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
Clade: Dinosauria
Order: Ornithischia
Family: Ceratopsidae
Subfamily: Centrosaurinae
Clade: Eucentrosaura
Tribe: 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 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 below follows a phylogenetic analysis including Rubeosarus by Chiba et al. (2017), who recovered it as the sister taxon of Styracosaurus:[5]

Centrosaurinae

Diabloceratops eatoni

Machairoceratops cronusi

Nasutoceratopsini

Avaceratops lammersi (ANSP 15800)

MOR 692

CMN 8804

Nasutoceratops titusi

Malta new taxon

Xenoceratops foremostensis

Sinoceratops zhuchengensis

Wendiceratops pinhornensis

Albertaceratops nesmoi

Medusaceratops lokii

Eucentrosaura
Centrosaurini

Rubeosaurus ovatus

Styracosaurus albertensis

Coronosaurus brinkmani

Centrosaurus apertus

Spinops sternbergorum

Pachyrhinosaurini

Einiosaurus procurvicornis

Pachyrostra

Achelousaurus horneri

Pachyrhinosaurus canadensis

Pachyrhinosaurus lakustai

Pachyrhinosaurus perotorum

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 3154267. PMID 21853043.
  5. ^ Kentaro Chiba; Michael J. Ryan; Federico Fanti; Mark A. Loewen; David C. Evans (2018). "New material and systematic re-evaluation of Medusaceratops lokii (Dinosauria, Ceratopsidae) from the Judith River Formation (Campanian, Montana)". Journal of Paleontology. in press. doi:10.1017/jpa.2017.62.