Photograph by Dr. Andolalao Rakotoarison
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Mini mum lives in the leaf litter along Madagascar’s eastern coast.

Photograph by Dr. Andolalao Rakotoarison

New staple-size frog is one of the tiniest ever discovered

“Astronomically small,” the newly discovered Malagasy amphibians have brains that could sit on a pin.

How many ways can you say “tiny?” How about miniature, miniscule, and minimum, for starters?

These adjectives not only describe three new species of frog from Madagascar, but also serve as their official scientific names.

Mini mum, Mini ature, and Mini scule “are astronomically small,” says Mark Scherz, an evolutionary biologist at Ludwig-Maximilians Universität in Munich, Germany, who described these and two other new tiny frog species in a new study published March 27 in the journal PLoS ONE. Mini is an all-new genus of frog. (Related: "Smallest Frogs Found—Each Tinier Than an M&M.")

“You could sit the brain on the top of a pin. It’s amazing that they have all the same organs you or I have in our bodies, but in a package that can fit four times on your own thumbnail.”

The smallest, Mini mum, is about the size of a standard paper staple, or about 8 to 10 millimeters long; the largest, Mini ature, measures 14.9 millimeters—about the length of a microSD card. The world's smallest known frog—and vertebrate—is a housefly-size frog that’s about 7.7 millimeters long.

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An adult male Mini mum, one of the world’s smallest frogs, rests on a fingernail with room to spare.

Each of the three amphibians exist only in one location in Madagascar. Mini mum in particular has an extremely limited range and known population, prompting the study authors to recommend a listing of critically endangered.

A family of microfrogs

The new frogs are part of an informal group called microfrogs, which belong to the family Cophylinae. Their discovery brings the total number of Malagasy microfrogs to 108; on average, 10 new species are identified and described per year in the country.

Scherz and colleagues have found more than 40 microfrogs since they began studying the species in 2014.

Of course, finding a new species is no small feat. (Read about a gecko found in Madagascar that sheds its skin on demand.)

Identifying superficial differences in similar-looking frogs is challenging in a normal-size animal; in microfrogs, it’s virtually impossible. But along with molecular and genetic work, microCT scanning enabled Scherz and team to examine minute differences in the teeth and bones of the various animals, helping make the case that they were indeed unique species.

It’s also not simple finding the animals, which live in the leaf litter of isolated forests in the island’s southeast, and within the dense bases of grass tussocks in the mountainous north. (See amazing photos of Madagascar.)

The frogs likely evolved their tiny stature to take advantage of ecological niches few other creatures can, for instance by hunting equally tiny prey such as ants, termites, and springtails.

What’s in a name?

Jim Hanken, an evolutionary biologist at Harvard who studies miniature South American amphibians, says the new analysis offers good bone, tooth, and molecular evidence to justify the creation of an entirely new genus.

These Tiny Frogs Are Some of the Most Toxic Animals in the World Scientists believe poison dart frogs assimilate plant poisons which are carried by their prey. Poison dart frogs raised in captivity and isolated from insects in their native habitat never develop poison.

He also appreciates the levity of the frogs’ names, but cautioned that comical names can become confusing—as often happens when animals are regrouped into new families, or it turns out that a chosen name was previously applied to another organism.

That’s what happened with a South American worm salamander originally named Oedipus complex (and its relative, rex), so when it was renamed Oedipina to avoid multiple usage, the original joke fell flat.

“There’s always the risk that when you do this witty stuff, someone will come along and change it,” Hanken says. (Read about seven tiny frog species found in Brazil.)

Scherz says he chose the names Mini mum, Mini ature, and Mini scule to pique the public’s interest.

“So much about science is dry,” he says. “If there’s anything we can do to make our science more approachable, we should do it.”