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Hypnovenator

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Hypnovenator
Temporal range: Early Cretaceous
(early–middle Albian), 112.1–106.4 Ma
Fossil remains and skeletal diagram of the holotype
Scientific classification Edit this 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.

Discovery and naming

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Hypnovenator type locality

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]

Life restoration

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 Mainland Japan.[5]

Classification

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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

Paleoecology

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Caudal vertebrae of the contemporary Tambatitanis

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]

Named dinosaur taxa from the formation include the neoceratopsian Sasayamagnomus and the titanosauriform sauropod Tambatitanis.[11][12] The monstersaurian lizard Morohasaurus has also been described.[13] 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.[14] Several dinosaurian oospecies (egg fossils) have also described, including Himeoolithus, Subtiliolithus, Nipponoolithus, and Prismatoolithus.[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]

See also

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References

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  1. ^ 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. PMC 11272788.
  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.
  3. ^ 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.
  4. ^ 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.
  5. ^ "丹波篠山市の恐竜化石を 新属新種「ヒプノヴェナトル・マツバラエトオオエオルム」と命名" [Dinosaur fossil from Tamba-Sasayama City named new genus and species "Hypnovenator matsubaraetoheorum"] (Press release). Museum of Nature and Human Activities, Hyogo. 2024-07-25. Archived from the original on 2024-07-25.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ Tanaka, Tomonori; Chiba, Kentaro; Ikeda, Tadahiro; Ryan, Michael J. (September 2024). "A new neoceratopsian (Ornithischia, Ceratopsia) from the Lower Cretaceous Ohyamashimo Formation (Albian), southwestern Japan". Papers in Palaeontology. 10 (5). doi:10.1002/spp2.1587.
  12. ^ 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.
  13. ^ 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.
  14. ^ 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.
  15. ^ 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.
  16. ^ Kusuhashi, Nao; Tsutsumi, Yukiyasu; Saegusa, Haruo; Horie, Kenji; Ikeda, Tadahiro; Yokoyama, Kazumi; Shiraishi, Kazuyuki (2013-05-22). "A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan". Proceedings of the Royal Society B: Biological Sciences. 280 (1759): 20130142. doi:10.1098/rspb.2013.0142. ISSN 0962-8452. PMC 3619506. PMID 23536594.
  17. ^ Ikeda, Tadahiro; Ota, Hidetoshi; Saegusa, Haruo (2015-01-02). "A new fossil lizard from the Lower Cretaceous Sasayama Group of Hyogo Prefecture, western Honshu, Japan". Journal of Vertebrate Paleontology. 35 (1): e885032. doi:10.1080/02724634.2014.885032. ISSN 0272-4634.
  18. ^ Ikeda, Tadahiro; Ota, Hidetoshi; Matsui, Masafumi (2016-06-01). "New fossil anurans from the Lower Cretaceous Sasayama Group of Hyogo Prefecture, Western Honshu, Japan". Cretaceous Research. 61: 108–123. doi:10.1016/j.cretres.2015.12.024. ISSN 0195-6671.
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