Hypnovenator matsubaraetoheorum Kubota et al., 2024 (new genus and species)
(Type specimen and schematic skeletal of Hypnovenator matsubaraetoheorum, with preserved bones in red and yellow, from Kubota et al., 2024)
Meaning of name: Hypnovenator = sleep [in Greek] hunter [in Latin]; matsubaraetoheorum = for Kaoru Matsubara and Takaharu Ohe [discoverers of part of the original fossil]
Age: Early Cretaceous (Albian), between 106.4–112.1 million years ago
Where found: Ohyamashimo Formation, Hyōgo, Japan
How much is known: Partial skeleton of one individual, including limb bones, gastralia (belly ribs), and two tail vertebrae.
Notes: Hypnovenator was a troodontid, a group of relatively small, bird-like theropods. It is the first troodontid to be named from Japan. Unlike other Early Cretaceous troodontids, but similar to many Late Cretaceous ones, Hypnovenator had feet in which the outermost metatarsal (long bone of the foot) was substantially wider at its base than the second innermost metatarsal. In troodontids, the outer two metatarsals supported the main weight-bearing toes on each foot, whereas the second innermost toe was typically held off the ground. The relatively more robust outer metatarsal in Hypnovenator and later troodontids may therefore be a specialization towards greater running ability.
Several other troodontids, namely Sinornithoides, Mei, and Sinovenator, are known from one or more specimens that appear to have been preserved while they were sitting down (perhaps even sleeping). The folded posture of the limbs in the type specimen of Hypnovenator suggests that it may have died in a similar pose as well.
Reference: Kubota, K., Y. Kobayashi, and T. Ikeda. 2024. Early Cretaceous troodontine troodontid (Dinosauria: Theropoda) from the Ohyamashimo Formation of Japan reveals the early evolution of Troodontinae. Scientific Reports 14: 16392. doi: 10.1038/s41598-024-66815-2
