A small pod of 150 calls Melbourne home, with researchers initially thinking they were part of the bottlenose dolphin family.
It wasn't until researchers conducted nearly eight years of analysis on DNA and skeletons that they realised they'd stumbled upon a completely new species.
Burrunan, the name given to the dolphins, is an Aboriginal word meaning 'large sea fish of the porpoise kind'.
Unlike bottlenose dolphins, Burrunans are slightly smaller, have a stubbier snout, are lighter in colouring, and have a accentuated dorsal fin.
Kate Charlton-Robb, a marine biologist at Monash University, said the discovery was extremely exciting as they were unlike any other dolphin in the world.
'The results were pretty amazing because we found some big genetic differences,' Ms Charlton-Robb explained.
'These dolphins are completely different to any others in the world.
'They're actually a very old, new species, that's been living right under our noses all this time.'