What on Earth is a Urolite?

Every heard of a urolite? Me neither. What about a coprolite? I suspect more people have probably heard of these.

Coprolites are fossilized feces or poop. There's nothing disgusting about them, the material has been completely mineralized and it's no worse than handling a rock (although when I pass one around the geology lab, some students are very reluctant to even touch it). Here are a couple of samples I have in my lab (I don't know what animal left these coprolites).

Coprolites are ichnofossils or trace fossils in that they record a trace of an organism's activity (rather than a fossil of the organism itself). Paleontologists find coprolites useful since they can often provide information about the animal's digestive system and diet - below are microscopic views of coprolites from a scientific paper studying the diet of a group of herbivorous dinosaurs.

I happened to stumble on a paper recently that introduced me to urolites. Urolites are another type of ichnofossil that are formed from sediments disturbed by the urine stream of an animal (hence the "uro" part of the name). In the case of the paper I read, urine streams from early Cretaceous Period dinosaurs in Brazil. Here's a picture from the paper of some urolite examples.

and a drawing illustrating the concept.

The authors said these fossils compared well to similar features formed by modern ostrich urinating in sand. They also claimed that this is the first direct evidence of liquid waste elimination by dinosaurs.

While not the sexiest of fossils, it's always neat to see what we can see and learn by careful observation of the world around us.