Spotting

Description:

On Sunday, April 5, 2015, my parents dropped off their rottweiler for us to watch while they went out of town. She's living in the backyard. Within an hour, she found some creature's leg bone and devoured most of it; I threw away what was left. Today, Tuesday, April 7, I went outside to look for "treasures" to clean up. Imagine my surprise when I found, next to one of the piles, an animal pelvis - connected to the other leg bone! Attached are photos from how I found it and cell phone photos of the bone from different angles. The upper anatomy of the animal hasn't been found. Any ideas?

Notes:

- No holes or other signs of digging in the yard - Purchased this house in 2012 - From 2011-2012, the backyard was landscaped