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Found almost a century ago in the Sahara desert, analysis of the only well-preserved crocodile skullCrocodylus checchiai, seven million years old, reveals anatomical details similar to modern American species, placing it at the base of the evolutionary tree.
According to the work, some specimens would have swum from Africa to America during the Miocene.
Crocodylus checchiai, acrocodile seven million years old, whose skull was excavated almost a century ago at the As Sahabi site (Libya), shares with the fourcurrent American species (Crocodylus intermedius, C. moreleti, C. acutus YC. rhombifer) numerous anatomical peculiarities.
This is now confirmed by a study, published in the journalScientific Reports. These cranial similarities place it at the base of theevolutionary tree as an ancestor of the genusCrocodylus In America.
The oldest fossils of this taxon in the New World are about five million years old, and researchers postulate that some specimens ofC. checchiai (or a similar and still unknown form) crossed theAtlantic Ocean from Africa to South America, where they adapted and diversified.
"It may seem like an incredible feat for a crocodile," he explains.Massimo delfino, researcher at the University of Turin in Italy and the Institut Català de Paleontologia Miquel Crusafont (ICP). Among today's crocodiles there are species capable of tolerating the high salinity of sea water and making large movements in the open sea taking advantage of surface currents.
“Studies carried out with satellite tracking have shown that Australian crocodiles can travel distances of more than 500 kilometers across the sea in a few weeks”, Recalls the researcher.
Fossils of the crocodile ancestor skull
Delfino, together with other Italian researchers from the University of Rome and the University of Florence, analyzed the fossil using non-invasive methods at the MG Vannini Hospital (Rome). Thanks to a computed tomography scanner, they obtained high-resolution images of the exterior and interior of the skull.
From the information obtained, the scientists concluded that it was aadult specimen and they estimated the length of the body at more than three meters. The anatomical details also allowed to carry out aphylogenetic analysis, that is, to reconstruct the evolutionary history of this group by comparing their anatomical characteristics by means of asoftware specific.
The site ofAs Sahabi It is located about 130 km from the city of Ajdabiya, in the Libyan part of the Sahara desert. Currently it is an extremely arid area, but during the Upper Miocene it was a territory crossed by rivers and covered with extensive vegetation in which a great diversity of fauna inhabited, including large mammals and reptiles.
During the 30s of the last century, some Italian geologists and paleontologists such asArdito Desio, Giuseppe Stefanini YCarlo Petrocchi They starred in several scientific expeditions that uncovered a large number of mammal, fish and reptile fossils, including five perfectly preserved crocodile skulls, including the subject of this research.
Unfortunately, during World War II many of the fossils housed in the Tripoli Museum of Natural History were destroyed or lost. The fate of some of the skulls that were sent to Naples was no better. Due to the bombings and looting of the middle of the last century, its trace was lost and only two of the skulls deposited in Rome were preserved.
Almost a century later, the study researchers have been able to study the only (the other is missing) skull "surviving" from this journey, which is currently preserved in theUniversity Museum of Earth Sciences from the University of Rome La Sapienza.
Delfino, M., Iurino D., Mercurio B., Piras P., Rook L. & Sardella R. (2020). "Old African fossils provide new evidence for the origin of the American crocodiles".Scientific ReportsJuly 23, 2020.