I was cruising with my pair (levels 25 and 42) through that canyon on the west, then suddenly tek rex jumped off the cliff to roar at us. I didn't see his level at first so I was unsure and thought to turn around and run, but decided to stay and fight. I didn't fight him, I ATE HIM IN LITERALLY 3 BITES! It was level 4, didn't even take any damage and my other allo didn't even take part. If it's so, I presume I could take down level 20 to 30 rexes easy with these guys. I have a rec at home, but he's just for showing off, tame allow for business!
The Allosaurus is a very useful creature, they can be used for meat harvesting, base guards, kibble, etc. Allos are also very useful for bosses, I would recommend mixing some of these (preferably mate boosted) with rexes for the bosses.