Amphicoelias

Amphicoelias was a long-necked sauropod dinosaur that lived in western North America during the Late Jurassic period, around 150 million years ago. Based on the valid type species Amphicoelias altus, it was a slender, long-tailed animal measuring around 25 metres in total length. It is famous in palaeontological history because Edward Drinker Cope assigned a colossal fossil vertebra to another species, Amphicoelias fragillimus, in 1878. That bone was subsequently lost, leaving only field notes and drawings behind, and recent restudy suggests it represented a distinct giant rebbachisaurid named Maraapunisaurus. The actual Amphicoelias was a more modestly proportioned diplodocid closely comparable in size and anatomy to Diplodocus.

A lost giant vertebra once assigned to this genus likely belonged to a rebbachisaurid and was renamed Maraapunisaurus.

Where and when

Amphicoelias lived in the Late Jurassic, from 155 to 148 million years ago (Kimmeridgian-Tithonian age). Its remains come from United States, in the Morrison Formation.

The numbers

Length 23 m (estimates run from 20 to 25 m). Mass about 19 t. Hip height about 4.5 m. That is 13.2 human-lengths, or 2.01 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.

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