DNA Analysis of Extinct Horned Crocodile Reveals New Spot in Family Tree of True Crocodiles

The extinct horned crocodile (Voay robustus) is believed to have lived among humans in Madagascar a long time ago before it died out.

A study led by scientists from the American Museum of Natural History recently uncovered information about them that could open doors in understanding the story of crocodiles alive today, according to Phys.org.

The scientists analyzed ancient DNA of the extinct horned crocodile and found that the species was closely related to true crocodiles, such as the famous Nile crocodile. The findings contradict most recent scientific findings on the evolutionary relationships of horned crocodiles and suggest that the ancestors of modern crocodiles most likely came from Africa.

They published their study entitled "Paleogenomics illuminates the evolutionary history of the extinct Holocene "horned" crocodile of Madagascar, Voay robustus," in the journal Communications Biology.

Controversial Spot of Extinct Horned Crocodile in the Tree of Life

AMNH research associate Evon Hekkala, an assistant professor at Fordham University and the lead author of the study, said that the crocodile has been living in Madagascar when people were building pyramids and probably still alive when pirates came to the island.

However, they died out just before humans had genomic tools that will help scientists understand the relationships of living things, according to the science news outlet.

When humans arrived in Madagascar about 9,000 to 2,500 years ago, many species started to go extinct. These include giant tortoises, elephant birds, dwarf hippos, many lemur species, horned crocodiles.

Early Madagascar explorers noted that residents of the island have referred to two types of crocodiles: one is a large, robust crocodile, and the other a more gracile animal that prefers rivers. However, the former went extinct, and only the latter, known as the Nile crocodile, persists until today.

The classification of the horned crocodile in the tree of life remained controversial even after 150 years of scientific investigation, according to SciTech Daily. When it was first discovered in the 1870s, experts believe that it belonged to the true crocodiles that include the Nile, Asian, and American crocodiles.

However, it changed in the early part of the 20th century because experts thought the specimens look like ancient Nile crocodiles. Then, it was debunked again when a study based on physical characteristics of the specimens showed that it was not a true crocodile but that it belongs to the group of dwarf crocodiles.

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Extinct Horned Crocodile Gained Spot in Tree of Life Thanks to Ancient DNA

According to Science Daily, the scientists analyzed the ancient DNA of the extinct horned crocodile taken from the two skulls that have been at the Museum since the 1930s.

Co-author George Amato, the emeritus director of the Museum's Institute for Comparative Genomics said that they have tried to sequence DNA from the fossils before but the lack of technology has prevented their success.

With the help of modern technology, they were able to get DNA from the fossil and finally examined the crocodile's place in the evolutionary tree.

Their findings suggest that horned crocodiles are right next to the true crocodile branch of the tree of life, which means that they are the closest species to the common ancestor of modern crocodiles. Scientists noted that the results were surprising and very informative.

"The placement of this individual suggests that true crocodiles originated in Africa and from there, some went to Asia and some went to the Caribbean and the New World," Amato said.