PaleoBios 20( l):l-6, April 15, 2000
1   20(10 I'niversin of California Museum of Paleontology
Terminal Pleistocene armadillo {Dasypus) remains
from the Ozark Plateau, Missouri, USA
BLAINK W. SCHUBERT1 and RUSSELL W. GRAHAM2
'Geology Section, Research and Collections Center, Illinois State Museum, Springfield, II. 62703;
2Earth and Space Sciences, Denver Museum of Natural History, Denver, CO 80205
Seven osteoderms, tentatively referred to Dasypus cf. /). bcllns, were recovered from excavations in the entrance of
Little Beaver Cave (LBC), Missouri. Morphologically, /). bdlus (beautiful armadillo) is a poorly defined species and
its relationship to other extinct Dasypodidae and the extant D. novemcinctus(nine-banded armadillo) has not been
adequately established. An accelerator mass spectrometer radiocarbon date (11,000 + 60 yr B.P.) on a buckler
osteoderm from LBC represents a new terminal date for Dasypodidae in the contiguous United States, prior to the
historic invasion by /). novemcinctus in the latter half of the 19th century. The LBC nonanalog fauna ranges in age
from - 13,000 10,000 yr 15.P., and is composed of >3() mammal species with four extinct and eight extralimital
taxa. Morphological similarities suggest that late Pleistocene Dasypus had thermal tolerance levels like /).
novemcinctus. If this inference is correct, the association of a strong boreal component with Dasypus at LBC
suggests high levels of equability (reduced seasonality) for the terminal Pleistocene Ozarks.
INTRODUCTION
The (jugulates (Dasypodidae, Pampatheriidae, and
Glyptodontidae) first appear in the North American fossil
record late in the Biancan Land Mammal Age (late
Pliocene). Their arrival was but a small part of a faunal
interchange that occurred between North and South
America following the development of a land connection
between the continents. In North America, the oldest
armadillo remains of the family Dasypodidae are assigned to
Dasypus bdlus (Simpson 1929) and are from the late
Pliocene of Florida (Webb 1974; Robertson 1976) and
Nebraska (Voorhics 1987; as Dasypus cf. D. bdlus). No
other extinct dasypodids have been described from North
America. Dasypus bcllns (beautiful armadillo) has been re-
ported from over 50 localities, all from within the contigu-
ous United States.
The only extant armadillo in North America is the nine-
banded armadillo (Dasypus novemcinctus Linnaeus 1758).
Although this species currently inhabits much of the eastern
United States, no prehistoric accounts have been verified
from the region. The apparent absence of D. novemcinctus
in the late Pliocene and Pleistocene of North America may
reflect the true absence of this taxon, or could be a result of
misidentifications of the larger form (D. bdlus) based on
size and/or chronologic placement. Other than size, no
morphological criteria exist in the literature for separating
these two forms. If the gray area between D. bdlus And D.
novemcinctus were not enough to cause taxonomic confu-
sion, the lack of D. bcllns identifications outside the United
States and existence of similar, yet uncompared, extinct
taxa from South America, further emphasize the need for
taxonomic work.
Here, we describe fossil osteoderms referred to Dasypus
cf. D. bdlus from latest Rancholabrean deposits in Little
Beaver Cave, Missouri, and briefly discuss the taxonomic
status and paleobiology of North American Dasypus. This
record represents a terminal date for the /). bdlus form and
currently marks the last occurrence of Dasypus'va the United
States before the late Holoccne migration of D.
novemcinctus.
LITTLE BEAVER CAVE
Location—Little Beaver Cave is located in south-central
Missouri (Phelps County) among the rolling, cave-rich hills
of the Ozark Plateau (Fig. 1). The exact location is on file
in the Missouri Speleological Survey database stored at the
Missouri Department of Natural Resources, Division of
Geology and Land Survey, Rolla, Missouri. The cave is
formed in Ordovician dolomite in the uppermost portion
of the Gasconade Formation. The entrance is at an eleva-
tion of 262 m on the west slope of Little Beaver Valley. The
Figure 1. Location of Little Beaver Cave (clot), other Late Glacial
(13,000-10,000 yr B.P.) records of Dasypus (triangles), and
distribution of modern   /).  novemcinctus (shaded area) (after
FAl'NMAP 1^94 1.
2
PALEOBIOS, VOL 20, NUMBER 1, 2000
passage length is relatively small (-150 m) and ends in a
breakdown room. Overall, the cave can be described as a
horizontal sinuous tube, choked with sediment. The en-
trance area was enlarged through sediment removal by a
previous owner during the 1960s and was used for storing
vehicles and other supplies (Schubert 1997). Prior to this
enlargement, sediments at the entrance were only about 1
m from the ceiling (Bretz 1956). The cave is discussed in
more detail by Schubert (1997). In 1991, Milton Varney of
St. James, Missouri discovered bones and teeth along the in
situ unexcavated north wall of the entrance and sent some
of the remains to Russ Graham at the Illinois State Museum
for identification. The representation of extinct species in
Mr. Varney's collection led to a small-scale systematic
excavation of the site in 1994 and 1995.
Fauna—The entrance deposit is the result of a low angle
talus flow thai entered the cave through the current en-
trance. Colluvial and fluvial movement of sediments from
the overlying hill slope was the mechanism responsible for
this aggradation. The remains in the deposit are highly
fragmentary, probably as a result of carnivore digestion,
trampling, and transport. Because any small to medium-
size animal could have used the entrance area for various
purposes, the taphonomy of the site is quite complex. The
relatively low levels of corrosion, high degree of fragmenta-
tion, dominance of small animal remains, and dimensions
of the cave suggests that small mammalian carnivores are
responsible for the bulk of the deposit (Schubert, in prepa-
ration).
The LBC fauna consists of at least 36 mammalian spe-
cies, including extinct, extralimital, and locally extant taxa.
Besides D. cf. D. bellus, the following extinct species are
represented: Mejjalonyx jeffersonii (Dcsmarcst 1822)
(Jefferson's ground sloth), Mylobyns nasutus (Leidy 1869)
(long-nosed peccary), and Platyjjonus cotnpressus Le Conte
1848 (flat-headed peccary). At least twenty-three percent
of the extant mammalian species recovered do not currently
occur in the local community. Recovered extralimital taxa
with modern counterparts occurring near or on the edge of
the Ozarks are Blarina cf. B. brevkauda (Say 1823) (north-
ern short-tailed shrew), Spermophilus (Ictidomys Allen 1877)
(ground squirrel), Microtus pennsylvanicus (Ord 1815)
(meadow vole), and Eretbizon dorsatum (Linnaeus 1758)
(porcupine). Further removed and highly boreal extralimi-
tal taxa include Tamiasciurus Troucssart 1880 (red squir-
rel), Cletbrionomys Tilesius 1850 (red-backed vole),
Phenacomys Merriam 1889 (heather vole or tree mouse),
and Microtusxanthof/natbus(Leach 1815) (yellow-cheeked
vole). Reptiles, amphibians, fish, and aquatic mollusks arc
also abundant in the deposit but have yet to be analyzed.
Additional reports are being prepared on the terrestrial
gastropods, reptiles, and amphibians (Mead and Schubert,
in preparation), and the mammalian fauna is described in
Schubert (in preparation). All specimens are cataloged in
the Geology Collections of the Illinois State Museum
(ISM).
Age—Seven accelerator mass spectrometric (AMS) ra-
diocarbon dates are available from the Little Beaver Cave
deposit (Schubert, in preparation). These dates range from
- 10,000 to 13,000 yr B.P. One of the dates (11,000 + 60
yr B.P. CAMS-24426) was on a Dasypus buckler osteoderm
like the one shown in big. 2. All dates were on XAD-
decalcified (purified) collagen protein (Stafford et al. 1991).
The target samples were prepared by Tom Stafford and the
dates were processed at the Lawrence Livermore National
Laboratory's ("enter for Accelerator Mass Spectrometry in
California.
SYSTEMATIC PALEONTOLOGY
Order: Xenarthra Cope 1889
Family: Dasypodidae Bonaparte 1838
Genus: Dasypus Linnaeus 1758
Species: Dasypus cf. D. bcllus (Simpson 1929)
Material —ISM 492803, one complete imbricating
osteoderm. ISM 495814, posterior section of imbricating
osteoderm. ISM 595909, 595910 and ISM 595912, three
undifferentiated osteoderms. ISM 595911, two buckler
osteodcrms (one was used for an AMS date and was not
cataloged).
Description—The osteoderms follow the typical mor
phology of specimens identified as D. bcllus (Fig. 2; Simpson
1929; Holmes and Simpson 1931; Kurten and Anderson
1980). Descriptive terminology follows Edmund (1985).
Using the methodology of Klippel and Parmalee (1984),
the complete imbricating osteoderm (ISM 492803) has a
maximum width of 10.5 mm and a maximum thickness of
3.8 mm. These measurements place the specimen in the
lower size range of D. bcllus, but still well above modern D.
novemcinctus as measured by Klippel and Parmalee (1984).
Three of the osteoderms (ISM 595909, 595910, and
595912) are heavily corroded and may have been digested
by carnivores.
Remarks—There is clearly a problem in the identifica
tion ol\ Dasypus bcllus. It has been over 70 years since G.G.
Simpson described D. bellus (as Tatu bcllus) from the
Seminole Field site in Florida (Simpson 1929). In the
diagnosis of the species, the only noted difference between
D. bellus and D. novemcinctus was the larger size of the
former. Simpson goes on to mention that D. bellus is
apparently closely related to D. novemcinctus, but may be
more closely related to extinct forms from South America.
Since Simpson's work, no additional criteria have been
given for separating the two North American Dasypus taxa.
Our intention in this report is not to assess whether the two
forms are conspecific, but to point out the tenuous nature
of their separation. Species descriptions require morpho-
logical criteria for justification and an etymology of the
given name. The description of D. bellus is lacking both
(Simpson 1929).
Some attempts have been made to quantify size differ-
ences in D. bellus and D. novemcinctus using osteoderms
SCHUBERT & GRAHAM-LATE PLKISTOCENF. ARMADILLOS

B
Figure 2. Dasypuscf. D. beUusostCoderms from Little Beaver Cave.
A. Imbricating band osteoderm, ISM492803. B. Buckler ostcoderm,
ISM59591L Scale bar- 1 cm.
(Klippcl and Parmalec 1984; Martin 1974). The high num-
ber of dense dermal osteoderms in armadillos accounts for
the abundance of these remains in some paleontological
sites. Buckler osteoderms are highly variable in size and
shape, and because there are so many in each individual
Dasypus specimen,  it  is difficult  to compare sizes. The
moveable imbricating band osteoderms are fewer in num-
ber and have been used to plot size ranges of D.
novemcinctus and D. bcllus (Martin 1974: Klippcl and
Parmalec 1984).
For Rancholabrean deposits imbricating osteoderms
identified as D. bellns vary greatly in width and thickness
(Table 1). In general the sites with more specimens have a
wider range of imbricating osteoderm sizes (e.g., Crank-
shaft Cave, MO, width O.R. 7.9-18.4 mm, mean 12 mm,
N = 221; from Klippcl and Parmalec 1984; table 3).
Although some of the Midsouth deposits tend to have
smaller average sizes (as noted in Klippcl and Parmalec
1984; Guilday and McCrady 1966) these sites also have a
low number of recovered osteoderms (e.g.. Cheek Bend
Cave, TN, width O.R. 7.6-12.0 mm, mean 9.9 mm, N =
10; from Klippcl and Parmalec 1984; table 3). Irvingtonian
and Blancan sites with Dasypus are not numerous, but
exceedingly large specimens have not been recovered. It is
important to note that the D. novemcinctus measured by
Klippcl and Parmalec do not reflect the extent of variation
in the modern population, as only three specimens were
analyzed. Thus the overlap between D. bcllus and modern
D. novemcinctus will certainly be larger as more 1).
novemcinctus comparative specimens are analyzed. Klippcl
and Parmalec (1984) imply this when they note that the
largest modern specimen they studied was approximately
half the weight of nine-banded armadillos reported from
Texas by Hall (1981).
Because no morphological characters are known for
separating the two North American Dasypus forms and
there is an ever increasing gray area in size distinction, some
identifications have tended to rely more on temporal and
biogeographic assumptions. For these reasons, we tenta-
tively identify the remains from I.BC as Dasypus cf. /).
bcllus. Until a thorough osteological analysis of Dasypodinac
is accomplished we will not understand the relationship of
D. bcllus to D. novemcinctus or other large dasvpodines
from other regions. Many basic questions have to be an-
Tablc 1. Summary of imbricating osteoderm measurements from Blancan-Pleistocene localities and modern comparatives (from Klippcl
and Parmalec 1984). Table includes the Blancan specimen from the Big Springs Local Fauna (Voorhies 1987) and the LBC specimen,
both identified as /). cf. /). bcllus. Measurements in millimeters.
Species/Age	Localities (N)	Osteoderms (N)	Width (O.R.)	Maximum Thickness (O.R.)
/). novemcinctus				
Recent	----------	342*	3.5-9.0	0.9-2.6
D. bcllus and				
D. cf. /). bellns				
Rancholabrean	14	474	5.9-18.4	1.9-7.1
Irvingtonian	1	21	6.2-10.3	2.7-6.8
Blancan	2	U	8.2-12.4	2.9-6.5
*Th
c mod
lern scutes are from three specimens which do not reflect the total range variation of the modern species.
4
PALEOBIOS, VOL 20, NUMBER 1, 2000
swered, for example, (1) whether or not D. bellus and D.
novemcinctus arc clinal and/or temporal variations of the
same paratypic species, and (2) if" D. bellus is conspccific
with extinct armadillos known from South America. If the
latter is the case, the generic status of D. bellus may need to
be scrutinized as well.
ZOOGEOGRAPHY, PALHOFCOLOGY AND
EXTINCTION
The smaller extant form, D. novemcinctus, is a recent
northern migrant. In fact, there are no unequivocal prehis-
toric records of its occurrence in the United States. Dalqucst
(1967) reported /). novemcinctus from the Slaton Quarry
(Illinoian) in Texas. Because of its temporal placement this
specimen is now considered to be a small D. bellus (Kurtcn
and Anderson 1980; Klippel and Parmalee 1984). The only
prehistoric Holocene specimen of D. novemcinctus in the
United States is an osteoderm roughly associated with a
- 3000 year old charcoal date from the base of a clay unit in
Miller's Gave, Texas (Patton 1963). The age of the
osteoderm is questionable because the specimen was in
surface sediments and could just as well represent an his-
toric armadillo (Lundelius 1967). Furthermore, it is also
possible that the dated charcoal has been redeposited.
Dasypus novemcinctus began to expand its range into Texas
in the mid to late 1800s and has continued to adjust its
northern range (Humphrey 1974; Klippel and Parmalee
1984). The species now covers much of central and eastern
North America (Fig. 1) where it thrives in warm moist
environments, ('old winter temperatures in the north and
aridity in the west seem to control its distribution.
Because the two North American variants of Dasypus are
morphologically similar, D. novemcinctus has been used as
an ecological analog for D. bellus (Slaughter 1961; Kurtcn
and Anderson 1980; Klippel and Parmalee 1984). The diet
of/), novemcinctus consists mainly of insects (McBcc and
Baker 1982), and it is thought that the availability of insect
food must therefore have played a major role in the distri-
bution of D. bellus. Reliance on insects implies that food
sources could be limited by winter seasonal extremes, and
thus survival of the species relied on temperatures above
freezing (McNab 1980). In addition to the problem of
starvation during cold spells, Dasypus have a high thermal
conductance, a low metabolic rate, and do not hibernate,
which makes even relatively short periods of freezing tem-
peratures fatal (McNab 1980).
Modern /). novemcinctus are quite variable in size
throughout their range (Wetzel and Mondolfi 1979; Hall
1981; Klippel and Parmalee 1984). This confirms the no-
tion that Dasypus is somewhat plastic in size. Although the
larger Dasypus variant could not physiologically survive
severe winter extremes (as discussed in McNab 1980), it
seems reasonable that Dasypus under less seasonal extremes
(particularly fewer number of days at freezing or below), in
conjunction with an overall cooler climate, would find
increased  size advantageous (Bergmann's rule).  It also
seems plausible, knowing the rapid dispersal potential of
modern Dasypus, that D. bellus could have had cyclic distri-
bution fluctuations moving into more northern areas din-
ing times of reduced seasonality.
Dasypus disappeared from North America at the end of
the Pleistocene. Whether or not this marks the extinction
of a species or extinction of a variant that lives on today in
the comparatively smaller D. novemcinctus has yet to be
determined. The terminal record for Pleistocene Dasypus in
North America is the 11,000 + 60 yr B.P. date reported
here. Prior to this analysis, the latest date for D. bellus was
from Blackwater Draw, New Mexico, where the youngest
associated date was 11,040 + 500 yr B.P. on carbonized
plants (Graham 1987; FAUNMAP Working Group 1994).
Dates of -9,550 yr B.P. (Ben Franklin local fauna, Texas;
Slaughter and Hoover 1963) and -7,200 yr B.P. (Miller
Gave, Texas; Patton 1963) have also been given as terminal
dates for D. bellus. These dates are now considered to be
erroneous because they were either on weakly associated
charcoal or conventional "bone collagen," which gives only
a minimum date.
In their review, Klippel and Parmalee (1984) note that
many faunas in North America contain both boreal mam-
mals and the "cold intolerant" Dasypus. Conventionally,
such faunas have been interpreted as either representing a
temporally mixed assemblage or an ecological community
that no longer exists due to changes in environment and
climate. New methods of radiocarbon dating individual
bones using specific amino acids (Stafford ct al. 1987;
Stafford et al. 1991) confirms that late Pleistocene commu-
nities were composed of species whose modern distribu
tions are disjunct (Stafford et al. 1999). This supports the
hypothesis that mammalian species react to climatic and
environmental change based on their own tolerance limits
and that biological communities are far from static. Among
the dated taxa by Stafford ct al. (1999) that were shown to
have co-existed temporally, were D. bellus and the boreal
Microtus xanthognathus, a species that is only found today
in Alaska and Northern Canada. Approximately 2400 km
separates the modern distributions of /). novemcinctus and
M. xanthognathus. The presence of the relatively cold
intolerant Dasypus with the boreal M. xanthognathus has
been referred to as a nonanalog association (Stafford et al.
1999) and is strong evidence that reduced levels of season
ality (compared to today) characterized some areas during
the late Pleistocene (Hibbard 1960; Graham and Mead
1987).
Although /). bellus has been recorded from numerous
Rancholabrean sites with boreal mammals, the I.BG fauna
is the first terminal Pleistocene locality with this disjunct
association. The mammalian fauna from LBC is
nonanalogous, with 23% of the mammals being extralimi-
tal, most of which occur exclusively in more boreal habitats
today. The strong boreal component in association with
SCHUBERT & GRAIIAM-IATE PLEISTOCENE ARMADILLOS
5
Dasypus suggests high levels of equability for the latest
Pleistocene Ozarks. The complete absence of Dasypus at
the beginning of the Holocene in North America may
reflect an inability of this animal to adapt to rapid climatic
change and the onset of colder winters.
ACKNOWLEDGEMENTS
We wish to thank the landowner Debra Beaty and the
Illinois State Museum for their support in the Little Beaver
Cave project. Thanks to Milton Varney whom discovered
the deposit and brought it to the attention of the Illinois
State Museum. We greatly appreciate the excavation assis-
tance of Rick Toomey, Dustin Schubert, Tom Stafford,
Wayne Luzardi, Mike Held, and Bjorn Held. Our thanks
are extended to Lee Anna and Sara Graham for help with
screenwashing matrix. We thank Greg McDonald, Tony
Barnosky, and an anonymous reviewer for their critical
reviews and Jim Mead for comments on an earlier version
of this manuscript. Portions of the Little Beaver Cave
project were funded by grants from the Missouri Speleo-
logical Survey, the Quaternary Studies Program, Flagstaff,
Arizona, and the Illinois State Museum.
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