . H o r n c o r e circumference ( a t r i g h t angle t o longitudinal a x i s ) , 8. Cranial width (between u p p e r c e n t r e s of h o r n c o r e b u r r s ) , 9 . C r a n i a l w i d t h ( a t cons t r i c t i o n between h o r n c o r e s and o r b i t s ) .
bEstimated measurement.
MAMMOTHS, BISON AND TIME IN NORTH AMERICA
C.R. HARI N G TON
ABSTRACT N o r t h American Land M a m m a l Ages a r e v a l u a b l e i n a p p r o x i m a t i n g geol o g i c a l t i m e i n t h e Q u a t e r n a r y , p a r t i c u l a r l y where o t h e r more p r e c i s e d a t i n g methods ( s u c h as r a d i o c a r b o n , t e p h r a and p a l e o m a g n e t i c ) a r e l a c k i n g . Mammoths and b i s o n a r e D a r t i c u l a r l y im-oortant f o s s i l i n d i c a t o r s , f o r t h e e a r l i e s t mammoth r e m a i n s i n N o r t h America m a r k t h e b e g i n n i n g of t h e I r v i n g t o n i a n Land M a m m a l Age ( a b o u t 1 . 8 m i l l i o n y e a r s a g o ) , and t h e e a r l i e s t b i s o n r e m a i n s m a r k t h e b e g i n n i n g of t h e Ranchola b r e a n Land M a m m a l Age ( a b o u t 1 . 2 m i l l i o n y e a r s a g o ) . I t i s w o r t h n o t i n g t h a t t h e R a n c h o l a b r e a n may h a v e o c c u r r e d e a r l i e r i n n o r t h e r n N o r t h America t h a n i n s o u t h e r n N o r t h America, b e c a u s e b i s o n seem t o have been d e l a y e d i n p e n e t r a t i n g t h e s o u t h e r n p l a i n s . The main m o r p h o l o g i c a l c h a n g e s s e e n i n mammoths and b i s o n as t i m e proceeded were, r e s p e c t i v e l y : ( a ) a n i n c r e a s e i n number and c o m p r e s s i o n of enamel p l a t e s , and a t h i n n i n g o f enamel i n m o l a r t e e t h ; and ( b ) a t l e a s t during t h e l a s t 1 2 , 0 0 0 y e a r s , a tendency t o p r o g r e s s i v e reduction i n s i z e of h o r n c o r e s .
More s p e c i f i c a l l y , s o u t h e r n a n d w o o l l y mammoths seem t o b e u s e f u l i n d i c a t o r s o f e a r l y ( N e b r a s k a n t o Kansan) and l a t e ( m a i n l y W i s c o n s i n ) Pleistocene deposits, respectively. Small-horned b i s o n a r e g e n e r a l l y u s e f u l time-guides f o r t h e l a s t 1 2 , 0 0 0 y e a r s , whereas s t e p p e b i s o n u s u a l l y i n d i c a t e d e p o s i t s o l d e r t h a n 1 2 , 0 0 0 BP. INTRODUCTION
Mammoths a n d b i s o n , two i m m i g r a n t s from E u r a s i a , a r e p a r t i c u l a r l y i m p o r t a n t b e c a u s e t h e y have b e e n u s e d b y Savage ( 1 9 5 1 ) i n e s t a b l i s h i n g I r v i n g t o n i a n and R a n c h o l a b r e a n N o r t h American Land M a m m a l Ages. T h i s i s a m a j o r d i v i s i o n of t h e Q u a t e r n a r y ( a p p r o x i m a t e l y t h e l a s t 2 m i l l i o n y e a r s o f g e o l o g i c a l t i m e ) b a s e d on f o s s i l v e r t e b r a t e a s s e m b l a g e s ( F i g u r e 1 ) . Savage e m p h a s i z e d t h a t t h e terms I r v i n g t o n i a n and R a n c h o l a b r e a n are b a s e d on f a u n a l names and o n a n i m a l s w i t h i n t h o s e f a u n a s from C a l i f o r n i a , and t h a t t h e y a r e e n t i r e l y s e p a r a t e from r o c k f o r m a t i o n a l names. Ke i n d i c a t e d t h a t t h e e a r l i e s t mammoth r e m a i n s mark t h e b e g i n n i n g o f t h e R a n c h o l a b r e a n . I r o n i c a l l y , t h e l a t t e r a g e a l m o s t came t o a n end a b o u t 1890 due t o human o v e r h u n t i n g of b i s o n ( R o e , 1 9 7 0 ; B a n f i e l d , 1 9 7 4 ) . The e x a c t t i m e d e m a r c a t i o n o f t h e s e a g e s m a y , p e r h a p s , o n l y b e e s t a b l i s h e d on a r e g i o n a l b a s i s and i n t h e f u t u r e , when t h e r e i s b e t t e r geochronological c o n t r o l over middle Pleistocene land mammal faunas. P r e s e n t l y , I s u g g e s t t h a t mammoths f i r s t e n t e r e d North America a b o u t 1 . 8 m i l l i o n y e a r s a g o d u r i n g t h e Nebraskan G l a c i a t i o n and a t t h e b e g i n n i n g o f t h e Q u a t e r n a r y , and t h a t b i s o n f i r s t e n t e r e d N o r t h America d u r i n g t h e Kansan G l a c i a t i o n a b o u t 1 . 2 m i l l i o n y e a r s a g o ( F i g u r e 1 ) . Of course, t h e e a r l i e s t t i m e s of e n t r y o f mammoths and b i s o n i n t o n o r t h e r n North America would p r e c e d e t h e t i m e s t h e y became e s t a b l i s h e d i n t h e s o u t h .
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F i g u r e 1 Suggested chronology and r e g i o n a l d i s t r i b u t i o n of Chronomammoths a n d b i s o n i n N o r t h A m e r i c a d u r i n g t h e q u a t e r n a r y . l o g i c a l d a t a i n t h r e e columns on l e f t are approximate, (modified from E r i c s o n a n d W o l l i n ( 1 9 6 8 ) , M a g l i o ( 1 9 7 3 ) a n d K u r t e n a n d A n d e r s o n (1980)), and p h y l o g e n i e s a r e h i g h l y s i m p l i f i e d . For example, I have n o t d e a l t w i t h t h e o r i g i n o f t h e d w a r f mammoths o f S a n t a R o s a I s l a n d , C a l i f o r n i a ( S t o c k and F u r l o n g 1 9 2 8 ) . Also, I have avoided t h e i s s u e of t h e pres e n c e o f s t e p p e - l i k e b i s o n o n t h e p l a i n s u n t i l m o r e i s known a b o u t t h e i r g e o l o g i c a l a g e and a f f i n i t i e s . P e r h a p s s t e p p e b i s o n ( e . g . Bison +rassicornis f r o m M a s s a c h u s e t t s r a d i o c a r b o n d a t e d a t a p p r o x i m a t e l y 2 1 , 2 0 0 BP ( R o m e r 1 9 5 1 ) ) p e n e t r a t e d t h e p l a i n s a s e c o n d t i m e before t h e p e a k of t h e l a s t g l a c i a t i o n . Some o f t h e s e s t e p p e - l i k e f o r m s may a l s o r e p r e s e n t smaller-horned d e r i v a t i v e s of g i a n t b i s o n s t o c k . ?fagnetic: Normal p o l a r i t y ( b l a c k ) from t o p t o b o t t o m Brunhes, Jaran i l l o , Olduvai; reversed p o l a r i t y (white). G l a c i a l s (black) and Interg l a c i a l ~ : N (Nebraskan); A (Aftonian); K (Kansan); Y (Yarmouth); I ( I l l i n o i a n ) ; S ( S a n g a m o n ) ; W ( W i s c o n s i n ) ; EI ( H o l o c e n e last 10,000 vears). N o t e b r e a k i n s c a l e a t GJ/H b o u n d a r y . E a c h o f t h e t w o c o l u m n s o n t h e r i g h t d e a l i n g w i t h mammoths a n d b i s o n a r e s u b d i v i d e d i n t o B e r i n g i a ("RER." - u n g l a c i a t e d p a r t s o f e a s t e r n S i b e r i a , B e r i n g I s t h m u s , A l a s k a a n d Yukon) on t h e l e f t , a n d P l a i n s ("PL." h e a r t l a n d o f t h e c o n t i n e n t ) on t h e r i g h t , i n o r d e r t o show p o s s i b l e r e l a t i o n s h i p s b e t w e e n p o p u l a t i o n s i n t h o s e r e g i o n s . Dashed l i n e s i n d i c a t e p o i n t s of Freatest u n c e r t a i n t y . Upright arrowh e a d s mark e v i d e n t times of e x t i n c t i o n s .
-
-
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301
MAMMOTES Mammoth remains. particularly complete molar teeth, are sometimes useful biostratigraphic indicators, for they are commonly widespread geographically and they tend to preserve well. The most primitive species known from North America, the southern mammoth (Mummuthus m e r i d i o n a l i s l probably entered this continent from Eurasia near the beginning of the Quaternary, when Repenning recognizes an invasion of rodents including P l i o m y s and S y n a p t o m y s (ReDenninp, 1980; Harington, 1980a). Severalmolars from the northern Yukon resemble those of the most advanced southern mammoth stock (Eacton Stage) or Eurasia, and I suspect that they represent the earliest North American mammoths (Harington 1977; Figure 2). This species also appears to be present in the Wellsch Valley fauna in Saskatchewan, where it may have lived Rearly 1.7 million years ago (A. PTacS. Stalker, .sers. commun., 1976), and at Bruneau, Idaho about 1.36 million years ago (Maglio, 1973). North American steppe mammoths (Mummuthus c o l u m b i and/or Mammuthus a r m e n i a c u s ) are the least valuable biostratigraphically and their origins present problems (Harington 1980b). It is now widely accepted that the Columbian mammoth (Mammuthus c o l u m b i , under which I include the imperial mammoth, Mammuthus i m p e r a t o r , following Kurtgn and Anderson 1980) arose from the southern mammoth in North America ( e . g . MagliO, 1973). As an alternative, I propose that steppe mammoths reached North America from Eurasia, replacing southern mammoths during the Kansan Glaciation about 1.2 million years ago. I think that they invaded with primitive muskoxen like S o e r g e l i a and E u c e r a t h e r i u m and perhaps Phenacomys, C J e t h r i o n o m y s , TJeodon and P i t y m y s (Repenning's (1980) "Irvingtonian II" microtines ) , From the evidence I have seen, I can only stress the similarities of Eurasian and North American steppe mammoths. Some specimens I have referred to Mammuthus c f . a r m e n i a c u s from the northern Yukon may record the earliest North American entry of steDpe mammoths from Eurasia (Harington, 1977). Also, Savage's (1951) description and measurements of Mammuthus c o l u m b i molars from Irvingtonian localities fit well with those of the Eurasian steppe mammoths now included in Mammuthus armeni a c u s . Further, Henry Fairfield Osborn (1942), a paleontologist with great experience in studying elephants, derived Columbian mammoths from Eurasian steppe mammoths now included in Mammuthus a r m e n i a c u s by Maglio (1973). If, indeed, Eurasian and North American steppe mammoths are not synonymous, we need a way of differentiating them -- preferably on molar characteristics. Although Maglio (1473) states that the North American lineage leading from southern to Columbian mammoths has broader molars, most steppe mammoth molars I have measured from the northern Yukon are slightly narrower than the average of a sample from Eurasia (Harington, 1977). Steppe mammoths (Figure 3) seem to have occupied North America for more than 1 million years. The most advanced type (sometimes considered as a separate species, Mammuthus j e f f e r s o n i i ) survived on the olains until about 11,000 years aqo (Kurtgn and Anderson, 1980). Evidently some steppe mammoths lived in eastern Ferinpia ?urine: the ?eak of the liisconsin Glaciation approximately 20,000 years ago (Harington, 1980b). Figure 1
Continued
Mammoths: s o u t h e r n (Mummuthus m e r i d i o n a l i s ) ; s t e p p e ( M , a r m e n i a c u s a n d / o r M . c o l u m b i ) ; w o o l l y IM. p r i m i g e n i u s i .
-
steppe (earliest(?) Bison a l a s k e n s i s , a n d l a t e s t - B . c r a s s { c o r n i s : s o m e t i m e s t h e y a r e g r o u p r d u n d e r t h e name B . p r i s c u s ) ; g i a n t (B. l a t i f r o n s ) ; " o c c i d e n t a l i s - a n t i q u u s ~ o m p l e x ' ' I~B . b i s o n o c c i d e n t a l i s e v i d e n t l y d e r i v e d f r o m s t e p p e b i s o n s t o c k i n B e r i n g i a ; B . bison antiquus e v i d e n t l y derived from g i a n t bison s t o c k i n t h e p l a i n s ) ; wood (B. b i s o n a t h a b a s c a e - e v i d e n t l y d e r i v e d m a i n l y f r o m B . b i s o n o c c i d e n t a l i s s t o c k on t h e n o r t h e r n and w e s t e r n f l a n k s of t h e Canadian p l a i n s ) ; p l a i n s (B. b i s o n b i s o n - e v i d e n t l y d e r i v e d f r o m " o c c i d e n t a l i s antiquus" s t o c k on t h e p l a i n s ) . Bison:
302
Figure 2
llammoth t e e t h a r e o f t e n u s e f u l i n d i c a t o r s o f g e o l o g i c a l age and p a s t environment. The l o w e r t h i r d m o l a r o n t h e l e f t ( g r i n d i n g s u r f a c e shown w i t h e n a m e l p l a t e s i n b l a c k ) i s f r o m a s o u t h e r n mammoth (Mummuthus m e r i d i o n a l i s ) f r o n O l d Crow B a s i n , Yukon T e r r i t o r y , a n d s h o w s t h e " p r i m i t i v e " c o n d i t i o n of r e l a t i v e l y few, t h i c k , widely-spaced enamel plates. The l o w e r t h i r d m o l a r o n t h e r i g h t , from a w o o l l y mammoth (Mammuthus p r i m i g e n i u s ) f r o m t h e same r e g i o n o f t h e Y u k o n , s h o w s t h e " a d v a n c e d " c o n d i t i o n i n v o l v i n g more numerous, t h i n n e r , more compressed enamel p l a t e s . I n k s k e t c h by C h a r l e s Douglas.
However w o o l l y mammoths (Mammuthus p r i m i g e n i u s ) w e r e dominant t h e r e d u r i n g t h a t p e r i o d . C o n c e i v a b l y s t e p p e a n d w o o l l y mammoths may h a v e s h a r e d t h e i r r a n g e b o t h n o r t h and s o u t h o f t h e W i s c o n s i n i c e s h e e t s . Woolly mammoths ( F i g u r e 4 ) m i g r a t e d f r o m E u r a s i a t o N o r t h America i n l a t e I l l i n o i a n or e a r l y W i s c o n s i n t i m e ( H a r i n g t o n , 1 9 8 0 a ) . I n t h e s o u r c e a r e a , n o r t h e a s t e r n S i b e r i a , a n e a r l y tyDe o f w o o l l y mammoth i s known from t h e Utka Beds ( p r o b a b l y l a t e I l l i n o i a n ) , and t h e a d v a n c e d t y p e was e s t a b l i s h e d t h e r e by e a r l y W i s c o n s i n t i m e (Iedoma S u i t e ) ( S h e r , 1 9 7 1 ) . E v i d e n t l y w o o l l y mammoths f i r s t r e a c h e d t h e n o r t h e r n p l a i n s ( M e d i c i n e Hat, A l b e r t a ) d u r i n g t h e e a r l y W i s c o n s i n ( S t a l k e r and C h u r c h e r , 1 9 7 0 ) . The s p e c i e s s p r e a d t o e a s t e r n Canada d u r i n g t h e m i d W i s c o n s i n a b o u t 4 5 , 0 0 0 y e a r s a g o ( C h u r c h e r , 1 9 6 8 a ) . It seems t o h a v e occupied d i s c o n t i n u o u s t u n d r a - l i k e r a n g e s o u t h o f t h e Wisconsin i c e s h e e t , e x t e n d i n g from s o u t h e r n B r i t i s h Columbia t o s o u t h e r n O n t a r i o , a n d p e r h a p s f a r t h e r e a s t w a r d . S c a t t e r e d f o s s i l s of' o t h e r t u n d r a a d a p t e d m a m m a l s i n c l u d i n g lemmings, t u n d r a muskoxen and c a r i b o u a l s o o c c u r i n t h i s zone ( H a r i n g t o n a n d Ashworth, i n p r e p a r a t i o n ) . Woolly mammoths d i e d o u t i n N o r t h America a b o u t 1 3 , 0 0 0 y e a r s a g o . I c o n s i d e r t h i s s p e c i e s t o b e a n i n d i c a t o r of Wisconsin-age d e p o s i t s i n s o u t h e r n Canada and n o r t h e r n U n i t e d S t a t e s , a t l e a s t .
303
Figure 3
a N o r t h A m e r i c a n s t e p p e mammoth T h e y seem t o h a v e b e e n t h e m o s t common a n d w i d e s p r e a d o f N o r t h A m e r i c a n mammoths. I n k s k e t c h by C h a r l e s D o u g l a s .
Figure 4
R e s t o r a t i o n o f a w o o l l y mammoth (Mammuthus p r i m i g e n i u s ) . T h e y w e r e a d a p t e d t o t u n d r a - l i k e r a n g e and were w e l l a d a p t e d t o c o l d c o n d i t i o n s . I n k s k e t c h by Charles Douglas.
Restoration of
(Marnrnuthus c o z u m b i ) .
304
BISON The s t u d y of N o r t h A m e r i c a n f o s s i l b i s o n i s f r a u g h t w i t h p r o b l e m s . E x p e r t s d i s a g r e e on many p o i n t s : n a m e l y , g e o l o g i c a l a g e b e y o n d 4 0 , 0 0 0 BP, phylogeny and d i s t r i b u t i o n a l h i s t o r y . I think that clarification o f many o f t h e s e p r o b l e m s d e p e n d s upon g a i n i n g a b e t t e r p e r s p e c t i v e on t h e h i s t o r y of E u r a s i a n f o s s i l b i s o n . To t h i s e n d , D . M . S h a c k l e t o n a n d M . L . W e s t o n , s p o n s o r e d by t h e N a t i o n a l Museum of N a t u r a l S c i e n c e s , b e g a n a s t u d y i n 1 9 7 9 . They a r e p r o c e s s i n g b i o s t r a t i g r a p h i c a n d n e t r i c d a t a on w e s t e r n E u r o p e a n f o s s i l s . Data f r o m 185 s k u l l s , 1 6 m a n d i b l e s a n d 1 6 8 p o s t c r a n i a l e l e m e n t s were c o l l e c t e d f r o m b i s o n f o s s i l s i n Soviet i n s t i t u t i o n s i n 1982.
B i s o n h a d e n t e r e d c e n t r a l A l a s k a by K a n s a n ( ? ) t i m e a c c o r d i n g t o r e m a i n s from t h e Fox G r a v e l u n i t n e a r F a i r b a n k s . The a g e e s t i m a t e r e s t s on P 6 w 6 ' s ( 1 9 7 5 a , b ) s t r a t i g r a p h i c i n t e r p r e t a t i o n of a n e x p o s u r e a t Eva C r e e k . O t h e r e a r l y s p e c i m e n s of b i s o n f r o m A l a s k a a r e f r o m d e p o s i t s of p o s s i b l e Yarmouth I n t e r g l a c i a l a g e n e a r B a l d w i n P e n i n s u l a ; I l l i n o i a n age n e a r F a i r b a n k s ( a f i s s i o n - t r a c k age of approximately 450,000 y e a r s f r o m t h e E a s t e r Ash Bed s u g g e s t s t h a t B i s o n r e m a i n s f r o m t h i s p a r t of t h e G o l d H i l l L o e s s may b e I l l i n o i a n i n a g e (T.L. P & w & , p e r s . commun., 1 9 8 2 ) ) ; a n d Sangamon I n t e r g l a c i a l a g e n e a r T o f t y . A s n o p u b l i s h e d d e s c r i p t i o n s of t h e s e f o s s i l s a r e a v a i l a b l e , i t i s d i f f i c u l t t o know w h e t h e r t h e y s h o u l d b e t r e a t e d m e r e l y a s B i s o n s p . , or w h e t h e r - a s seems l i k e l y - t h e y r e p r e s e n t s t e p p e b i s o n ( s e n s u Kurt6n and Anderson, 1980). I n t h e Yukon, I h a v e c o l l e c t e d s t e p p e b i s o n s p e c i m e n s w i t h unu s u a l l y l a r g e h o r n c o r e s ( B i s o n a t a s k e n s i s ) , one o f w h i c h y i e l d e d a r a d i o c a r b o n d a t e of >39,000 BP ( 1 - 5 4 0 5 ) . I c o n s i d e r i t t o be a s u i t a b l e a n c e s t o r for l a t e r , s m a l l e r - h o r n e d s t e p p e b i s o n ( B i s o n c r a s s i c o r n i s ) and t h e g i a n t b i s o n ( B i s o n Z a t i f r o n s ) of s o u t h e r n North America, and t o be c l o s e l y r e l a t e d t o , i f not.synonymous w i t h , Bison p r i s c u s gigas ( H a r i n g t o n a n d C l u l o w , 1 9 7 3 ; H a r i n g t o n , 1 9 8 0 a ) . The l a t t e r b i s o n was widespread i n E u r a s i a d u r i n g t h e middle P l e i s t o c e n e ( e q u i v a l e n t i n age f r o m Yarmouth t o Sangamon t i m e i n F l e r o v ' s ( 1 9 7 2 ) t e r m i n o l o g y ) . The e a r l i e s t o c c u r r e n c e s o f b i s o n on t h e p l a i n s a D p e a r t o be o f Yarmouth a g e i n C a n a d a ( S t a l k e r a n d C h u r c h e r , 1 9 7 0 ) a n d of p o s t - Kansan t o e a r l y I l l i n o i a n a g e i n t h e U n i t e d S t a t e s ( S c h u l t z and H i l l e r u d , 1977). Giant b i s o n are f i r s t d e f i n i t e l y r e c o r d e d there i n l a t e I l l i n o i a n time a n d seem t o h a v e s u r v i v e d u n t i l l a t e W i s c o n s i n t i m e ( K u r t 6 n a n d Anderson, 1980). N o r t h e r n s m a l l - h o r n e d b i s o n , or w e s t e r n b i s o n ( B i s o n b i s o n o c c i d e n t a Z i s ) e v i d e n t l y a r o s e from stepDe b i s o n ( B i s o n c r a s s i c o r n i s : F i g u r e 5 ) s t o c k i n B e r i n g i a t o w a r d t h e c l o s e of t h e l a s t g l a c i a t i o n . P r o b a b l y warmer, m o i s t e r c o n d i t i o n s o c c u r r i n g i n B e r i n g i a t h e n , a n d t h e r e s u l t i n g more h e a v i l y - w o o d e d t e r r a i n c o n t r i b u t e d t o t h e d e m i s e of s t e p p e b i s o n a n d t h e r i s e of w e s t e r n b i s o n ( H a r i n g t o n , 1 9 7 7 ) . T h e s e b i s o n s p r e a d r a p i d l y s o u t h w a r d , p o s s i b l y m i x i n g w i t h s o u t h e r n smallhorned b i s o n ( B i s o n b i s o n a n t i q u u s ) t h a t had evolved from l a r g e r - h o r n e d s t o c k s o u t h o f t h e W i s c o n s i n i c e s h e e t s ( G u t h r i e , 1 9 7 0 ) . It i s d i f f i c u l t t o u n t i e t h i s k n o t . For example, I have examined s k u l l s w i t h horncores t h a t r e p r e s e n t n e a r l y every p o s s i b l e combination of c h a r a c t e r s thought t o be d i a g n o s t i c of Bison b i s o n o c c i d e n t a Z i s and Bison b i s o n a n t i q u u s . For u t i l i t a r i a n r e a s o n s , I c a l l t h i s m o s a i c " t h e o c c i d e n t a l i s I n f a c t , such small-horned b i s o n a r e g e n e r a l l y usea n t i q u u s complex". f u l i n d i c a t o r s o f 1 2 , 0 0 0 - 6 , 0 0 0 BP d e p o s i t s . I t i s i n t e r e s t i n g t o s p e c u l a t e on t h e e v o l u t i o n o f modern b i s o n from t h e i r small-horned b i s o n a n c e s t o r s . A s a h y p o t h e s i s f o r t e s t i n g , I suggest t h a t t h e Hypsithermal (about 7,000-5,000 BP) p l a c e d r e l a t i v e l y g r e a t a n d s u d d e n s t r e s s o n s m a l l - h o r n e d b i s o n h e r d s t h a t were b e s t a d a p t e d t o w o o d l a n d o r p a r k l a n d c o n d i t i o n s , a n d t h a t some were a b l e t o a d a p t t o l i f e on t h e a r i d g r a s s l a n d s ( p l a i n s b i s o n , B i s o n b i s o n b i s o n ) w h i l e o t h e r s withdrew northward and westward f o l l o w i n g t h e r e t r e a t i n g m a r g i n s of t h e b o r e a l a n d s u b a l p i n e f o r e s t , o r r e m a i n e d i n s u c h a r e a s (wood b i s o n , B i s o n b i s o n a t h a b a s c a e ) . Adaptation of plains bison
305
Figure 5
R e s t o r a t i o n o f s t e p p e b i s o n (Bison crassicornis) bulls fighting. This species w a s most common in u n g l a c i a t e d a r e a s of A l a s k a and t h e Y u k o n d u r i n g the last glaciation. Based o n skeletal material from a late-Wisconsin site near Dawson, Yukon Territory. Ink sketch b y Bonnie Dalzell.
p r o b a b l y i n v o l v e d s u b s t a n t i 2 1 morDhologica1 and b e h a v i o u r a l c h a n g e s , w h e r e a s I s u s p e c t t h a t wood b i s o n d i f f e r l i t t l e ( e x c e p t f o r s m a l l e r h o r n s ) from B i s o n b i s o n o c e i d e n t a Z i s ( H a r i n g t o n , 1 9 7 7 ) . A b i s o n s k u l l from B a n f f , A l b e r t a y i e l d i n g a r a d i o c a r b o n d a t e of 3,240 5 90 B P (1-11654) i n d i c a t e s t h a t some w e s t e r n b i s o n s u r v i v e d t h i s p e r i o d o f c r i s i s i n i n t e r m o n t a n e p o c k e t s (Appendix; F i g u r e s 6 , 7 ) . T h i s i s i n c o n t r a s t t o l a r g e s a m p l e s o f s k u l l s b e s t r e f e r r e d t o modern b i s o n o f s i m i l a r g e o l o g i c a l a g e from s i t e s f a r t h e r e a s t n e a r F o r t S a s k a t c h e w a n , A l b e r t a , where I h a v e b e e n c o l l e c t i n g , and n e a r B o t t r e l l , A l b e r t a where L . V . H i l l s and M . Wilson ( p e r s . commun., 1 9 8 1 ) have b e e n collecting.
CONCLUSION I n summary, d i v i s i o n of t h e N o r t h American Q u a t e r n a r y i n t o I r v i n g t o n i a n and R a n c h o l a b r e a n Land M a m m a l Ages i s g e n e r a l l y u s e f u l n a r t i c u l a r l y where more p r e c i s e p h y s i c a l d a t i n g t e c h n i q u e s ( e . g . r a d i o c a r b o n , t e p h r a , p a l e o m a g n e t i c ) a r e n o t a p p l i c a b l e , and where m i c r o t i n e ( e . 9 . t h e O n d a t r a i d a h o e n s i s + a n n e e t e n s -+ n e b r a c e n s i s + z i b e t h i c u s l i n e a g e e x t e n d i n g from e a r l y I r v i n g t o n i a n t o Recent ( N e l s o n and Semken, 1 9 7 0 ) ) , and o t h e r u s e f u l i n d i c a t o r s , s u c h a s S o e r g e Z i a ( H a r i n g t o n , 1 9 7 7 ) , c o n s t i t u t e s u p p l e m e n t a r y f o s s i l e v i d e n c e o f g e o l o g i c a l a g e . Remains o f s o u t h e r n and w o o l l y mammoths seem to b e u s e f u l i n d i c a t o r s of e a r l y ( N e b r a s k a n t o Kansan) and l a t e ( m a i n l y W i s c o n s i n ) P l e i s t o c e n e d e p o s i t s , respectively. S t e p p e mammoth r e m a i n s , a l o n e , a r e n o t v e r y u s e f u l i n t h i s regard. Small-horned b i s o n a r e g e n e r a l l y u s e f u l time-guides f o r t h e l a s t 1 2 , 0 0 0 y e a r s , whereas s t e p p e b i s o n a r e i n d i c a t i v e o f d e p o s i t s o l d e r t h a n 1 2 , 0 0 0 B P . G f a m t b i s o n a r e n o t as u s e f u l i n t h i s r e s p e c t a s t h e y seemed t o b e a d e c a d e a g o , f o r t h e y e v i d e n t l y s u r v i v e d from t h e Yarmouth I n t e r g l a c i a l t o l a t e W i s c o n s i n t i m e . The main m o r p h o l o g i c a l c h a n g e s s e e n i n m o l a r s o f t h e r e l a t i v e l y " p r i m i t i v e " s o u t h e r n mammoth t o t h e r e l a t i v e l y "advanced" w o o l l y mammoth a r e : a n i n c r e a s e i n number and c o m p r e s s i o n of enamel p l a t e s ; and a t h i n n i n g of enamel a s t i m e p r o c e e d e d . I n bison, at l e a s t during the l a s t 1 2 , 0 0 0 y e a r s , t h e r e i s t e n d e n c y t o p r o g r e s s i v e r e d u c t i o n i n s i z e of horncores (Wilson, 1980).
306
F i n a l l y , I wish t o emphasize t h e p o s s i b i l i t y t h a t t h e Rancholabrean may h a v e o c c u r r e d e a r l i e r i n n o r t h e r n N o r t h A m e r i c a ( K a n s a n ? ) t h a n i n s o u t h e r n N o r t h A m e r i c a ( Y a r m o u t h ? ) , b e c a u s e b i s o n seem t o h a v e b e e n delayed i n penetrating the southern p l a i n s . ACKNOWLEDGEYENTS I a m g r a t e f u l t o : Edward J . Hart ( A r c h i v e s of t h e C a n a d i a n R o c k i e s ) f o r t h e l o a n of t h e b i s o n s k u l l from B a n f f , Alberta; Harry F o s t e r ( N a t i o n a l Museums o f C a n a d a ) f o r p h o t o g r a p h s o f t h a t s k u l l ; C h a r l e s H . D o u g l a s ( N a t i o n a l Museum o f N a t u r a l S c i e n c e s ) , a n d B o n n i e D a l z e l l for t h e i n k s k e t c h e s ; a n d Mrs. G a i l R i c e f o r t y p i n g t h e manuscript.
The B a n f f A r c h i v e s B i s o n I n t h e l a t e s u m m e r o f 1 9 6 7 , Mrs. C a t h a r i n e TAJhyte c o l l e c t e d a damaged p o s t e r i o r c r a n i a l f r a g m e n t of a n a d u l t b i s o n ( F i g u r e s 6 , 7) unc o v e r e d by a b u l l d o z e r o p e r a t o r e x c a v a t i n g t h e f o u n d a t i o n o f t h e Archives of t h e Canadian Rockies b u i l d i n g i n Banff, A l b e r t a . The s p e c i m e n c a m e f r o m a d e p t h o f a p p r o x i m a t e l y s e v e n f e e t ( 2 . 1 m) i n " g l a c i a l s i l t " ( b u f f sandy s i l t m a t r i x was found i n c a v i t i e s i n t h e c r a n i a l bone). R a d i o c a r b o n a n a l y s i s of bone c o l l a g e n from t h e b a s e of t h e c r a n i u m y i e l d e d a d a t e o f 3 , 2 4 0 ? 9 0 BP ( 1 - 1 1 6 3 8 ) , w h i c h a p p r o x i m a t e l y d a t e s t h e s t r e a m t e r r a c e f r o m w h i c h t h e s p e c i m e n was d e r i v e d . It i s noteworthy t h a t N. Rutter considered t h e t e r r a c e s i n t h i s a r e a u n l i k e l y t o b e o l d e r t h a n 3 , 5 0 0 BP ( W i l s o n , 1 9 7 5 ) , b e f o r e t h e s p e c i m e n was d a t e d . T h i s Banff t e r r a c e i s e v i d e n t l y c o r r e l a t i v e w i t h t h e l a t e T 2 t e r r a c e d e p o s i t s i n t h e Bow V a l l e y f a r t h e r e a s t ( M . W i l s o n , p e r s . commun., 1 9 8 1 ) .
On t h e b a s i s o f t h e r e l a t i v e l y l o n g ( c o m p a r e d t o m o d e r n b i s o n ) e s t i m a t e d s p r e a d o f t h e h o r n c o r e s ( a p p r o x i m a t e l y 7 8 0 mm), t h e r a t h e r n a r r o w ( c o m p a r e d t o Bison b i s o n a n t i q u u s ) f r o n t a l r e g i o n b e t w e e n h o r n c o r e s a n d o r b i t s ( 3 0 1 mm), a n d t h e b a c k s w e p t h o r n c o r e s ( F i g u r e 6 ; T a b l e l), I c o n s i d e r t h a t t h e s p e c i m e n i s b e s t r e f e r r e d t o t h e w e s t e r n bison (Bison bison occidentaZis). T h e r e f o r e , some b i s o n w i t h m a r k e d c h a r a c t e r i s t i c s of w e s t e r n b i s o n , s u r v i v e d i n a t l e a s t one p o c k e t n e a r t h e e a s t e r n f l a n k o f t h e Rocky M o u n t a i n s u n t i l a b o u t 3 , 0 0 0 y e a r s a g o , w h e r e a s c o n t e m p o r a n e o u s b i s o n f r o m two s i t e s f a r t h e r e a s t ( s e e t e x t ) i n A l b e r t a a r e b e s t r e f e r r e d t o modern b i s o n . S i n c e w e s t e r n b i s o n occ u r r e d n e a r C o c h r a n e a s e a r l y a s 1 1 , 0 0 0 BP ( C h u r c h e r , 1 9 6 8 b , 1 9 7 5 ) , t h e s p e c i e s o c c u p i e d t h i s p a r t o f w e s t e r n A l b e r t a f o r some 8 , 0 0 0 y e a r s . P e c u l i a r f e a t u r e s of t h e Banff specimen a r e t h e pronounced dep r e s s i o n s on t h e r i g h t ( m e d i a l t o t h e r i g h t o r b i t ) and l e f t ( m e d i a l t o t h e l e f t hornbase) f r o n t a l s : apparently t h e s e depressions are not due t o e r o s i o n d u r i n g t r a n s p o r t i n a stream b e d , b u t r e s u l t e d f r o m damage (by f i g h t i n g o r p o s s i b l y d i s e a s e ? ) i n l i f e .
***
307
Figure 6
Figure 7
Dorsal Q i e w of a bison s k u l l fragment from a l o w terrace a t Banff, Alberta. Bone f r o m t h i s s p e c i m e n h a s b e e n r a d i o c a r b o n d a t e d a t a b o u t 3 , 2 4 0 BP i n d i c a t i n g t h a t t h e r e were some l a t e - s u r v i v i n g w e s t e r n b i s o n ( B i s o n bison o c c i d e n t a z i s ) i n p o c k e t s n e a r t h e moutain Front.
P o s t e r i o r view of t h e western bison c r a n i a l fragment shown i n F i p u r e 6 .
308
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--
, 1980, Morphological d a t i n g of l a t e Quaternary bison on t h e northern plains: s a n a d i a n J o u r . A n t h r o p o l o g y , v . 1 , n o . 1, p . 81-85. T a b l e 1.
Specimen Banff Archives site, Alberta a
Measurements o f a p o s t g l a c i a l w e s t e r n b i s o n (Bison bison occidentalis) c r a n i a l fragment from Banff, Alberta
1 780b
2 800b
3
Measurements 4 5
265
380b
82b
(mm)a 6 85
7 260b
8
9
325
301
1. S p r e a d o f h o r n c o r e s ( t i p t o t i p ) , 2 . Greatest spread of horncores (on o u t s i d e c u r v e ) , 3. Horncore l e n g t h on upper c u r v e ( t i p t o b u r r ) , 4. Horncore l e n g t h on lower c u r v e ( t i p t o b u r r ) , 5. V e r t i c a l d i a m e t e r of horncore (at r i g h t a n g l e t o l o n g i t u d i n a l a x i s ) , 6 . T r a n s v e r s e d i ameter of h o r n c o r e ( a t r i g h t a n g l e t o l o n g i t u d i n a l a x i s ) , 7 . H o r n c o r e circumference ( a t r i g h t angle t o longitudinal a x i s ) , 8. Cranial width (between u p p e r c e n t r e s of h o r n c o r e b u r r s ) , 9 . C r a n i a l w i d t h ( a t cons t r i c t i o n between h o r n c o r e s and o r b i t s ) .
bEstimated measurement.