Epachthosaurus

Epachthosaurus was a moderately sized titanosaur sauropod that inhabited what is now Patagonia during the early Late Cretaceous. Measuring approximately eighteen to twenty metres in length and weighing over ten tonnes, it was a hefty four-legged herbivore capable of stripping foliage from high tree branches as well as browsing at lower levels. Discovered in Chubut Province, Argentina, it is notable for being one of the best-preserved basal titanosaurians. A well-preserved specimen includes an articulated skeleton with limbs and vertebrae that crucially retain archaic accessory joints between the backbones, features typically missing in more derived titanosaurs. This unique skeletal mix makes Epachthosaurus an essential reference genus for reconstructing the transition from primitive sauropods to the highly specialised titanosaurs that dominated the Southern Hemisphere until the close of the Mesozoic.

It provides crucial evolutionary insight because it retains hyposphene-hypantrum vertebral articulations lost in more derived titanosaurs.

Where and when

Epachthosaurus lived in the Late Cretaceous, from 100.5 to 89.8 million years ago (Cenomanian-Turonian age). Its remains come from Argentina, in the Bajo Barreal Formation.

The numbers

Length 19 m (estimates run from 17 to 20 m). Mass about 11 t. Hip height about 4.5 m. That is 10.9 human-lengths, or 1.65 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, first ma, last ma, hip height.

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