The ancestor of the four modern species of American crocodiles could be African species Crocodylus checchiai, who lived about seven million years ago. To such conclusion the paleontologists studied the skull of this reptile with the help of new technologies. Previously it was thought that American crocodiles are descended from the Nile. However, whichever of these two species either had an ancestor of American crocodiles, there is no doubt that he lived in Africa and managed to cross the Atlantic, noted in an article for the journal Scientific Reports.
North American alligators (Alligator mississippiensis) and caimans from Central and South America is well known to anyone interested in wildlife. Far fewer people know that in America and on the Caribbean Islands inhabited by these crocodiles of the genus Crocodylus: Cuban (C. rhombifer), American (C. acutus), orinocco (C. intermedius) and Central American (C. moreletii).
All these species form a single evolutionary branch. She is relatively young: it is believed that its ancestors lived in Africa and crossed the Atlantic ocean from five to eleven million years ago. It is sometimes argued that these ancestors were Nile crocodiles (C. niloticus) — this view from a molecular point of view have the closest modern relative of the American crocodile. However, in the discussion about the evolution of this group still lacked a solid paleontological arguments.
A team of researchers headed by Massimo Delfino (Delfino Massimo) from the University of Turin decided to fill this gap. They focused on fossil species of crocodiles C. checchiai, the remains of which was first discovered in 1938 at the site of As-Sahabi in the North of Libya, and described in 1947. Many of the early specimens of this species were lost during the Second world war, however, the authors managed to find one of them in the collection of the University of Rome.
Using modern technology, researchers have re-described the skull of C. checchiai. In particular, using tomography, they were able to study the internal structure that were inaccessible to palaeontologists the first half of the twentieth century. The obtained results were compared with the taxonomic features of the living crocodiles and the most ancient of the American crocodile is now extinct C. falconensis from the early Pliocene of Venezuela (5.3 to 3.6 million years ago).
The analysis revealed that the C. checchiai and all the American crocodile thing in common — the hill in the middle of the muzzle. All African species it is absent. This means that C. checchiai, and not the Nile crocodile, should be considered the closest relative of the African American branch. Moreover, it could be their direct ancestor, because he lived about seven million years ago, which fits into the time period when these crocodiles are assumed to have appeared in America.
In Mesozoic crocodiles and their relatives were much more diverse than it is today. Some members of the superorder of crocodylomorphs even walked on two legs. According to recent research, these beings have left traces of age 125-112 million years around the South Korean city of Gyeongju. Previously they have been attributed to pterosaurs.