Considering how big they were, it's amazing how dinosaurs can hide in plain sight. The latest example comes from Yemen (on the southern Arabian peninsula), where researchers have found the trackmarks of an eleven-strong herd of sauropods, as well as some giant, bipedal ornithopods.

These tracks were laid down about 150 million years ago; how come they weren't they discovered until now? As explained by Science Daily, the footprints of giant dinosaurs are simply too big to register as such to the average human--and in any case, the tracks were partially obscured by tens of millions of years of debris.

Besides providing evidence of herding behavior in sauropods, these footprints are important because very few dinosaurs have been discovered on the Arabian peninsula--which, by the way, was covered with thick vegetation, and not sand dunes, back in the Jurassic period.