Monday , December 11 2017

Pakakali rukwaensis: Paleontologists Discover New Carnivore from Oligocene Epoch

An international team of paleontologists from the United States, Australia and Tanzania has discovered a new species of hyaenodont that lived 25 million years ago during the Oligocene epoch, in what is now the Rukwa Rift Basin, Tanzania.

Artist’s reconstruction of Pakakali rukwaensis. Image credit: NSF / Ohio University.

Artist’s reconstruction of Pakakali rukwaensis. Image credit: NSF / Ohio University.

The new carnivore is named Pakakali rukwaensis and belongs to an extinct lineage of placental mammals called Hyaenodonta (hyaenodonts).

The fossil was unearthed in the fossil-rich beds of the Nsungwe Formation in southwestern Tanzania.

As reported in the journal PLoS ONE, it gives paleontologists a glimpse of hyaenodont anatomy before modern carnivores invaded the African continent, revealing that Pakakali rukwaensis was about the size of a bobcat.

“After the extinction of the non-avian dinosaurs 66 million years ago, hyaenodonts were the main predators on the African continent,” said Ohio University paleontologists Nancy Stevens and Matthew Borths.

“Between 23 and 25 million years ago, ancient relatives of modern dogs, cats and hyenas arrived in Africa, where they coexisted with hyaenodonts for millions of years. But eventually, hyaenodonts went extinct.”

Pakakali rukwaensis provides new information — based on teeth, biogeography and phylogenetic analysis — about the transition of carnivores in older ecosystem types to carnivores in today’s African ecosystems,” said Dr. Judy Skog, program director in the National Science Foundation’s Division of Earth Sciences, which funded the research.

“The shift from hyaenodonts to modern carnivores in Africa is like a controlled experiment,” Dr. Borths added.

“We start with only hyaenodonts. Then the relatives of cats and dogs arrive. They coexist for a few million years, then the hyaenodonts are driven to extinction and we’re left with ‘The Lion King.’ With Pakakali rukwaensis, we can start to unravel that extinction. Were the lineages competing? Were they adapting differently to a drier, more open landscape?”

According to the team, Pakakali rukwaensis was discovered in the same rocks as the oldest fossil evidence of the split between Old World monkeys and apes.

At that time, the ecosystem was undergoing dramatic climate and tectonic upheavals as Africa collided with Eurasia and the modern East African Rift System formed.

“Based on the findings of the study, hyaenodonts may have been pushed to become more specialized meat-eaters due to competition from other species,” the paleontologists explained.

“That dietary specialization may have made hyaenodonts more vulnerable to extinction in the changing African ecosystem by leaving them with fewer food choices.”

“The environment containing Pakakali rukwaensis reveals a fascinating window into extinction. It highlights the vulnerability of carnivorous species to rapid environmental change, a topic we are grappling with on the African continent today,” Dr. Stevens said.

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M.R. Borths N.J. Stevens. 2017. The first hyaenodont from the late Oligocene Nsungwe Formation of Tanzania: Paleoecological insights into the Paleogene-Neogene carnivore transition. PLoS ONE 12 (10): e0185301; doi: 10.1371/journal.pone.0185301

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