Bear-Dog Trackway

Middle Miocene Barstow Formation

Fossil Bone Basin, Mojave Desert, California

A year 1964 scientific excavation of a giant bear-dog trackway (the scratch-claw marks along the bedding surface)--genus-species Amphicyon ingens--from the middle Miocene Barstow Formation, preserved on a bedding plane of lithified volcanic tuff, originally deposited into clear lake waters whose normal freshwater alkalinity was interrupted on occasion by evaporative periods and enormous quantities of volcanic ash ejecta which, eventually reworked by erosion and redeposited as firm mudflats, provided a perfect medium (analogous to wet concrete) to preserve the trackways of horses, camels, pronghorns, gomphothere proboscideans, and bear-dogs. The trackways are now found along the tilted and folded bedding planes of those lithified volcanic tuffs.

Paleoichnologists estimate that the bear-dog that made these tracks had a stride of 245 centimeters (eight feet).

Photograph from a specific scientific paper.

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