GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 118-21
Presentation Time: 9:00 AM-6:30 PM


ERDMAN, Jonathan, Geological Sciences, University of Idaho, 875 Perimeter Drive, Moscow, ID 83844

75% of a complete mammoth skeleton was excavated from an ancient hot springs deposit near Soda Springs, Idaho in 1966. Analysis of the skeleton is being undertaken to determine its systematic taxonomy and placement within the Mammuthus phylogeny. Here, molar measurements of 100 - 120 mm in length and a width of 90 mm were taken to account for anterior wear and loss of the molars, resulting in the estimation of 5 enamel plates worn down and lost. These 5 enamel plates were added to the 9 plates observed on the worn occlusal surface to determine the mammoth was on its 3rd molar set out of 6, indicating that the mammoth was a juvenile ranging from 6 – 15 years old. The plate count and lamellar frequency of 8 suggests that this mammoth was a hybrid of the M. primigenius (Woolly) and M. columbi (Columbian) species, known as M. jeffersonii (Jeffersonian) based on Enk and others (2016, Front. In Eco. & Evo.). A crown height of 140 mm was compared against the 90 mm width to obtain a hypsodonty index measurement of 155.56 to standardize the mammoth’s molar characteristics to a molar size of 100 mm and confirm that the mammoth specimen is comparable to other Jeffersonian Mammoth measurements on the North American continent (Lister, 2017, Quat. Int.).

Radiocarbon AMS dating on the mammoth specimen’s molar was also conducted and yielded an age of 11,700 +/- 40 years, which is the timeframe for the last glacial retreat in North America and Jeffersonian hybridization observed in the fossil record (Pichardo, 2001, Anthro. Anzeiger). The mammoth skeleton in this study represents one of the last specimens in North America before their ultimate demise. Thus far, specimens of M. jeffersonii have only been found in deposits dated during this glacial retreat, approximately 19 – 11.5 Ka, coinciding with the megafaunal extinction that wiped out mammoths and other large mammals on a planet-wide scale (Haynes, 2002, World Arch.). While Jeffersonian Mammoths have only been recovered from sites on the east coast and west, as far as California and Arizona, this is the first mammoth reported in Idaho that is considered a M. jeffersonii. Future studies of this specimen will help to better constrain the paleogeographic distribution of this mammoth hybrid species and the interaction between M. columbi and M. primigenius in western North America.