Brontosaurus

Brontosaurus Temporal range: Late Jurassic (Kimmeridgian to Tithonian), 156.3–146.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Holotype specimen of B. excelsus (YPM 1980), Peabody Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Superfamily:	†Diplodocoidea
Family:	†Diplodocidae
(unranked):	†Apatosaurinae
Genus:	†Brontosaurus Marsh, 1879
Type species
†Brontosaurus excelsus Marsh, 1879
Referred species
†Brontosaurus parvus (Peterson & Gilmore, 1902) †Brontosaurus yahnahpin (Filla & Redman, 1994)
Synonyms
Elosaurus Peterson & Gilmore, 1902 Eobrontosaurus Bakker, 1998 Synonyms of B. excelsus Brontosaurus amplus Marsh, 1881 Apatosaurus excelsus (Marsh, 1879) Riggs, 1903 Apatosaurus amplus (Marsh, 1881) Riggs, 1903 Atlantosaurus excelsus (Marsh, 1879) Steel, 1970 Atlantosaurus amplus (Marsh, 1881) Steel, 1970 Synonyms of B. parvus Elosaurus parvus Peterson & Gilmore, 1902 Apatosaurus parvus (Peterson & Gilmore, 1902) Upchurch et al., 2004 Synonyms of B. yahnahpin Apatosaurus yahnahpin Filla & Redman, 1994 Eobrontosaurus yahnahpin (Filla & Redman, 1994) Bakker, 1998

Brontosaurus (/ˌbrɒntəˈsɔːrəs/;^[1][2] meaning "thunder lizard" from the Greek words βροντή, brontē "thunder" and σαῦρος, sauros "lizard") is a genus of herbivorous sauropod dinosaur that lived in present-day United States during the Late Jurassic period. It was described by American paleontologist Othniel Charles Marsh in 1879, the type species being dubbed B. excelsus, based on a partial skeleton lacking a skull found in Como Bluff, Wyoming. In subsequent years, two more species of Brontosaurus were named: B. parvus in 1902 and B. yahnahpin in 1994. Brontosaurus lived about 156 to 146 million years ago (mya) during the Kimmeridgian and Tithonian ages in the Morrison Formation of what is now Utah and Wyoming. For decades, the animal was thought to have been a taxonomic synonym of its close relative Apatosaurus, but a 2015 study by Emmanuel Tschopp and colleagues found it to be distinct. It has seen widespread representation in popular culture, being the archetypal "long-necked" dinosaur in general media.

The anatomy of Brontosaurus is well known, with fossils demonstrating that it was large, long-necked, and quadrupedal with a long tail terminating in a whip-like structure. The cervical vertebrae are notably extremely robust and heavily-built, in contrast to its lightly built relatives Diplodocus and Barosaurus. The forelimbs were short and stout whereas the hindlimbs were elongated and thick, supported respectively by a heavily built shoulder girdle and pelvis. Several size estimates have been made, with the largest species B. excelsus reaching up to 21–22 m (69–72 ft) from head to tail and weighing in at 15–17 t (17–19 short tons), whereas the smaller B. parvus only got up to 19 m (62 ft) long. Juvenile specimens of Brontosaurus are known, with younger individuals growing rapidly to adult size in as little as 15 years.

Brontosaurus has been classified within the family Diplodocidae, which was a group of sauropods that had shorter necks and longer tails compared to other families like brachiosaurs and mamenchisaurs. Diplodocids first evolved in the Middle Jurassic but peaked in diversity during the Late Jurassic with forms like Brontosaurus before becoming extinct in the Early Cretaceous. Brontosaurus is a genus in the subfamily Apatosaurinae, which includes only it and Apatosaurus, which are distinguished by their firm builds and thick necks. Although Apatosaurinae was named in 1929, the group was not used validly until an extensive 2015 paper, which found Brontosaurus to be valid. However, the status of Brontosaurus is still uncertain, with some paleontologists still considering it a synonym of Apatosaurus.

Being from the Morrison Formation, Brontosaurus coexisted with a menagerie of other taxa such as the sauropods Diplodocus, Barosaurus, and Brachiosaurus; herbivorous ornithischians Stegosaurus, Dryosaurus, and Nanosaurus; as well as the carnivorous theropods Allosaurus, Marshosaurus and Ceratosaurus. This formation was a hotspot of sauropod biodiversity, with over 16 recognized genera, which resulted in niche partitioning between different sauropods.