The Shasta ground sloth (Nothrotheriops shastensis) is not very common at Rancho La Brea. It is smaller than the more common Harlan's ground sloth and belongs to a family of sloths called Megatheriidae. The skeleton on exhibit at the Page Museum was the first ever in the world to be mounted. It was not made of real bone however because at the time there was so little known about these animals that it was decided to mount a plaster cast replica. Since that time numerous other specimens have been found in caves. Research on dung from these caves has suggested that this animal was more of a dry environment dweller and thus was not that common in the Los Angeles basin.
The only evidence of Shasta ground sloth in the Project 23 excavations is from this patella or knee cap which is an enlarged sesamoid bone that articulates with the femur and protects the knee joint.