Brontomerus (from Greek bronte meaning "thunder", and merós meaning "thigh") is a possibly dubious 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 expert John "Jack" Stanton McIntosh.
Temporal range: Lower Cretaceous, Aptian–Albian
|Artist's restoration of Brontomerus utilizing its large abductor muscles to defend against a predator|
Taylor, Wedel & Cifelli, 2011
B. mcintoshi Taylor, Wedel & Cifelli, 2011 (type)
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 ilium 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 tonnes, 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.
Fossils of Brontomerus were recovered from a quarry at the top of the Ruby Ranch Member of the Cedar Mountain Formation in eastern Utah, United States. 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 as 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.
Based on phylogenetic analysis using a 50% majority rule tree, Brontomerus was initially 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. The tree can be seen below:
A more recent phylogenetic analysis of the Titanosauriformes determined Brontomerus to be a nomen dubium due to the holotype's fragmentary, nondiagnostic nature.
Dr. Michael Taylor, one of the dinosaur's describers, hypothesizes that the strong thigh muscles of Brontomerus 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 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 Utahraptor and Deinonychus.
Dr. Matthew 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", and there is minimal speculation that Brontomerus may have been predatory and would require extra power in locomotion to feed; it would be the first carnivore among any sauropod discovered. 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.
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 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma (million years ago). The Albian is preceded by the Aptian and followed by the Cenomanian.Apatosaurinae
Apatosaurinae is the name of a subfamily of diplodocid sauropods that existed between 157 and 150 million years ago in North America. The group includes two genera for certain, Apatosaurus and Brontosaurus, with at least five species. Atlantosaurus and Amphicoelias might also belong to this group.Below is a cladogram of apatosaurinae interrelationships based on Tschopp et al., 2015.Brasilotitan
Brasilotitan is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous (early Maastrichtian) Adamantina Formation of Brazil. The type species is Brasilotitan nemophagus.Cetiosauridae
Cetiosauridae is a family of sauropod dinosaurs. While traditionally a wastebasket taxon containing various unrelated species, some recent studies have found that it may represent a natural clade. Additionally, at least one study has suggested that the mamenchisaurids may represent a sub-group of the cetiosaurids, which would be termed Mamenchisaurinae.Diplodocinae
Diplodocinae is an extinct subfamily of diplodocid sauropods that existed from the Late Jurassic to Early Cretaceous of North America, Europe and South America, about 161.2 to 136.4 million years ago. Genera within the subfamily include Tornieria, Supersaurus, Leinkupal, Galeamopus, Diplodocus, Kaatedocus and Barosaurus.Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).Eomamenchisaurus
Eomamenchisaurus (meaning "dawn Mamenchisaurus") is a genus of mamenchisaurid sauropod dinosaur from the Middle Jurassic of Yuanmou, Yunnan, China. The type species is E. yuanmouensis, described by Lü Junchang et al. in 2008.Ferganasaurus
Ferganasaurus was a genus of dinosaur first formally described in 2003 by Alifanov and Averianov. The type species is Ferganasaurus verzilini. It was a sauropod similar to Rhoetosaurus. The fossils were discovered in 1966 in Kyrgyzstan from the Balabansai Formation and date to the Callovian stage of the Middle Jurassic.Flagellicaudata
Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.Gravisauria
Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.Huangshanlong
Huangshanlong is a genus of mamenchisaurid dinosaurs native to the Anhui province of China. It contains a single species, Huangshanlong anhuiensis. H. anhuiensis represents, along with Anhuilong and Wannanosaurus, one of three dinosaurs fround in Anhui province.Kaijutitan
Kaijutitan (meaning "Kaiju titan" after the type of Japanese movie monsters) is a genus of basal titanosaur dinosaur from the Sierra Barrosa Formation from Neuquén Province in Argentina. The type and only species is Kaijutitan maui.Matt Wedel
Mathew John Wedel is an American paleontologist. He is associate professor at the Western University of Health Sciences Department of Anatomy in California. Mathew studies sauropods and the evolution of pneumatic bones in dinosaurs. At Western University, Mathew teaches gross anatomy. He has authored papers naming Aquilops (2014), Brontomerus (2011), and Sauroposeidon (2000).Along with paleontologists Darren Naish and Mike P. Taylor, he founded the paleontology blog Sauropod Vertebrae Picture of the Week.Michael P. Taylor
Michael P. Taylor (born 12 March 1968) is a British computer programmer with a Ph.D in palaeontology. To date, he has published 18 paleontological papers and is co-credited with naming three genera of dinosaur (Xenoposeidon in 2007 with Darren Naish, Brontomerus in 2011 with Matt J. Wedel and Richard Cifeli, and Haestasaurus in 2015 with Paul Upchurch and Phil Mannion).Along with paleontologists Darren Naish and Matt Wedel, he founded the paleontology blog Sauropod Vertebra Picture of the Week, where he blogs as Mike Taylor.
He lives in Ruardean, Gloucestershire, England.Pilmatueia
Pilmatueia is a diplodocoid sauropod belonging to the family Dicraeosauridae that lived in Argentina during the Early Cretaceous.Sibirotitan
Sibirotitan ("Siberian titan") is a genus of somphospondyl sauropod from the Ilek Formation of Russia. The type and only species is S. astrosacralis.Somphospondyli
Somphospondylans are an extinct clade of titanosauriform sauropods that lived throughout the world from the Late Jurassic through the Cretaceous in North America, South America, Europe, Asia, Africa and Australia. The group can be defined as "the most inclusive clade that includes Saltasaurus loricatus but excludes Brachiosaurus altithorax". Features found as diagnostic of this clade by Mannion et al. (2013) include the possession of at least 15 cervical vertebrae; a bevelled radius bone end; sacral vertebrae with camellate internal texture; convex posterior articular surfaces of middle to posterior caudal vertebrae; biconvex distal caudal vertebrae; humerus anterolateral corner "squared"; among multiple others.Tambatitanis
Tambatitanis is an extinct genus of titanosauriform dinosaur from the Early Cretaceous (probably early Albian) of Japan. It is known from a single type species, Tambatitanis amicitiae. It was probably around 14 meters long and its mass was estimated at some 4 tonnes. It was a basal titanosauriform and possibly belonged to the Euhelopodidae.Tastavinsaurus
Tastavinsaurus is a genus of sauropod dinosaur belonging to the Titanosauriformes. It is based on a partial skeleton from the Early Cretaceous of Spain. The type species is Tastavinsaurus sanzi, named in honor of the Rio Tastavins in Spain and Spanish paleontologist José Luis Sanz.Tengrisaurus
Tengrisaurus (meaning "Tengri lizard") is a genus of lithostrotian sauropod, from the Early Cretaceous (Barremian-Aptian), of the Murtoi Formation, Russia. It was described in 2017 by Averianov & Skutschas. The type species is T. starkovi.