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Oldest Crocodilian Eggshells in Australia Identified as Mekosuchine, Dating to 55 Million Years

Microscopy plus geochemistry point to lake‑margin nesting, reinforcing evidence that extinct mekosuchines occupied unusual niches including possible tree‑climbing hunters.

Overview

  • Fragments from the Tingamarra clay deposit at Murgon, Queensland, were formally described as Wakkaoolithus godthelpi in the Journal of Vertebrate Paleontology.
  • The study, led by Xavier Panadès i Blas with collaborators from the Institut Català de Paleontologia and UNSW, analyzed eggshell microstructure and chemical signals to infer nesting behavior.
  • Findings align with prior fossil evidence that mekosuchines were ecologically diverse, with some terrestrial forms, possible semi‑arboreal 'drop crocs,' and riverine species reaching at least five metres.
  • The research highlights that modern saltwater and freshwater crocodiles arrived in Australia about 3.8 million years ago, long after mekosuchines dominated inland waterways.
  • Authors propose mekosuchines declined as landscapes dried and waterways shrank, facing new crocodilian competitors and fewer large prey, and urge routine collection and analysis of eggshells in future digs.