Some 280 million years in the past, a big predator glided by the chilly waters of a supercontinent within the Southern Hemisphere. The eight-foot-long hunter had tiny limbs, an eel-like physique and a flat head stuffed with jutting fangs. And in response to current concepts about vertebrate evolution, it shouldn’t have existed.

“It was displaced in time, displaced regionally and likewise far too huge,” mentioned Claudia Marsicano, a paleontologist on the College of Buenos Aires and an creator of a paper describing the animal in the journal Nature on Wednesday. “There have been lots of issues that made it distinctive.”

The enormous salamander-like creature, which Dr. Marsicano and her colleagues named Gaiasia jennyae, might solely have been a relic of a household thought to have been extinct for thousands and thousands of years. Their discovering may recommend that further analysis on the emergence of tetrapods — vertebrates with 4 limbs and ft as a substitute of fins — is so as.

Spencer Lucas, a paleontologist on the New Mexico Museum of Pure Historical past and Science who was not concerned within the examine, mentioned that the invention “isn’t sufficient to drive a rethink of most of what we take into consideration late Paleozoic tetrapod evolution. However it’s a nudge in that route.”

Dr. Marsicano and her colleagues found Gaiasia fossils in 2014 and 2015 throughout successive expeditions to the brutal deserts of the Huab Basin of northwest Namibia in Southern Africa. They recovered fossils from 4 animals, together with a pair of skulls and a virtually full skeleton.

Piecing collectively the specimens, the crew says that Gaiasia belonged to a household of bigheaded, swamp-dwelling vertebrates known as colosteids. This household had cut up off from different land animals lengthy earlier than the ancestors of extra trendy lineages like amphibians, reptiles and mammals advanced.

Roughly 400 million years in the past, colosteids and different early tetrapods advanced from fish amid equatorial jungles. Paleontologists’ understanding of the Paleozoic Period comes virtually completely from the examine of deposits present in North America and Europe, mentioned Jason Pardo, a paleontologist on the Discipline Museum in Chicago and an creator on the paper.

So when archaic tetrapods disappeared from these jungles 307 million years in the past, researchers assumed they went extinct in all places.

However Gaiasia turned up in rocks 20 million years later than anticipated, Dr. Marsicano mentioned, early within the Permian Interval. And whereas beforehand identified members of the creatures’ household had skulls that might slot in an individual’s hand, Dr. Marsicano mentioned, Gaiasia’s cranium reached two ft lengthy or extra, making it the most important animal of its sort ever discovered.

The surroundings that Gaiasia lived in was notably intriguing. Throughout the early Permian, what’s right this moment Namibia lay alongside the southern supercontinent of Gondwana, a panorama thick with partitions of glaciers and chilly, temperate forests like these present in Canada or Norway.

Gaiasia’s look in such a panorama can be like discovering a crocodile dwelling fortunately in a lake in Manitoba, Dr. Pardo mentioned, “however this animal was actually in a position to make a dwelling and get fairly massive in that surroundings.”

Within the jungles across the Equator, competitors with huge fish — and later, the bigger family members of recent amphibians — might need stored early tetrapods small, the crew concluded. However these animals appear to have had higher luck within the cool waterways within the shadow of Gondwana’s glaciers even because the Equator’s tropical forests splintered into dryer ecosystems stuffed with finbacked predators like Dimetrodon.

Gaiasia and its habitat add an intriguing wrinkle to the story of tetrapod evolution, Dr. Marsicano mentioned. Researchers have tended to imagine that almost all tetrapods advanced within the tropics and lingered there, with extra specialised teams spreading into cooler climates solely round 280 million years in the past. Gaiasia’s presence, alternatively, means that its ancestors reached excessive latitudes earlier than that point.

Early tetrapods “had been extra tailored to several types of environments from the start,” Dr. Marsicano mentioned.

Whereas the worldwide story of tetrapod evolution relies largely on knowledge from fossils present in North America and Europe, Dr. Pardo mentioned, the invention of Gaiasia highlights the significance of finding out websites in South America and Africa, which have historically been marginalized in paleontology.

“Getting these faunas from the Southern Hemisphere is basically crucial to understanding the story of our personal lineages,” Dr. Pardo mentioned. “Particularly the query of whether or not these are simply native tales, versus one thing occurring on a world scale.”