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Amphicoelias is a genus of herbivorous sauropod dinosaur. It includes what has sometimes been estimated to be the largest dinosaur specimen ever discovered, originally named “A. fragillimus”. Based on surviving descriptions of a single fossil bone, scientists had over the years estimated A. fragillimus to have been the longest known animal at 58 metres in length, with potentially a mass of up to 122.4 tonnes.

However, because the only fossil remains were lost at some point after being studied and described in the 1870s, evidence survived only in drawings and field notes. More recent analysis of the surviving evidence, and the biological plausibility of such a large land animal, has suggested that the enormous size of this animal were over-estimates due partly to typographical errors in the original 1878 description.

Name: Amphicoelias (Double hollow).

Phonetic: Am-fee-see-le-as.
Named By: Edward Drinker Cope – 1878.
Synonyms: Amphicoelias latus.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Sauropodomorpha, Sauropoda, Diplodocoidea.
Species: A. altus (type), A. fragillimus.
Diet: Herbivore.
Size: Uncertain due to lack of and subsequent loss of remains, but estimated between 40 and 60 meters long.
Known locations: USA, Colorado.
Time period: Kimmeridgian to Tithonian of the Jurassic.
Fossil representation: Fragmentary and isolated remains, original fossils are now lost.

Scientific classification

  • Kingdom: Animalia
  • Phylum: Chordata
  • Clade: Dinosauria
  • Order: Saurischia
  • Suborder: Sauropodomorpha
  • Clade: Sauropoda
  • Clade: Flagellicaudata
  • Family: Diplodocidae
  • Genus: Amphicoelias Cope, 1878
  • Type species: Amphicoelias altus


Amphicoelias fragillimus was collected by Oramel Lucas, a fossil collector employed by E. D. Cope, shortly after he was hired by Cope in 1877. Lucas discovered a partial vertebra of the new sauropod species in Garden Park, north of Cañon City, Colorado, close to the quarry that yielded Camarasaurus. The vertebra was in poor condition, but astonishingly large, measuring 1.5 metres (4.9 ft) up to 2.7 metres (8.9 ft) in height.

Lucas shipped the specimen to Cope in the spring or early summer of 1878, and Cope published it as the holotype specimen (catalogue number AMNH 5777) of a new species, A. fragillimus, that August.

The name derives from the Latin fragillimus (“very fragile”), referring to the delicateness of the bone produced by very thin laminae (vertebral walls). As revealed in Cope’s notebooks, which he recorded based on Lucas’ report on excavation site locations in 1879, the specimen came from a hill south of the Camarasaurus quarry now known as “Cope’s Nipple.” While Cope originally wrote that the site belonged to the Dakota Formation, the presence of dinosaurs such as Camarasaurus in the same rocks indicates that they probably belong to the Morrison Formation, which places the age of the site at 150 million years ago in the late Jurassic period, specifically the Tithonian age.


Amphicoelias was a herbivore. It lived in the Jurassic period and inhabited North America. Its fossils have been found in places such as Colorado, Wyoming and Mashonaland West.


Amphicoelias fragillimus is only known from one enormous fragmented vertebra (about 4.9 feet, or 1.5 meters tall) (Cope, 1878), which has been lost. If complete, the vertebra would probably have been well over 8 feet tall (2.7 meters).

Carpenter (2006) estimated the length of A. fragillimus at 190 feet long (about 58 meters), which is within the range suggested by Paul (1994) of 40-60 meters or 131-196 feet . Even conservative estimates of 130 feet (40 meters) would still make A. fragilimus by far the longest animal ever found.

Classification and species

Edward Drinker Cope described his finds in two 1878 issues of the American Naturalist, and assigned them to the new genus Amphicoelias. He placed it in a unique family, Amphicoeliidae, though this is now considered a nomen oblitum (forgotten name).

The genus is usually assigned to the family Diplodocidae, though some modern analyses have found it at the base of the larger group Diplodocoidea or as a diplodocid incertae sedis (uncertain placement).[13] The first named species in the genus, Amphicoelias altus (holotype specimen AMHD 5764), was discovered by Cope in 1877. But while it is only represented by a partial skeleton, there are enough diagnostic characteristics to provisionally define the genus. A. altus is known from better remains, but is smaller than A. fragillimus. Cope also named a second species in 1878: Amphicoelias latus.

Amphicoelias images

Also more: Ammosaurus 

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