Back in the Permian period some 278 million years ago, North America and western Europe were located near the equator, and an ice age had just ended in the southern supercontinent Gondwana. With this new access, land-dwelling vertebrates were beginning to colonize high-latitude regions. Researchers working in what’s now northeastern Brazil have discovered the fossils of two new species of aquatic, carnivorous amphibians. They’re described in Nature Communications this week.
Most of what we know about tetrapods (four-legged vertebrates) from this time comes from just a few sites in North America and Europe. So researchers had almost no idea what was present in the southern tropics – and how similar or dissimilar they were to animals living near the equator. "This area in Brazil has almost never been paleontologically sampled before for tetrapods from this time period," study co-author Kenneth Angielczyk from the Field Museum tells IFLScience. He and a team led by Juan Cisneros of Universidade Federal do Piauí in Brazil have been working in the area for over four years. "It’s taken that long just to figure out where to look for interesting fossils," he adds.
Eel-like Timonya anneae was an aquatic amphibian with a big head, robust shoulders, a long body, and very short limbs. A fossilized skull with forelimbs and part of a backbone is pictured to the right. This new member of Dvinosauria likely had external gills, like a modern-day axolotl or mudpuppy. And based on CT scans, the conical teeth on the roof of its mouth were much larger than the ones on its lower jaw. These fangs probably helped them pierce and hold on to insects and small fish.
The other new species they discovered is called Procuhy nazariensis. The new genus name means "fire frog" in the local Timbira language, referring to the location where part of its skull and lower jaw were discovered: Pedra de Fogo Formation (or "Rock of Fire" in Portuguese), named for the flint in the area. It was a distant frog relative that belonged to the Trimerorhachidae family of Dvinosaurs.
Additionally, the team also found fossils belonging to a giant amphibian from the family Rhinesuchidae (though they can’t say for sure if it’s a new species) as well as a lizard-looking reptile that could possibly be Captorhinus aguti. And while these animals might not be new to science, finding them here was unexpected. This reptile has only ever been found in North America, and known Rhinesuchids lived much later and much farther south.
"In recent times, tropical areas have served as a cradle of biodiversity. New species arise at a higher rate, and then they disperse elsewhere," Angielczyk says. "Rhinesuchids might have originated in the tropics and dispersed later – like what we see today." Tetrapod groups common in later temperate communities were already present in tropical Gondwana at the beginning of the Permian.
Together, the animals provide a snapshot of what a tropical lake community looked like 278 million years ago in Brazil, and they’re also helping researchers better understand the wave of animals spreading south from the equator to higher latitude regions. "We thought they’d look more like things you’d find in southern Africa," Angielczyk says, "but overall, the fauna seems to have more of a North American or equatorial appearance to them." Dispersal into Gondwana was well underway.
[H/T Field Museum]
Images in the text: Juan Cisneros (middle), J.C. Cisneros et al., 2015 Nature Communications (bottom)