<P> The smallest sea urchin, Echinocyamus scaber, has a test only 6 mm across . </P> <P> Patiriella parvivipara is the smallest starfish, at only 5 mm across . </P> <P> The smallest vertebrates (and smallest amphibians) known are Paedophryne amauensis frogs from Papua New Guinea, which range in length from 7.0--8.0 millimetres (0.28--0.31 in), and average 7.7 millimetres (0.30 in). Previously, the title of smallest vertebrate was held by members of the fish genus Paedocypris of Indonesia . </P> <P> The world's smallest fish based on the minimum size at maturity is Paedocypris progenetica from Indonesia, with mature females measuring as little as 7.9 mm (0.31 in) in standard length . This fish, a member of the carp family, has a translucent body and a head unprotected by a skeleton . </P>

What is the smallest vertebrate in the world