Dining in the Pleistocene—Who’s on the menu?
Matthew J. Kohn
Moriah P. McKay
Department of Geological Sciences, 701 Sumter Street, EWS 617, University of South Carolina, Columbia,
South Carolina 29208, USA
James L. Knight
Department of Geological Sciences, 701 Sumter Street, EWS 617, University of South Carolina, Columbia, South Carolina 29208,
USA, and South Carolina State Museum, 301 Gervais Street, Columbia, South Carolina 29201, USA
ABSTRACT
The Camelot local fauna, a new fossil locality in southeastern South Carolina, has yielded a spectacularly abundant and well-preserved late Irvingtonian (ca. 400 ka) megafauna,
including saber-toothed cat (Smilodon fatalis), wolf (Canis armbrusteri), cheetah (Miracinonyx inexpectatus), ‘‘camels’’ (Hemiauchenia macrocephala and Paleolama mirifica), tapir
(Tapirus veroensis), deer (Odocoileus virginianus), sloth (Megalonyx jeffersoni), and horse
(Equus sp.). Of particular interest is the number of well-preserved fossil teeth and the
ability to decipher paleoecologies and paleodiets, especially for carnivores, by using carbon
isotope compositions (d13C) of these teeth. P. mirifica, M. jeffersoni, O. virginianus, and T.
veroensis have the lowest d13C values (216‰ to 213‰, Vienna Peedee belemnite standard); C. armbrusteri, S. fatalis, and H. macrocephala have intermediate values (213‰ to
28‰); and Equus sp. has the highest values (27‰ to 21‰). High (.25‰) vs. low
(#29‰) d13C values for herbivores indicate local habitats dominated by warm-climate
grasses vs. trees and shrubs. The high d13C values for Equus sp. indicate the presence of
grasslands, whereas the low d13C values for the other herbivores generally indicate the
presence of forests. Although few data are available for carnivores, moderate d13C values
for C. armbrusteri indicate that it preyed mainly upon forest herbivores. S. fatalis appears
to have preferred marginal woodland-grassland areas.
Keywords: megafauna, paleoecology, stable isotopes, teeth, diet, Pleistocene.
INTRODUCTION
A new megafauna fossil locality, the Camelot local fauna, has been discovered near
Harleyville, Dorchester County, South Carolina, United States (Fig. 1), and has proved
significant for several reasons. First, the site
is one of the most productive and diverse
middle Pleistocene sites in eastern North
America outside of Florida, and it contains
some of the best-preserved examples of specific taxa such as saber-toothed cats (Smilodon
fatalis) outside of the La Brea tar pits, California. Second, the age of the fauna (late Irvingtonian, or ca. 400 ka, as determined
biostratigraphically and by stratigraphic inference) corresponds to the last time in Earth’s
history that insolation closely matched modern values, so that paleoclimate and
paleoecology should be most comparable to
modern conditions before human influences
(e.g., Droxler et al., 2003).
Most important for this study, the site has
yielded sufficient numbers of teeth that multiple carbon and oxygen isotope analyses
could be collected on both herbivores and carnivores to determine feeding ecologies. Destructive analysis of fossil carnivore teeth is
rarely permitted because they are uncommon
and particularly valuable for paleontological
studies. Consequently, in this study we were
able to provide important constraints not only
on what local habitats existed and how they
compared with modern conditions in South
Carolina, but also how different herbivores
and carnivores partitioned those habitats. Previous studies have made progress in understanding the feeding ecology of many of these
species, both herbivorous and carnivorous
(e.g., Koch et al., 1998; Feranec and MacFadden, 2000; Feranec, 2003, 2004; Palmqvist
et al., 2003; Coltrain et al., 2004). However,
in past investigations of S. fatalis and Canis
Figure 1. Outline of state of South Carolina,
United States, showing locations of major
cities (dots) and Harleyville fossil locality
(star).
sp., the paleohabitats that were present did not
include isotopically distinct C4 grasslands, and
consequently interpretation of habitat use by
these carnivores was equivocal. For example,
Coltrain et al. (2004) could conclude that S.
fatalis consumed ruminants, but not where
those ruminants lived. Our data are unique in
clearly demonstrating a preference by S. fatalis and C. armbrusteri for forests and marginal woodland-grassland areas.
STABLE ISOTOPES OF TEETH
Teeth contain biogenic Ca-phosphate with a
major substitution of CO3 for PO4 and OH
groups. Stable isotope compositions of biogenic tissues have been reviewed several
times (e.g., Koch, 1998; MacFadden, 2000;
Kohn and Cerling, 2002) and, generally
speaking, ‘‘you are what you eat’’; i.e., the
isotope composition of whatever you eat plus
several physiological and fractionation factors
define your isotope composition. For carbon,
different plants have different d13C values,
and this isotopic discrimination is passed on
to their consumers. Virtually all dicots (e.g.,
trees, shrubs, herbs) and many cool-climate
monocots (grasses) use the C3 photosynthetic
pathway and have low d13C values of
;225‰ to 230‰ (Vienna Peedee belemnite
q 2005 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected].
Geology; August 2005; v. 33; no. 8; p. 649–652; doi: 10.1130/G21476.1; 2 figures; Data Repository item 2005123.
649
standard [VPDB]), whereas many warmclimate monocots use the C4 photosynthetic
pathway and have high d13C values of
;211‰ to 213‰ (VPDB). The larger isotopic range for C3 plants in part reflects ecosystem specifics; e.g., closed-canopy forests
have the lowest d13C values, reflecting carbon
recycling of leaf litter.
Today, South Carolina exhibits mixed habitats from open grassland to closed-canopy
forest, and native grass genera are roughly
50:50 C3 vs. C4 varieties (Leithead et al.,
1971). For wild herbivores, the isotopic offset
between tooth enamel and diet is ;114‰
(Cerling and Harris, 1999). Consequently, accounting for an ;1.5‰ decrease in d13C due
to recent fossil fuel burning (Friedli et al.,
1986), we expect isotopic compositions of
fossil herbivore tooth enamel to be #;214‰
for closed-canopy occupancy vs. ;212‰ for
normal woodland (Passey et al., 2002). Consumption of grass (mixed C3 1 C4) would impart values $;29‰, and exclusive (C3 1
C4) grassland occupancy would yield average
values of ;25‰. Carnivores have a d13C offset of ;12‰–3‰ relative to their prey (e.g.,
Gröcke, 1997; Koch, 1998), but the internal
fractionation of apatite relative to other body
tissues is ;3‰ smaller (Lee-Thorp et al.,
1989; Gröcke, 1997), yielding an ;113‰–
14‰ offset relative to habitat, i.e., boundaries
for closed-canopy, woodland, and at least partial grassland occupancy at ;214‰ to
215‰, 29‰ to 210‰, and 25‰ to 26‰,
respectively.
A final complication of stable isotopes in
teeth is that enamel is preferred for analysis
because it is least susceptible to diagenetic alteration, yet it mineralizes progressively along
the length of the tooth. Diet and climate
change seasonally, so enamel is isotopically
zoned, with low vs. high d18O values in the
winter vs. summer (e.g., Kohn and Cerling,
2002). Because of how we sample teeth (Kohn
et al., 2002), a range of compositions is retrieved, reflecting seasonal changes in climate
and diet. There has been little comparison of
this intratooth compositional variability vs. interindividual compositions, which could affect
the number of teeth required to obtain reliable
paleoecological restorations. For example,
Clementz and Koch (2001) found large d13C
and d18O differences among M3 teeth of deer
from central coastal California (;61.5‰,
1s), which might be interpreted to mean that
different individuals have rather different
compositions, and that many teeth must be
sampled to be representative. However, (1)
large deer have an ;1.5 yr range in the time
of M3 appearance (Kierdorf and Kierdorf,
2000), (2) the total mineralization interval for
M3 tooth enamel is likely only a few months,
and (3) the seasonal isotopic range in meteoric
650
water d18O is several per mil for coastal California (International Atomic Energy Agency,
1992). Consequently, the isotopic variation
observed by Clementz and Koch (2001) may
reflect differences in tooth mineralization time
among individuals that in fact share similar
compositions. This view is consistent with the
minimally destructive sampling approach used
in this study.
SAMPLES AND ANALYSIS
Samples were obtained from fluvial gravel
deposits overlying Eocene limestone. The faunal assemblage closely matches that of the late
Irvingtonian Coleman 2A site in Florida, including such key species as Sigmodon bakeri
(cotton rat), C. armbrusteri, T. veroensis, and
an as-yet undescribed tortoise in the genus
Hesperotestudo. Bison sp., whose first appearance defines the Rancholabrean, is absent.
Dental characteristics for M. jeffersoni and S.
fatalis suggest evolutionary grades early in the
temporal distribution of those species, consistent with a late Irvingtonian age. The only
strata of remotely comparable age are the correlative Ladson and Canepatch Formations
(Edwards et al., 2000), dated as 400–500 ka
(Cronin et al., 1981; Szabo, 1985). Morgan
and Hulbert (1994) assigned an age of 300–
500 ka to Coleman 2A, and given the occurrence of interglacial fauna, plus stratigraphic
considerations, correlation with isotope stage
11 (i.e., ca. 400 ka) is most likely (Szabo,
1985). Note that although paleofloral observations are available for late Pleistocene South
Carolina, we are unaware of any floral data
for ca. 400 ka.
Compositions (see GSA Data Repository)1
were collected from fossil tooth enamel of
saber-toothed cat (Smilodon fatalis), wolf (Canis armbrusteri; related to Canis dirus, the
dire wolf), ‘‘camels’’ (Hemiauchenia macrocephala and Paleolama mirifica), tapir (Tapirus veroensis), deer (Odocoileus virginianus),
and horse (Equus sp.). Orthodentine (‘‘hard’’
dentine) from sloth (Megalonyx jeffersoni)
was also analyzed, but compositions should be
viewed cautiously as diagenetic resistance has
not been evaluated. Fossil bones and a tooth
of cheetah (Miracinonyx inexpectatus) have
been recovered, but no teeth were available for
analysis. Modern teeth of deer and horse from
near Columbia, South Carolina (Fig. 1), were
analyzed to compare with fossils (Table DR2;
see footnote 1). It has been supposed that wild
mammal compositions may be affected by
1GSA Data Repository item 2005123, Tables
DR1–DR4, stable isotope compositions and statistical tests for late Irvingtonian and modern faunas
of South Carolina, is available online at www.
geosociety.org/pubs/ft2005.htm, or on request from
[email protected] or Documents Secretary,
GSA, P.O. Box 9140, Boulder, CO 80301-9140,
USA.
nursing (e.g., Bryant et al., 1996). Although
this assumption lacks support either from data
or modeling (e.g., Kohn et al., 1998), none of
the teeth sampled should have formed during
nursing.
Teeth were sampled by removing a strip of
enamel along the crown of each tooth, from
the occlusal surface to the cervical margin.
This strip was subsampled with a spatial resolution of 1.5 mm. For most taxa, this likely
represents an interval of a few weeks to a couple of months of tooth growth per subsample
(Kohn, 2004). Note that enamel mineralization rates are unknown for ground sloths, and
for carnivores are only well characterized for
canines: $1 mm/month (Feranec, 2004). Subsamples were cleaned of adhering dentine,
split to 2–3 mg, ground with a mortar and pestle, then chemically processed and analyzed
for the d13C and d18O of the CO3 component
according to the preferred protocols of Koch
et al. (1997), i.e., use of H2O2 and Ca-acetate
buffer pretreatments, and analysis in an automatic carbonate device at 90 8C. The d18O
(Vienna standard mean ocean water
[VSMOW]) and d13C (VPDB) compositions
of phosphate standard NBS-120c (n 5 14)
were 28.25‰ 6 0.12‰ and 26.56‰ 6
0.04‰ (61s), respectively.
A d18O vs. d13C plot (Fig. 2) shows a large
range in d13C values (15‰) for the fossil
teeth. Equus sp. has the highest d13C values
(27‰ to 21‰), C. armbrusteri, S. fatalis,
and H. macrocephala have intermediate d13C
(213‰ to 28‰), and T. veroensis, O. virginianus, M. jeffersoni, and P. mirifica have
the lowest d13C (216‰ to 213‰). These
compositions are generally consistent with
other studies of Pleistocene herbivores from
Florida (Koch et al., 1998; Feranec and
MacFadden, 2000; Feranec, 2003). For oxygen, d18O values show less variation (5‰),
and broadly similar compositions, as expected
for temperate settings with moderate to high
humidity (Kohn, 1996). Compositions generally exhibit systematic changes along the
length of a tooth, representing preserved isotopic seasonality. This zoning and the clearly
resolvable differences in d13C values among
taxa support an absence of diagenetic alteration; otherwise, isotope compositions would
converge and systematic zoning would likely
be suppressed.
Modern vs. fossil deer teeth have significantly different d13C values, indicating a difference in habitat occupancy. Modern and fossil horse have different d18O values, which
likely reflect geographic effects on local water
compositions.
Statistical measures (Tables DR3, DR4; see
footnote 1) were used to examine comparability of means (t-tests) and isotopic range (Ftests). For comparing means, more conservaGEOLOGY, August 2005
Figure 2. Plot of d18O vs. d13C of teeth from South Carolina, United States. Broken lines
roughly delineate carbon isotopic bounds on local habitats: deep forest (closed canopy, C3
dominated), woodlands (C3 dominated), mixed grasslands (C31C4), and grasslands (C4 dominated). Modern data for deer (Odocoileus) and horse (Equus) have been increased by 1.5‰
to account for fossil fuel burning (Friedli et al., 1986). Occurrence of high d13C values for
Equus implies presence of mixed C3 1 C4 grasslands, whereas low d13C values for other
taxa imply woodlands and deep forest, similar to mix of habitats observed today in South
Carolina. Relatively low vs. intermediate d13C values for Canis armbrusteri vs. Smilodon
fatalis imply that they hunted primarily in forests vs. in marginal forest-grassland areas.
Symbols for Megalonyx are lighter gray because diagenetic alteration could bias compositions. VPDB—Vienna Peedee belemnite; VSMOW—Vienna standard mean ocean water.
tive tests (e.g., ANOVA) yield p-values within
a factor of ;2 for p . 0.0001. For t-tests,
taking p $ 0.025 indicates compositional
groupings for (fossil) O. virginianus 1 T. veroensis 6 M. jeffersoni, for H. macrocephala
1 S. fatalis, and for modern 1 fossil Equus
sp. For F-tests, taking p $ 0.05 indicates similarly high compositional variability for modern Equus sp. 1 fossil Equus sp. 1 C. armbrusteri 1 H. macrocephala 1 modern O.
virginianus 6 P. mirifica, and similarly low
variability for S. fatalis 1 T. veroensis 1 fossil O. virginianus 6 P. mirifica. All other
comparisons yielded significant differences,
including t-tests and F-tests for modern vs.
fossil deer.
DISCUSSION
One important result of the stable isotope
analysis is the wide range of d13C values, with
specific taxa exhibiting specific ranges of
composition. Although there are few samples
per taxon, these data nonetheless imply that
the region had a range of habitats partitioned
by different taxa according to feeding strategy.
We interpret the high and intermediate d13C
values for Equus sp. as indicating the presence
of a grass-dominated habitat, most likely with
a mix of C3 and C4 grasses. We cannot rule
out (C3) browsing (e.g., Berger, 1986; see also
GEOLOGY, August 2005
Feranec and MacFadden, 2000) or migration
between different habitats. Nonetheless, some
d13C values for fossil Equus sp. approach pure
C4 graze, and in the southeastern United
States, C3 and C4 grasses always coexist today. The simplest interpretation is that grasslands or savannas were present nearby with a
mix of C3 1 C4 grasses (e.g., Koch et al.,
1998).
In contrast, the lowest d13C values for P.
mirifica 1 T. veroensis 1 O. virginianus imply the presence of closed-canopy (deep) forest, again consistent with Koch et al. (1998).
We interpret the moderate d13C values for H.
macrocephala to indicate more open woodlands, although the higher values for H. macrocephala suggest mixed feeding (Feranec
and MacFadden, 2000; Feranec, 2003). Because higher d13C and d18O compositions correlate for H. macrocephala, it is possible that
its diet changed seasonally, from winter
browse to summer graze. We view M. jeffersoni compositions cautiously, but they are
consistent with expectations that it was a forest dweller that browsed on leaves, twigs, and
perhaps nuts (Kurten and Anderson, 1980, p.
138), which would yield low d13C and low
d18O values (Kohn, 1996). The unusually low
isotopic variability could reflect its unusual
diet, or alternatively point to diagenetic alteration of orthodentine.
Overall, the carbon isotope data for the
herbivores indicate a mix of habitats occupied
and partitioned by different species—
grassland (Equus sp.), relatively open woodland (H. macrocephala, and closed-canopy
forest (P. mirifica, T. veroensis, O.
virginianus)—similar to the mix of habitats
observed today. The large compositional ranges exhibited by Equus sp. (modern and fossil),
H. macrocephala, and modern O. virginianus
are consistent with opportunistic exploitation
of a variety of food resources and/or habitats,
as exhibited today by Equus sp. and O. virginianus. The more restricted ranges for the
other herbivorous taxa may indicate more restricted diets, i.e., niche partitioning. It is noteworthy that d13C values for modern deer, if
corrected for fossil fuel burning, would span
219‰ to 28‰ (Fig. 2; Land et al., 1980;
Cormie and Schwarcz, 1994; Clementz and
Koch, 2001), indicating that deer now range
at minimum from deep forest to mixed marginal woodland-grassland habitats. The Pleistocene megafauna extinction apparently allowed deer to expand into the newly available
niches; conceivably dietary opportunism conferred extinction resistance to deer (Graham
and Lundelius, 1984).
The two carnivores show differences in isotope composition that reflect their diets and
presumed habitat preferences. In both cases,
d13C values #210‰ suggest that woodland
herbivores were their primary prey. However,
S. fatalis appears to have consumed prey from
marginal areas between open woodlands and
grasslands, whereas C. armbrusteri occupied
deeper forest to open woodland. The small vs.
large compositional ranges for S. fatalis vs. C.
armbrusteri suggest rather restricted vs. more
varied diets, i.e., S. fatalis may have consumed prey from marginal areas exclusively,
whereas C. armbrusteri hunted and/or scavenged in a larger range of habitats. An open
woodland or mixed woodland-grassland habitat for S. fatalis is consistent with limb-bonelength ratios, which strongly suggest it was an
ambush predator (Gonyea, 1976; van Valkenburgh and Sacco, 2002). Similarly low d13C
values for S. fatalis were interpreted to indicate preferential predation of C3 consumers at
La Brea, California (Feranec, 2004). However,
this inference is not very restrictive ecologically as grasslands containing C3, not C4,
grasses have now been inferred there (Coltrain
et al., 2004), and there is little isotopic distinction among (C3) forests, C3 grasslands, or
mixed open woodland plus C3 grassland. Our
data are the first that unequivocally demonstrate low d13C values for S. fatalis and C.
armbrusteri, despite the presence of C4 grasses. Clearly, if these two carnivores did not ex651
clusively hunt in the grasslands, then some
other carnivore could have exploited this habitat. M. inexpectatus had the limb morphology
of a pursuit predator (van Valkenburgh and
Sacco, 2002) and likely filled this niche.
In sum, the inferred habitats of late Irvingontonian South Carolina (ca. 400 ka) were
likely quite similar to modern conditions, as
expected from the comparability of insolation
and of deep-sea records at 400 ka vs. today
(e.g., Droxler et al., 2003). The grassland, forest, and deep forest were partitioned among
various herbivores and carnivores. Apparently
S. fatalis preferred mixed grassland-forest,
consistent with limb morphologies, whereas
C. armbrusteri preferred forests, but possibly
exploited a greater range of habitats.
ACKNOWLEDGMENTS
We thank all the volunteer collectors, especially
Vance McCollum. Special thanks to J.M. Law for
laboratory assistance and to Rich Familia, Giant Resource Recovery, Inc., and the staff of the Giant
Cement quarry, Harleyville, South Carolina, for access to and support at the fossil site. Field work was
supported by the Palmetto chapter of the Explorer’s
Club. Analytical work was funded by National Science Foundation grant EAR-9909568 to Kohn.
REFERENCES CITED
Berger, J., 1986, Wild horses of the Great Basin:
Social competition and population size: Chicago, University of Chicago Press, 326 p.
Bryant, J.D., Froelich, P.N., Showers, W.J., and
Genna, B.J., 1996, A tale of two quarries; biologic and taphonomic signatures in the oxygen isotope composition of tooth enamel phosphate from modern and Miocene equids:
Palaios, v. 11, p. 397–408.
Cerling, T.E., and Harris, J.M., 1999, Carbon isotope fractionation between diet and bioapatite
in ungulate mammals and implications for
ecological and paleoecological studies: Oecologia, v. 120, p. 347–363, doi: 10.1007/
s004420050868.
Clementz, M.T., and Koch, P.L., 2001, Differentiating aquatic mammal habitat and foraging
ecology with stable isotopes in tooth enamel:
Oecologia, v. 129, p. 461–472.
Coltrain, J.B., Harris, J.M., Cerling, T.E., Ehleringer,
J.R., Dearing, M.-D., Ward, J., and Allen, J.,
2004, Rancho La Brea stable isotope biogeochemistry and its implications for the palaeoecology of late Pleistocene, coastal southern California: Palaeogeography, Palaeoclimatology,
Palaeoecology, v. 205, p. 199–219, doi:
10.1016/j.palaeo.2003.12.008.
Cormie, A.B., and Schwarcz, H.P., 1994, Stable isotopes of nitrogen and carbon of North American white-tailed deer and implications for paleodietary and other food web studies:
Palaeogeography, Palaeoclimatology, Palaeoecology, v. 107, p. 227–241, doi: 10.1016/
0031-0182(94)90096-5.
Cronin, T.M., Szabo, B.J., Ager, T.A., Hazel, J.E.,
and Owens, J.P., 1981, Quaternary climates
and sea levels of the U.S. Atlantic Coastal
Plain: Science, v. 211, p. 233–240.
Droxler, A.W., Poore, R.Z., and Burckle, L.H.,
2003, Earth’s climate and orbital eccentricity:
The marine isotope stage 11 question: Wash-
652
ington, D.C., American Geophysical Union,
240 p.
Edwards, L.E., Gohn, G.S., Bybell, L.M., Chirico, P.G.,
Christopher, R.A., Frederiksen, N.O., Prowell,
D.C., Self-Trail, J.M., and Weems, R.E., 2000,
Supplement to the preliminary stratigraphic database for subsurface sediments of Dorchester
County, South Carolina: U.S. Geological Survey
Open-File Report 00-049-B, http://pubs.usgs.
gov/of/of00-049/ChapB/ChapBtxt.html.
Feranec, R.S., 2003, Stable isotopes, hypsodonty,
and the paleodiet of Hemiauchenia (Mammalia, Camelidae), a morphological specialization creating ecological generalization: Paleobiology, v. 29, p. 230–242.
Feranec, R.S., 2004, Isotopic evidence of sabertooth development, growth rate, and diet from
the adult canine of Smilodon fatalis from Rancho La Brea: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 206, p. 303–310,
doi: 10.1016/j.palaeo.2004.01.009.
Feranec, R.S., and MacFadden, B.J., 2000, Evolution of the grazing niche in Pleistocene mammals from Florida: Evidence from stable isotopes: Palaeogeography, Palaeoclimatology,
Palaeoecology, v. 162, p. 155–169, doi:
10.1016/S0031-0182(00)00110-3.
Friedli, H., Loetscher, H., Oeschger, H., Siegenthaler, U., and Stauffer, B., 1986, Ice core record
of the 13C/12C ratio of atmospheric CO2 in the
past two centuries: Nature, v. 324,
p. 237–238.
Gonyea, W.J., 1976, Behavioral implications of
saber-toothed felid morphology: Paleobiology,
v. 2, p. 332–342.
Graham, R.W., and Lundelius, E.L., Jr., 1984, Coevolutionary disequilibrium and Pleistocene
extinctions, in Martin, P.S., and Klein, R.G.,
eds., Quaternary extinctions; a prehistoric revolution: Tucson, University of Arizona Press,
p. 223–249.
Gröcke, D.R., 1997, Stable-isotope studies on the
collagenic and hydroxylapatite components of
fossils: Palaeoecological implications: Lethaia, v. 30, p. 65–78.
International Atomic Energy Agency, 1992, Statistical treatment of data on environmental isotopes in precipitation: Vienna, International
Atomic Energy Agency Technical Report
no. 331: 781 p.
Kierdorf, U., and Kierdorf, H., 2000, Comparative
analysis of dental fluorosis in roe deer (Capreolus capreolus) and red deer (Cervus elaphus): Interdental variation and species differences: Journal of Zoology, v. 250, p. 87–93.
Koch, P.L., 1998, Isotopic reconstruction of past continental environments: Annual Review of Earth
and Planetary Sciences, v. 26, p. 573–613, doi:
10.1146/annurev.earth.26.1.573.
Koch, P.L., Tuross, N., and Fogel, M.L., 1997, The
effects of sample treatment and diagenesis on
the isotopic integrity of carbonate in biogenic
hydroxylapatite: Journal of Archaeological
Science, v. 24, p. 417–429, doi: 10.1006/
jasc.1996.0126.
Koch, P.L., Hoppe, K.A., and Webb, S.D., 1998,
The isotopic ecology of late Pleistocene mammals in North America: Part 1, Florida: Chemical Geology, v. 152, p. 119–138, doi:
10.1016/S0009-2541(98)00101-6.
Kohn, M.J., 1996, Predicting animal d18O: Accounting
for diet and physiological adaptation: Geochimica et Cosmochimica Acta, v. 60, p. 4811–4829,
doi: 10.1016/S0016-7037(96)00240-2.
Kohn, M.J., 2004, Tooth enamel mineralization in
ungulates: Implications for recovering a primary isotopic time-series: Comment: Geochimica et Cosmochimica Acta, v. 68,
p. 403–405.
Kohn, M.J., and Cerling, T.E., 2002, Stable isotope
compositions of biological apatite: Reviews in
Mineralogy and Geochemistry, v. 48,
p. 455–488.
Kohn, M.J., Schoeninger, M.J., and Valley, J.W.,
1998, Variability in herbivore tooth oxygen
isotope compositions: Reflections of seasonality or developmental physiology?: Chemical
Geology, v. 152, p. 97–112.
Kohn, M.J., Miselis, J.L., and Fremd, T.J., 2002,
Oxygen isotope evidence for progressive uplift of the Cascade Range, Oregon: Earth and
Planetary Science Letters, v. 204, p. 151–165,
doi: 10.1016/S0012-821X(02)00961-5.
Kurten, B., and Anderson, E., 1980, Pleistocene
mammals of North America: New York, Columbia University Press, 442 p.
Land, L.S., Lundelius, E.L.J., and Valastro, S.,
1980, Isotopic ecology of deer bones: Palaeogeography, Palaeoclimatology, Palaeoecology,
v. 32, p. 143–151, doi: 10.1016/00310182(80)90037-1.
Lee-Thorp, J.A., Sealy, J.C., and van der Merwe,
N.J., 1989, Stable carbon isotope ratio differences between bone collagen and bone apatite,
and their relationship to diet: Journal of Archaeological Science, v. 16, p. 585–599.
Leithead, H.L., Yarlett, L.L., and Shiflet, T.N., 1971,
100 native forage grasses in 11 southern
states: Washington, D.C., U.S. Department of
Agriculture Soil Conservation Service, 216 p.
MacFadden, B.J., 2000, Cenozoic mammalian herbivores from the Americas: Reconstructing
ancient diets and terrestrial communities: Annual Review of Ecology and Systematics,
v. 31, p. 33–59, doi: 10.1146/annurev.
ecolsys.31.1.33.
Morgan, G.S., and Hulbert, R.C., Jr., 1994, Overview of the geology and vertebrate biochronology of the Leisey Shell Pit local fauna,
Hillsborough County, Florida, in Hulbert,
R.C., Jr., et al., eds., Early Pleistocene of Florida: Florida Museum of Natural History Bulletin, v. 37, p. 1–92.
Palmqvist, P., Groecke, D.R., Arribas, A., and Farina, R.A., 2003, Paleoecological reconstruction of a lower Pleistocene large mammal
community using biogeochemical (d13C, d15N,
d18O, Sr:Zn) and ecomorphological approaches: Paleobiology, v. 29, p. 205–229.
Passey, B.H., Cerling, T.E., Perkins, M.E., Voorhies,
M.R., Harris, J.M., and Tucker, S.T., 2002, Environmental change in the Great Plains: An
isotopic record from fossil horses: Journal of
Geology, v. 110, p. 123–140, doi: 10.1086/
338280.
Szabo, B.J., 1985, Uranium-series dating of fossil
corals from marine sediments of southeastern
United States Atlantic Coastal Plain: Geological Society of America Bulletin, v. 96,
p. 398–406.
van Valkenburgh, B., and Sacco, T., 2002, Sexual
dimorphism, social behavior, and intrasexual
competition in large Pleistocene carnivorans:
Journal of Vertebrate Paleontology, v. 22,
p. 164–169.
Manuscript received 17 December 2004
Revised manuscript received 18 February 2005
Manuscript accepted 21 February 2005
Printed in USA
GEOLOGY, August 2005