Kuru (after Kurukullā, a Tibetan Buddhist deity) is a genus of dromaeosaurid theropod from the Late Cretaceous Barun Goyot Formation of Mongolia. The genus contains only a single species, the type species Kuru kulla, which is known from a fragmentary skeleton including a partial skull.
Discovery and naming
The holotype of Kuru kulla was discovered by an American-Mongolian expedition at Khulsan in the Gobi Desert, Mongolia, on 5 July 1991, only hours before the discovery of the related taxon Shri and was reposited at the Institute of Geology at the Mongolian Academy of Sciences in Ulaanbaatar. The specimen was given the designation IGM 100/981 and consists of a fragmentary skeleton including a right premaxillary bone, the right lacrimal bone, a partial right dentary, the right surangular bone, 14 presacral vertebrae, three caudal vertebrae, fragments of both upper limb bones, a fragmentary ilium, distal ends of both pubes, both femora, a right tibia, and fragments of the right and left feet. The quality of the preservation was inconsistent when the specimen was fossilized, and it is generally poorly-preserved when compared to the remains of the contemporaneous Shri.
In 1992, the holotype was reported as a distinct dromaeosaurid taxon at a Society of Vertebrate Paleontology conference in Toronto, Canada. In their paper describing the large dromaeosaurid Achillobator, Perle and colleagues listed a bibliographic entry titled "Morphology of a Dromaeosaurian dinosaur - Airakoraptor from the Upper Cretaceous of Mongolia".
However, this bibliographic entry is believed to be an error as no such paper is known to exist and it is probably a reference to an unpublished work or an abstract from a conference. This would mean the name "Airakoraptor" is a nomen nudum and is therefore invalid. Napoli and colleagues, in their formal description of Kuru, presume that the name "Airakoraptor" means "Kumis thief", after kumis, also known as "airag" or "airak", a donkey-milk product made in Central Asia. In their description, Napoli and colleagues also explicitly state that the naming of Kuru is not a reference to the disease of the same name.
In 2006, its surangular bone was described in the paper which named the dromaeosaurid Tsaagan. However, later that year, this specimen was confused with the so-called "Zos Wash specimen" found in 1998, which was catalogued under the number IGM 100/3503 and referred to the genus Velociraptor. The holotype was formally described and named in 2021 by James G. Napoli, Alexander Altieri Ruebenstahl, Bhart-Anjan Singh Bhullar, Alan Hamilton Turner, and Mark Allen Norell.
Description
Kuru is a small-bodied eudromaeosaur, similar in size to Velociraptor. The holotype specimen is known from an incomplete skeleton that is overall similar to other known eudromaeosaurs, indicating that in life it would have resembled its better-understood relatives like Velociraptor and Tsaagan. Napoli and colleagues distinguished Kuru from all other eudromaeosaurs by identifying several autapomorphies including: a deep groove in front of the anterior margin of the external naris, a small horn-like projection on the lacrimal bone, two foramina on the rear of the surangular bone, and pleurocoels on the dorsal vertebrae which are shifted forward compared to related taxa.
Napoli and colleagues in their description of the holotype note that the body proportions indicate that Kuru had a more robust skull than related eudromaeosaurs, but also had proportionally longer limbs and a reduced "killing claw" in its second toe. No study of its functional anatomy has been completed, but the authors hypothesize that these traits suggest slight ecological differences between Kuru and its closest relatives.
Skull
The cranium is represented by the anterior part of the right premaxilla (in front of the nostril) and the posterior half of the right lacrimal bone. The premaxilla has only two dental alveoli preserved, but Napoli and colleagues stated that it likely had four premaxillary teeth, which is the condition seen in all toothed theropods. Several features on the surface of the bone are also preserved. The most prominent of these is a c-shaped groove which is anterior to the naris. A similar structure is present in the premaxillae of the related taxa Tsaagan and Linheraptor, but it is much less pronounced in these genera.