Leaellynasaura amicagraphica

Leaellynasaura amicagraphica was a small plant-eating dinosaur from the Eumeralla Formation of Victoria, which lay within the Antarctic Circle during the Early Cretaceous. Its secure remains are much less complete than many popular reconstructions imply: the name is based on a toothed upper-jaw bone, with closely associated skull-roof and braincase material. Numerous postcranial bones from Dinosaur Cove were historically referred to the species, producing the familiar reconstruction with an exceptionally long tail, but later taphonomic work showed that several animals were mixed at the locality and many of those assignments cannot be demonstrated.

Its fossils occur between approximately 108 and 105 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The holotype is a left maxilla bearing small leaf-shaped cheek teeth suitable for cutting vegetation. A nearby skull roof and natural brain endocast preserve large orbital regions, although claims that enlarged eyes were a special adaptation to polar darkness remain uncertain. Traditionally referred limb and tail bones suggest a lightly built biped with long hind limbs and a very elongated balancing tail, but these postcranial proportions cannot presently be assigned to Leaellynasaura with confidence. No skin or feather-like covering is directly preserved.

• Small maxilla with closely spaced, leaf-shaped cheek teeth
• Delicate skull roof and braincase from the holotype locality
• Large orbital region in the referred skull material
• Light, bipedal body plan inferred from related ornithischians
• Elongated tail traditionally reconstructed from disputed material

Volunteer Michelle Colwell found the key fossil in 1987 during a dig led by Thomas Rich and Patricia Vickers-Rich at Dinosaur Cove on the Cape Otway coast. Rich and Vickers-Rich named Leaellynasaura amicagraphica in 1989. The genus honours their daughter Leaellyn, while the species name recognized the Friends of the Museum of Victoria and National Geographic Society. Museums Victoria preserves the holotype maxilla NMV P185991 and associated skull material. A 2016 reappraisal clarified that the fossil bed contains disarticulated remains from multiple small ornithischians.

Discovery credit: Michelle Colwell.

Naming authors: Thomas H. Rich, Patricia Vickers-Rich.

Dinosaur Cove lay at a high southern palaeolatitude within the Antarctic Circle. The Eumeralla Formation preserves cool-temperate river floodplains with conifers, ferns and other vegetation. Seasonal light varied strongly, but the climate supported diverse dinosaurs, small mammals, turtles, lungfish and other vertebrates. Winter darkness does not imply a permanently frozen landscape.

The cheek teeth indicate herbivory, and a small bipedal body would have allowed agile movement through floodplain vegetation. Seasonal darkness inspired hypotheses about enhanced vision, migration and winter survival, but none is established by direct evidence. No nest, trackway or monospecific bonebed demonstrates herding or parental care. The long-tail balance and display ideas often attached to the animal depend on postcranial fossils whose identity is disputed.

• It lived at a latitude that was inside the Early Cretaceous Antarctic Circle.
• The genus honours Leaellyn Rich, daughter of the palaeontologists who named it.
• The holotype is a toothed upper-jaw bone, not the long-tailed skeleton shown in many reconstructions.
• Its original fossils are held by Museums Victoria in Melbourne.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   Polar dinosaurs and biotas of the Early Cretaceous of southeastern Australia

   Thomas H. Rich, Patricia Vickers-Rich · National Geographic Research 5(1), 15–53 · 1989

2. 02
   Sedimentological reappraisal of the Leaellynasaura amicagraphica holotype locality in the Lower Cretaceous of Victoria, Australia, with taphonomic implications for the taxon

   Matthew C. Herne, Alan M. Tait, Steven W. Salisbury · New Mexico Museum of Natural History and Science Bulletin 71, 121–147 · 2016

   Open source
3. 03
   Leaellynasaura amicagraphica specimen P185990

   Museums Victoria Collections

   Open source
4. 04
   Leaellynasaura amicagraphica

   Australian Museum

   Open source