Rubeosaurus

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Rubeosaurus
Temporal range: Late Cretaceous, 74.6 Ma
Rubeosaurus ovatus.jpg
Holotype specimen
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Ornithischia
Family: Ceratopsidae
Subfamily: Centrosaurinae
Clade: Centrosaurini
Genus: Rubeosaurus
McDonald & Horner, 2010
Type species
Styracosaurus ovatus
(Gilmore, 1930)
Species
  • R. ovatus (Gilmore, 1930)

Rubeosaurus (meaning "bramble or thornbush lizard") is a genus of ceratopsian dinosaur which lived in what is now North America. Rubeosaurus fossils have been recovered from strata of the upper Two Medicine Formation of the Upper Cretaceous of Montana, dating to 74.6 million years ago.[1]

History of discovery[edit]

Nasals of specimen MOR 492

The holotype specimen, USNM 11869, is composed of a partial parietal and was discovered by George F. Sternberg in 1928. A second specimen, MOR 429, is composed of a partial skull including a partial left premaxilla, co-ossified left and right nasals with horncore, partial left postorbital with horncore, and a nearly complete right parietal with two spikes. It was discovered in 1986.[1]

This genus was named by Andrew T. McDonald and John R. Horner in 2010, and the type species is Rubeosaurus ovatus. Formerly this species was assigned to Styracosaurus.[2] It is found as the sister taxon to Einiosaurus. It is notable for its large broad–based nasal horn and the ornamentation of its bony frill: there were one or two pairs of straight spikes on the edge, with the two spikes closest to the midline pointing so that they converged.[1] Immature specimens referred to a separate genus, called Brachyceratops, may be juvenile Rubeosaurus.[1][3]

Juvenile specimen[edit]

In 2007, Michael J. Ryan and colleagues suggested that Brachyceratops was possibly the juvenile form of Rubeosaurus.[3] A 2011 study supported this idea for the most mature specimen of Brachyceratops, USNM 14765, which shows one unique newly evolved feature (apomorphy) in common with Rubeosaurus to the exclusion of other centrosaurines. However, the same study suggested that because the holotype specimen of Brachyceratops is too incomplete and juvenile to preserve any determinable apomorphies, Brachyceratops must be considered a nomen dubium, and cannot be a senior synonym of Rubeosaurus.[4]

Classification[edit]

Life restoration
Artist's restoration of a juvenile Rubeosaurus

The cladogram presented here follows Ryan et al. (2016), which recovered it as the sister taxon of Styracosaurus:[5]


Centrosaurinae

Diabloceratops eatoni



Nasutoceratopsini

Avaceratops lammersi (ANSP 15800)



MOR 692



CMN 8804



Nasutoceratops titusi



Malta new taxon





Xenoceratops foremostensis




Albertaceratops nesmoi




Sinoceratops zhuchengensis



Wendiceratops pinhornensis




Pachyrhinosaurini

Einiosaurus procurvicornis




Achelousaurus horneri


Pachyrhinosaurus

Pachyrhinosaurus canadensis




Pachyrhinosaurus lakustai



Pachyrhinosaurus perotorum






Centrosaurini


Rubeosaurus ovatus



Styracosaurus albertensis






Spinops sternbergorum



Centrosaurus apertus




Coronosaurus brinkmani










See also[edit]

References[edit]

  1. ^ a b c d Andrew T. McDonald & John R. Horner, (2010). "New Material of "Styracosaurus" ovatus from the Two Medicine Formation of Montana". Pages 156–168 in: Michael J. Ryan, Brenda J. Chinnery-Allgeier, and David A. Eberth (eds), New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium, Indiana University Press, Bloomington and Indianapolis, IN.
  2. ^ Gilmore, Charles W. (1930). "On dinosaurian reptiles from the Two Medicine Formation of Montana". Proceedings of the United States National Museum. 77 (16): 1–39. doi:10.5479/si.00963801.77-2839.1. 
  3. ^ a b Ryan, Michael J.; Holmes, Robert; Russell, A.P. (2007). "A revision of the late Campanian centrosaurine ceratopsid genus Styracosaurus from the Western Interior of North America" (PDF). Journal of Vertebrate Paleontology. 27 (4): 944–962. doi:10.1671/0272-4634(2007)27[944:AROTLC]2.0.CO;2. Retrieved 2010-08-19. 
  4. ^ McDonald, A. T. (2011). Farke, Andrew Allen, ed. "A Subadult Specimen of Rubeosaurus ovatus (Dinosauria: Ceratopsidae), with Observations on Other Ceratopsids from the Two Medicine Formation". PLoS ONE. 6 (8): e22710. doi:10.1371/journal.pone.0022710. PMC 3154267Freely accessible. PMID 21853043. 
  5. ^ Ryan, M.J.; Holmes, R.; Mallon, J.; Loewen, M.; Evans, D.C. (2017). "A basal ceratopsid (Centrosaurinae: Nasutoceratopsini) from the Oldman Formation (Campanian) of Alberta, Canada". Canadian Journal of Earth Sciences. 54. doi:10.1139/cjes-2016-0110.