Nigersaurus, a Cretaceous hedge-trimmer
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.
Bora has more, and you can read the original on PLoS.
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