Last August, when I was at the Sci Foo camp, Paul Sereno brought along the skull of one of his latest discoveries…and whoa, is it ever a weird one. This is Nigersaurus taqueti, an herbivorous dinosaur with specializations for ground-level grazing. Look at this picture; in reality, it's even more striking.
Those jaws and teeth—they are so neatly squared off and flat-edged. In addition, the skull itself on the spinal column is turned habitually downward. This is a creature that kept its face pressed to the ground as it nibbled its way across the landscape.
Another feature that was apparent is that the skull is awesomely light — it's mostly empty spaces with a delicate webwork of bony struts holding it together. It's so specialized it's almost comical, and you can imagine something like this appearing on the Flintstones as a lawn mower or hedge trimmer.
Sereno PC, Wilson JA, Witmer LM, Whitlock JA, Maga A, et al. (2007) Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230