Hypnovenator | |
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Fossil remains and skeletal diagram of the holotype | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Troodontidae |
Subfamily: | † Troodontinae |
Genus: | † Hypnovenator Kubota, Kobayashi & Ikeda, 2024 |
Species: | †H. matsubaraetoheorum |
Binomial name | |
†Hypnovenator matsubaraetoheorum Kubota, Kobayashi & Ikeda, 2024 | |
Hypnovenator (meaning "sleep hunter") is an extinct genus of troodontid theropod dinosaurs from the Early Cretaceous (Albian) Ohyamashimo Formation of Japan. The genus contains a single species, H. matsubaraetoheorum, known from a partial skeleton. Hypnovenator is the only troodontid currently known from Japan, and it represents the oldest definitive member of the subgroup Troodontinae.
The Hypnovenator holotype specimen, MNHAH D1033340, was discovered in sediments of the Ohyamashimo Formation (lower Sasayama Group) in Nishikosa, Tamba-Sasayama city, of Hyōgo Prefecture, Japan. Much of the known material was discovered in September 2010 by a group of amateur fossil hunters during the construction of the Hyogo Prefectural Tamba Namikimichi Central Park. Subsequent expeditions in July of the following year by the prefecture’s Museum of Nature and Human Activities revealed an additional block containing material belonging to the same individual. The specimen is somewhat fragmentary, comprising bones of both the axial and appendicular skeleton. These include two caudal vertebrae with a chevron, two ribs, several gastralia, most of the left arm—including the humerus, radius, ulna, carpal, metacarpals, and most of the phalanges and manual unguals—and some of the legs, including part of the left femur, tibia, and fibula, right tibia, both astragali, and several partial metatarsals and pedal phalanges (toe bones). [1]
Prior to a formal description of the fossil material, it was mentioned in conference abstracts in 2012 and 2023. [2] [3] It was also mentioned in a Research Square preprint in early 2024, under the binomial name "Hypnovenator sasayamaensis". [4]
In mid-2024, Katsuhiro Kubota, Yoshitsugu Kobayashi, and Tadahiro Ikeda described Hypnovenator matsubaraetoheorum as a new genus and species of troodontid dinosaurs based on these fossil remains. The generic name, Hypnovenator, is combines the Ancient Greek word "hypnos", meaning "sleep", with the Latin word "venator", meaning "hunter", referencing the sleeping position the holotype was preserved in, similar to some Chinese troodontids like Mei and Sinornithoides . The specific name, matsubaraetoheorum, honors Kaoru Matsubara and Takaharu Ohe the discoverers of the Hypnovenator holotype. [1]
Hypnovenator represents the twelfth validly named non-avian dinosaur described from Japan. [5]
Kubota et al. (2024) scored the Hypnovenator fossil material into phylogenetic matrix of Sellés et al. (2021), [6] itself a derivative of a large phylogenetic analysis intended to test the relationships of all major maniraptoromorph groups. [7] Kubota et al. recovered it as a basal member of the Troodontinae, as the sister taxon of the younger Mongolian Gobivenator , making Hypnovenator the oldest known troodontine. Their results are displayed in the cladogram below: [1]
Troodontidae |
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Hypnovenator is known from the Ohyamashimo Formation (Sasayama Group), which dates to the early–middle Albian age from the end of the Early Cretaceous. [1] These layers are predominantly made up by sandstones, mudstones, and conglomerates. The depositional environment represents a fluvial system with a subhumid to semi-arid climate. [10] Dinosaur teeth are common in various localities throughout this formation including those belonging to other theropods (dromaeosaurids, therizinosaurs, and tyrannosauroids) as well as sauropods, ankylosaurs, and iguanodontians. [11] Several dinosaurian oospecies (egg fossils) have also described, including Himeoolithus , Subtiliolithus , Nipponoolithus , and Prismatoolithus . [12] The monstersaurian lizard Morohasaurus and the titanosauriform sauropod Tambatitanis are known from the formation. [13] [14] Fossils of an unnamed neoceratopsian, including several skull bones, are also known from the formation. [15] Although not specified as this Formation in original descriptions, Sasayama Group have some other fossil fauna known, such as eutherian Sasayamamylos , [16] scincomorph Pachygenys , [17] two frogs Hyogobatrachus and Tambabatrachus . [18]
Troodontidae is a clade of bird-like theropod dinosaurs from the Late Jurassic to Late Cretaceous. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discoveries of complete and articulated specimens, have helped to increase understanding about this group. Anatomical studies, particularly studies of the most primitive troodontids, like Sinovenator, demonstrate striking anatomical similarities with Archaeopteryx and primitive dromaeosaurids, and demonstrate that they are relatives comprising a clade called Paraves.
Troodon is a former wastebasket taxon and a potentially dubious genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period. It includes at least one species, Troodon formosus, known from Montana. Discovered in October 1855, T. formosus was among the first dinosaurs found in North America, although it was thought to be a lizard until 1877. Several well-known troodontid specimens from the Dinosaur Park Formation in Alberta were once believed to be members of this genus. However, recent analyses in 2017 have found this genus to be undiagnostic and referred some of these specimens to the genus Stenonychosaurus some to the genus Latenivenatrix, and some to the genus Pectinodon. The genus name is Ancient Greek for "wounding tooth", referring to the teeth, which were different from those of most other theropods known at the time of their discovery. The teeth bear prominent, apically oriented serrations. These "wounding" serrations, however, are morphometrically more similar to those of herbivorous reptiles, and suggest a possibly omnivorous diet.
Philip John Currie is a Canadian palaeontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton. In the 1980s, he became the director of the Canada-China Dinosaur Project, the first cooperative palaeontological partnering between China and the West since the Central Asiatic Expeditions in the 1920s, and helped describe some of the first feathered dinosaurs. He is one of the primary editors of the influential Encyclopedia of Dinosaurs, and his areas of expertise include theropods, the origin of birds, and dinosaurian migration patterns and herding behavior. He was one of the models for palaeontologist Alan Grant in the film Jurassic Park.
Fukuiraptor was a medium-sized megaraptoran theropod dinosaur of the Early Cretaceous epoch that lived in what is now Japan. Fukuiraptor is known from the Kitadani Formation and possibly also the Sebayashi Formation.
Siamosaurus is a genus of spinosaurid dinosaur that lived in what is now known as China and Thailand during the Early Cretaceous period and is the first reported spinosaurid from Asia. It is confidently known only from tooth fossils; the first were found in the Sao Khua Formation, with more teeth later recovered from the younger Khok Kruat Formation. The only species Siamosaurus suteethorni, whose name honours Thai palaeontologist Varavudh Suteethorn, was formally described in 1986. In 2009, four teeth from China previously attributed to a pliosaur—under the species "Sinopliosaurus" fusuiensis—were identified as those of a spinosaurid, possibly Siamosaurus. It is yet to be determined if two partial spinosaurid skeletons from Thailand and an isolated tooth from Japan also belong to Siamosaurus.
The Kitadani Formation is a unit of Lower Cretaceous sedimentary rock which crops out near the city of Katsuyama in Fukui Prefecture, Japan, and it is the primary source of Cretaceous-aged non-marine vertebrate fossils in Japan. Dinosaur remains are among the fossils that have been recovered from the formation, but it also preserves a diverse assemblage of plants, invertebrates, and other vertebrates. Most, if not all, of the fossil specimens collected from the Kitadani Formation are reposited at the Fukui Prefectural Dinosaur Museum.
The Kuwajima Formation is an Early Cretaceous geologic formation in Japan. Its precise age is uncertain due to a lack of identifying fossils, and it was previously considered likely Valanginian to Hauterivian in age. However, it is now considered to probably be Barremian in age. Dinosaurs and other vertebrates has been recovered from the Kaseki-kabe "Fossil-bluff" locality in the uppermost part of the formation.
The Okurodani Formation is an Early Cretaceous geologic formation in central Honshu, Japan. Part of the Tetori Group, it primarily consists of freshwater continental sediments deposited in a floodplain environment, with occasional volcanic tuffite horizons. It has an uncertain age, probably dating between the Hauterivian and Aptian. An indeterminate iguanodontian dinosaur tooth has been recovered from the formation. Many other fossil vertebrates are known from the KO2 locality
Monstersauria is a clade of anguimorph lizards, defined as all taxa more closely related to Heloderma than Varanus. It includes Heloderma, as well as several extinct genera, such as Estesia, Primaderma and Gobiderma, but this group was found to be polyphyletic in the most recent and complete squamate phylogenetic analysis by Reeder et al. (2015).
Geminiraptor is a genus of troodontid theropod dinosaur that lived in North America during the Early Cretaceous period. Geminiraptor was a small, ground-dwelling bipedal carnivorous paravian. The type species of Geminiraptor is G. suarezarum.
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Tambatitanis is an extinct genus of titanosauriform dinosaur from the Early Cretaceous of Japan. It is known from a single type species, Tambatitanis amicitiae, which is known from the Sasayama Group. It was probably around 14 m (46 ft) long and its mass was estimated at some 4 tonnes. It was a basal titanosauriform and possibly belonged to the Euhelopodidae. The holotype was collected between 2006 and 2010.
Nipponoolithus is an oogenus of fossil egg native to Japan. It is one of the smallest known dinosaur eggs, and was probably laid by some kind of non-avian maniraptor.
Incognitoolithus is an oogenus of medioolithid fossil bird egg. It is notable for bearing evidence of predation, possibly from a bird pecking the eggshell.
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Yamatosaurus is a genus of basal hadrosaurid from the Late Cretaceous (Maastrichtian)-aged Kita-Ama Formation of Awaji Island, Japan. The genus contains a single species, Yamatosaurus izanagii.
Morohasaurus is an extinct genus of cf. monstersaurian squamates know from a single left dentary from the Early Cretaceous (?Albian) Ohyamashimo Formation of the Sasayama Group in Tamba City, Hyogo Prefecture, Japan. The type and only species is Morohasaurus kamitakiensis.
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