In Southwestern Texas, reports of 6 foot tall Theropod-like animals have been reported. They are named "Mountain Boomers", after the much smaller Collared Lizard, a lizard which is also called the Mountain Boomer.

These animals might be the same as the smaller River Dinos. Like the River Dinos, it has also been suggested that these could possibly be an undiscovered species of bipedal iguanid lizards.