sabre toothed cat
This partial fossilized jaw is from a baby Smilodon fatalis. At the time of the cat's death, one of its adult canines (inside, top) was erupting alongside the baby canine (bottom).Wysocki, Feranec, Tseng, and Bjornsson

The large fang-like teeth of the extinct sabre-toothed cat may have emerged in later life despite growing at twice the speed of modern day lion's teeth.

The animal, which is often mistakenly called the sabre-toothed tiger, had protruding canines that grew to around 7 inches (22cms) when the species roamed North and South America around 10,000 years ago.

It has remained unclear at what point in its life that its fearsome fangs may have reached full size, but from using a specimen from the La Brea Tar Pits, LA, a team of scientists from Clemson University combined data from stable oxygen isotope analyses, micro-computed tomography, along with previous studies to establish the growth rate.

Lead author Aleksander Wysocki and colleagues were able to determine that the adult teeth, with exception of its large upper canines, of the sabre-toothed cat would have been fully formed by a maximum of 22 months. Its fangs wouldn't have been fully developed until it was around three years old, according to the report in PLOS One.

However, such were the size of the teeth that they grew at 6mm a month - twice the rate of an African Lion's teeth.

Wysock said: "Despite having canine crown heights that were more than twice those of the lion, it didn't require twice as much time to develop its canines."