RESURRECTING THE STORY OF OLD MAMMOTH FOSSIL BONES FROM SODA SPRINGS, IDAHO

Mammoths were endemic on the North American mainland continent during the late Pleistocene to early Holocene and are considered a keystone species in paleoecology. We examined the skeletal remains of a mammoth excavated from southeastern Idaho in 1966 to provide insight into its depositional age, taxonomy, ontogeny, diagenetic alteration, and osteology. This multidisciplinary analysis revealed the first M. jeffersonii reported in Idaho that was most likely a male mammoth approximately 2.65m (8.7 ft) tall, between 18-28 years old, living 11,700 +/- 40 years ago. After extracting and sequencing mtDNA from the molar, the results confirmed that the mammoth belonged to haplogroup F (Enk et al., 2016), the lineage of North American mammoths that include M. columbi and M. jeffersonii. While overlap and variability in molar measurements certainly represents the extent of ambiguity associated with taxonomic identification as well as within-species morphological heterogeneity, this variability is also consistent with the current hypothesis which suggests that substantial gene flow occurred between haplogroups C and F (Enk et al., 2016), which contain the well-known M. primigenius and M. columbi. M. jeffersonii could either be a hybrid of the aforementioned species from introgression or it could also represent continued evolutionary advancement of M. columbi and should be considered a subspecies (Enk et al., 2016; Widga et al., 2017).

The skeletal remains of the Soda Spring mammoth were preserved in an ancient hot spring deposit after partial disarticulation and have indicators that it had possible pre-mortem injuries. CT scans revealed a partially healed internal fracture on the inside of the right calcaneum bone and potential ulcers on the surface of subchondral leg bones and on the seventh thoracic vertebra. Post-mortem gnaw marks on the vertebra and rib bones from rodents, small carnivores, and large carnivores indicate subaerial exposure before burial. This mammoth was one of the last mammoths in mainland North America before the species’ ultimate extinction.