Diprotodon, Owen, 1838

Price, Gilbert J., 2008, Taxonomy and palaeobiology of the largest-ever marsupial, Diprotodon Owen, 1838 (Diprotodontidae, Marsupialia), Zoological Journal of the Linnean Society 153 (2), pp. 369-397 : 382

LANCEFIELD SWAMP DIPROTODON

DENTAL MORPHOMETRIC AND MORPHOLOGICAL

COMPARISON

The Diprotodon assemblage is represented by dentary and maxillary fragments, but is dominated by isolated teeth. Both size classes are undoubtedly represented in the deposit and the ratio of largeto small-form individuals is approximately 1:1. One dentary ( NMVP151805-6 ) represents a juvenile small-form individual. The individual appears to be of similar morphological age to the juvenile largeform individual ( QMF6633 ; Fig. 9F ) from the Darling Downs (as determined by similar molar eruption patterns). The Lancefield Swamp specimen lacks the distinctive ‘chin’; the ventral margin of the horizontal ramus is more convex; and the posterior portion of the dentary is curved, similar to that of more mature individuals. Generally , from the limited number of dentaries available, no specific morphological differences were observed in comparison with either large- and/or small-form individuals of the Darling Downs , Bacchus Marsh and Lake Callabonna assemblages. Some dentaries show evidence of abrasion, possibly suggesting post-mortem fluvial transport .

More than 70 teeth were examined in the Lancefield Swamp collection. Tooth morphologies are identical to those of all other aforementioned localities, and thus do not warrant additional description. As the assemblage is dominated by isolated teeth, it is not possible to assign the majority of teeth to specific size classes. The mean molar teeth dimensions vary little in comparison with other assemblages, and the means overlap at less than one standard deviation for most measurements ( Tables 2, 3). However, similar to aforementioned examples from the Lake Callabonna Diprotodon assemblage, some teeth (e.g. P 3 and M 4) are larger than corresponding teeth in other populations. However, like those from Lake Callabonna, such teeth are represented by few specimens, and for reasons described above, the differences are probably the result of sampling biases.

Figures

Figure 9. Line drawings of morphological variation in Diprotodon dentary shape (all specimens from the Darling Downs). A, QMF36129, small form. B, QMF1517, small form. C, QMF319, large form. D, QMF6569, large form. E, QMF10311, large form. F, QMF6633, juvenile large form. Numerals on line drawings denote character variations: 1, anterior portion of ramus gently curved in lateral aspect; 2, anterior portion of ramus expanded and angular in lateral aspect; 3, ventral margin of horizontal ramus straight; 4, ventral margin of horizontal ramus slightly concave; 5, posterior portion of dentary gently curved; 6, posterior portion of dentary angular.