New Guinea frog is world’s tiniest vertebrate

By AAP with Natsumi Penberthy 12 January 2012
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Less than 8mm long, a minuscule brown frog is a new world record holder.

THE DISCOVERY OF the world smallest known vertebrate, a tiny tropical frog, has opened up a discussion on extreme size in animals.

With voices hardly louder than an insect’s buzz, the tiniest frogs ever recorded have been found on the island of Papua New Guinea. The two species are each smaller than a coin and hop around in the leaf litter on the rainforest floor.

The smaller of the two new frogs found, Paedophryne amauensis, comes in on average at 7.7mm, while its cousin Paedophryne swiftorum measures just over 8mm. Both are less than half the size of a 5c Australian coin (or a US dime, pictured). 

“It was particularly difficult to locate Paedophryne amauensis due to its diminutive size and the males’ high pitched insect-like mating call,” says Chris Austin an associate professor at Louisiana State University who made the discovery during a three-month research expedition to PNG. 

Record-breaking frog

“It’s a great find. The ecosystems [that both of] these extremely small frogs occupy are very similar, primarily inhabiting leaf litter on the floor of tropical rainforest environments,” Chris says. His findings are published this week in the journal PLoS ONE

Of 60,000 known vertebrates, the largest is the blue whale with an average length of over 25m, and the smallest was previously thought to be the transparent Indonesian fish, Paedocypris progenetica (8mm in length).

Because of this, some experts thought that extremes of size in vertebrates might be associated with the buoyancy of aquatic environments – however, both new species of frogs are terrestrial.

“The size limit of vertebrates, or creatures with backbones, is of considerable interest to biologists because little is understood about the functional constraints that come with extreme body size, whether large or small,” says Chris.

“We believe these [new frogs] aren’t just biological oddities, but instead represent a previously undocumented ecological guild – they occupy a habitat niche that no other vertebrate does.”

In fact, judging by the frequency of male mating calls they heard, Chris says the diminutive frogs might be spaced as close as 50cm from each other on ground beneath the leaves.