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 clade.
| Hypnovenator | |
|---|---|
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| Fossil remains and skeletal diagram of the holotype | |
Scientific classification 
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| 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
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| Binomial name | |
| †Hypnovenator matsubaraetoheorum Kubota, Kobayashi & Ikeda, 2024
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Discovery and naming
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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]
Classification
editKubota et al. (2024) scored the Hypnovenator fossil material into phylogenetic matrix of Sellés et al. (2021),[5] itself a derivative of a large phylogenetic analysis intended to test the relationships of all major maniraptoromorph groups.[6] 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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Paleoecology
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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.[9] 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.[10] Several dinosaurian oospecies (egg fossils) have also described, including Himeoolithus, Subtiliolithus, Nipponoolithus, and Prismatoolithus.[11] The monstersaurian lizard Morohasaurus and the titanosauriform sauropod Tambatitanis are the only other reptiles named from body fossils from the formation.[12][13] Fossils of an unnamed neoceratopsian, including several skull bones, are also known from the formation.[14]
See also
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References
edit- ^ a b c d Kubota, K.; Kobayashi, Y.; Ikeda, T. (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.
- ^ Saegusa, Haruo; Ikeda, Tadahiro; Handa, Kumiko (2012). Additional dinosaur materials from the Sasayama Group of Hyogo Prefecture, SW Japan (PDF). The Palaeontological Society of Japan.
- ^ Tanaka, Tomonori; Chiba, Kentaro; Ikeda, Tadahiro; Kubota, Katsuhiro (2023). Examination on the newly identified elements and phylogenetic position of a theropod dinosaur from the Ohyamashimo Formation of the Sasayama Group in Tambasasayama City, Hyogo, Japan (PDF). The Palaeontological Society of Japan.
- ^ Kubota, Katsuhiro; Kobayashi, Yoshitsugu; Ikeda, Tadahiro (2024-06-07). "Early Cretaceous Troodontine Troodontid (Dinosauria: Theropoda) from the Ohyamashimo Formation of Japan Reveals the Early Evolution of Troodontinae". Research Square (preprint). doi:10.21203/rs.3.rs-4459611/v1.
- ^ Sellés, A. G.; Vila, B.; Brusatte, S. L.; Currie, P. J.; Galobart, A. (2021). "A fast-growing basal troodontid (Dinosauria: Theropoda) from the latest Cretaceous of Europe". Scientific Reports. 11: 4855. doi:10.1038/s41598-021-83745-5. PMC 7921422.
- ^ Hartman, Scott; Mortimer, Mickey; Wahl, William R.; Lomax, Dean R.; Lippincott, Jessica; Lovelace, David M. (2019). "A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight". PeerJ. 7: e7247. doi:10.7717/peerj.7247. PMC 6626525. PMID 31333906.
- ^ Norell, Mark A.; Clark, James M.; Demberelyin, Dashzeveg; Rhinchen, Barsbold; Chiappe, Luis M.; Davidson, Amy R.; McKenna, Malcolm C.; Altangerel, Perle; Novacek, Michael J. (1994-11-04). "A Theropod Dinosaur Embryo and the Affinities of the Flaming Cliffs Dinosaur Eggs". Science. 266 (5186): 779–782. doi:10.1126/science.266.5186.779. ISSN 0036-8075.
- ^ Tsuihiji, Takanobu; Barsbold, Rinchen; Watabe, Mahito; Tsogtbaatar, Khishigjav; Suzuki, Shigeru; Hattori, Soki (2015-10-01). "New material of a troodontid theropod (Dinosauria: Saurischia) from the Lower Cretaceous of Mongolia". Historical Biology. 28 (1–2): 128–138. doi:10.1080/08912963.2015.1005086. ISSN 0891-2963.
- ^ Hayashi, Keiichi; Fujita, Saki; Koarai, Kazuto; Matsukawa, Masaki (2017-09-15). "Stratigraphy and paleoenvironment of the Cretaceous Sasayama Group in the Sasayama area, Hyogo Prefecture, western Japan". The Journal of the Geological Society of Japan. 123 (9): 747–764. doi:10.5575/geosoc.2017.0016. ISSN 0016-7630.
- ^ Kubota, Katsuhiro. "日本産の中生代恐竜化石目録 2022年版" [A list of Mesozoic dinosaur fossils from Japan in 2022] (PDF). Bulletin of the Gunma Museum of Natural History. 27: 157–170.
- ^ Tanaka, Kohei; Zelenitsky, Darla K.; Therrien, François; Ikeda, Tadahiro; Kubota, Katsuhiro; Saegusa, Haruo; Tanaka, Tomonori; Ikuno, Kenji (2020). "Exceptionally small theropod eggs from the Lower Cretaceous Ohyamashimo Formation of Tamba, Hyogo Prefecture, Japan". Cretaceous Research. 114: Article 104519. Bibcode:2020CrRes.11404519T. doi:10.1016/j.cretres.2020.104519. S2CID 219449961.
- ^ Ikeda, T.; Ota, H.; Tanaka, T.; Ikuno, K.; Kubota, K.; Tanaka, K.; Saegusa, H. (2021). "A fossil Monstersauria (Squamata: Anguimorpha) from the Lower Cretaceous Ohyamashimo Formation of the Sasayama Group in Tamba City, Hyogo Prefecture, Japan". Cretaceous Research. 130: Article 105063. doi:10.1016/j.cretres.2021.105063. S2CID 239230916.
- ^ Saegusa, H.; Ikeda, T. (2014). "A new titanosauriform sauropod (Dinosauria: Saurischia) from the Lower Cretaceous of Hyogo, Japan". Zootaxa. 3848 (1): 1–66. doi:10.11646/zootaxa.3848.1.1. PMID 25112425.
- ^ Tanaka, Tomonori; Chiba, Kentaro; Ikeda, Tadahiro; Kubota, Katsuhiro (2023). Phylogenetic position of a ceratopsian dinosaur from the Lower Cretaceous Ohyamashimo Formation (Albian) of the Sasayama Group in Tambasasayama City, Hyogo, Japan (PDF). The Palaeontological Society of Japan.