Miocene Fossil from Africa Provides New Evidence for Origin of American Crocodiles

Exploring Prehistoric Life
Paleontologists
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Tuesday, July 28, 2020

Life appearance of Crocodylus checchiai from As Sahabi, Libya. Image credit: D.A. Iurino.

A team of paleontologists from Italy and Spain has compared the only well-preserved skull of Crocodylus checchiai, an extinct species of crocodile that lived in what is now Libya about 7 million years ago (Miocene epoch), to those of the four living species of crocodiles from the Americas and found that the ancient African reptile is closely related to the American crocodiles. The findings suggest that crocodiles may have migrated from Africa to America during the Miocene.

The skull and associated lower jaw of an adult Crocodylus checchiai were collected in 1938 at the paleontological site of As Sahabi in northern Libya.

The specimen was described in 1947 by the Italian paleontologist Angiola Maria Maccagno and then hosted in the collections of the Istituto di Paleontologia dell’Università di Roma.

In order to improve the knowledge about Crocodylus checchiai and its possible relationships with the American crocodiles, Dr. Massimo Delfino from the Università di Torino and the Universitat Autònoma de Barcelona and his colleagues tried to locate the original Crocodylus checchiai skull.

The researchers succeeded in finding it in the collection of the Museo Universitario di Scienze della Terra of Sapienza University of Rome.

They then used computed tomography (CT) imaging to re-examine the well-preserved specimen.

The 7-million-year-old skull of Crocodylus checchiai from As Sahabi, Libya, in dorsal (a1, a2), ventral (b1, b2), right lateral (c1, c2) and left lateral (d1, d2) views. Anatomical abbreviations: bo – basioccipital, bs – basisphenoid, ect – ectopterygoid, en – external naris, f – frontal, if – incisive foramen, itf – infratemporal fenestra, j – jugal, l – lacrimal, m – maxilla, n – nasal, o – orbit, pa – parietal, pal – palatine, pf – prefrontal, pm – premaxilla, po – postorbital, pt – pterygoid, q – quadrate, qj – quadratojugal, soc – supraoccipital, sof – suborbital fenestra, sq – squamosal, stf – supratemporal fenestra, t – tooth. Scale bar – 10 cm. Image credit: Delfino et al, doi: 10.1038/s41598-020-68482-5.

They identified several new inner structures including a protrusion in the middle of the snout that has not been identified on any other African crocodile species.

This unique structure, called the mid-rostral boss, is also present in the four living American crocodile species: Crocodylus intermedius, C. moreletii, C. acutus and C. rhombifer, and indicates a close evolutionary relationship between Crocodylus checchiai and the crocodiles from the Americas.

“Analyses of the evolutionary relationships between species suggest that Crocodylus checchiai may be part of the same lineage as the four American crocodile species,” the scientists said.

“The remains of Crocodylus checchiai have been dated to around 7 million years ago while the oldest remains of an American crocodile, the extinct Crocodylus falconensis, have been dated to around 5 million years ago.”

“Based on these findings, we propose that crocodiles reached America by migrating westwards from Australasia via Africa.”

The findings were published in the journal Scientific Reports.

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M. Delfino et al. 2020. Old African fossils provide new evidence for the origin of the American crocodiles. Sci Rep 10, 11127; doi: 10.1038/s41598-020-68482-5

Source: www.sci-news.com/