Anatomy of Thylacoleo
of Australia's most fantastic beasts, the extinct Thylacoleo carnifex, or "meat-cutting marsupial lion,"
possessed a host of physical traits unseen in any single creature alive today.
These included features especially suited to a carnivorous hunter, including
retractable, catlike claws, a kangaroo's tail, and jaw muscles that
delivered a bite stronger than a lion's. Altogether, says paleontologist
Rod Wells, Thylacoleo
resembled something designed by committee. Referring back to the image at right, learn more below about the
marsupial lion's singular anatomy and what it reveals of the
animal's predatory life in Pleistocene Australia.—Rima Chaddha
and powerful, this is a tail befitting an active predator, yet its closest
match today is found in one of Australia's most famous herbivores, the
kangaroo. The tail contains narrow bones called chevrons that protect the
animal's blood vessels at the point where the appendage bends on the
ground. This bone structure allows kangaroos to tripod themselves for balance
when standing upright (see image at left). Experts believe Thylacoleo used its tail similarly after it caught its prey,
freeing its front paws to get a solid grip on its victim as its powerful jaws
dealt the deathblow.
carnifex held great strength in
its legs, but scars indicating that muscles attached low on its thighbones
suggest that it probably lacked the flexibility to move at high speed. This has
led some paleontologists to posit that the animal carefully stalked its prey
like Tasmanian devils and large cats do today, possibly dropping onto its
victims from trees. Despite its common name, however, the marsupial lion bears no
relation to the big cats. Note: The skeleton image at the top of this page is greatly foreshortened; the hind legs and forelegs are actually the same length.
claws and toes adapted for grasping show that the marsupial lion, which is thought to have lived
in a shrubby woodland environment, might have climbed trees. Indeed, one of its
nicknames is "drop cat" for its possible tactic of dropping onto
prey from trees. Similar skeletal structure and dexterity can be seen in
arboreal opossums today, giving their paws a handlike appearance, as seen here.
Front leg and
the great English anatomist Sir Richard Owen first described Thylacoleo in 1859, he called it one of the "fellest
and most destructive of predatory beasts." Scientists today, who unlike
Owen have articulated fossil skeletons to work with, concur with his
assessment. The animal had powerful front legs and large, slashing claws on its
thumbs, a trait unseen in any of its distant living herbivorous relatives. And
as on its hind paws, Thylacoleo's
forepaws had retractable claws, similar to those of a common house cat. The
marsupial lion probably used these claws to climb trees and to secure its prey
the koala, Thylacoleo was a
diprotodontian. Meaning "two front teeth," the term refers to the
two prominent incisors jutting from its lower jaw. It was due in part to this
morphology, which formed a forward dental structure analogous to a
parrot's beak, that many early experts maintained that Thylacoleo fed mainly if not solely on plants. But modern
anatomists disagree. Strong jaw muscles and sharp, shearing premolars gave the
marsupial lion what is believed to be the most powerful bite for its size of
any known species, living or extinct.
had a sizeable and highly
developed nasal cavity, which suggests that—not surprisingly for a
predator—it had a strong sense of smell. It would have used this ability
to track down its prey and probably also carrion to supplement its diet. In
addition, structures in the palate indicate the presence of a specialized organ
that could detect chemical scents called pheromones. These compounds help
the modern Tasmanian devil (left) and many other animals find mates by enabling males,
for one thing, to assess females' reproductive receptiveness.
scans and molds made from the inside of Thylacoleo's skull have allowed researchers to examine
the most obvious physical characteristics of the animal's brain. From the
size and prominence of the marsupial lion's cerebral lobes, scientists
have determined that the animal relied heavily on its keen senses of hearing,
sight, and smell. And as with modern predators like the tiger, other physical
structures such as Thylacoleo's
nasal cavity and the large nerves that led to its eyes support this.
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