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Early land animals skipped the tadpole phase

Early land animals skipped the tadpole phase

Summary

Scientists have found that early land animals called tetrapods, which lived over 300 million years ago, did not have a tadpole stage like many modern amphibians do. Instead, these ancient animals grew directly into miniature adults without undergoing a watery larval phase.

Key Facts

  • Early tetrapods were ancient vertebrates that started living on land more than 300 million years ago.
  • Scientists assumed early tetrapods had a tadpole-like stage because modern amphibians do, but there was no previous evidence.
  • A new study examined fossils of embolomers, large predators from that time with features like both crocodiles and eels.
  • Researchers found a tiny young embolomer fossil with no signs of external gills or a tadpole phase.
  • The fossil had an internal yolk sac, indicating large, nutrient-rich eggs similar to reptiles and birds, not small amphibian-like eggs.
  • Another small embolomer fossil confirmed the absence of a tadpole phase.
  • The findings suggest these early tetrapods developed directly into miniature adults without metamorphosis.
  • This challenges long-held ideas about the early life cycles of animals that first moved from water to land.
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