For the first time ever, we’ve been able to prove that some dinosaurs had hooves, thanks to two remarkably well-preserved mummified dinosaurs retrieved from Wyoming’s Badlands. The specimens are the duck-billed dinosaurs Edmontosaurus annectens that, thanks to a "fluke preservation event" are near-perfect 66 million years later.

Known as “clay templating,” that process essentially encased the dinosaurs shortly after burial with a mask of clay no thicker than 1/100th of an inch, or about 0.3 millimeters. “This is a mask, a template, a clay layer so thin you could blow it away,” said senior author Paul Sereno, PhD, Professor of Organismal Biology and Anatomy at UChicago in a statement. “It was attracted to the outside of the carcass in a fluke event of preservation.”

Using hospital and micro-CT scans, thin sections, X-ray spectroscopy, clay analyses, and examination of the discovery site, a team of scientists were able to figure out how that “fluke event” played out. After death, the dinosaurs were briefly baked under the Sun before a flash flood submerged their carcasses.

A thin biofilm then covered their fleshy surface and electrostatically pulled clay out of the wet sediment, forming a wafer-thin layer that would preserve them in three dimensions. The result is two unprecedented specimens that have already provided a glut of dinosaur firsts.