Herne (2009) argued that, unlike more advanced ornithischians, Leaellynasaura lacked ossified tendons in its tail.

[4] However, in a subsequent revision of fossil material attributed to Leaellynasaura Herne (2013) could not confidently assign the postcranial skeletons with long tails (or indeed any fossils other than the holotype incomplete cranium MV P185991, right maxilla MV P186352 and left maxillary tooth MV P186412, all from late Aptian-early Albian Eumeralla Formation) to Leaellynasaura amicagraphica.

[8] Position according to Herne et al., 2019:[8] Heterodontosauridae Eocursor Thyreophora Lesothosaurus Agilisaurus Hexinlusaurus Yandusaurus Nanosaurus Jeholosauridae Thescelosauridae Marginocephalia Parksosaurus Talenkauen Macrogryphosaurus Gasparinisaura Galleonosaurus Leaellynasaura Anabisetia Diluvicursor Hypsilophodon Iguanodontia Leaellynasaura was an Australian polar dinosaur.

Because of the Earth's tilt, Leaellynasaura and its contemporaries would still have been living under conditions with extended periods of both daylight and night.

A skull fragment interpreted as being from Leaellynasaura has been reported as showing enlarged eyes and the suggestion of proportionally large optic lobes, implying an adaptation to low-light conditions.