Complex sentence: The animals that plunged first were killed from the fall and their remains were contorted, with twisted spines, and covered by following bison from the stampede, theorized to have run in a north-south direction with the hunters upwind of the southerly wind.
Split into simpler sentences: The animals that plunged first were killed from the fall and their remains were contorted, with twisted spines, and covered by following bison from the stampede. The bison were theorized to have run in a north-south direction with the hunters upwind of the southerly wind.