In order for a species to be considered as an animal, it has to have a backbone. Despite there being a lot of debate over this, scientists have discovered that the smallest animal to ever live is the tiny stout infantfish. The stout infantfish is no bigger than the width of a pencil and is found in the area of the Australian Great Barrier Reef and the Coral sea.
It has been found that the tiny stout infantfish has only six different species. The largest specie is the female and measures in at a weeny 8.4 millimetres. The male on the other hand is slightly bigger and measures just over a quarter of an inch, or even millimetres. If you put 500,000 of these tiny creatures together they would weigh no more than a pound in weight.
The first stout infantfish was discovered in 1979 and officially given the title of the world's smallest animal.