'A completely different story': 300 million-year-old fossils reveal the first vertebrate land dwellers weren't what we thought, researchers claim

Key Points:

• Newly discovered fossils of crocodile-like early tetrapods, called embolomeres, reveal that these ancient creatures developed directly from hatchlings to adults without a tadpole-like larval stage, challenging previous assumptions about amphibian-like life cycles in early land vertebrates.
• The study, published in Science, suggests that early tetrapods relied on direct development, similar to humans, which may have simplified their transition from aquatic to terrestrial environments during the Devonian to Permian periods.
• Fossils from Mazon Creek, Illinois, showed no evidence of external gills or metamorphosis, indicating that early tetrapods did not undergo amphibian-like developmental stages, a finding supported by examination of other related fossils.
• While the study challenges some traditional views, experts caution that it does not drastically overturn scientific understanding, noting that variability in early tetrapod development was already recognized within the field.
• Researchers emphasize the importance of revisiting and questioning established scientific assumptions, as these new findings provide fresh insights into the reproductive and developmental biology of early vertebrate life on land.