The "weird and wonderful Jurassic platypus dinosaur" you are referring to is likely the _Ornithorhynchus Anatinus_ or 'Platypus'. While the platypus is a fascinating and unique creature, it is not a dinosaur. It is a mammal, and one of only five species of monotremes, mammals that lay eggs. The platypus is native to eastern Australia and is one of the country's most iconic animals.