Denversaurus (meaning "Denver lizard") is a genus of panoplosaurin nodosaurid dinosaur from the late Maastrichtian of Late Cretaceous Western North America. Although at one point treated as a junior synonym of Edmontonia by some taxonomists, current research indicates that it is its own distinct nodosaurid genus.
| Denversaurus Temporal range: Late Cretaceous,
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| Skeleton cast of Denversaurus ("Tank"), Houston Museum of Natural Science | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Thyreophora |
| Clade: | †Ankylosauria |
| Family: | †Nodosauridae |
| Subfamily: | †Nodosaurinae |
| Clade: | †Panoplosaurini |
| Genus: | †Denversaurus Bakker, 1988 |
| Type species | |
| †Denversaurus schlessmani Bakker, 1988
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| Synonyms | |
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Discovery and naming
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In 1986, the paleontologists Kenneth Carpenter and Brent Breithaupt described DMNH 468 which was a specimen of a late Maastrichtian nodosaurid, tentatively assigned to Edmontonia sp., discovered from the lower Hell Creek Formation of South Dakota.[1]
In 1988, Robert Thomas Bakker decided to split the genus Edmontonia. The species Edmontonia rugosidens was made into a separate genus named Chassternbergia and DMNH 468 was designated as a holotype of a new genus and species. The type species of this genus was Denversaurus schlessmani. The generic name referred to the Denver Museum of Natural History at Denver, Colorado. The specific name honoured Lee E. Schlessman, a major benefactor of the museum and the founder of the Schlessman Family Foundation.[2]
The holotype consists of a skull without the lower jaws and a number of osteoderms of the body armour. It is part of the collection of the Denver Museum of Nature and Science after which the genus was named. Bakker referred a second fossil to the species, specimen AMNH 3076, a skull found by Brown and American Museum of Natural History paleontologist Roland T. Bird at the Tornillo Creek in Brewster County, Texas, in a layer of the poorly dated Upper Cretaceous Aguja Formation, possibly from the Maastrichtian too.[2] However, subsequent studies reassigned AMNH 3076 to Edmontonia, probably E. longicpes.[3][4][5]
The validity of Denversaurus was disputed in a 1990 paper on ankylosaurian systematics by Kenneth Carpenter, who noted that Bakker's diagnosis of Denversaurus was based primarily on Bakker's artistic restoration of the holotype in an uncrushed state. Since DMNH 468 was found crushed, Carpenter assigned Denversaurus back to Edmontonia sp., even though he noted its similarity to Edmontonia rugosidens.[3] A number of workers treated Denversaurus as synonymous with either E. rugosidens[6] or E. longiceps,[7] or alternatively as a valid species of Edmontonia: E. schlessmani.[8][9]
In 1988, fossil hunters found a partial nodosaurid skeleton consisting of the fragmentary skull, parts of postcranial skeleton and seventy-five osteoderms from the Lance Formation of Niobrara County, Wyoming, nicknamed "Tank", which has been tentatively assigned to as Edmontonia sp. in 1994.[10] It was part of the collection of the Rocky Mountain Dinosaur Resource Center under inventory number BHI 127327, referred to as Edmontonia schlessmani by Carpenter et al. (2013),[11] and is now under the inventory number FPDM-V9673.[12][13]
In the 2015 thesis, Michael Burns revisited the systematics of latest Cretaceous nodosaurids from the Western Interior. According to Burns, Denversaurus is likely a valid taxon based on its phylogenetic position.[14] Recent phylogenetic analyses included Denversaurus as a valid genus closely related to Edmontonia.[15][16]
Description
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In 2010, American paleontologist Gregory S. Paul estimated the length of Denversaurus at 6 metres (20 ft) and its body mass at 3 tonnes (3.3 short tons).[9]
Robert T. Bakker considered Denversaurus distinct from Edmontonia and Chassternbergia in having a skull that was wide at the rear and a more rearward position of the eye sockets.[2] The holotype skull has a length of 496 millimetres and a rear width of 346 millimetres. In the referred specimen AMNH 3076, these proportions are less extreme, measuring 395 millimetres long with a rear width of 220 millimetres. According to American paleontologist Kenneth Carpenter, the greater width of both the holotype and the referred specimen was due to crushing.[3]
In 2015, vertebrate anatomist and paleontologist Michael Burns published an abstract concluding that Denversaurus was different from Edmontonia, but similar to Panoplosaurus in having inflated, convex, cranial sculpturing with visible sulci, or troughs, between individual top skull armour elements, but is distinct from Panoplosaurus in having a relatively wider snout.[14]
Classification
editIn 1988, Bakker placed Denversaurus within Edmontoniidae, the presumed sister group of Nodosauridae within Nodosauroidea that would not have been Ankylosauria, but the last surviving Stegosauria.[2] However, these hypotheses have not been confirmed by modern cladistic analysis. Whether it presents a separate species or is identical to E. rugosidens or E. longiceps, Denversaurus material is considered nodosaurid and ankylosaurian. Paul suggested that it was the direct descendant of E. longiceps.[9] Burns recovered Denversaurus as the sister species of Panoplosaurus.[14] Denversaurus is the latest known member of Thyreophora.[2]
References
edit- ^ Carpenter, Kenneth; Breithaupt, Brent (1986). "Latest Cretaceous Occurrence of Nodosaurid Ankylosaurs (Dinosauria, Ornithischia) in Western North America and the Gradual Extinction of the Dinosaurs". Journal of Vertebrate Paleontology. 6 (3): 251–257. Bibcode:1986JVPal...6..251C. doi:10.1080/02724634.1986.10011619. ISSN 0272-4634. JSTOR 4523098.
- ^ Jump up to: a b c d e Bakker, R.T. (1988). "Review of the Late Cretaceous nodosauroid Dinosauria: Denversaurus schlessmani, a new armor-plated dinosaur from the Latest Cretaceous of South Dakota, the last survivor of the nodosaurians, with comments on Stegosaur-Nodosaur relationships". Hunteria 1(3): 1-23.(1988).
- ^ Jump up to: a b c Carpenter, K. 1990. "Ankylosaur systematics: example using Panoplosaurus and Edmontonia (Ankylosauria: Nodosauridae)", In: Carpenter, K. & Currie, P.J. (eds) Dinosaur Systematics: Approaches and Perspectives, Cambridge University Press, Cambridge, pp. 281-298
- ^ Vickaryous, Matthew K. (2006). "New information on the cranial anatomy of Edmontonia rugosidens Gilmore, a Late Cretaceous nodosaurid dinosaur from Dinosaur Provincial Park, Alberta". Journal of Vertebrate Paleontology. 26 (4): 1011–1013. doi:10.1671/0272-4634(2006)26[1011:niotca]2.0.co;2. S2CID 130696265.
- ^ Miyashita T, Arbour VM, Witmer LM, Currie PJ (2011). "The internal cranial morphology of an armoured dinosaur Euoplocephalus corroborated by X-ray computed tomographic reconstruction". Journal of Anatomy. 219 (6): 661–75. doi:10.1111/j.1469-7580.2011.01427.x. PMC 3237876. PMID 21954840.
- ^ W. P. Coombs and T. A. Deméré. 1996. A Late Cretaceous nodosaurid ankylosaur (Dinosauria: Ornithischia) from marine sediments of coastal California. Journal of Paleontology 70(2):311-326
- ^ M. K. Vickaryous, T. Maryanska, and D. B. Weishampel. 2004. Ankylosauria. In D. B. Weishampel, P. Dodson, and H. Osmolska (eds.), The Dinosauria (second edition). University of California Press, Berkeley 363-392
- ^ Hunt, A.P. and Lucas, S.G., 1992, "Stratigraphy, Paleontology and age of the Fruitland and Kirkland Formations (Upper Cretaceous), San Juan Basin, New Mexico", New Mexico Geological Society Guidebook, 43rd Field Conference, San Juan Basin, volume 4, p. 217-240
- ^ Jump up to: a b c Paul, G.S. (2010). The Princeton Field Guide to Dinosaurs, Princeton University Press.
- ^ Derstler, K. (1994). "Dinosaurs of the Lance Formation in eastern Wyoming". In Nelson, G. E. (ed.). The Dinosaurs of Wyoming. Wyoming Geological Association Guidebook, 44th Annual Field Conference. Wyoming Geological Association. pp. 127–146.
- ^ Carpenter, K.; DiCroce, T.; Kinneer, B.; Simon, R. (2013). "Pelvis of Gargoyleosaurus (Dinosauria: Ankylosauria) and the Origin and Evolution of the Ankylosaur Pelvis". PLOS ONE. 8 (11): e79887. Bibcode:2013PLoSO...879887C. doi:10.1371/journal.pone.0079887. PMC 3828194. PMID 24244573.
- ^ Sonoda, T.; Noda, Y. (2016). "Transfer of museum collection from the Hayashibara Museum of Natural Sciences to the Fukui Prefectural Dinosaur Museum" (PDF). Memoir of the Fukui Prefectural Dinosaur Museum. 15: 93–98.
- ^ Greenfield, T. [@TylerGreenfieId] (2021-07-22). "This should be a helpful reference for anyone wanting to reconstruct Denversaurus, this is the cervical armor arrangement of "Tank" (FPDM-V9673)" (Tweet) – via Twitter.
- ^ Jump up to: a b c Bruns, M.E. (2015). Intraspecific variation in the armoured dinosaurs (Dinosauria: Ankylosauria) (PhD thesis). University of Alberta Library. doi:10.7939/R39K46485.
- ^ Raven, T. J.; Barrett, P. M.; Joyce, C. B.; Maidment, S. C. R. (2023). "The phylogenetic relationships and evolutionary history of the armoured dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. 21 (1). 2205433. Bibcode:2023JSPal..2105433R. doi:10.1080/14772019.2023.2205433. S2CID 258802937.
- ^ Soto Acuña, Sergio; Vargas, Alexander O.; Kaluza, Jonatan (2024). "A new look at the first dinosaur discovered in Antarctica: reappraisal of Antarctopelta oliveroi (Ankylosauria: Parankylosauria)". Advances in Polar Science. 35 (1): 78–107. doi:10.12429/j.advps.2023.0036.