A new genus and species of large theropod dinosaur being named Alpkarakush kyrgyzicus has been discovered in the Middle Jurassic Balabansai Formation in the northern part of the Fergana Depression, Kyrgyzstan.
Life reconstruction of Alpkarakush kyrgyzicus. Image credit: Joschua Knüppe.
Alpkarakush kyrgyzicus roamed our planet during the Callovian age of the Jurassic period between 165 and 161 million years ago.
The ancient predator was 7 to 8 m (23-26 feet) in body length, and had an extremely protruding ‘eyebrow’ on the so-called postorbital bone, a skull bone behind the eye opening, which indicates the presence of a horn at this point.
Alpkarakush kyrgyzicus belongs to Metriacanthosauridae, a group of medium to large-sized allosauroid theropod dinosaurs that are characterized by high arched skulls, plate-like elongate neural spines, and slender hindlimbs.
“Theropod dinosaurs are one of the most important large groups of dinosaurs, including well-known predators, such as Tyrannosaurus and Allosaurus, as well as modern birds,” said Professor Oliver Rauhut from the SNSB – Bayerische Staatssammlung für Paläontologie und Geologie and his colleagues.
“A variety of theropods are known from the Mesozoic Era, the age of the dinosaurs.”
“Just as lions today are mainly found in Africa and tigers only in Asia, Allosaurus, for example, was widespread in the Jurassic of North America and south-western Europe, while the similarly sized metriacanthosaurs lived in China.”
“However, the region in between, i.e. between central Europe and East Asia, was so far terra incognita — no large Jurassic predatory dinosaurs were previously known from this huge region.”
Two specimens of Alpkarakush kyrgyzicus were recovered from the upper section of the Balabansai Formation close to the town of Tashkumyr, Jalal-Abad, Kyrgyzstan.
“The type specimen represents a subadult individual, whereas the smaller specimen is a juvenile, possibly indicating gregarious behavior,” the paleontologists said.
“Alpkarakush kyrgyzicus is the first diagnosable theropod species from the Jurassic of Central Asia west of China.”
They suggest that metriacanthosaurid dinosaurs originated in South-East Asia in the latest Early or Early Middle Jurassic and rapidly became the dominant group of theropodan apex predators in many ecosystems in the continent in the Jurassic.
“Although the affiliation of Alpkarakush kyrgyzicus with the metriacanthosaurids is not necessarily a surprise, this discovery closes a huge gap in our knowledge of the Jurassic theropods,” Professor Rauhut said.
“It leads us to important new insights into the evolution and biogeography of these animals.
The discovery is reported in a paper published this month in the Zoological Journal of the Linnean Society.
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Oliver W.M. Rauhut et al. A new theropod dinosaur from the Callovian Balabansai Formation of Kyrgyzstan. Zoological Journal of the Linnean Society 201 (4): zlae090; doi: 10.1093/zoolinnean/zlae090
