Wells, Horton and Rodgers, (1982) have conducted studies of the morphology
and development of wear patterns on the teeth of the species Thylacoleo
carnifex. They examined the striations produced by the grinding
of food against the tooth enamel of known carnivores and herbivores and
compared their findings with similar marks on the fossil teeth of Thylacoleo.
The wear patterns created by food passing down the enamel surface of the
Thylacoleo
teeth were similar to those present on the teeth of known carnivores but
were not like those seen on herbivore teeth. They resolved that the
mandibular (lower) teeth retained a stabbing or piercing action, while
the maxillary (upper) teeth functioned as both an anvil against which food
is held and a "stone" against which the lowers are sharpened. Thylacoleo's
large premolars have a crescent-shaped slicing edge. As these
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| The
enormous upper incisor teeth are well preserved and easily visible in this
specimen of a Thylacoleo skull. The reddish ochre colouration
of this fossil is caused by a thin coating of silt particles rich in iron
oxide. Most of the cave fossils found in South Australia exhibit
this characteristic. If the encrustation is completely removed, such
bones are often surprisingly white, and have the appearance of being quite
recent. |
|
edges
pass each other during a bit, all the shearing forces are directed upon
two converging points.This action is further emphasized by the fine serrated
enamel margins of the teeth, which generate an effect similar to the cutting
edge of a steak knife.
Also, wear on the maxillary incisors created a blunted, semi-circular wear
surface; in contrast, wear on the mandibular incisors held a sharp triangular
outline from which fine, serrated ridges descended. Examination of
the jaw mechanics of the complete Thylacoleo material indicates
a possum-like jaw musculature designed for stabbing with the mandibular
incisors and slicing with the enormous premolars. All evidence suggests
a carnivorous marsupial of diprotodontid ancestry, not a plant-eater. |
The adaptations of Thylacoleo's limb were for climbing and gripping
rather than running and walking, while the absence of interlocking canines
as a method of holding prey was compensated for by the large, hooded claw
of the thumb. Thylacoleo may well have seized prey by grasping it
with its powerful hands, then killed it by strangulation or suffocation
in a similar manner as do lions and cheetahs (Schaller, 1972); combined
use of incisors and premolars would quickly strip the prey's skeleton of
hide and flesh.
Solid evidence of thylacoleonid predation has come from examinations of
incised bones initially reported from Queensland (De Vis, 1883) and Victoria
(Spencer and Walcott, 1911) and more recently from Lancefield in Victoria
(Horton et al., 1979; Horton and Wright, 1981). Horton and Wright
(1981) studied deep v-shaped incisions on ribs and limb bones of kangaroos
and made note that "The Lancefield bones suggest that the species (Thylacoleo)
was a meat-eater and give no indication that it was a bone-crusher".
Their proposition gains support from the absence of completely severed
bones in coproloites (scats), characteristic of the bone-eating and crushing
Tasmanian devil (Sarcophilus harrisii).
What animals were preyed upon by Thylacoleo? Wells, Horton
and Rodgers (1982) note that the animal's size itself makes it an unlikely
predator of arboreal species, which are capable of moving through the highest
branches with ease.
|
The remains of Thylacoleo are often found in association with those
of the extinct leaf-eating kangaroos of the genus Sthenurus.
Possibly, Thylacoleo preyed upon these and other kangaroo species
and dragged its prey into trees, as does the leopard, removing it from
the reach of scavenging animals such as the Tasmanian devil. This
view harmonizes well with all of the available evidence and provides a
niche for a carnivore, which avoids competition with the thylacine (Thylacinus)
the only other large predatory Australian marsupial known to have existed.
Recent findings of fossil material |
.
Mandible
section of Sthenurus, an extinct genus of large kangaroos from the
Pleistocene epoch. Could this and
other
macropods have been the main prey of Thylacoleo?
This
specimen is from the Wellington Caves of New
South
Wales. Length - 125 mm. |
. |
have extended the geographic
distribution of Thylacoleo to the Pleistocene deposits of the Lake
Eyre Basin; indeed it is present in most Late Pleistocene faunas throughout
the whole of the Australian continent. With the exception of the
Victoria Cave Deposit at Naracoorte (Wells, et al., 1984), its numbers
are usually low, which is in agreement with an animal filling the niche
of top carnivore.
Thylacoleo appears to have vanished along with
many of the large marsupial herbivores during a time of great aridity which
occurred about 18,000 years ago. It was a period when the great ice
sheets of the northern hemisphere reached their maximum.
.
| Life
reconstructions of large, leaf-eating sthenurine kangaroos from the Pleistocene
deposits of Lake Callabonna in South Australia: Sthenurus tindalei
(background), and the much larger Sthenurus stirlingi in the foreground.
Courtesy: Frank Knight. |
Until quite recently,
Thylacoleo carnifex was the only representative
of the family Thylacoleonidae, but discoveries in mid-Tertiary sediments
of Queensland, the Northern Territory and South Australia (Archer and Wade,
1976; Archer and Rich, 1982; Clemens and Plane, 1974; Pledge, 1977) indicate
an older diversification of these fascinating marsupial carnivores (Archer
and Dawson, 1982). Presently, these earlier species are known mainly
from teeth, skull and jaw fragments. While much smaller in dimension
than
T. carnifex, species of the Tertiary, such as Wakaleo alcootensis,
Wakaleo
oldfieldi,
Wakaleo vanderleuri (mid-Miocene) and
T. hill
(? Pliocene), all exhibit the same characteristic slicing premolars of
their much larger Pleistocene relative. |
