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,
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.
|Thylacine (Thylacinus cynocephalus)
|Fox (Vulpes vulpes)
|Wolf (Canis lupus)
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
Thylacine Specimen Database Fourth revision 2011.
| 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 Thylacinus 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 (dentes decidui) 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.
Consequently, these functional dentes permanentes will be in use
throughout the animal's life.
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 4th Revision 2011.
| A thylacine skull is
classified as "adult" with the eruption of the fourth upper molar teeth.
Historically, George P. Harris (1808), in
description of the dental formulae of the thylacine wrote: "Twelve
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 (1824b):
|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".
is characterised by enamel rills or folds along the ridge of the crown
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
(specimen NMS Z1993.70).
Courtesy: National Museum
of Scotland (Edinburgh).
Courtesy: Oxford University
Museum of Natural History.
Comparison of the dentitions
of the juvenile and adult thylacine skull.
Photos: International Thylacine
Specimen Database 4th Revision 2011.
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, these teeth become shorter with age. Moeller (1997)
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.