Summary of the Snowmastodon Project Special VolumeA high-elevation, multi-proxy biotic and environmental record of MIS 6–4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA

Abstract

In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of past plant communities between ~140 and 55 ka, including all of MIS 5. At an elevation of 2705 m, the Ziegler Reservoir fossil site also contained thousands of well-preserved bones of late Pleistocene megafauna, including mastodons, mammoths, ground sloths, horses, camels, deer, bison, black bear, coyotes, and bighorn sheep. In addition, the site contained more than 26,000 bones from at least 30 species of small animals including salamanders, otters, muskrats, minks, rabbits, beavers, frogs, lizards, snakes, fish, and birds. The combination of macro- and micro-vertebrates, invertebrates, terrestrial and aquatic plant macrofossils, a detailed pollen record, and a robust, directly dated stratigraphic framework shows that high-elevation ecosystems in the Rocky Mountains of Colorado are climatically sensitive and varied dramatically throughout MIS 5.

Fossil and genomic evidence constrains the timing of bison arrival in North America

“…We assembled mitochondrial genomes for 35 ancient bison, including the Ch'ijee's Bluff steppe bison and a giant long-horned bison from a site near Snowmass, Colorado (24). Of these, 21 were not associated with any stratigraphic or age information, and were sent to accelerator mass spectrometry (AMS) radiocarbon dating facilities for dating using ultrafiltered collagen (Dataset S1).…”

“…In Yukon, a fossil assemblage in stratigraphic association with the Middle Pleistocene Gold Run tephra (735 ± 88 kyBP) includes horse (Equus), proboscideans (Mammuthus), sheep (Ovis), and biostratigraphically diagnostic microtine rodent species, but bison fossils are absent (21)(22)(23). The oldest site in the midcontinental United States possessing both bison and a firm chronology is near Snowmass, Colorado, where bison fossils were recovered within sediments associated with the last interglaciation (MIS 5d), thus dating to ∼120 kyBP (24). Bison fossils also occur at American Falls, Idaho, associated with a lava-dammed lake that dates to ∼72 kyBP (8,25).…”

“…Bison fossils also occur at American Falls, Idaho, associated with a lava-dammed lake that dates to ∼72 kyBP (8,25). Bison from both of these sites represent the giant long-horned bison, B. latifrons (24,25), generally considered to be the earliest form of bison developed in the continental United States.…”

“…However, recent advances in paleogenomics have expanded the range of fossils from which DNA can be recovered (32). Capitalizing on these, we used a hybridization capture approach to enrich for bison mitochondrial DNA from both the Ch'ijee's Bluff bison and from a giant long-horned bison from Snowmass (DMNH EPV.67609) that dates to the last interglaciation, ∼120 kyBP (24). We recovered a complete mitochondrial genome (159× coverage) from the Ch'ijee's Bluff bison and a near-complete mitochondrial genome (6.6× mean coverage) from the Snowmass bison (Materials and Methods).…”

Preserved Proteins from Extinct Bison latifrons Identified by Tandem Mass Spectrometry; Hydroxylysine Glycosides are a Common Feature of Ancient Collagen

“…This closed drainage basin established a relatively unique environment that resulted in the exceptional preservation of plant material, insects (52), and vertebrate bones (49). In particular, a cranial specimen from extinct Bison latifrons was unearthed from the Biostratigraphic Zone/Marine Oxygen Isotope Stage (MIS) 5d, which dates back to ϳ120 ky (53,54).…”