Giant crocodile killed a 175-pound sloth 13 million years ago

Prehistoric sloth unearthed in the Amazonian rainforest was killed by a giant crocodile that stalked the swamps 13 million years ago, bite-scarred shin bone reveals

  • Shin of the 175-pound sloth was found in Peru in 2004 and has been studied  
  • Scientists found a total of 46 tooth marks on the bone from repeated grasping
  • Believe it is from a juvenile member of the crocodilian species Purussaurus 

A giant ground sloth the size of a large capybara was killed by a 13-foot long juvenile crocodilian 13 million years ago, a study reveals. 

The 175-pound animal’s shin from a hind leg was found in modern-day Peru in 2004 and analysis reveals it dates back to when the area was a proto-Amazonian wetland. 

Researchers analysing the bone believe the leg was clenched in the powerful jaws of the Purussaurus, the giant Miocene caiman which grew up to 20 ft long. 

However, it is thought this specific predator was a youngster who was yet to reach its full size when it killed the sloth. 

Pictured, an artist’s impression of a Purussaurus attacking a sloth. A prehistoric sloth unearthed in the Amazonian rainforest was killed by the biggest known species of crocodilian to ever lived, reveals new research

Pictured, the shin bone of the giant sloth as it was seen in 2004 when first spotted by archaeologists in Peru 

The 46 teeth marks on the bone present key clues as to the identity of the animal responsible for the bite.  

Writing in their paper, academics from Universidad Peruana Cayetano Heredia in Peru believe the predator grasped repeatedly at the leg and may have even tried to rip the limb from the body of the sloth. 

A process of elimination removed six of the seven known crocodilians from this period of time for being either too small, weak or different shaped teeth. 

The proto-Amazonian wetlands in which the battle occurred had not yet been conquered by mammals and the only land-dwelling carnivores were a handful of marsupials.

However, the dentition did not align with the tooth marks of these animals, leaving the Purussaurus as the only possible perpetrator.  

Corresponding author Dr Rodolfo Salas-Gismondi, of Cayetano Heredia University, Lima, said: ‘The bone bore 46 tooth marks. The 13-stone creature was meandering the swamps of primitive Amazonia.

‘Unexpectedly, the Purussaurus leapt out and captured it by the lower hindlimb.

‘The bite was so powerful many teeth perforated the shinbone and collapsed extensive portions of the outer layer. The ground sloth did not survive.’

The fossil remains of 22 Ice Age sloths the size of elephants have been found preserved in asphalt in Ecuador, researchers have reported.

The specimens — which include 15 adults, 5 juveniles and two newborns or fetuses — were unearthed from the Tanque Loma site on the country’s Santa Elena peninsula.

Weighing in at several tons, the sloths — of species Eremotherium laurillardi — had the ability to walk on two legs and move fast, unlike their languid modern relatives. 

Instead of falling into a tar pit and getting stuck, experts believe the giant animals died 20,000 years ago from drinking water contaminated by their own faeces.

They were then preserved by being coated in seeping asphalt, along with an ancient horse, a deer, an armadillo-like pampathere, and an elephant-like gomphothere.

The study of the fossilised remains has been led by University of California Los Angeles palaeontologist Emily Lindsey, who is also an assistant curator and excavation site director at the famous La Brea Tar Pits.

‘For years, everyone has thought of the classic scenario at the La Brea Tar Pits, where a large herbivore would get stuck in asphalt, then a bunch of carnivores would be attracted to the trapped animal and get stuck… etc,’ Dr Lindsey told Gizmodo. 

‘Nothing got stuck at Tanque Loma! The animals died in an aquatic setting like many other fossil sites, and the bones just fortuitously got preserved by seeping asphalt.

‘It blew my mind when I first realised that,’ she added. 

Purussaurus was capable of performing the ‘death roll’ manoeuvre today’s crocodiles use to kill and this was likely the fate which befell the sloth, researchers believe. 

The giant cayman was an apex predator and fed on large vertebrates, snakes, turtles, mammals and birds, and had a bite twice as powerful as T Rex’s.

Following the demise of the dinosaurs, the Purussaurus was the largest predator the world had seen and has no parallel in the modern world.

Dr Salas-Gismondi said: ‘The bite force of an adult Purussaurus has been calculated as being more than four times the strongest bite ever measured in the modern animal kingdom – the saltwater crocodile.

‘With this bite force, adult Purussaurus individuals were able to incorporate to their diet anything, no matter the size or hardness!’

Purussaurus thrived across Amazonia until around seven million years ago and their skulls have been found all over South America. 

Dr Salas-Gismondi said the Purussaurus and the ground sloth inhabited an area known as the Pebas System.

This was a predominantly aquatic environment of lakes and swamps that flourished in northwestern South America between 20 and 11 million years ago.

‘Purussaurus was probably lurking from the swamps and the ground sloth might have roamed the shores of lakes and swamp to eat plants,’ explains Dr Salas-Gismondi.

‘This proto-Amazonian ecosystem occurred before the onset of the Amazon River System and was characterised by the extensive diversification and abundance of crocodiles and aquatic molluscs.

‘Seven crocodile species have been documented living together 13 million years ago, including three small ones that might have fed upon molluscs.

‘The top predator of this ecosystem was the giant caiman Purussaurus. 

‘All the palaeontological evidence supporting knowledge about this ecosystem was recovered in the rocks of the Pebas Formation of the Peruvian Amazonia by our international team.’ 

The full findings are described in the journal Biology Letters.  

The fossilised bone included the claw of the sloth (pictured). After being discovered in 2004, researchers were unable at the time to identify how the animal died but fresh analysis has solved the conundrum 

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