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Identification of Fossil Solves a Long-Time Mystery for Scientists

One of the mysteries of paleontology has persisted for more than 100 years – the classification of the Necrolestes patagonensis fossil. An international team of researchers, including Carnegie Museum of Natural History scientist John Wible, has found an answer – it’s a mammal. What it was has remained an enigma, even though three “beautiful” fossils of it were found in South America in 1891.

“You would think with beautiful material that you ought to be about to figure out what it is, but nobody has been able to do it, even though we had very nice, fairly complete specimens,” said Wible, “and the reason nobody has been able to do it is because the things that Necrolestes was related to, much older in the fossil record, weren’t found until about 20 or fewer years ago.”

That recent discovery of Necrolestes’ relatives presents another mystery. It moves forward the endpoint for the fossil’s evolutionary lineage by 45 million years. That means that particular family of mammals survived the extinction event that wiped out the dinosaurs. This is an example of what scientists call the Lazarus Effect, in which a group of organisms is found to have survived far longer than previously thought.

“Necrolestes is about 16 million years old, its closest relative is about 61 million years old, so there’s a 45 million year gap between this animal and its closest relative,” said Wible.

That means scientists now have to work to fill a 45 million year gap in Necrolestes’ lineage.

“It had to have some relatives in the fossil record for that lineage to survive that long, so now we have to go back to South America and work harder to find relatives to Necrolestes and its closest ancestor,” said Wible.

Necrolestes Patagonensis (which translates to grave robber) had an upturned snout and large limbs for digging. The scientific paper resolving the mystery appears in the Proceedings of the National Academy of Sciences USA.