Seventy million years ago a hadrosaur (duck-billed dinosaur) died at or near the shore of a lake in what is now Hidalgo County, New Mexico. The large animal's body came to rest on the shoreline, pressing its flesh deep into the mud. Soon, it was buried in mud, eventually to a thousand feet or more, which hardened and perfectly preserved an impression of the rear flank of the animal. The sandstone encasing the fossil is called the Ringbone Formation.

Extremely rare skin impressions are the only evidence we have for the external appearance of dinosaur skin. Enough bones and ossified (bony) tendons were found along with the skin to show that it was a hadrosaur; however, without a skull paleontologists are unable to determine exactly which hadrosaur species this specimen represents.