Thescelosauridae
Thescelosauridae is a clade of neornithischians from the Cretaceous of Asia, North America and possibly South America. The group was originally used as a name by Charles M. Sternberg in 1937, but was not formally defined until 2013, where it was used by Brown and colleagues as the group uniting Thescelosaurus and Orodromeus, based on their phylogenetic results.[1][2] During a phylogenetic revision of neornithischians by Clint Boyd in 2015, the authorship of Thescelosauridae was given to Brown and colleagues, which meant that the similar name Parksosauridae, informally defined in 2002 by Buchholz, would have had priority over Thescelosauridae. The two clades had slightly different definitions, with Parksosauridae referring to all animals closer to Parksosaurus than Hypsilophodon, but they contained the same taxa so Boyd used Parksosauridae under the assumption it had priority.[3] However, in formalizing the clade following the regulations of the PhyloCode, Madzia, Boyd, and colleagues identified in 2021 that Sternberg was the proper authority for Thescelosauridae, giving it priority over Parksosauridae. As well, they gave Thescelosauridae the definition of the largest clade containing Thescelosaurus neglectus but not Iguanodon bernissartensis, as long as Hypsilophodon foxii was not in the group, modifying previous definitions for Thescelosauridae in order to maintain its modern use, so that the clade was not applied if Thescelosaurus fell within Hypsilophodontidae, a family that has not been recently used but may be revived if the systematic position of Hypsilophodon was solidified at some point in the future.[1] Madzia et al. identified the analysis of Madzia et al. in 2018 as the reference analysis for the name Thescelosauridae, an analysis based on a revised version of the 2015 Boyd analysis.[1][4]
| Neornithischia |
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| Thescelosaurids Temporal range: Early–Late Cretaceous, | |
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| Mounted specimen of Thescelosaurus, Burpee Museum of Natural History | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Neornithischia |
| Family: | †Thescelosauridae Sternberg, 1937 |
| Subfamilies[1] | |
| Synonyms[1] | |
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History
Although Hypsilophodontidae was interpreted as a natural group in the early 1990s,[5][6] this hypothesis has fallen out of favor and Hypsilophodontidae has been found to be an unnatural family composed of a variety of animals more or less closely related to Iguanodontia (paraphyletic), with various small clades of closely related taxa.[7][8][9][10][11] "Hypsilophodontidae" and "hypsilophodont" are better understood as informal terms for an evolutionary grade, not a true clade. Thescelosaurus has been regarded as both very basal[6] and very derived[9] among the hypsilophodonts. One issue that has potentially interfered with classifying Thescelosaurus is that not all of the remains assigned to T. neglectus necessarily belong to it.[12] Clint Boyd and colleagues found that while the clade Thescelosaurus included the genus Bugenasaura and the species that had been assigned to that genus, there were at least two and possibly three species within Thescelosaurus, and several specimens previously assigned to T. neglectus could not yet be assigned to a species within the genus.[7] It appears to be closely related to Parksosaurus,[7][9][10][13][14] although this relationship has been called into question.[15]
The dissolution of Hypsilophodontidae was followed by the recognition of the distinct family Parksosauridae by Buchholz in 2002, defined as the most inclusive clade containing Parksosaurus warreni, but not Hypsilophodon foxii, Dryosaurus altus, or Iguanodon bernissartensis.[16][3] Boyd et al. (2009) and Brown et al. (2011) found North American "hypsilophodonts" of Cretaceous age to sort into two related clusters, one (Orodrominae) consisting of Orodromeus, Oryctodromeus, and Zephyrosaurus, and the other (Thescelosaurinae) consisting of Parksosaurus and Thescelosaurus.[7][13] Brown et al. (2013) recovered similar results, with the addition of the new genus Albertadromeus to the Orodromeus clade (called Orodrominae) and several long-snouted Asian forms (previously described under Jeholosauridae)[8] to the Thescelosaurus clade (called Thescelosaurinae).[14]
References
- Madzia, D.; Arbour, V.M.; Boyd, C.A.; Farke, A.A.; Cruzado-Caballero, P.; Evans, D.C. (2021). "The phylogenetic nomenclature of ornithischian dinosaurs". PeerJ. 9: e12362. doi:10.7717/peerj.12362. PMC 8667728. PMID 34966571.
- Brown, C.M.; Evans, D.C.; Ryan, M.J.; Russell, A.P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology. 33 (3): 495–520. doi:10.1080/02724634.2013.746229. S2CID 129160518.
- Boyd, Clint A. (2015). "The systematic relationships and biogeographic history of ornithischian dinosaurs". PeerJ. 3 (e1523): e1523. doi:10.7717/peerj.1523. PMC 4690359. PMID 26713260. Retrieved 5 January 2016.
- Madzia, D.; Boyd, C.A.; Mazuch, M. (2017). "A basal ornithopod dinosaur from the Cenomanian of the Czech Republic". Journal of Systematic Palaeontology. 16 (11): 967–979. doi:10.1080/14772019.2017.1371258. S2CID 90008574.
- Sues, Hans-Dieter; Norman, David B. (1990). "Hypsilophodontidae, Tenontosaurus, Dryosauridae". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (1st ed.). Berkeley: University of California Press. pp. 498–509. ISBN 978-0-520-06727-1.
- Weishampel, David B.; Heinrich, Ronald E. (1992). "Systematics of Hypsilophodontidae and Basal Iguanodontia (Dinosauria: Ornithopoda)" (PDF). Historical Biology. 6 (3): 159–184. doi:10.1080/10292389209380426. Retrieved 2007-03-10.
- Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke, Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology. 29 (3): 758–770. doi:10.1671/039.029.0328. S2CID 84273584.
- Han, Feng-Lu; Paul M. Barrett; Richard J. Butler; Xing Xu (2012). "Postcranial anatomy of Jeholosaurus shangyuanensis (Dinosauria, Ornithischia) from the Lower Cretaceous Yixian Formation of China". Journal of Vertebrate Paleontology. 32 (6): 1370–1395. doi:10.1080/02724634.2012.694385. S2CID 86754247.
- Norman, David B.; Sues, Hans-Dieter; Witmer, Larry M.; Coria, Rodolfo A. (2004). "Basal Ornithopoda". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 393–412. ISBN 978-0-520-24209-8.
- Weishampel, David B.; Jianu, Coralia-Maria; Csiki, Z.; Norman, David B. (2003). "Osteology and phylogeny of Zalmoxes (n.g.), an unusual euornithopod dinosaur from the latest Cretaceous of Romania". Journal of Systematic Palaeontology. 1 (2): 1–56. doi:10.1017/S1477201903001032. S2CID 86339025.
- Varricchio, David J.; Martin, Anthony J.; Katsura, Yoshihiro (2007). "First trace and body fossil evidence of a burrowing, denning dinosaur". Proceedings of the Royal Society B: Biological Sciences. 274 (1616): 1361–1368. doi:10.1098/rspb.2006.0443. PMC 2176205. PMID 17374596.
- Butler, Richard J.; Upchurch, Paul; Norman, David B. (2008). "The phylogeny of the ornithischian dinosaurs". Journal of Systematic Palaeontology. 6 (1): 1–40. doi:10.1017/S1477201907002271. S2CID 86728076.
- Brown, Caleb M.; Boyd, Clint A.; Russell, Anthony P. (2011). "A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America". Zoological Journal of the Linnean Society. 163 (4): 1157–1198. doi:10.1111/j.1096-3642.2011.00735.x.
- Brown, Caleb Marshall; Evans, David C.; Ryan, Michael J.; Russell, Anthony P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology. 33 (3): 495–520. doi:10.1080/02724634.2013.746229. S2CID 129160518.
- Herne, Matthew C.; Nair, Jay P.; Evans, Alistair R.; Tait, Alan M. (2019). "New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999". Journal of Paleontology. 93 (3): 543–584. doi:10.1017/jpa.2018.95.
- Buchholz, P. W. (2002). "Phylogeny and biogeography of basal Ornithischia". In Brown, D. E. (ed.). The Mesozoic in Wyoming. Casper: Tate Geological Museum. pp. 18–34.
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