Early land animals skipped the tadpole stage

Without the stage of tadpole and metamorphosis, however, the transition from water to land was much more difficult than we thought.

Amphibian innovation

“We have a lot of ideas in our field that take less,” Pardo said. One of those theories was that the familiar aquatic larval stage made the transition from water to land easier for early tetrapods. Although direct development, without much modification at the beginning of the animal’s life, may seem like a simple solution to this problem, it probably makes the life of young embolomers more difficult.

The first problem they faced was being attached to the same place throughout their lives. Unlike amphibian tadpoles, they live in the same natural environment as juveniles and adults up to three meters long and have to compete with each other for resources. Then there was the problem of supporting their body on the ground. The team noted in the paper that young embolomers had weak, underdeveloped legs at hatching, which may have prevented them from walking long distances across land. It is possible that he was stuck wherever he broke.

“It makes it difficult not to have the tadpole part,” Pardo said.

He said that this is evidence that amphibian metamorphosis is not an ancient stone of evolution that helped the first animals to increase in water and conquer the world, which was preserved in frogs or modern frogs. In fact, it may be an innovation that amphibians developed later in response to the challenges posed by the transition from water to land.

“It could be something unique to amphibians that have been known to have adapted to living on land,” said Pardo. Instead of being old, it can be fresh, new and exciting.

Science, 2026. DOI: 10.1126/science.aeb7635