Drop a dime in the middle of an eastern New Guinea rainforest, and you might squash a newly discovered frog species. Paedophryne amauensis has taken the top spot as the world's smallest vertebrate, with an average adult size of 7.7 millimeters in length, less than half the diameter of a U.S. dime. That beats out the former record holder, an Indonesian fish from the carp family whose females grow to about 7.9 millimeters. The new frog species lives in rainforest leaf litter, likely dining on springtails, mites, and ticks, the researchers report online today in PLoS ONE. They also discovered a second tiny frog species, Paedophryne swiftorum, in New Guinea, which grows to between 8.3 and 8.9 millimeters. Miniaturization is nothing new for frogs. The 29 smallest species all come in under 13 millimeters. The researchers propose that the repeated evolution of extreme small size in frogs, coupled with their exclusivity to moist habitats, has allowed them to exploit the nooks and crannies in the vegetation of the rainforest floor.
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