Particle.news

First Fossil Egg of a Mammal Ancestor Confirms Egg-Laying in Proto-Mammals

Synchrotron scans of a Lystrosaurus embryo identify an unfused jaw that indicates soft, yolk-rich eggs suited to post-extinction stress.

Overview

  • The peer-reviewed study, published Thursday in PLOS ONE, reports the first fossil egg containing a Lystrosaurus embryo.
  • Advanced X-ray CT at the European Synchrotron Radiation Facility revealed an unfused lower jaw, showing the animal died before hatching.
  • The researchers conclude Lystrosaurus laid soft-shelled eggs, which rarely preserve, explaining the lack of prior direct evidence.
  • The egg appears large for the animal and likely yolk-rich, producing precocial young well adapted to heat and drought after the End-Permian die-off.
  • The specimen, found in 2008 in South Africa’s Karoo Basin by John Nyaphuli, offers clues that researchers say can inform how species cope with rapid climate stress today.