The last of the three is _Thylacoleo carnifex_, so named on account of
its supposed carnivorous habits. In the adult the dentition (fig. 11)
is i. 3/1, c. 1/0, p. + m. 4/3, total 24. The first upper incisor is
much larger than the others; canine and first two premolars
rudimentary. In the lower jaw there are also one or two small and
early deciduous premolars; third premolars of both jaws formed on the
same type as that of the rat-kangaroos, but relatively much larger;
molars rudimentary, tubercular. The functional teeth are reduced to
one pair of large cutting incisors situated close to the middle line,
and one great, cutting, compressed premolar, on each side above and
below. As already mentioned, _Thylacoleo_ was originally regarded as a
carnivorous creature, but this view was subsequently disputed, and its
diet supposed to consist of soft roots, bulbs and fruits, with an
occasional small bird or mammal. Recently, however, the pendulum of
opinion has swung back towards the original view: and Dr R. Broom
believes _Thylacoleo_ to have been "a purely carnivorous animal, and
one which would be quite able to, and probably did, kill animals as
large or larger than itself." The affinities of the creature are
clearly with the phalangers.
By means of the little musk-kangaroo, the cuscuses and phalangers
constituting the family _Phalangeridae_, are so closely connected with
the kangaroos, or _Macropodidae_, that in the opinion of some
naturalists they ought all to be included in a single family, with
three sub-families. Theoretically, no doubt, this is correct, but the
typical members of the two groups are so different from one another
that, as a matter of convenience, the retention of the two families
seems advisable. From the _Phascolomyidae_, the two families, which
may be collectively designated Phalangeroidea, differ by the
circumstance that in the skull the tympanic process of the alisphenoid
covers the tympanic cavity and reaches the paroccipital process. The
tail is long and in some cases prehensile; the first hind-toe may be
either large, small or absent; the dentition usually includes three
pairs of upper and one of lower incisors, and six or seven pairs of
cheek-teeth in each jaw; the stomach is either simple or sacculated,
without a cardiac gland; and there are four teats.
With the exception of the aberrant long-snouted phalanger, the members
of the family _Phalangeridae_ have the normal number of functional
incisors, in addition to which there may be one or two rudimentary
pairs in the lower jaw. The first in the upper jaw is strong, curved
and cutting, the other two generally somewhat smaller; the single
lower functional incisor large, more or less inclined forwards;
canines 1/(1 or 0) upper small or moderate, conical and sharp-pointed;
lower absent or rudimentary; premolars variable; molars 3/3, or 2/2,
with four obtuse tubercles, sometimes forming crescents. Limbs
subequal. Fore-feet with five distinct subequal toes with claws.
Hind-feet short and broad, with five well-developed toes; the first
large, nailless and opposable; the second and third slender and united
by a common integument as far as the claws. Caecum present (except in
_Tarsipes_), and usually large. The lower jaw has no pocket on the
outer side. All are animals of small or moderate size and arboreal
habits, feeding on a vegetable or mixed diet, and inhabiting
Australia, Papua and the Moluccan Islands.
[Illustration: From Gould.