Therizinosaurus

Those massive claw bones measured up to a metre long — the longest claws of any animal ever discovered! When scientists first found them in 1948, the claws were so weird they thought they belonged to a giant turtle (that's why the species name means 'turtle-shaped'). Only later did researchers realise these bizarre weapons belonged to a dinosaur.

Instead of the slim, athletic build of most meat-eating dinosaurs, therizinosaurs evolved a huge pot-bellied body with extra-wide hips. All that belly space housed a massive gut needed to break down tough plants — like having a built-in fermentation tank. Scientists figured this out from well-preserved relatives, since no body bones have been found for Therizinosaurus itself.

A super-long, flexible neck let this dinosaur reach high into the treetops like a prehistoric giraffe. Combined with those raking claws, it could feed in ways surprisingly similar to giant ground sloths that evolved millions of years later. Scientists worked this out from relatives like Erlikosaurus, which has a beautifully preserved skull and neck bones.

Forget speed — these legs were built for stability. Unlike most theropods with three toes, therizinosaurs walked on four weight-bearing toes, creating a wide, flat foot more like their ancient plant-eating ancestors than their speedy meat-eating cousins. This sturdy base supported an animal that may have weighed as much as 5,000 kg — about as heavy as an elephant!

A close relative called Beipiaosaurus was found covered in fuzzy feathers plus strange ribbon-like plumes along its neck and body — making it one of the best examples of a feathered non-bird dinosaur. Since this smaller cousin was so fluffy, scientists believe Therizinosaurus probably rocked a similar feathery look, though no skin impressions have been found yet.