Patagonia Egg, Wyoming Mummies Reveal Dinosaur Soft Tissue

Argentina’s CONICET team unearthed an exceptionally well-preserved, ~70-million-year-old dinosaur egg in Río Negro, Patagonia identified as belonging to the small theropod Bonapartenykus and thought to contain embryonic remnants from a probable fossil “nursery” that could shed light on growth and parental behavior. Separately, University of Chicago researchers reexamined early-1900s Edmontosaurus finds from east-central Wyoming and showed that skin, spikes and — for the first time in a reptile — hooves are preserved as delicate clay-impression “mummies” formed by clay templating and microbial biofilms in oxygenated river deposits. The team mapped a distinct “mummy zone” in the Hell Creek/Lance formations and reported additional juvenile and adult mummies. Imaging and geochemical analyses enabled detailed full-body reconstructions (including a fleshy neck/trunk crest and a tail spike row), identified the earliest known tetrapod hooves, and improved reconstructions of hadrosaur anatomy and locomotion. Together, the Patagonia egg and the Wyoming mummies provide complementary, high-fidelity windows into dinosaur development, soft-tissue anatomy and life history.