Greatest size difference between tadpole and adult frog of same species

Normally, the tadpole of a frog or toad species is much smaller than the adult frog of that same species. Ironically, however, the record for the greatest size difference between a tadpole and an adult frog of the same species is held by a genus in whose species, uniquely, the tadpole is a veritable giant and is actually much larger than the adult frog. The genus in question is Pseudis, related to the tree frogs, and its seven species, all of which are native to South America, are the appropriately named paradoxical frogs, of which Pseudis paradoxa is the best known. Native to the island of Trinidad and also to the Amazon on the nearby South American mainland, the tadpole reaches a maximum length of 16.8 cm, but as it metamorphoses into a frog it dramatically shrinks in size, becoming an adult frog measuring no more than 6.5 cm long, but often less. Indeed, tadpoles are frequently up to four times as long as adult frogs in this species This dramatic transformation from a giant tadpole into a small adult frog seems so unlikely on first sight that early scientists believed that the two forms belonged to separate species, refusing to believe for some time that such an extraordinary intraspecific transformation was actually possible.