OF THYLACOLEO CARNIFEX:
which is commonly referred to as the "marsupial lion", was a rather robustly
built Pleistocene animal which was approximately the size of a large leopard
or medium-sized African lion. It had a broad skull with a blunt rostrum
and forward facing binocular eyes. The dentition of
is among its most peculiar features. Its dental formula is expressed
as I 3/1, C 1/0, P 3/3, M 1/2. This dentition is essentially similar
to that of the phalangerid marsupials, except that there is a reduction
in the size and number of molars. Thylacoleo's enormous caniniform
maxillary first incisors, semi-procumbent, laniariform mandibular first
incisors, and the gigantic upper and lower slicing third premolars (P3/3)
are sure to attract the attention of even those who lack a specific interest
in mammalian dental anatomy!
The maxillary canine (C1/) along with the first two
premolars (P1/1, P2/2) are very reduced and generally considered to be
functionless. Thylacoleo's dentition is so very unique that
it has created a number of different views on the phylogenetic position
of the animal and generated great debates regarding its feeding habits.
Features of the skull, particularly the dentition, were virtually the only
evidence for early discussions of
Thylacoleo, as until quite recently,
the postcranial skeleton was only known from a few isolated limb bones
which had been recovered in the proximity of Thylacoleo skulls.
reconstruction of Thylacoleo carnifex.
Following will be an
explanation of the discovery and interpretation of the various pieces of
fossil material which have been found of Thylacoleo carnifex.
A functional interpretation of the feeding habits and locomotion of Thylacoleo
will be presented based upon examination of the known, as well as some
THE FIRST DISCOVERIES AND DESCRIPTIONS:
plate from an 1838 work by T.L. Mitchell depicting some of Owen's drawings
of fossils from the Wellington Caves of New South Wales. Among them
are teeth which would later be classified as those of Thylacoleo.
|| The first
evidence for the existence of
Thylacoleo came from some material
collected in the early 1830s from the Wellington Valley region, New South
Wales, by Major (later Sir) Thomas Mitchell. Incisor and premolar
teeth, now known to be of Thylacoleo, were depicted in Mitchell's
1838 work "Three Expeditions into the Interior of Eastern Australia", but
were not detailed in the Zoological Appendix to volume 2 contributed by
Professor Richard Owen, the well known English palaeontologist. Owen's
opinion (1877, vol. 1: 107) was that the premolar, the "large, two-fanged
sectorial tooth", was so extraordinary in form that it was quite impossible
to make a determination of the animal's characters without an examination
of more substantial material.
Afterward, Owen obtained
fragments of left and right maxillae, each including P3/
and M1/, and a section of a left dentary with P/3
intact but bearing only the roots of M/1 and M/2.
These specimens had been discovered in the bed of a tributary of the Condamine
River, Queensland, but no date of when they had been found was recorded.
Lydekker's 1887 "Catalouge of the Fossil Mammalia in the British Museum
(Natural History)" lists M3653 and M3654, the right and left maxillary
fragments of Thylacoleo from Queensland, as having been figured
by Owen in 1887 and bestowed by him to the Museum.
Owen described the material
from the Condamine River and commented on the position of the "working
surfaces" of both the maxillary and mandibular sectorials in his summary
of research on the fossil mammals of Australia (1877). He made note
of the vertical striae which could be seen on them and concluded that these
teeth functioned as shearing blades used in the cutting of meat.
However, he could find no indication of how the animal fit in taxonomically
among its marsupial or placental relatives.
Studies conducted by
M. E. Finch (1982) of the specimens M3653 and M3654 have shown the presence
of a well defined ridge near the posterior end of the wear facet of each
maxillary and mandibular "carnassial" and a second, more definite ridge
at the interrootial level on the occlusal surface of M3654. The latter
ridge is not developed in other specimens available for study and the former
is usually only a low boundary between the wear facets which result from
contact of the lower carnassial and the adjacent lower first molar.
Owen made mention that the ridges were similar to those seen in the sectorial
teeth of Felis spelaea and Hyena spelaea, however, on present
evidence is can be considered quite probable that the Condamine animal
had been afflicted with a deformity of, or damage to, its mandibular dentition
during life, leading to a peculiar wear pattern on the maxillary premolar.
Fragmentary skull material
of Thylacoleo was collected by W. Adeney in 1845 from his land at
Lake Colongulac, some eighty miles southwest of Melbourne, Victoria, and
was forwarded a year later by Dr. H. Hobson of Melbourne to Owen at the
British Museum. Included was a cranium with an incomplete posterolateral
surface and missing its zygomatic arches. Also in this series was
a maxillary fragment which retained the carnassial premolar and the single
molar, which was shown to be part of the fragmentary cranium. Owen
conceived that any valid interpretation of the similarities and functionality
of this amazing material could only be based upon detailed comparisons
of Thylacoleo with a variety of other mammals. Such examinations
were not completed until 1858, when Owen presented his research to the
Royal Society. Included in his account was information about a cast
of a mandibular section which he had received from Samuel Stutchbury, Geological
Surveyor of New South Wales. This cast consisted of much of the ramus
and included the carnassial premolar (P/3), M/1,
and the alveolus of M/2, and it easily indicated the
nature of the characters of the symphysis. This initial account of
was based upon fossil material from two widely separated locales, the skull
from Victoria and the mandible from King Creek, Darling Downs, Queensland.
The definitive description of the species was not published until 1859,
as only an abstract and an article 'Odontology' appeared in the 1858 edition
of the Encyclopaedia Britannica.
An even earlier reference
to Thylacoleo is to be found in Gervais' "Zoologie et Paleontologie
Francaises" published in sections between the years of 1848 and 1852, but
no dates are stated for the individual sections. Apparently, when
Gervais visited Owen in London in 1848, he was shown the lake Colungulac
fossils during a discussion on the affinities of Hyenodon, a placental
creodont which at the time was thought by many authorities to be a marsupial.
Gervais states in his book that Owen had named the Australian material
but provided no description of it. This reference to Thylacoleo
was apparently unknown to Stutchbury who, in a technical report (1853)
to the Colonial Secretary, had given the name Schizodon
to the original
specimen of the mandibular cast which he had provided to Owen after making
a comparison of the carnassial with that figured by Mitchell (1838).
Owen (1859) makes note that even if Schizodon Stutchbury had priority
over Thylacoleo, it was a homonym of Schizodon Agassiz and
Waterhouse, names which had been assigned to a fish in 1829 and to a mammal
in 1842, respectively.
In his paper of 1859,
Owen gave a condensed yet comprehensive description of the Lake Colongulac
and Darling Downs material. However, he stated Hodgson's Creek rather
than King Creek as the source of the mandible.
| In the
paper, he used the species name carnifex but did not specify a holotype
which has led Mahoney and Ride (1975) to record as syntypes both the cranium
and the mandible upon which Owen's description is based. Based upon
extensive comparisons between Thylacoleo and and the marsupial carnivores
(Sarcophilus) ursinus and Thylacinus harrisii, and
also with Felis spelaea, the placental cave lion, Owen had no doubt
that Thylacoleo was a marsupial. He pointed out its
large posterior palatal vacuities, the position of the basicranial foramina,
the participation (though a small one) of the alisphenoid in the auditory
bulla whilst the tympanic process was essentially free, the extension of
the lachrymal bone on to the face, the extraorbital position of the lachrymal
foramen and the rather small size of the brain in relation to skull size.
He proposed that Thylacoleo was most closely related to the dasyurids
and to Dasyurus ursinus in particular "although the interval be
still very great between them" (Owen 1859: 321).
famous British vertebrate palaeontologist Sir Richard Owen. He was
one of the first scientists to author accounts of Thylacoleo.