A newly-identified species of sabre-toothed cat which lived nine to ten million years ago has been found in northern China.
Amphimachairodus hezhengensis becomes the earliest known member of the Amphimachairodus genus which lived in Europe, Asia and North America. Amphimachairodus was the most widely distributed and successful sabre-toothed cat genus in the late Miocene – a period of Earth’s history that extends from about 23 million to 5.3 million years ago.
The new species is known from deposits dating to the Turolian age of the Miocene epoch. The fossils were found in the Linxia Basin, located on the north-eastern border of the Tibetan Plateau.
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Amphimachairodus hezhengensis was roughly 2 metres long, or roughly the size of a lion or small tiger. It would have been smaller than the archetypal sabre-toothed cat, Homotherium.
Analysis of a nearly complete A. hezhengensis skull fossil shows features typical of its genus, but also some peculiar morphology. It has a wide forehead, long snout and small incisors.
Some of the new species’ cranial traits resemble those of Homotherium, “…suggesting potentially similar adaptations,” note the authors of a study describing Amphimachairodus hezhengensis published in the Proceedings of the Royal Society B.
“The long snout, laterally oriented and posteriorly located orbit of Amphimachairodus suggest a better ability to observe the surrounding environment, rather than targeting single prey, pointing to an adaptation to the open environment or social behaviour,” the researchers say.
Changes in hunting behaviour as environmental shifts were underway in the Turolian age appear to have been a major factor in the evolution of sabre-toothed cats and their dispersal around the world.
“The early arid environment in the Linxia Basin, probably due to the uplift of the Tibetan Plateau to a significant height at this time, provides an environmental trigger for the appearance of open-environmental adaptions among mammals,” the researchers note.
“Open environments also benefit social behaviour, due to the increasing visibility of carnivores to each other, and also of preys, which makes them more difficult to catch,” they add.
The palaeontologists also note that rapid morphological and social changes in Amphimachairodus hezhengensis may have been spurred on by the presence of other large carnivores in the Linxia Basin during the Turolian.
Among these were a huge hyena, Dinocrocuta gigantea, which weighed approximately 380 kilograms and could crack bone with its powerful jaws. Two as yet undescribed species of bear were also around at the time.