The Surprising Science of Dinosaur Pee

These are strange times for paleontology. Finding dinosaur bones is great, and then the more we know about ancient species, the more we can recognize other clues. Fossilized coprolites, or poop, give us more clues. And now scientists are finding evidence of dino pee.

The first possible dinosaur pee trace to be discovered was described only recently. At a 2002 meeting of the Society of Vertebrate Paleontology, Katherine McCarville and Gale Bishop reported on a strange “bathtub-shaped depression” among dozens of dinosaur tracks just south of La Junta, Colorado. The scour, set in the 150 million year old stone of a long-lost lakeshore, measures approximately ten feet long, five feet wide, and ten inches deep. The shape is similar to splats McCarville and Bishop created by streaming water onto sand.

There was no sign of rock overhangs or other structures that could have spilled water onto the ground at the fossil site. The only sources for an elevated stream of fluid, McCarville and Bishop pointed out, were sauropods like Apatosaurus and theropods such as Allosaurus that criss-crossed the shore. The shallow pit could have held the liquid waste of a dinosaur.

Exactly what species of dinosaur created the trace is impossible to say, but, McCarville and Bishop suggested, “The volume of fluid required to form a scour structure as large as the one in question suggests it may represent the expulsion of liquid urine from one of the sauropod dinosaurs crossing the tracksite.” All the more reason to be wary should you ever find yourself standing below a Diplodocus.

But wait a minute: did dinosaurs really pee like that? They are related to birds, and birds just relieve themselves of urine and excrement at the same time, as you can see in any chicken coop or on any statue. Of course, there were many types of dinosaurs, as there are many types of birds today. Brian Switek looks at the research in dinosaur urination, including a modern bird found to rain down the same way, at Laelaps.

(Image credit: Alexander Hüsing)

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