Palaeogene Crocodile Fossil Suggests Crocodiles Quick to Exploit Dinosaur Extinction

The fossilised remains of an ancient crocodile have been discovered by a team of American scientists whilst working underground exploiting a rich, fossiliferous seam in a Colombian coal mine.   This crocodile has been identified as a new species and at more than six metres long it was a sizeable reptile, one whose ancestors survived the Cretaceous mass extinction event and quickly adapted to exploit predatory niches once occupied by the Dinosauria.

The new species of crocodile was discovered by a team of University of Florida researchers, led by Jonathan Bloch Associate Curator of Vertebrate Palaeontology at the Florida Museum of Natural History assisted by Carlos Jaramillo, a palaeobotanist with the Smithsonian Tropical Research Institute.

A Picture of Alex Hastings with the Fossils from the Crocodile Specimens

Assembling the fossil evidence for Acherontisuchus

Picture Credit: Kristen Grace/Florida Museum of Natural History

This crocodile Acherontisuchus guajiraensis is just one of a number of amazing fossil discoveries made by the research team as they explore the underground strata which represent sediments laid down in a tropical Amazon-like environment approximately sixty million years ago.  A species of super-thick shelled Chelonian had been described recently, the  reason for the strong carapace being revealed with the discovery of fossils of this fearsome crocodile.

To read more about this discovery: Fossil Turtle Had Super-Thick Shell to Defend Itself from Predators

Perhaps the most astonishing discovery made to date in the Cerrejón coal mine was the fossils of an enormous snake, the largest known in the fossil record.  The snake, a constrictor is estimated to have measured more than fifteen metres long and weighed as much as 1,200 kilogrammes.  The snake was named Titanoboa cerrejonensis it would have been an apex predator in the rain forest environment but from our research the paper’s published indicate that this snake was more closely related to Boas than to the Amazon’s largest snake – the Anaconda.

To read more about Titanoboa: Titanoboa – Super huge Snake of the Tertiary

The holotype specimen for this new species was actually collected  by Alex Hastings, a University of Florida PhD student in the department of geological sciences.  The coal mine is a particularly unpleasant place to work.  The coal seams can spontaneously combust and they give off a powerful and very unpalatable sulphurous odour.  This coupled with the extreme heat and humidity makes the excavation of fossils extremely difficult.

A. guaijraensis was a member of a crocodile family that were not direct ancestors of today’s crocodiles, gharials, caiman or alligators, but this discovery is important as it is helping scientists to build up a picture of ecosystems in the aftermath of the Cretaceous mass extinction event.  Judging by the size of this new crocodile species and Titanoboa it seems that sixty million years ago reptiles still ruled the world, at least in South America.

It seems that the Acherontisuchus genera survived the cataclysm that led to the Dinosaurs demise and interestingly, this fossil is the first evidence of a large crocodile member of this genera being associated with a freshwater habitat.  Previously, all fossil evidence of large crocodiles ascribed to the Acherontisuchus genera had been found in association with marine environments.  This suggests that crocodiles were quick to adapt to and exploit niches vacated by other animals that did not survive the mass extinction event.

An Illustration of Acherontisuchus guaijraensis

Colombia – sixty million years ago

Picture Credit: Florida Museum of Natural History

Commenting on this discovery, student Alex Hastings stated:

“One of the questions about this group was how were they able to survive – what advantages did they [Acherontisuchus genera] have?  What this new crocodile really contributes to is that it is the first evidence of a large-bodied member of this group being found in freshwater.  Before now, it was thought that only baby crocodiles would spend any appreciable amount of time in freshwater and that adults spent most of their time in a saltwater environment.”

The size estimates for this new species have been scaled up from the larger of two individual specimens discovered at the site.  Based on an analysis of the limited skull and jaw material, scientists have described this crocodile as having a long narrow snout, superficially resembling that of an extant gharial.  It seems from the shape of the jaws that this crocodile was primarily a piscivore (fish-eater).  The Cerrejón coal mine is proving to be a rich source of evidence about tropical Palaeogene environments just a few million years after the dinosaurs disappeared.  We suspect that more amazing fossils await discovery, perhaps another big crocodile, one that could even match the likes of Sarcosuchus imperator in terms of size.

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