Australia: The Land Where Time Began

A biography of the Australian continent 

Leaellynasuara amicagraphica                                                                      

This was a Hypsilophodont dinosaur from the Early Cretaceous of Victoria, Australia. It was characterised by large eyes and an endocast of the brain case showed that its brain  had enlarged optic lobes. In modern animals these adaptations indicate a nocturnal habit, but as the part of Australia in which it was found was at that time inside the Antarctic Circle it probably indicates that it was active during the 3-month nights endured by the flora and fauna of the area at that time. 

A study of the bone growth showed they had continuous bone growth as in warm-blooded animals, as opposed to the cycles of growth found in cold-blooded animals. There was also a burst of rapid growth followed by a slowing of the growth rate, probably when the animal approached maturity. Together with the other unusual features such as large eyes, enlarged optic lobes and the area it lived in, close to the South Pole, this indicates that it was probably active during the 3-month Antarctic night. Such adaptations would have been necessary to have a lifestyle that must have been very unusual, and probably unique, for a dinosaur.

Another piece of circumstantial evidence for its Antarctic nightlife is the finding that the bones of some specimens showed signs of osteomyelitis (bone infections). It would be expected that a small animal such as leaellynasaurs would not have lasted long if they were slowed down by sore legs or feet, as there were predators in the area such as Allosaurus and some dromaeosaurids, which lacked the adaptations for the cold and dark, so wouldn't have been a threat during the night. 

They have been found in the Otway and Strzelecki Ranges, and coastal sites like Dinosaur Cove, all in Victoria.

Sources & Further reading

  1. Long, John A, 1998, Dinosaurs of Australia and New Zealand and other animals of the Mesozoic Era, University of New South Wales Press, 1998
Last Updated 01/09/2011 


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                                                                                           Author: M.H.Monroe  Email:     Sources & Further reading