Longest dinosaur tail relative to body size

Relative to body size, the dinosaur with the longest tail was Leaellynasaura amicagraphica – a small herbivorous bird-hipped (ornithischian) dinosaur that existed 120–125 million years ago during the Early Cretaceous Period in what is today southern Australia. Its total length was 3 m, but its 2.25-m tail alone measured three times the length of its head, neck, and body combined, and contained more than 70 bones.