MEANING: Sleep hunter
PERIOD: Early Cretaceous
CONTINENT: Asia
Hypnovenator is a small troodontid dinosaur that lived about 110 million years ago in the Early Cretaceous of what is now Japan. Troodontids were closely related to birds, and had many superficial similarities, including their lightly built frame, and feathered integument. Hypnovenator was about 1 m in length, and stood on two long legs, allowing for swift running capability. These highly adapted limbs also allowed for the larger sickle-like toe claw on each foot to be held above the ground, keeping them sharp, even as it navigated its terrain.
Abstract from paper: A new troodontid dinosaur, Hypnovenator matsubaraetoheorum gen. et sp. nov., is described based on an articulated postcranial skeleton recovered from the fluvial deposits of the Albian Ohyamashimo Formation of the Sasayama Group in Tambasasayama City, Hyogo Prefecture, Japan. Hypnovenator is distinguished from other troodontids by four autapomorphies and a combination of additional features. Our phylogenetic analysis positions Hypnovenator as the oldest and one of the most basal troodontines, forming a clade with Gobivenator mongoliensis. The discovery of Hypnovenator suggests that small-bodied maniraptorans with a sleeping posture were common not only in environments with volcanic and eolian events or alluvial systems but also in fluvial systems. Geometric morphometric analysis of manual ungual phalanges shows that manual ungual phalanges I and III of Hypnovenator exhibit considerable morphological variation but are functionally similar, which differs from those of non-troodontine troodontids, reflecting the transition of manual motion within Troodontinae. Hypnovenator also has mosaic features in the pes related to cursoriality. This study reveals that asymmetrical arctometatarsus occurred by the Albian, and some morphological changes, such as shorter digit IV than digit III and non-ungual phalanges of digits III with roller joints and digit IV with weakly ginglymoid articulation, arose during the early Late Cretaceous.
Hypnovenator is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Hypnovenator is a troodontid. Troodontidae is a family of theropod dinosaurs which are closely related to birds. Many genera are known only from teeth, and this has led to much debate and reclassification over the course of the history of paleontology. The oldest definitive troodontid is known from the Late Jurassic of Wyoming. Over the Cretaceous, they radiated throughout western North America, Asia, and Europe, suggesting a mostly Laurasian distribution.
Troodontids are small, bird-like, gracile maniraptorans. They have unique skull features, such as large numbers of closely spaced teeth in the lower jaw. They are also equipped with sickle-claws and raptorial hands, similar to the closely related dromaeosaurs. Troodontids also had unusually large brains and eyes, suggesting that they were behaviourally advanced and had keen senses.