According to a team of scientists headed by Dr Ross MacPhee from the American Museum of Natural History, South American native ungulates – the last of which went extinct roughly 10,000 years ago – are actually related to mammals like horses, tapirs, and rhinoceroses, rather than elephants and other species with ancient ties to Africa as some paleontologists have believed.

South American ungulate mammals Macrauchenia patachonica. Image credit: Olga Kobrina / CC BY 3.0.

“Fitting South American ungulates to the mammalian family tree has always been a major challenge for paleontologists, because anatomically they were these weird mosaics,” explained Dr MacPhee, the senior author on the study, published in the journal Nature.

The scientists analyzed fragments of collagen – a structural protein found in all animal bones – recovered from 48 fossils of South American ungulate mammals Toxodon platensis and Macrauchenia patachonica.

They were able to conclusively show that the closest living relatives of these species were the Perissodactyla (odd-toed ungulates), a group that includes horses, rhinos, and tapirs.

“By selecting only the very best preserved bone specimens and with various improvements in proteomic analysis, we were able to obtain roughly 90 percent of the collagen sequence for both species. This opens the way for various other applications in paleontology and paleoanthropology, which we are currently exploring,” said study lead author Frido Welker of the Max Planck Institute for Evolutionary Anthropology and the University of York.

The results support the idea that the ancestors of Toxodon platensis and Macrauchenia patachonica came from North America more than 60 million years ago, probably just after the mass extinction that killed off non-avian dinosaurs and many other vertebrates.

Because the South American ungulates were such a large and varied group, it is not clear whether other lineages not studied by the team all had the same origin.

“People have been successful in retrieving collagen sequences from specimens dating up to 4 million years old, and this is just the start. On theoretical grounds, with material recovered from permafrost conditions, we might be able to reach back 10 million years,” said co-author Prof Matthew Collins of the University of York, UK.

Source: sci.news