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The post-cranial skeleton refers to all or part of the skeleton behind
the skull (cranium, mandibles and hyoid) i.e., the vertebrae, ribs, pelvis,
scapulae, clavicles and limb bones.
The number of vertebrae in Thylacinus is similar to that of Sarcophilus
and Dasyurus; 7 cervical, 13 thoracic, and 6 lumbar. However,
the thylacine has only two sacral vertebrae instead of three, as is the
case with the other two genera, and the tail has 25 vertebrae instead of
20 or 21 (Moeller 1968). Vestigial clavicles and epipubic bones are
the two most notable features of the post-cranial skeleton. |
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Thylacine
skeleton. Specimen Z 1919.330.46. Courtesy: National Museum
of Wales (Cardiff).
Photo: International Thylacine
Specimen Database 5th Revision 2013.
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Since the thylacine has evolved for running instead of climbing, the clavicles
have become narrow, curved structures 5 cm (2 in.) long (Cunningham 1882). |
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Thylacine
clavicles (circled). Courtesy: Museum Victoria specimen NMV C28178.
Photo: International Thylacine
Specimen Database 5th Revision 2013.
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The epipubic bones of the thylacine, though still present, have been reduced
to a pair of "small, oblong, flattened fibro-cartilages, imbedded in
the internal pillars of the abdominal rings, and (they) appear each
as a thickened part of the tendon of the oblique abdominal muscle, which
forms the above pillar" (Owen 1843).
In marsupials, the epipubic bones are often called the "marsupial bones"
because they are believed to help support the mother's pouch. However,
the fact that they are present in pre-marsupial fossil mammal taxa indicates
that these structures are of quite ancient evolutionary origin, and that
pouch support was not their original function.
Guiler
(1985) notes: "The marsupial bones are used as a support for the pouch
in other marsupials and it might be expected that an active predatory thylacine
carrying four young in its pouch would require more support to help carry
the young during hunting. There is nothing to suggest that the pouch
young quitted the pouch at an early stage thus reducing the load upon the
pouch and its supports. The reason for the rudimentary nature of
these bones must be a matter for speculation".
Modern-day researchers are of the opinion that the epipubic bones assist
in locomotion by supporting muscles that flex the thigh (White 1989). |
