Lessemsaurus

Lessemsaurus is a large herbivorous sauropodomorph discovered in the Los Colorados Formation of La Rioja Province, Argentina. Living in the Late Triassic around 210 million years ago, this animal grew to around nine metres in length and weighed roughly four tonnes. Named by palaeontologist José Bonaparte after popular science author Don Lessem, it is the name-bearing member of Lessemsauridae. Its skeleton features remarkably tall neural spines on the vertebrae and columnar limbs adapted to supporting immense body mass on all fours. Bone histology reveals that Lessemsaurus underwent seasonal growth spurts, demonstrating that early sauropodomorphs developed an independent evolutionary pathway to colossal body size long before true sauropods dominated the Middle and Late Jurassic landscapes.

It proved that sauropodomorphs achieved multi-tonne gigantism thirty million years before true sauropods.

Where and when

Lessemsaurus lived in the Late Triassic, from 215 to 208 million years ago (Norian age). Its remains come from Argentina, in the Los Colorados Formation.

The numbers

Length 8.5 m (estimates run from 8 to 9 m). Mass about 3.7 t. Hip height about 2.5 m. That is 5 human-lengths, or 0.76 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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