Â鶹ÒùÔº

An international team of paleontologists has spent more than 15 years excavating and studying fossils from Africa to expand our understanding of the Permian, a period of Earth's history that began 299 million years ago and ended 252 million years ago with our planet's largest and most devastating mass extinction.

Led by researchers at the University of Washington and the Field Museum of Natural History, the team is identifying the animals that thrived in southern Pangea—the planet's single supercontinent at the time—just before the so-called "Great Dying" wiped out about 70% of terrestrial species, and an even larger fraction of marine ones.

"This mass extinction was nothing short of a cataclysm for life on Earth, and changed the course of evolution," said Christian Sidor, a UW professor of biology and curator of vertebrate paleontology at the UW Burke Museum of Natural History & Culture. "But we lack a comprehensive view of which species survived, which didn't, and why. The fossils we have collected in Tanzania and Zambia will give us a more global perspective on this unprecedented period in our planet's natural history."

Sidor and Kenneth Angielczyk, curator of paleomammalogy at the Field Museum, are co-editors of published Aug. 7 in the Journal of Vertebrate Paleontology featuring the team's recent discoveries about the myriad of animals that made Permian Africa their home. These include saber-toothed predators, burrowing foragers and a large, salamander-like creature.

All these finds were excavated in three basins across southern Africa: the Ruhuhu Basin in southern Tanzania, the Luangwa Basin in eastern Zambia and the Mid-Zambezi Basin in southern Zambia. Most were discovered by team members on multiple, month-long excavation trips to the region over the past 17 years. Others were analyses of specimens dug up decades prior that had been stored in museum collections.

"These parts of Zambia and Tanzania contain absolutely beautiful fossils from the Permian," said Sidor. "They are giving us an unprecedented view of life on land leading up to the mass extinction."

Starting in 2007, Sidor and his team, including UW students and postdoctoral researchers, made five trips to the Ruhuhu Basin and four to the Mid-Zambezi and Luangwa basins, all in cooperation with the Tanzanian and Zambian governments. The researchers trekked between field sites miles apart to collect fossils. They stayed in villages or camped in the open—once waking during the night to the ground-quaking stomps of a nearby elephant herd. All fossils collected by the team will be returned to Tanzania and Zambia after researchers have completed their analyses.

The Permian is the endpoint of what paleontologists call the Paleozoic Era. During this time, animal life—which evolved first in Earth's oceans—began to colonize land and complex terrestrial ecosystems developed. By the Permian, a diverse array of amphibian and reptile-like creatures roamed environments ranging from early forests to arid valleys. The end-Permian mass extinction—whose precise cause scientists are still debating—obliterated many of these ecosystems and ushered in the Mesozoic Era, which saw the evolution of dinosaurs, as well as the first birds, flowering plants and mammals.

For decades, scientists' best understanding of the Permian, the Great Dying and the start of the Mesozoic came from the Karoo Basin in South Africa, which contains a near-complete fossil record of periods before and after the mass extinction. But beginning in the 1930s, paleontologists realized that basins in Tanzania and Zambia contain fossil records of this time range that are almost as pristine as the Karoo's.

The excavation trips by Sidor, Angielczyk and their colleagues represent the largest analysis to date of the region's fossil record from before and after the Great Dying. In 2018, they published a comprehensive analysis of the post-Permian animals of the Ruhuhu and Luangwa basins. These new papers look further back into the Permian.

"The number of specimens we've found in Zambia and Tanzania is so high and their condition is so exquisite that we can make species-level comparisons to what paleontologists have found in South Africa," said Sidor. "I know of no better place on Earth for getting sufficient detail of this time period to make such detailed conclusions and comparisons."

The team's papers describe a number of new species of dicynodonts. These small, burrowing, reptile-like herbivores first evolved in the mid-Permian. By the time of the mass extinction, dicynodonts—many of whom sported a beak-like snout with two small tusks that likely aided burrowing—were the dominant plant-eaters on land. The team's findings also include several new species of large, saber-toothed predators called gorgonopsians, as well as a new species of temnospondyl, a large salamander-like amphibian.

"We can now compare two different geographic regions of Pangea and see what was going on both before and after the end-Permian mass extinction," said Sidor. "We can really start to ask questions about who survived and who didn't."