A rich fossil deposit in northeastern Brazil has provided paleontologists with a new look at a time when many strange amphibians—including a "fire frog"—thrived in ancient swamps.

The unusual fossil amphibians, described by Field Museum paleontologist Kenneth Angielczyk and colleagues in Nature Communications on November 5, were found in Brazil’s Paranaíba Basin and date back to the early part of the Permian period, about 278 million years ago.

Fossils have been known from this area for decades, but, Angielczyk says, it was the search for a particular kind of animal that drew him and his co-authors to take another look.

“We actually got started there with the hope of finding early therapsids"—protomammal human cousins that thrived during the Permian.