According to a study published Thursday, the various species of crocodiles that furrow rivers and brackish roads in the Americas, from Florida to Peru, come from Africa.
They may have descended, the researchers speculate, from a single pregnant specimen that swayed along currents from the Atlantic Ocean to the New World at least five million years ago, probably longer.
Based on the high-tech analysis of a skull fragment discovered in the Libyan desert in 1939, the findings are bolstered by genetic evidence pointing in the same direction, they reported in the journal Scientific Reports.
“This is a really exciting discovery,” lead authors Massimo Delfino of the University of Turin and Dawid Iurino, a paleontologist at Sapienza University in Rome, told AFP by email.
“Supports the results of molecular biologists who proposed that the origin of American crocodiles should be found in Africa.”
The narrative outside of Africa is based on a reexamination of the skull and upper jaw of a seven-million-year-old fossil that had been hidden for decades in the drawer of a university museum.
It belonged to an extinct species called Crocodylus checchiai.
Using CT scans and 3D modeling, the scientists identified a telltale bulge in the middle of the animal’s snout that is not found in any other African crocodile, alive or extinct, but present in all four species currently found in the Americas.
In the world of paleontology, this is pretty close to a smoking gun.
“Our results are solid,” the researchers said when asked if the evidence was conclusive.
“The main problem for paleobiologists is the rarity and fragmentary nature of the fossil remains.”
Four other fossils unearthed in Libya at the same time, including a complete skull and jaw, were either destroyed during World War II or lost.
C. checchiai rewrites the story of how crocodiles spread across the planet in at least two ways.
– Lost link –
It supports the long-overdone hypothesis that the giant, meat-rending reptiles, first emerging from Asia, arrived in America before moving to Africa, and not the other way around.
The long-neglected fossil also supplants another African contender, Crocodylus niloticus, also known as the Nile crocodile, as the closest ancestor of the American species.
“According to our results, C. checchiai nests between the Nile crocodile and the American species,” the authors told AFP.
“It represents the missing link between the African and American lineages.”
“Therefore, we can assume that one or more specimens, perhaps a pregnant woman, were dispersed from Africa to America about seven million years ago, at least five million.”
A current cousin, the Australian saltwater crocodile, has shown that such a journey is possible and that satellite tracking can travel 500 kilometers (310 miles) in about a month while passively transported by ocean currents.
More closely related to birds than dinosaurs, egg-laying crocodiles have been around for approximately 55 million years.
There are 16 species distributed in the tropics of Africa, Asia, Australia and, of course, the Americas.
They range in size from less than two meters (six feet) for the dwarf crocodile, to more than seven meters and 1,000 kilos (2,200 pounds) for saltwater species.
Carnivores can replace each of their 80 teeth up to 50 times during their lifespan, which can exceed 60 years.
© 2020 AFP
