Sabertooth kittens had thick bones

Glacial tumors have unusually strong bones from birth

Saber-toothed cats had unusually strong paws with thick bones - so they could hold even large prey. © RAlf Power
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Already the babies were stronger: The saber-toothed cats possessed unusually strong bones already from birth. Fossil comparisons reveal that the kitten's paws were significantly thicker and more robust than those of other predators of the same age. If the saber-toothed kittens then grew up, their bones only increased in length. This clarifies the long-standing question of how and when the glacial cats came to their paws.

Strong, clawed paws, long, dagger-shaped canines and the size of a full-grown lion: The saber-toothed cats, which were widespread in North America and Europe until about 10, 000 years ago, were among the dominant predators of the last ice age. They did not even shrink from large and well-endowed prey such as mammoths, mastodons or bisons. Typically, the saber-toothed cats seized their prey with their powerful forelegs, held it, and then bit their throat with their long canine teeth.

Pitch pit as ice age mass grave

Fossil finds show that the saber-toothed cats had unusually strong and thick bones. Especially her front paws were optimally adapted to the ability to hold even large prey. Until now, however, it was unknown when the big cats developed these powerful bones: Did they develop during their growing up? And how did this bone growth take place?

A unique opportunity to clarify this is provided by the La Brea Pit Mines in California. Thousands of animals died here 40, 000 to 10, 000 years ago and were trapped and preserved by the sticky asphalt. Among the fossils are also hundreds of saber-toothed cats of the species Smilodon fatalis of different ages - from the juvenile to the adult predator.

Fossil leg bones of Smilodon fatalis from the juvenile to the adult. © K. Long

Already stronger from birth

Katherine Long of California State Polytechnic University and her colleagues have now examined these bones more closely and compared them with those of other extinct and recent big cats. display

The surprising result: Contrary to expectations, the saber-toothed cats did not develop their fat bones until they grew up. Instead, the kittens were born with unusual, robust bones. "The bones of the forelegs of Smilodon fatalis pups are about the same length as the tiger, but the bones of the leg bones are significantly thicker and they have broad margins with strong bony wisps, " reports Long.

Bone growth like other cats

Then, when the saccoids grew, their bone growth followed the same pattern as with all other cats: the long bones became longer and thinner than even thicker. But because the kittens already started with significantly heavier bones, their skeleton remained more robust than that of other big cats, as the researchers report.

These results not only clear the origin of the thick slobber tooth bones, but also show that bone growth in the catlike species apparently followed a rather rigid pattern as early as the Ice Age. However, the saber-toothed cats "tricked" this scheme by providing more favorable starting conditions from the outset. (PLoS ONE, 2017; doi: 10.1371 / journal.pone.0183175)

(PLOS, 28.09.2017 - NPO)