MORPHOMETRIC AND AGE ANALYSIS OF MAMMOTH MOLARS FROM THE PRATUM-RUTSCHMAN/QUALEY SITE, MARION COUNTY, OREGON

On Friday 25 August 1967 remains of a mammoth were discovered in a peat bog in Pratum, a small farming community northeast of Salem, Oregon. The bones were recovered during backhoe excavations to create a farm pond. Two molars were found in association with a tusk, femur, and partial pelvis. The finders report that the post-cranial elements and tusk have since disintegrated; however the molars remain for study and analysis. The landowner, Roy Rutschman, retained possession of the tusk and post-cranial elements, while equipment operator Norm Qualey kept the molars. The current condition of the pond and site are presently unknown. The farm was sold several years ago, and Mr. Rutschman has since passed away. The find was noted in a local newspaper, The Silverton Appeal, on 31 August 1967. However, until now no scientific research has been conducted on this find. Mr. Qualey loaned the Pratum molars to the junior author (SJC), and graciously consented to allow for their sampling and analysis. While mammoth finds are fairly common in the area, detailed palaeontological analysis of such finds has rarely been attempted. The presence of two relatively complete molars allows us to diagnose this mammoth for both species and age.

For this study both molars were analyzed for the following qualitative and quantitative attributes: position (hemisphere (upper/lower) and side (left/right)), plate count (Pl), overall length (Lg), width (W), height (Ht), weight (Wt), enamel thickness (En), and lamellar frequency (Lf), molar number, species and age. The teeth were also analyzed for length/lamellae ratio (=Lg/Pl), and hypsodonty ratio (=Ht x 100/W). By comparing the attribute scores from the Pratum molars with comparable data for four species of North American mammoths, our analysis indicates that the two molars from Pratum are the left and right upper fifth molars (LM⁵ and RM⁵) of a Columbian mammoth (Mammuthus columbi). Based on the number of plates in wear on the occlusal surface of these molars, when compared to comparable data for modern African and Asian elephants, the Pratum mammoth was roughly 22±3 years of age at death. In terms of modern elephant social structure, this would classify the Pratum mammoth's social age group as “early prime adult”. Samples from these molars will be sent to labs for radiocarbon and stable isotope analysis.