Mammal Ancestors Laid Soft Eggs

High‑resolution CT and synchrotron scans of curled Lystrosaurus embryos show unfused jawbones and egg‑like posture consistent with development inside soft, yolk‑rich eggs rather than live birth. The shells didn’t mineralize, so the discovery relies on preserved embryonic anatomy and advanced imaging to infer reproductive mode. — This changes the public and scientific story about the evolution of mammal reproduction by providing direct fossil evidence that egg‑laying persisted in the lineage leading to mammals, which affects how we think about life‑history evolution and resilience after mass extinctions.