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The thylacine is the largest marsupial carnivore to exist
into modern times. Although resembling a canid in its external
appearance, its dentition is unique. Below is a comparison between
the dental formula of the thylacine, fox and wolf. Dental formulae
are used to indicate the number of each type of tooth (Incisor,
Canine,
Premolar
and Molar) for a given species. The dental formula
refers to one side of the lower and upper jaw and is doubled to obtain
the total complement of teeth for the animal.
| . |
I |
C |
P |
M |
Total |
| Thylacine (Thylacinus cynocephalus) |
4/3 |
1/1 |
3/3 |
4/4 |
46 |
| Fox (Vulpes vulpes) |
3/3 |
1/1 |
4/4 |
3/2 |
42 |
| Wolf (Canis lupus) |
3/3 |
1/1 |
4/4 |
3/2 |
42 |
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Dentition
of the adult thylacine skull. View
diagrams of complete dentition.
Left: the premaxillary bone
(PB) bearing the incisor teeth (1-4)
and maxillary bone (MB) bearing the
canine tooth (1), premolars (1-3) and molar teeth (1-4). Right: The
dentary (D) or mandible bears all four
types of tooth - incisors (1-3) canine (1), premolars (1-3) and molars
(1-4).
Photos: International
Thylacine Specimen Database 5th Revision 2013.
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| The jaws of the thylacine
are long, and the teeth of moderate size. In contrast to some of
the more specialised dasyurids, in which the tooth row has undergone a
shortening, that of the thylacine is elongate.
The most remarkable feature pertaining to marsupial dentition is that these
mammals only possess one set of teeth that are homologous
to the milk teeth in placentals. In marsupials, the only tooth that
is ever replaced is the third premolar in both the upper and lower jaws
(Flower
1867). This normally occurs during the pouch period, and is
therefore rarely seen. |
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Historical preparation
of an adult thylacine skull with bone removed to expose the tooth roots.
Specimen: NMS Z1886.16.10.
Courtesy: National Museum of Scotland (Edinburgh).
Photo: Nicholas Ayliffe
- International Thylacine Specimen Database 5th Revision 2013.
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A thylacine skull is considered "adult" with the eruption of the fourth
upper molar teeth, or in the case of reduction of one or more of the last
molar teeth, M3 should be fully erupted. Historically, George
P. Harris (1808), in his type
description of the dental formulae of the thylacine wrote: "Twelve
molars
in the upper jaw and 14 in the lower". As such, Harris was describing
a specimen in which the upper fourth molars had not yet erupted, and therefore,
on the basis of the complete dental formula, not deemed fully adult.
This omission was remarked upon by Temminck (1824,
pp. 21-72):
He (Harris)
or those charged to publish his manuscript made a serious fault, since
it enumerates the number of molars to the upper jaw as 6 on each row or
12 in total contrary to the fact that one finds 7 molars
everywhere in the 2 jaws and that the total number of death
teeth is 4 more than the true Dasyurids. It is more than probable
that Harris gave the indication of the dental system of a juvenile animal
but in this case should have made mention of it". |
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Juvenile
(specimen NMS Z1993.70).
Courtesy: National Museum
of Scotland (Edinburgh). |
Adult (specimen
OUM 7935).
Courtesy: Oxford University
Museum of Natural History. |
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Comparison of the dentitions
of the juvenile and adult thylacine skull.
Photos: International Thylacine
Specimen Database 5th Revision 2013.
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| Thylacine dentition
is characterised by enamel rills or folds along the ridge of the crowns
of the lower incisors. J. Grant (1846) provided the first description
of the enamel rills. Because of their depth, the crown rills produce
typical grinding patterns that change with age. This
loss of tooth structure is termed attrition. Dental attrition
is the result of the mechanical forces encountered
during feeding on solid food, and from direct contact with the opposing
teeth. Initially, the first visible signs of attrition are seen within
the surface enamel of the tooth, but over time this proceeds to the underlying
dentine. With specific reference to the incisors, they become shorter
with advancing age. Moeller
(1997)
showed
how changes observed in the grinding pattern of the crown of the lower
incisors could be used as a relatively accurate method of determining the
age of a thylacine from its skull. |
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