Brontomerus
Encyclopedia
Brontomerus is a genus
of camarasauromorph sauropod which lived during the early Cretaceous
(Aptian
or Albian
age, approximately 110 million years ago). It was named in 2011
and the type species is Brontomerus mcintoshi. It is probably a fairly basal camarasauromorph, though the taxon
is difficult to resolve due to incompleteness of the material. It is most remarkable for its unusual hipbones, which would have supported the largest thigh muscles, proportionally, of any known sauropod. The specific name is in honor of physicist and North American sauropod guru
John "Jack" Stanton McIntosh.
at the top of the Ruby Ranch Member of the Cedar Mountain Formation
in eastern Utah
, USA. The specimens were originally collected in 1994 and 1995 by a team of researchers from the Sam Noble
museum of Norman, Oklahoma
. It was named and described by Michael P. Taylor
, Mathew J. Wedel and Richard L. Cifelli, an international team from the University College London
, Western University of Health Sciences
and the Sam Noble Oklahoma Museum of Natural History. The fossils were recovered from a locality known at the Hotel Mesa Quarry in easternmost Grand County, Utah
. The site had been previously known to private collectors, who had already removed a considerable number of fossils, some of which may have been scientifically valuable. Exposed bones that remained were in various states of disrepair: some had even been broken and their pieces used to hold down a plastic tarpaulin. Due in part to this "pillaging" of the fossil site, the team was unable to recover more complete specimens.
of the smaller individual. Other recovered fossils include a crushed presacral centrum, several caudal vertebrae, a right-side dorsal rib, a large scapula
, and two partial sternal plates
. The adult specimen is thought to have weighed around six tons, and probably measured around 14 meters (46 ft) in length. The juvenile specimen had about a third of this length, and probably weighed around 200 kilograms and measured 4.5 meters (15 ft) in length.
Its assignment to a new species is based on several noteworthy autapomorphies
, including an oddly-shaped hipbone which would have permitted the attachment of unusually massive leg muscles. This unique ilium would have given it the largest leg muscles of any sauropod dinosaur. The ilium is unusual in being very deep and having a front part that is much larger than the part behind the hip socket.
using a 50% majority rule tree, Brontomerus is placed as a basal somphospondyl within Titanosauriformes
, in a trichotomy
with Euhelopus
and the Titanosauria. A strict consensus tree was also calculated, but yielded poorly resolved results.
and Deinonychus
.
Doctor Mathew Wedel, assistant professor of anatomy at the Western University of Health Sciences
in Pomona, California, has stated that since it has been commonly been assumed that sauropods tend to prefer drier, upload areas, perhaps Brontomerus may have used its powerful leg muscles for traversing rough, hilly terrain. He described the theoretical use of such muscles in this terrain as "a sort of dinosaur four-wheel drive."
In addition to powerful protraction muscles, the ilium of Brontomerus would have also anchored abductor muscles
, which are muscles used for drawing the leg laterally away from the body. These muscles would have been necessary for creating abduction torque when standing, and could have theoretically aided in an occasional bipedal stance or even limited bipedal walking. Another possible explanation for the proportionally large leg muscles is that they were used to control unusually long legs. While no material from the legs is known, the large anterior expansion of the scapula provides only weak support for this hypothesis. If this interpretation is correct, however, the morphology of Brontomerus may have resembled that of a giraffe
.
Despite these theories, the actual data on the ilium and its powerful muscles indicates only that the animal was "unusually athletic for a sauropod." The authors acknowledge that while the unusual qualities of the hipbone probably have some functional significance, it is difficult to assess without further information about the pelvis, femora and proximal caudals.
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 camarasauromorph sauropod which lived during the early 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...
(Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
or Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
age, approximately 110 million years ago). It was named in 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
and the type species is Brontomerus mcintoshi. It is probably a fairly basal camarasauromorph, though the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
is difficult to resolve due to incompleteness of the material. It is most remarkable for its unusual hipbones, which would have supported the largest thigh muscles, proportionally, of any known sauropod. The specific name is in honor of physicist and North American sauropod guru
Guru
A guru is one who is regarded as having great knowledge, wisdom, and authority in a certain area, and who uses it to guide others . Other forms of manifestation of this principle can include parents, school teachers, non-human objects and even one's own intellectual discipline, if the...
John "Jack" Stanton McIntosh.
Discovery
Fossils of Brontomerus were recovered from a quarryQuarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
at the top of the Ruby Ranch Member of the Cedar Mountain Formation
Cedar Mountain Formation
The Cedar Mountain Formation is the name given to distinctive sedimentary rocks in eastern Utah that occur between the underlying Morrison Formation and overlying Naturita Formation . It is composed of non-marine sediments, that is, sediments deposited in rivers, lakes and on flood plains...
in eastern Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, USA. The specimens were originally collected in 1994 and 1995 by a team of researchers from the Sam Noble
Sam Noble Oklahoma Museum of Natural History
The Sam Noble Oklahoma Museum of Natural History is a natural history museum in Norman, Oklahoma, operated by the University of Oklahoma. It is currently housed in a building on Chautauqua Avenue that opened on May 1, 2000. The museum's exhibits include a Native American gallery and collections of...
museum of Norman, Oklahoma
Norman, Oklahoma
Norman is a city in Cleveland County, Oklahoma, United States, and is located south of downtown Oklahoma City. It is part of the Oklahoma City metropolitan area. As of the 2010 census, Norman was to have 110,925 full-time residents, making it the third-largest city in Oklahoma and the...
. It was named and described by Michael P. Taylor
Mike Taylor (paleontologist)
Mike Taylor is a British computer programmer and amateur paleontologist. To date, he has published 13 paleontological papers and is co-credited with naming 2 dinosaur species .Along with paleontologists Darren Naish and Matt Wedel, he founded the paleontology blog .- References :...
, Mathew J. Wedel and Richard L. Cifelli, an international team from the University College London
University College London
University College London is a public research university located in London, United Kingdom and the oldest and largest constituent college of the federal University of London...
, Western University of Health Sciences
Western University of Health Sciences
Western University of Health Sciences is a non-profit, private, graduate school for the health professions. The university campus includes 11 major buildings on in downtown Pomona, California....
and the Sam Noble Oklahoma Museum of Natural History. The fossils were recovered from a locality known at the Hotel Mesa Quarry in easternmost Grand County, Utah
Grand County, Utah
Grand County is a county located in the U.S. state of Utah. As of 2000 the population was 8,485, and by 2005 had been estimated at 8,743. It was named for the Colorado River, which at the time of statehood was known as the Grand River. Its county seat and largest city is Moab.-Geography:According...
. The site had been previously known to private collectors, who had already removed a considerable number of fossils, some of which may have been scientifically valuable. Exposed bones that remained were in various states of disrepair: some had even been broken and their pieces used to hold down a plastic tarpaulin. Due in part to this "pillaging" of the fossil site, the team was unable to recover more complete specimens.
Description
Brontomerus is known from two fragmentary specimens differing in size, likely a juvenile and an adult. The researchers speculate that the adult may have been the mother of the juvenile. The type specimen, OMNH 66430, is represented by the left iliumIlium
-Places:* Ilion or, Latinized, Ilium, another name for the legendary city of Troy, hence the title of Homer's Iliad*Ilium , an ancient city in Epirus...
of the smaller individual. Other recovered fossils include a crushed presacral centrum, several caudal vertebrae, a right-side dorsal rib, a large scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
, and two partial sternal plates
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
. The adult specimen is thought to have weighed around six tons, and probably measured around 14 meters (46 ft) in length. The juvenile specimen had about a third of this length, and probably weighed around 200 kilograms and measured 4.5 meters (15 ft) in length.
Its assignment to a new species is based on several noteworthy autapomorphies
Autapomorphy
In cladistics, an autapomorphy is a distinctive anatomical feature, known as a derived trait, that is unique to a given terminal group. That is, it is found only in one member of a clade, but not found in any others or outgroup taxa, not even those most closely related to the group...
, including an oddly-shaped hipbone which would have permitted the attachment of unusually massive leg muscles. This unique ilium would have given it the largest leg muscles of any sauropod dinosaur. The ilium is unusual in being very deep and having a front part that is much larger than the part behind the hip socket.
Phylogeny
Based on phylogenetic analysisCladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
using a 50% majority rule tree, Brontomerus is placed as a basal somphospondyl within Titanosauriformes
Macronaria
Macronaria is a clade of sauropod dinosaurs from the Middle Jurassic to Late Cretaceous Periods of what are now North America, South America, Europe, Asia and Africa. The name means 'large nostrils' , in reference to the large nasal openings high on the head that probably supported fleshy...
, in a trichotomy
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
with Euhelopus
Euhelopus
Euhelopus is a genus of sauropod dinosaur that lived during the Early Cretaceous, between 130 and 112 million years ago . It lived in what is now Shandong Province in China. A large herbivore, it weighed approximately 15-20 tons and attained an adult length of 15m...
and the Titanosauria. A strict consensus tree was also calculated, but yielded poorly resolved results.
Morphology and behavior
Dr. Michael Taylor, one of the dinosaur's describers, theorizes that it can be determined that these muscles were probably used for functions other than speed. He points out that for fast movement, the strong muscles would be oriented at the back of the leg to pull it along, but the actual positioning of the muscles indicates they were more likely used to deliver a kick. This is due to the apparent anchoring of large femoral protraction muscles, which would have been used to move the leg forward powerfully. Large femoral retraction muscles, on the other hand, are needed to for fast forward locomotion, and the ilium of Brontomerus offers little attachment area for these, though this does not necessarily imply weak retraction muscles as these would have been mostly anchored on the tail-base rather than the ilium. The supposed kicks would have possibly been used for fighting over mates or in defense against predators, such as UtahraptorUtahraptor
Utahraptor is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period...
and Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...
.
Doctor Mathew Wedel, assistant professor of anatomy at the Western University of Health Sciences
Western University of Health Sciences
Western University of Health Sciences is a non-profit, private, graduate school for the health professions. The university campus includes 11 major buildings on in downtown Pomona, California....
in Pomona, California, has stated that since it has been commonly been assumed that sauropods tend to prefer drier, upload areas, perhaps Brontomerus may have used its powerful leg muscles for traversing rough, hilly terrain. He described the theoretical use of such muscles in this terrain as "a sort of dinosaur four-wheel drive."
In addition to powerful protraction muscles, the ilium of Brontomerus would have also anchored abductor muscles
Abduction (kinesiology)
Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist...
, which are muscles used for drawing the leg laterally away from the body. These muscles would have been necessary for creating abduction torque when standing, and could have theoretically aided in an occasional bipedal stance or even limited bipedal walking. Another possible explanation for the proportionally large leg muscles is that they were used to control unusually long legs. While no material from the legs is known, the large anterior expansion of the scapula provides only weak support for this hypothesis. If this interpretation is correct, however, the morphology of Brontomerus may have resembled that of a giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...
.
Despite these theories, the actual data on the ilium and its powerful muscles indicates only that the animal was "unusually athletic for a sauropod." The authors acknowledge that while the unusual qualities of the hipbone probably have some functional significance, it is difficult to assess without further information about the pelvis, femora and proximal caudals.