The drop shadow makes it look like the dinosaur is standing in front of a picture of a hill...

An easy way to make a shadow for a creature INSIDE a picture is to duplicate the image you want to shadow, then choose the UNDER layer and darken it to black with lightness (under saturation and hue) then use DISTORT (center manipulation square top edge) and pull the black image into the photo and shape where you want the shadow. Once placed use a blur filter (I use Gaussian) and then use opacity to get the right look. Takes some practice, and pay attention where shadows fall in the image so you can get it to match right... Just one way of doing it... (IMHO of course).. good luck author