The Internal Anatomy
of the Thylacine - A Historical Perspective
Professor Daniel John Cunningham (1850-1909), was Senior Demonstrator
in Anatomy at the University of Edinburgh (1876-1882) and chronologically
thereafter Professor of Anatomy at the Royal College of Surgeons of Ireland
(1882-1883), Trinity College Dublin (1883-1903), and Edinburgh University
(1903-1909). Whilst acting as Demonstrator in Edinburgh, Cunningham
wrote an extensive report on the anatomy of the Marsupialia collected during
the voyage of HMS Challenger, a memoir which established his reputation
as an able, descriptive anatomist and capable elucidator of difficult morphological
problems (Thomson 1909). Much of what we know today about the internal
anatomy of the thylacine is derived from Cunningham's meticulous anatomical
dissections, and published as part of the HMS Challenger report in 1882
HMS Challenger farewell
to Sydney, June 8th 1874.
Artist - John J. Arthur.
Courtesy: State Library of Victoria.
The HMS Challenger expedition returned to England in 1876 after circumnavigating
the world to learn more about the oceans. Aboard were the remains
of a male and female thylacine, preserved in barrels of spirit, presented
by the Governor of Tasmania (Sir
Charles Du Cane) whilst Challenger was berthed in Sydney (1874).
(female) 1883-8-22 (10,11,12).
Courtesy: British Museum
Source: ITSD 5th Revision 2013.
"The male had manifestly
been received in a very putrid state, but its long immersion in strong
spirit had considerably improved its condition. The female was in
an admirable state of preservation, and it is consequently from it that
the majority of the drawings have been taken and the description framed.
A special interest is attached to the anatomy of this animal, from the
very prevalent belief that the genus of which it is the sole member is
rapidly becoming extinct. Thus Owen, writing in 1842 speaks of it
as a species "whose term of existence seems fast waning to its close".
Cunningham opens his
report with a detailed comparison of the musculature of the fore and hind
limbs of the thylacine (Thylacinus cynocephalus) with that of a
specimen of the Spotted
cuscus (Phalangista maculata =Spilocuscus
maculatus) and of the Red-tailed
Phascogale (Phascogale calura),
highlighting both their structural similarities and differences.
He details the origin and insertion of the various muscle groups with respect
to the three species.
Due to the reduction
of the clavicle in the thylacine, a rerouting of the muscles normally attached
to it was noted. The cleido-mastoid
is partially inserted into the inner portion of the clavicle and partly
joins the clavicular area of the deltoid muscle. The scapular section
of the deltoid muscle is enlarged, and unlike the dasyurids, there is no
spinal section. The subclavian muscle
|cannot be inserted into the upper margin
of the clavicle. Instead, it runs beneath the clavicle, changes direction,
and inserts into the fascia which covers the supraspinatus. The supinator
longus is not well developed, and the anconeus externus is absent.
As an adaptation to running however, the triceps is quite large.
Also, the pectoralis minor is rather well developed compared to its usually
small size in dasyurids. The pectoralis quartus is small and quite
Cunningham begins his
summary on the structure of the internal organs with comments on the pericardium
and its specific attachments before proceeding to discuss the external
appearance and internal structure of the heart. He notes that the
thylacine's heart is narrow, elongated and pointed with a very capacious
right auricle and its appendix, whilst showing no indication of bifurcation
is peculiar on account of its great breadth. Cunningham then discusses
his observations on the internal structure of the chambers of the heart
and concludes by noting two distinguishing features of the marsupial heart;
the absence of all traces of an annulus ovalis and fossa ovalis and the
peculiar position of the right auricle of the orifices of the great cardiac
Plate IV - Thylacine, from "The Voyage of H.M.S. Challenger"
1 - Internal aspect of the thigh.
2 - Dissection to show the gluteus quartus muscle.
3 - Marsupial pouch of the female.
4 - Dissection of the marsupial pouch - teats left in position.
5 - Gluteal region and outer aspect of the thigh.