The first late middle Pleistocene Stegodon (Proboscidea, Stegodontidae) evidence found in Peninsular Malaysia

A maxillary left milk molar (dp3) of a Stegodon was discovered in a cave in northern Peninsular Malaysia. This finding represents the southernmost record of Stegodontidae in continental Asia. The half-exposed tooth was embedded in breccia attached to the cave wall. A micro-computed tomography (μCT) scanning was employed to virtually isolate the specimen from the matrix and to reconstruct a 3D model of the fossil for accurate measurements. No sign of wear or mechanical abrasion was observed in the specimen. Age determination on the matrix based on post-infrared infrared luminescence (pIR-IRSL) dating and U-series revealed a late middle Pleistocene age of between 233 ± 31 to 199 ± 28 ka. Detailed comparisons with specimens of Stegodon orientalis and Stegodon trigonocephalus revealed a number of differences in size and morphologies (development of posterior cingulum, presence of enamel tubercles at posterior cingulum, tapering of each plate lingual-buccally, thickness of the plates, and depth of the valley between plates) which are different to either of these species. The discovery of Stegodon in Peninsular Malaysia provides a better understanding of the distribution of this genus in the Sundaic subregion during the middle Pleistocene.

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