of Locomotory Adaptations:
specimen was the first virtually complete specimen of Thylacoleo
to be found and provides the basis for limb comparisons with those of mammal
species whose locomotory habits are known.
Howell (1944), Hildebrand (1954, 1961), Smith and Savage (1956) and Savage
(1977) have discussed various indices of intra- and inter-limb lengths
which are distinctive of different mammalian locomotory methods.
The morphological trends which become evident include the retention of
the primitive attribute of a somewhat shorter fore- than hind limb in quadrupedal
walking animals, the elongation of the distal limb structures in cursorial
forms (e.g. ungulates) and for the evolution of short yet strong legs in
fossorial and swimming species. However, one should bear in mind
that the forelimb may serve functions apart from locomotion, which may
modify the adaptation of the limb.
reconstruction of Thylacoleo carnifex. Courtesy: Mauricio
In this preliminary examination (Finch, 1982), measurements were made of
the length of the vertebral column (taken as atlas - last lumbar vertebra),
humerus, radius, metacarpal 3, femur and tibia. Attention was only
given to the Marsupialia, although the placental lion (Panthera leo)
was included for comparison. Skeletal elements from the collections
of the Western Australian Museum were made available by Dr. W. D. L. Ride.
Figures in parentheses give the number of specimens from which measurements
were made, and where possible, the measurements of both right and left
limbs of each animal were procured.
Family Dasyuridae: [Antechinus flavipes (1), Dasyurus geoffroii
( I ), Sarcophilus harrisii ( I )]
Families Thylacomyidae and Peramelidae: [Macrotis lagotis (1), lsoodon
Families Petauridae and Phalangeridae: [Pseudocheirus occidentalis
Family Vombatidae: [Lasiorhinus lalifrons (2), Vombatus
Family Phascolarctidae: [Phascolarctos cinereus (2)]
Families Macropodidae and Potoroidae: [Macropus sp. (1), Bettongia
The most useful comparisons which can be made in the instance of the Moree
are: (a) humerus + radius + metacarpal 3 / length of vertebral column (atlas
to last lumbar) x 100; (b) length of forelimb / length of hind limb x 100;
(c) length of tibia / length of femur x 100; (d) length of radius / length
of humerus x 100. The frequently used ratio of hind limb to vertebral
column length could not be evaluated since the pes was missing from the
Ratio (a), forelimb/vertebral column, distinguishes cursorial and saltatorial
forms. Animals belonging to the first two groups have a tendency
to exhibit comparatively long forelimbs in relation to the length of the
vertebral column. The forelimbs of Thylacoleo are notably
longer than those of such species as the arboreal Pseudocheirus
and Trichosurus and the smaller, cursorial
The ratios for the fossorial wombats, Vombatus and Lasiorhinus,
and the essentially saltatorial Bettongia,
Isoodon and Antechinus
are low, ranging from 43 to 53.
Ratio (b), the intermembral index, correspondingly allows the division
of cursorial and arboreal from saltatorial animals. It is notable,
however, that wombats tend to have limb ratios which are similar to those
of climbing animals. Again, Thylacoleo is grouped among the
larger, carnivorous forms.
Within the hind limb, the tibia/femur index (c) has been observed by Howell
(1944) to be high in saltatorial animals and in high-speed runners, but
low in walking forms such as cattle, lions, and hyenas. In this index,
can be placed amongst the placental lion and wombats. Obviously,
could not have been a speedy, cursorial animal and its femoro-tibial index
of 82 does not approach that of the arboreal possums,
and Pseudocheirus (102-103). The difference between Thylacoleo
and Sarcophilus is generally about 100 in unspecialised animals,
ris-approximately equal length.
The final ratio, (d), that of radius/humerus is usually 100 in unspecialised
animals, moving up to 140 in saltatorial types, to 120 in swift cursorial
forms and dropping down below 100 in fossorial and walking varieties.
The placental lion has a humero-radial index of merely 90 (Howell 1944)
regardless of its ability to make short bursts of speed. Among the
marsupials, Thylacoleo displays a much higher index (115) than its
placental counterpart and it is therefore grouped with animals which are
adapted to climbing rather than running or walking.
How the koala (Phascolarctos) is categorized among the four ratios
presents something of a puzzle. It appears close to Thylacoleo
in each instance, and there is reasonable dissimilarity in its indices
from those of the other arboreal marsupials, the possums. Archer
(1976) however, proposes that the Phascolarctidae and their close relations
the Vombatidae evolved directly from diprotodont ancestors bearing selenodont
teeth and that the Phalangerids are a completely independent evolutionary
lineage from the basic stock. This theory has gained support from
comparative serology studies performed by Kirsch (1977). If this
is the case, the divergence between the adaptations of koalas and possums
is not surprising.
Judging from the limb proportions studied, Thylacoleo appears to
have been a cursorial marsupial which was not capable of rapid locomotion.
It exhibited no climbing adaptations, although the relatively long radius
places it among the arboreal and saltatorial forms which have forelimbs
that are commonly used for manipulative and food gathering purposes as
well as for locomotion.
Based upon present studies, the image that has been formed of Thylacoleo
is that of a robustly built animal which normally has a deliberate walk,
but that may have also been capable of short bursts of speed. The
unusually long forelimb with its enormous claw on the first digit was probably
used in manipulating food toward the mouth, and would indicate a predatory
rather than scavenging nature. The pseudo-opposability of Thylacoleo's
powerful first digit suggests a scansorial habit to Wells and Nichol (1977)
and, considering the phalangerid characteristics of the Thylacoleonidae,
this may have been the case. Thylacoleo, the "pouched lion" may
have been more aptly named Thylacopardus or "pouched leopard" if
the complete skeleton had been available for examination in the nineteenth