Complex sentence: Ruins similar to those of Casas Grandes exist near Gila and Salinas in New Mexico, and in Colorado, and it may be that they each represent cultural groups related to the Mogollon culture.
Split into simpler sentences: Ruins similar to those of Casas Grandes exist near Gila and Salinas in New Mexico, and in Colorado. They may each represent cultural groups related to the Mogollon culture.