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The geographic distribution of the modern thylacine species, Thylacinus
cynocephalus, formerly extended throughout much of the Australian mainland
and New Guinea. Only within relatively recent times has the species
disappeared from these regions. Numerous examples of fossil and non-fossil
remains of the thylacine (dating from both the Pleistocene and Holocene)
have been found on the mainland, and there are many known depictions of
the thylacine in ancient Aboriginal rock art. A few fragments of
bone, found in association with a thylacine humerus discovered at Tunnel
Creek, Western Australia, have been radiocarbon dated at 0 ± 80
years BP, though this date may not apply to the humerus itself (Archer
1974). Apart from this discovery, the most recent finds are the 3,000
year old specimens from Padypadiy, Northern Territory (Calaby and White
1967) and Murray Cave, Western Australia (Archer 1974).
Palaeontological
evidence: |
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The classification of fossil thylacine material of Quaternary age has been
somewhat complicated because a number of nineteenth century taxonomists
failed to recognize the size variations which occur within T. cynocephalus.
For example, when DeVis (1894) received the left side of a skull discovered
at Ellagowan, on the Darling Downs, he made a comparison between it and
a single skull of the modern species. Finding the fossilized skull
to be somewhat larger, he declared it to be |
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| Plate
5 ("Cave Fossils") from Richard Owen's (1877) "Researches on
the fossil remains of the extinct mammals of Australia..." which depicts
Pleistocene marsupial fossils from the caves of New South Wales.
Included are some illustrations (second row of figures from the bottom)
of Thylacinus spelaeus (=cynocephalus). |
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that
of a separate species,
Thylacinus rostralis. Similarly, Thylacinus
breviceps was assumed by Krefft (1868) to be a small species, but was
actually an immature specimen of T. cynocephalus (Moeller 1968).
DeVis (1894) realized that T. major from the Wellington
Caves was identical to the widespread "cave tiger",
T spelaeus,
which Ride (1964) demonstrated to be the same as the modern species.
Ride (1964)
studied both fossil and recent examples of thylacine material from throughout
Australia. By measurement comparison, he was able to demonstrate
that T. spelaeus falls within the range of variation of T. cynocephalus.
However, he did not make a conclusive decision on T. rostralis,
commenting that the specimens found in the southwestern region of the continent
appeared to be smaller than average. To avoid the complications which
can occur when measuring juvenile skulls, Lowry (1972)
took measurements of the specimens' teeth, which do not grow continuously
throughout life. The fossils from the southwest were 10% smaller
than the average, and those from Eucla 13% smaller, but were still within |
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| the acceptable size range for a single
species. One could speak at length about the
studies which have been undertaken to verify the taxonomy of fossil thylacine
material of Quaternary age (Pleistocene and Holocene epochs). Historical
interest aside, this is unnecessary at this juncture, as it has been established
that all such specimens can be considered to belong to the modern species,
T.
cynocephalus. |
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Lateral
and dorsal views of a Pleistocene-age thylacine (T. cynocephalus)
skull found by palaeontologist R. A. Stirton at Lake Menindee, NSW, in
March 1953. Specimen UCMP 53038.
Courtesy:
Sarah Werning, University of California Museum of Paleontology (Berkeley).
Photos:
International Thylacine Specimen Database Sixth Revision (pending). |
Species names as
breviceps,
major,
rostralis
and spelaeus were used during the nineteenth century to describe
various Quaternary thylacine specimens from a number of different localities.
However, such names are no longer applied, as studies of said remains have
been unable to find any morphological distinctions which are significant
enough to warrant separate classifications. Variability in size can
be seen among specimens of Pleistocene and Holocene age from various localities,
with some being either somewhat larger or smaller than the average modern
T.
cynocephalus, but these size differences alone are not considered a
solid basis for making taxonomic distinctions. The size variations
are, most likely, simply due to factors such as sexual
dimorphism, or the particular environmental conditions under which
the animals lived. |
