The first known Protostega specimen (YPM 1408) was collected on July 4 by the 1871 Yale College Scientific Expedition, close to Fort Wallace and about 5 months before Cope arrived in Kansas.
 However the fossil that they found was never described or named.
It wasn't until E. D. Cope found and collected the first specimen of Protostega gigas in the Kansas chalk in 1871.
A variety of bones were found in yellow cretaceous chalk from a bluff near Butte Creek.
The first known Protostega specimen (YPM 1408) was collected on July 4 by the 1871 Yale College Scientific Expedition, close to Fort Wallace and about 5 months before Cope arrived in Kansas. However the fossil that they found was never described or named. It wasn't until E. D. Cope found and collected the first specimen of Protostega gigas in the Kansas chalk in 1871. A variety of bones were found in yellow cretaceous chalk from a bluff near Butte Creek.
Protostega