Macrauchenia patachonica is an ancient mammal classified through a genetic analysis

Reconstruction of Macrauchenia Patachonica (Image courtesy Jorge Blanco/American Museum of Natural History)
Reconstruction of Macrauchenia Patachonica (Image courtesy Jorge Blanco/American Museum of Natural History)

An article published in the journal “Nature Communications” describes a genetic research on Macrauchenia patachonica, a mammal that lived in South America between 7 million and 20,000 years ago. A team of researchers managed to extract mitochondrial DNA from a fossil discovered in southern Chile and compared it to that of other mammals establishing that the closest relatives to the genus Macrauchenia are perissodactyls, the order to which horses, rhinos and tapirs belong.

The first fossil belonging to the Macrauchenia genus was discovered in 1834 by Charles Darwin during his famous journey on the Beagle. The naturalist was carrying out one of his surveys, in this case in Patagonia, and was really puzzled by this mammal’s strange characteristics that in some respects resembled a camel, in some others a rhino and in others some other mammals.

At the return of the Beagle, Charles Darwin submitted the bones he discovered to the paleontologist Richard Owen, who found similarities with llamas and camels. The name Macrauchenia means “long-necked llama” and was chosen by Owen exactly for that resemblance. Over time, other fossils that were attributed to the genus Macrauchenia were found with the proposal of other species but there was also a controversy regarding these mammals’ taxonomic classification.

Charles Darwin and Richard Owen were also puzzled by the peculiar characteristics of Macauchenia patachonica and the issue went on until a few years ago. Just over two years ago an article published in the journal “Nature” described a biochemical research on this mammal. The DNA doesn’t preserve well in the warm and humid South American climate so the researchers decided to conduct a study based on collagen, a protein that can preserve much longer.

The amino acids that make up collagen contain a sort of genetic signature because their chemical structure is dictated by the specific DNA sequences of the organism that encodes the protein. This means that a collagen analysis and a comparison with that produced by other mammals can provide information about their relationships almost as much as a direct genetic confrontation.

According to the collagen test, the closest living relatives of Macauchenia patachonica are perissodactyls. Now this new research based on mitochondrial DNA made it possible to verify that result because it’s a genome passed from mothers to children so the differences show the closeness of relationships between two organisms.

Mitochondrial DNA is smaller than that of the nucleus and has multiple copies within the cells. The consequence is that it’s easier to extract enough fragments to reconstruct a complete version or at least most of it from ancient bones. In this case, the researchers managed to put together about 80% of that genome, a good amount to compare Macauchenia patachonica’s relationships.

The results of the mitochondrial DNA analysis confirmed those obtained from the 2015 collagen-based research showing that the closest living relatives of Macauchenia patachonica are perissodactyls. This type of analysis is more accurate and allowed to estimate that the separation of the Macrauchenia genus from the perissodactyla order occurred about 66 million years ago at time of the mass extinction that wiped out dinosaurs.

The confirmation of the previous research’s results is important and also shows the advances in genetic techniques that today allow to obtain at least mitochondrial DNA from ancient bones. Animals that for a long time caused perplexity in scientists because of their characteristics today can be classified with certainty.

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