Just before I took my son out to college in Bismarck, ND I got a Sigma 17-70 and a Tamron 70-200 as I planed on stretching the trip a bit to include Yellowstone etc. I really came to like he Sigma. This is an available light shot with the Sigma taken at the North Dakota Heritage Center in Bismarck. This is about a .3 second exposure with shake reduction on. It was taken with my K5-IIs.
The beast in the middle is called Bison Lantifrons which became extinct some 20,000 years ago. They were massive animals weighing in at 4,000 pounds or 1,800 kgs. The display shows it being attacked by two smilodons or sabre toothed cats. To compare it to modern bison in North America look at the display along the wall in the rear. There is another skull of this creature with two other skulls. The skull on the right side of the person is from a modern bison. They are half the size of this creature.