NEW GUINEA FROG
7.7 mm on average
Described in 2012 as the smallest known vertebrate, Paedophryne amauensis averages 7.7 mm. It calls from leaf litter at dawn and dusk with high notes that sound like an insect.
Compare sizesTHE SMALLEST BACKBONES
Smaller than
your fingernail.
Some adult frogs are smaller than a fingernail.
UNDER 1 CM fully grown
3,000-fold Spread of living vertebrate sizes
- Frogs in leaf litter
- Fish in peat swamps
- Bones lost to shrink
- Where the tiniest vertebrates live
Vertebrates, animals with a backbone, range more than 3,000-fold in size. At the tiny end are a handful of frogs and fish under a centimetre long. Scientists keep finding new ones, and the title of smallest keeps changing hands.
THE SHORT ANSWER
Frogs and fish
share the record.
Few vertebrates get this small.
Those that do are mostly frogs and fish.
PEAT-SWAMP FISH
Mature at 7.9 mm
Paedocypris progenetica lives in highly acidic blackwater peat swamps in Southeast Asia. In 2006 its smallest mature female, at 7.9 mm, made it the smallest vertebrate then recorded.
See the numbers
FLEA TOADS
Under 7 mm
Brazil's Atlantic rainforest flea toads include an individual of Brachycephalus pulex measured at 6.45 mm, and a new species described in 2024 at 6.95 mm.
How they shrinkA QUICK SIZE CHECK
How big is
the animal?
Pick an animal to see its recorded size in the scientific descriptions. The bar shows body length, from the tiniest to the biggest.
Frog sizes are snout-to-vent length; fish size is the smallest mature female. Records change as new species and specimens are measured.
THE COST OF BEING TINY
Shrinking
changes the body.
Miniaturisation is not just scaling down. The studies describe what tiny vertebrates lose or change along the way.
Fewer bones
The smallest vertebrates show loss, reduction or fusion of bones, along with fewer digits.
A baby-like skeleton
Paedocypris keeps larval features as an adult, including a largely cartilaginous skull roof.
No tadpole stage
Flea toads hatch from their eggs as fully formed miniatures of the adult, with no tadpoles.
Hard to find, hard to name
Tiny size affects how easily they are found and identified, so researchers now use calls and DNA to tell species apart.
TWO NUMBERS WORTH KNOWING
A huge range,
a tiny limit.
One figure for how much vertebrates vary,
one for how small the record frog is.
3,000-fold
Spread of living vertebrate sizes
Living vertebrates range in size over 3,000-fold, from frogs and fish under a centimetre to a blue whale averaging 25.8 m.
SIZE RANGE · PLOS ONE 2012
7.7 mm
Average size of Paedophryne amauensis
The New Guinea frog was described as the smallest known vertebrate species. For scale, the authors pictured it on a US dime, which is 17.91 mm across.
RECORD FROG · PLOS ONE 2012
FAPESP notes that flea toads are less than 1 cm long as adults, far smaller than a fingernail or a 50p coin.
A HIDDEN WAY OF LIFE
Not oddities,
a guild.
The 2012 study argued that the many separate origins of minute frogs are not just evolutionary outliers. They form an ecological guild living in moist leaf litter on tropical wet-forest floors.
The 2024 flea-toad study adds that the diversity of these miniature frogs may be far greater than we think, which makes describing them quickly important for their conservation.
Questions
Questions people ask
What is the smallest vertebrate in the world?
It depends on how you measure. A New Guinea frog averaging 7.7 mm was described as the smallest in 2012. A Brazilian flea toad individual has been measured at 6.45 mm, and a peat-swamp fish matures at 7.9 mm.
How small is the smallest frog?
Flea toads in Brazil's Atlantic rainforest are less than 1 cm long as adults. One Brachycephalus pulex adult measured 6.45 mm, and Brachycephalus dacnis, described in 2024, 6.95 mm.
What is the smallest fish?
Paedocypris progenetica from Southeast Asian peat swamps, described in 2006, with the smallest mature female measuring 7.9 mm.
Where do the tiniest frogs live?
In moist leaf litter on tropical forest floors, such as New Guinea for Paedophryne and the Atlantic rainforest of Brazil for flea toads.
Why do tiny frogs have fewer bones?
Miniaturisation in vertebrates often involves the loss, reduction or fusion of bones and fewer digits, according to the 2024 PeerJ study and earlier work it cites.
Where the facts come from
Updated
- PLOS ONE (2012): Ecological guild evolution and the discovery of the world's smallest vertebrate
- PMC: Paedocypris, comprising the world's smallest vertebrate, Proceedings of the Royal Society B (2006)
- PMC: Among the world's smallest vertebrates, a new miniaturized flea-toad, PeerJ (2024)
- Agência FAPESP: Less than 7 mm in length, this Atlantic Rainforest flea toad is the second-smallest vertebrate (2024)