It is Texas Croton (Croton texensis).
Unfortunately, there aren't very many decent pictures of it on the web. This is the best I've found:
http://twig.tamu.edu/Texas_cro...
It's a plant I know well, though.
It's a common pasture "weed" in the central/southern Great Plains. The seed pods are interesting, when the seeds are ripe, the pods explode and can fling the seeds several feet. Collect several handfuls of pods, put them in a bucket, and when they dry out it will sound like you have a popcorn popper going (sort of).
