Brachyceratops
Encyclopedia
Brachyceratops is a dubious
genus
of ceratopsian dinosaur
known only from partial juvenile specimens dating to the late Cretaceous
Period of Montana
, United States
.
Brachyceratops has historically been known entirely from juvenile remains, with one specimen having since been re-classified as Rubeosaurus ovatus
.
, was first discovered in the Two Medicine Formation
(Campanian
, about 74 million years old) on a Blackfoot
Indian Reservation
in Teton County
in north-central Montana
. The original find was made in August 1913 by C. W. Gilmore and his assistant J.F. Strayrer and was named and shortly described by Gilmore one year later. The generic name is derived from Greek
βραχύς, brachys, "short", κέρας, keras, "horn" and ὤψ, ops, "face", in reference to the short snout. The specific name refers to the provenance from Montana.
All that was found were incomplete and jumbled remains of five juvenile individuals of about 1.5 m (5 feet) in length. It has been speculated that these juveniles may have been nest mates that stayed together after hatching. The holotype
specimen is USNM 7951, a partial skull. The paratype
s are USNM 7952, a snout, USNM 7953, a partial skeleton with skull and USNM 7957, a foot. The material is disarticulated but the preservation is excellent. In 1917 Gilmore published a monography on Brachyceratops in which a reconstruction of the skeleton as a whole was given.
In 1934 Gilmore referred a larger subadult specimen, USNM 14765, to Brachyceratops. All specimens are currently part of the collection of the Smithsonian Institution
in Washington D.C., where a skeletal restoration is mounted.
As Brachyceratops is known only from the remains
of five juveniles — plus the subadult that Gilmore found about a mile from the original specimens —, it was long considered likely that these represented the immature forms of known centrosaurine ceratopsians, with Monoclonius
often suggested as the likeliest candidate. By 2011 however, several studies had shown that the single specimen which was adult enough to be compared with related species, USNM 14765, represented the juvenile form of the later-named Rubeosaurus
.
Among the five original specimens parts of three skulls were discovered, detached from their owner's body and fragmented. Despite this, the skull showed that the animal had only small bumps over the eyes rather than full-grown horns like in the more famous ceratopsians such as Triceratops. The nasal horn was thick and low, while its neck frill was moderately large. Unfortunately the specimens were incomplete so it cannot be determined if there were parietal openings in the frill like some other ceratopsians possessed.
, but its exact placement has been difficult to discover because it is known only from juvenile specimens. In 1997, Scott Sampson and colleagues re-examined Brachyceratops and noted that it is almost certainly the juvenile form of an already known centrosaurine dinosaur. However, because many features that distinguish ceratopsians from each other do not appear until adulthood, exactly which centrosaurine remained unknown, and Sampson et al. classified Brachyceratops as a nomen dubium, or dubious name. In 2007, Michael J. Ryan and colleagues suggested that Brachyceratops was possibly the juvenile form of Styracosaurus ovatus, which has since been reclassified as Rubeosaurus
. 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.
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of ceratopsian dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
known only from partial juvenile specimens dating to the late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period of Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
Brachyceratops has historically been known entirely from juvenile remains, with one specimen having since been re-classified as Rubeosaurus ovatus
Rubeosaurus
Rubeosaurus 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 between 75 and 74 million years ago...
.
Discoveries and species
Brachyceratops montanensis, the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, was first discovered in the Two Medicine Formation
Two Medicine Formation
The Two Medicine Formation is a geologic formation, or rock body, that was deposited between 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma , during Campanian time, and is located in northwestern Montana...
(Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
, about 74 million years old) on a Blackfoot
Blackfoot
The Blackfoot Confederacy or Niitsítapi is the collective name of three First Nations in Alberta and one Native American tribe in Montana....
Indian Reservation
Indian reservation
An American Indian reservation is an area of land managed by a Native American tribe under the United States Department of the Interior's Bureau of Indian Affairs...
in Teton County
Teton County
Teton County is the name of several counties in the United States:* Teton County, Idaho* Teton County, Montana* Teton County, Wyoming...
in north-central Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
. The original find was made in August 1913 by C. W. Gilmore and his assistant J.F. Strayrer and was named and shortly described by Gilmore one year later. The generic name is derived from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
βραχύς, brachys, "short", κέρας, keras, "horn" and ὤψ, ops, "face", in reference to the short snout. The specific name refers to the provenance from Montana.
All that was found were incomplete and jumbled remains of five juvenile individuals of about 1.5 m (5 feet) in length. It has been speculated that these juveniles may have been nest mates that stayed together after hatching. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen is USNM 7951, a partial skull. The paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
s are USNM 7952, a snout, USNM 7953, a partial skeleton with skull and USNM 7957, a foot. The material is disarticulated but the preservation is excellent. In 1917 Gilmore published a monography on Brachyceratops in which a reconstruction of the skeleton as a whole was given.
In 1934 Gilmore referred a larger subadult specimen, USNM 14765, to Brachyceratops. All specimens are currently part of the collection of the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...
in Washington D.C., where a skeletal restoration is mounted.
As Brachyceratops is known only from the remains
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
of five juveniles — plus the subadult that Gilmore found about a mile from the original specimens —, it was long considered likely that these represented the immature forms of known centrosaurine ceratopsians, with Monoclonius
Monoclonius
Monoclonius was a ceratopsian dinosaur from the Judith River Formation of Late Cretaceous Montana and Canada. It is often confused with Centrosaurus, a similar genus of ceratopsian . Monoclonius was described by Edward Drinker Cope in 1876...
often suggested as the likeliest candidate. By 2011 however, several studies had shown that the single specimen which was adult enough to be compared with related species, USNM 14765, represented the juvenile form of the later-named Rubeosaurus
Rubeosaurus
Rubeosaurus 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 between 75 and 74 million years ago...
.
Skull
Classification
Brachyceratops belonged to the CentrosaurinaeCentrosaurinae
The Centrosaurinae is a subfamily of ceratopsid dinosaurs named by paleontologist Lawrence Lambe, in 1915, with Centrosaurus as the type genus...
, but its exact placement has been difficult to discover because it is known only from juvenile specimens. In 1997, Scott Sampson and colleagues re-examined Brachyceratops and noted that it is almost certainly the juvenile form of an already known centrosaurine dinosaur. However, because many features that distinguish ceratopsians from each other do not appear until adulthood, exactly which centrosaurine remained unknown, and Sampson et al. classified Brachyceratops as a nomen dubium, or dubious name. In 2007, Michael J. Ryan and colleagues suggested that Brachyceratops was possibly the juvenile form of Styracosaurus ovatus, which has since been reclassified as Rubeosaurus
Rubeosaurus
Rubeosaurus 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 between 75 and 74 million years ago...
. 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
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
, and cannot be a senior synonym of Rubeosaurus.