A crocodile that lived more than six million years ago pointed to the maritime past of gharials

(ORDO NEWS) — Paleontologists have discovered fossils of a saltwater crocodile from the gharial family that lived off the Pacific coast of South America 19 million to 6.33 million years ago. The scientists named it Sacacosuchus cordovai.

Together with him, paleontologists found the fossil remains of another marine gharial, already known to science.

The discovery of another marine species of gharials suggests that this group was originally adapted to life in the sea, and only then some species, including the ancestors of modern gharials, became freshwater. The study was published in Proceedings of the Royal Society B.

Crocodylomorphs (Crocodylomorpha) have colonized the marine environment several times throughout their history.

Among them are teleosauroids (Teleosauroidea) and metriorhynchoidea (Metriorhynchoidea) from the talattosuchian group, some representatives of folidosaurids (Pholidosauridae), dirosaurids (Dyrosauridae) and crocodiles proper (Crocodylia), as well as thoracosaurs.

Metriorhynchidae (Metriorhynchidae) adapted best to life at sea: they even had to become viviparous, since they could not go on land.

A crocodile that lived more than six million years ago pointed to the maritime past of gharials 2
Diversity of marine crocodilomorphs throughout the Mesozoic and Cenozoic. Teleosauroids are shown in green, metriorhynchoids in blue, pholidosaurids in yellow, dirosaurids in gray, thoracosaurs and crocodiles proper in red. The height of the bar is the number of births. Red line – sea surface temperature

Ancient saltwater crocodiles belong to the Gavialoidea group. Today, gharialoids are represented only by freshwater forms: the Gangetic gharial (Gavialis gangeticus) and the gharial crocodile (Tomistoma schlegelii).

Most other modern crocodiles also live in fresh water, and only two species – combed (Crocodylus porosus) and sharp-snouted crocodile (C. acutus) – can live in salt water.

Saltwater crocodile fossils were studied by Rodolfo Salas-Gismondi of the Cayetano Heredia University in Lima and colleagues from Peru, the US and France.

Fossils have been found in marine deposits of the Chilcatay and Pisco formations in southern Peru. Scientists have found that the fossils belonged to gharials (Gavialidae): piscogavial (Piscogavialis jugaliperforatus), as well as an unknown species.

Paleontologists named the new gharial Sacacosuchus cordovai. The generic name is given in honor of the locality of Sakako, where the fossils were found, and the specific name is in honor of Professor Jesús Córdova for his contribution to the development of paleontology in Peru.

Scientists estimated the length of the type specimen of sakacosuchus at 4.31 meters, which is much less than that of the piskogavial, whose length reached 7.76 meters. For comparison: the maximum length of the modern Gangetic gharial is 6.25 meters.

Fossil ages of the piscogavial have ranged from 18.78 to 4.85 million years (Miocene and Pliocene) and those of the Sacacosuchus ranged from 19–18 to 6.33 million years (Miocene). Thus, sea gharials lived off the coast of South America for 14 million years.

Their fossils have been found along with typical marine vertebrates: sharks, whales, seals and water sloths. In addition, Sacacosuchus fossils belonged to individuals of different ages. All this suggests that these gharials really lived in the marine environment.

The more elongated jaws of the piscogavial indicate that it preyed on fish like the modern gharial, while sakacosuchus was a predator with a wide range of prey, like the modern gharial crocodile. Both types of ancient gharials kept in shallow water.

The discovery of the next marine gharial indicates that adaptations to life in the sea were characteristic of the common ancestor of the gharialoids, and only then some lines, including the ancestors of the Gangetic gharial and the gharial crocodile, inhabited the freshwater environment.

Paleontologists also conducted a biogeographic analysis, which showed that the gharialoids most likely originated on the Tethys coast or in northern Europe, from where they then spread throughout the world, including South America. Today gavialoids have survived only in South (gharial) and Southeast Asia (gharial crocodile).

A crocodile that lived more than six million years ago pointed to the maritime past of gharials 3
Phylogeny of crocodiles and their closest relatives (including thoracosaurs) with reconstruction of ancestral ranges. Tethys coast marked in yellow

The authors believe that the piskogavial and sakacosuchus were most likely killed by a change in sea level (regression), as well as the appearance of a cold Humboldt current.

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