The 36,000-year-old frozen specimen from Yakutia belongs to Homotherium latidens, a species of scimitar-toothed cat that inhabited Eurasia during the Pliocene and Pleistocene epochs, and significantly differs from a modern lion cub in the elongated front legs, the unusual shape of the muzzle with a large mouth opening and small ears, the very massive neck region, and the dark coat color.
Homotherium serum. Image credit: Sergiodlarosa / CC BY-SA 3.0.
Homotherium latidens was between 1.5 and 2 m in length, up to 1.1 m in height, and weighed up to 200 kg — about the average size of a modern lion or tiger.
However, its physical appearance differed from other big cats: the extinct species had long saber-like canines, a sloping back, and a short tail.
“Homotherium was widespread in the Plio-Pleistocene of Eurasia, Africa, and Americas,” said lead author Dr. Alexey Lopatin and his colleagues.
“For a long time, the latest presence of Homotherium in Eurasia was recorded in the Middle Pleistocene.”
“A significant event was the discovery of the mandible of the Late Pleistocene Homotherium latidens from the North Sea, which is dated to 28,000 years ago.”
“The largest number of Late Pleistocene finds of Homotherium is concentrated in North America (more than 30 localities), where they traditionally classified in the species Homotherium serum.”
In their new study, the authors examined the frozen mummified carcass of a Homotherium latidens cub found in the Pleistocene permafrost at the locality of Badyarikhskoe on the Badyarikha River in the northeast of Yakutia, Siberia.
“The numerous bones of mammoth fauna representatives are collected from the loess-like loams of the Yedoma horizon in this locality,” they said.
According to the researchers, the Badyarikha specimen is approximately 36,000 years old.
“The specimen includes the head and the anterior part of the body preserved approximately to the caudal edge of the chest,” they said.
“There are also incomplete pelvic bones articulated with the femur and shin bones.”
“They were found encased in a piece of ice along with the front part of the cub.”
The team’s analysis shows that most of the postcranial features of Homotherium latidens can be traced already at the age of three weeks.
“The length of the preserved part of the Homotherium cub body from the nose tip to the gap in the chest region (at the level of the 12th vertebra) is 248 mm,” the scientists said.
“The body is covered with short, thick, soft, dark brown fur with hair about 20-30 mm long. The fur on the back and neck is longer than on the legs.”
“On the upper lip two rows of vibrissae are clearly visible, mostly broken off at a height of 3-5 mm from the roots.”
“In the region of the mouth corner, the hair is significantly elongated.”
“The general morphology of the skull is typical of a juvenile felid,” they added.
“The skull is also distinguished by a relatively longer facial region, a rounded braincase, expanded zygomatic arches, a wide area of premaxillaries, and large upper deciduous incisors.”
“The nasal bones of the Homotherium cub compared to a lion cub are greatly shortened and widened.”
“The neck is longer and more than twice as thick as that of a lion,” they said.
“The difference in thickness is explained by the large volume of muscles, which is visually observed at the site of separation of the skin from the mummified flesh.”
“The length of the forelimbs in the Homotherium cub is 18-23% greater than that in the lion cub.”
“At the same time, the body length of the latter is equal to the dimension of Homotherium or exceeds it by approximately 10%.”
“The increased size of the oral fissure indicates for wide mouth gape adaptation.”
“The front paw of the Homotherium cub has a rounded shape. Its width is almost equal to its length, in contrast to lion cubs with their elongated and relatively narrow front paw.”
“All claws are sharp and strongly curved. In cross section, the claws are laterally compressed and have the same shape as in the lion cub.”
“The wide paw, the subsquare shape of its pads, and the absence of a carpal pad are adaptations to walking in snow and low temperatures.”
“The small, low auricles and absence of the carpal pad in the Badyarikha Homotherium contrast with the taller auricles and normally developed pads in the lion cub. All these features can be interpreted as adaptations to living in cold climate.”
The discovery of a Homotherium latidens cub radically expands the understanding of distribution of the genus and confirms its presence in the Late Pleistocene of Asia.
“For the first time in the history of paleontological research, the external appearance of an extinct mammal that has no analogues in the modern fauna has been studied directly,” the authors concluded.
Their paper was published this week in the journal Scientific Reports.
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A.V. Lopatin et al. 2024. Mummy of a juvenile sabre-toothed cat Homotherium latidens from the Upper Pleistocene of Siberia. Sci Rep 14, 28016; doi: 10.1038/s41598-024-79546-1
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