Saber Toothed Tigers

Paleontologists from the Royal Ontario Museum and the University of Toronto have found and examined the fossilized remains of two subadult and one adult saber-toothed tigers (Smilodon fatalis) — likely a mother and two adolescents — in the Pleistocene coastal deposits in Ecuador. Their results show that saber-toothed tigers had a unique growth strategy that combined a growth rate that is similar to a tiger and the extended growth period of a lion.

An artist’s impression of Smilodon fatalis. Image credit: Sergio De la Rosa / CC BY-SA 3.0.

Smilodon is a genus of extinct felids that lived in the Americas during the Pleistocene epoch, between 2.5 million and 10,000 years ago.

Commonly known as saber-toothed tigers, it includes three recognized species: Smilodon fatalis, S. gracilis, and S. populator.

“The saber-toothed cat Smilodon occurred throughout North America and South America during the Pleistocene,” said lead author Ashley Reynolds and colleagues.

“Of the three recognized species, Smilodon fatalis is the most completely known, with thousands of well-preserved specimens in collections from so-called ‘tar pits’.”

“Without the necessary evidence to determine associations between individuals of Smilodon fatalis due to reworking and time-averaging, inferences about social behavior are exceptionally difficult to infer from such ‘predator trap’ deposits. Thus, smaller fossil assemblages of associated individuals preserved in fluviodeltaic depositional environments may be more useful for inferring aspects of life history and social behavior in these carnivores.”

“We describe a multiple individual association of Smilodon fatalis preserved in a fluviodeltaic depositional setting in Ecuador,” they added.

“Our analysis suggests that this assemblage is best interpreted as a part of a family group derived from a catastrophic mass mortality event, and thereby provides unique insights into the life history of this iconic predator.”

Smilodon fatalis cubs. Image credit: Danielle Dufault, Royal Ontario Museum.

The fossilized partial jaws and skeletal elements from at least two subadult siblings and a single mature individual of Smilodon fatalis were found at the Coralito locality in Ecuador.

“Our study started out as a simple description of previously unpublished fossils,” Reynolds said.

“But when we noticed the two lower jaws we were working on shared a type of tooth only found in about 5% of the Smilodon fatalis population, we knew the work was about to become much more interesting.”

Reynolds and co-authors found that they were likely looking at three related individuals: one adult and two young adolescents.

They determined that the siblings were at least two years old, an age at which some living big cats, such as tigers, are already independent.

“The social lives of these iconic predators have been mysterious, in part because their concentration in tar seeps leaves so much room for interpretation,” said Dr. Kevin Seymour, co-author of the study.

“This historic assemblage of saber-cat fossils from Ecuador was formed in a different way, allowing us to determine the two juveniles likely lived, and died, together — and were therefore probably siblings.”

A paper on the findings was published this week in the journal iScience.

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Ashley R. Reynolds et al. Smilodon fatalis siblings reveal life history in a saber-toothed cat. iScience, published online January 7, 2021; doi: 10.1016/j.isci.2020.101916