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Tiny chameleon species is the world's smallest reptile

The male nano-chameleon measures less than an inch in length, making it the world's smallest non-avian reptile, according to researchers. Photo by Frank Glaw
The male nano-chameleon measures less than an inch in length, making it the world's smallest non-avian reptile, according to researchers. Photo by Frank Glaw

Feb. 1 (UPI) -- The body of the nano-chameleon, a new species discovered in Madagascar, measures just over a half-inch in length -- with its tail, the male chameleon measures just less than an inch -- according to researchers.

The diminutive dimensions make the nano-chameleon, Brookesia nana, the smallest known non-avian reptile, according to a new paper published recently in the journal Scientific Reports.

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Researchers from Germany and Madagascar found both a male and female specimen during an expedition through remote forest. The female was nearly twice the size of the male, but imaging analysis showed both specimens were mature adults.

"With the aid of micro-CT scans -- essentially three-dimensional X-rays -- we were able to identify two eggs in the female specimen, and so demonstrate that it is an adult," study co-author Mark D. Scherz, a researcher at the University of Potsdam in Germany, said in a news release.

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Imaging showed the male had well-developed genitals, suggesting the specimen also represented a fully mature nano-chameleon.

The genitals of male lizards are called hemipenes, and they're often used to distinguish reptile species from one another.

When researchers compared the hemipenes of the new species with those of 51 other chameleon species, they found the smallest species tend to have the largest genitals relative to body size. The nano-lizard boasted the fifth largest genitals of the 51 surveyed species.

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Scientists suspect the enlarged genitals of smaller lizards are likely inspired by the size discrepancy between males and females -- a phenomenon called sexual size dimorphism.

"As a result, the extremely miniaturized males of the small species need relatively larger genitals, in order to successfully mate with the larger females," said co-author Miguel Vences of the Technical University of Braunschweig.

"There are numerous extremely miniaturized vertebrates in Madagascar, including the smallest primates and some of the smallest frogs in the world, which have evolved independently," said Andolalao Rakotoarison of the University of Antananarivo in Madagascar.

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But while many of Madagascar's smallest species live on peripheral islands, the nano-chameleon hails from the center of island nation.

"The 'island effect,' that causes species on small islands to get smaller in body size, which has been invoked for other small chameleons, does not make sense in this case, because Brookesia nana lives in the mountains on mainland Madagascar," said co-author and Antananarivo researcher Fanomezana Ratsoavina.

The tiny new species' closest relative is another chameleon from the same interior mountains. The natural leaf chameleon, Brookesia karchei, is twice the size of the nano-chameleon.

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"That shows that this extreme miniaturization has arisen convergently in these chameleons," said co-author Jörn Köhler from the Hessische Landesmuseum in Darmstadt, Germany.

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Researchers suspect the nano-chameleon is confined to a relatively small geographic range and ecological niche within the Madagascar mountains.

Though the species faces pressure from deforestation, the area where the two specimens were found was recently designated a protected area.

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