Giant Miocene Caiman Preyed on Ground Sloths

Friday, August 28, 2020

Life reconstruction of the putative attack of a young to sub-adult Purussaurus on the ground sloth Pseudoprepotherium in a swamp of proto-Amazonia. Image credit: Jorge A. González.

Purussaurus, a top predator that lived in the wetlands of proto-Amazonia between 6 and 13 million years ago (Miocene epoch), hunted not only aquatic animals but also land-dwelling creatures like ground sloths, according to a paper published in the journal Biology Letters.

Following the extinction of non-avian dinosaurs, the largest continental predator was neither a mammal nor a bird, but the giant caiman Purussaurus.

This carnivorous animal inhabited South America during the middle and late Miocene, when a system of wetlands flourished in northwestern Amazonia.

Purussaurus exceeded 10 m (33 feet) long and had a broad, massive skull and robust jaws with conical and blunt teeth.

In October 2004, Dr. François Pujos of the Instituto Argentino de Nivología and colleagues discovered Miocene-epoch bonebeds near Iquitos City in Peru.

One bonebed preserved swamp deposits bearing diverse aquatic and land-dwelling vertebrate assemblages, particularly rich in fish, turtle, reptile and mammal remains.

Among the fossils, the paleontologists found a 13-million-years-old severely damaged long bone of a massive mammal.

The team’s preliminary examination of the specimen revealed 46 tooth marks that were inflicted prior to fossilization.

Left tibia of Pseudoprepotherium and mapping of the bite marks: photograph and schematic drawing in anterior (i and ii) and posterior (iii and iv) views. Image credit: François Pujos & Rodolfo Salas-Gismondi, doi: 10.1098/rsbl.2020.0239.

In a new study, Dr. Pujos and his colleague, Dr. Rodolfo Salas-Gismondi from the Universidad Peruana Cayetano Heredia, aimed to identify the putative perpetrator of the attack and its victim.

They found that the bone belonged to Pseudoprepotherium, a middle-sized ground sloth (body weight – 78.5 kg, equivalent to a large capybara) that lived in Colombia, Brazil and Venezuela during the Miocene.

“The combination of round and bisected, shallow pits and large punctures that collapsed extensive portions of cortical bone points to a young or sub-adult Purussaurus neivensis (approximately 4 m, or 13.1 feet, in total length) as the perpetrator,” the researchers said.

“The pattern of tooth marks suggests that the perpetrator attacked and captured the ground sloth from the lower hind limb, yet an attempt of dismembering cannot be ruled out.”

“This discovery from the Peruvian Amazonia provides an unusual snapshot of the dietary preferences of Purussaurus,” they added.

“It also reveals that prior to reaching its giant size, young individuals might have fed upon terrestrial mammals of about the size of a capybara.”


François Pujos & Rodolfo Salas-Gismondi. 2020. Predation of the giant Miocene caiman Purussaurus on a mylodontid ground sloth in the wetlands of proto-Amazonia. Biol. Lett 16 (8): 20200239; doi: 10.1098/rsbl.2020.0239