Jun 20, 2026 05:16 PM
Ancient Crocodile-Like Babies Challenge What We Know About Tetrapod Evolution
https://www.discovermagazine.com/ancient...tion-49268
EXCERPTS: Life on land likely evolved when one of our ancient fish ancestors developed legs and came ashore. These early creatures, known as tetrapods — creatures with four limbs — would eventually evolve into the birds, reptiles, amphibians, and mammals of today.
Previous studies suggest that these early tetrapods may have been similar to modern-day amphibians because they likely laid eggs and, when the young hatched, underwent a tadpole-like phase before morphing into their full-grown forms.
New findings of fossilized baby tetrapods may, however, be shaking up our understanding of how these creatures grew into adulthood. Published in the journal Science, these early fossils suggest that these creatures skipped the tadpole phase of their metamorphosis and were not as similar to modern-day amphibians as previously thought.
“When a lot of us were in high school, we were taught this simplified story of evolution: that some fish evolved into amphibians, and some of those amphibians evolved into reptiles, and some of those reptiles evolved into mammals. And our study shows that this basic underlying premise, that the first four-legged vertebrates grew up like amphibians, is wrong,” Jason Pardo, a research associate at the Field Museum in Chicago and the study’s co-lead author, said in a press release.
[...] “We looked at a number of different species that represent different lineages in the transition from fish to tetrapods, and what we found is that none of them have anything that looks remotely like a tadpole. And if you don't have a tadpole, then you don't have a metamorphosis,” Pardo said. “These early tetrapods’ life cycles are more like ours, or like those of fish, than they are like amphibians.”
These results are changing what previous studies have found and rewriting the previously held hypothesis that mammals and reptiles likely evolved from an amphibian-like animal. “The story was that metamorphosis is the tool by which animals made the transition from fossil to land. That story doesn’t work anymore; it’s dust in the wind,” Pardo said... (MORE - missing details)
https://www.discovermagazine.com/ancient...tion-49268
EXCERPTS: Life on land likely evolved when one of our ancient fish ancestors developed legs and came ashore. These early creatures, known as tetrapods — creatures with four limbs — would eventually evolve into the birds, reptiles, amphibians, and mammals of today.
Previous studies suggest that these early tetrapods may have been similar to modern-day amphibians because they likely laid eggs and, when the young hatched, underwent a tadpole-like phase before morphing into their full-grown forms.
New findings of fossilized baby tetrapods may, however, be shaking up our understanding of how these creatures grew into adulthood. Published in the journal Science, these early fossils suggest that these creatures skipped the tadpole phase of their metamorphosis and were not as similar to modern-day amphibians as previously thought.
“When a lot of us were in high school, we were taught this simplified story of evolution: that some fish evolved into amphibians, and some of those amphibians evolved into reptiles, and some of those reptiles evolved into mammals. And our study shows that this basic underlying premise, that the first four-legged vertebrates grew up like amphibians, is wrong,” Jason Pardo, a research associate at the Field Museum in Chicago and the study’s co-lead author, said in a press release.
[...] “We looked at a number of different species that represent different lineages in the transition from fish to tetrapods, and what we found is that none of them have anything that looks remotely like a tadpole. And if you don't have a tadpole, then you don't have a metamorphosis,” Pardo said. “These early tetrapods’ life cycles are more like ours, or like those of fish, than they are like amphibians.”
These results are changing what previous studies have found and rewriting the previously held hypothesis that mammals and reptiles likely evolved from an amphibian-like animal. “The story was that metamorphosis is the tool by which animals made the transition from fossil to land. That story doesn’t work anymore; it’s dust in the wind,” Pardo said... (MORE - missing details)