Overview
- Researchers report in a PLOS ONE paper that specimen NMQR 3636 contains an articulated embryonic skeleton interpreted as preserved inside an egg, a first direct embryonic record for a non-mammalian synapsid of this age.
- The fossil was found in South Africa in 2008 and was digitally examined with high-resolution synchrotron X-ray tomography at ESRF’s BM18 beamline, using roughly 17–18 micrometer voxels to reconstruct the tiny bones without cutting the specimen.
- Anatomical markers such as an unfused lower jaw and a tightly curled posture led authors to conclude the animal died before hatching rather than being a newly hatched juvenile.
- The team did not detect a mineralized shell and infers a relatively large, soft (leathery) egg that would lower surface-to-volume ratio and help limit water loss, a trait the authors propose could have aided survival after the Permian–Triassic extinction.
- Authors and reporters stress the egg interpretation is based on imaging and comparative anatomy and that reproductive traits are one plausible factor among others—including rapid growth and burrowing behavior—in explaining Lystrosaurus’ post-extinction success.