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20h ago

Wyoming Edmontosaurus ‘Mummies’ Are Clay Templates That Reveal Earliest Hooves

A University of Chicago study in Science finds microbial biofilms drew clay onto desiccated carcasses, creating a thin mask that captured lifelike skin contours.

A thin layer of clay over the fossilized skeleton of the juvenile Edmontosaurus preserved large areas of scaly, wrinkled skin and a fleshy crest over its back.
Image
Lead study author Paul Sereno of the University of Chicago marvels at the preserved hooves on the foot of an adult mummy of Edmontosaurus.
The scaly skin of a crest over the back of the juvenile duck-billed dinosaur Edmontosaurus annectens, estimated to be about 2 years old at the time it died.

Overview

  • The study documents wedge-shaped hooves on the hind toes, marking the earliest hooves in a land vertebrate and the first confirmed hooved reptile.
  • Two Edmontosaurus annectens from eastern Wyoming—a two-year-old juvenile and a young adult—preserve a fleshy midline crest and a full row of tail spikes.
  • Imaging and microanalyses show the apparent skin is a sub-millimeter clay layer formed on microbial biofilms, with no detectable original organic tissue.
  • The authors propose a drought-to-flash-flood sequence that desiccated carcasses, then rapidly buried them as clay accreted to the biofilm to mold external details.
  • All known specimens cluster within a roughly 10-kilometer “mummy zone” in the Lance Formation, providing a framework and toolkit to target further finds.