Moving lights, haze to show the rays, top down light and its either there is lights from the sides or the light is reflected the floor and thus lights the bottom bit of the Triceratops a little.
In this picture, the patterns on the moving lights helped to texturize the dinosaur's skin, also giving the floor its "rough" rock texture. Wonder if hte lighting is grey?
The haze and rays bring out the scope of the ray, encompassing the T-rex. Putting the ENTIRE dino in the spotlight? Plus the haze also acts to the atmosphere of the dino age,