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Small lizard species

Jaragua lizard (adult female), from Beata Island, on U.S. dime.

Photo credit: Copyright S. Blair Hedges

The world's smallest lizard has been discovered on a tiny Caribbean island off the coast of the Dominican Republic. The newly discovered species not only ranks as the smallest lizard, but it also is the smallest of all 23, 000 species of reptiles, birds, and mammals, according to a paper to be published in the December issue of the Caribbean Journal of Science by Blair Hedges, an evolutionary biologist at Penn State, and Richard Thomas, a biologist at the University of Puerto Rico.

So small it can curl up on a dime or stretch out on a quarter, a typical adult of the species, whose scientific name is " Sphaerodactylus ariasae, " is only about 16 millimeters long, or about three quarters of an inch, from the tip of the snout to the base of the tail. It shares the title of "smallest" with another lizard species named Sphaerodactylus parthenopion, discovered in 1965 in the British Virgin Islands. Hedges and Thomas discovered small groups of the new species living in a sink hole and a cave in a partially destroyed forest on the remote island of Beata, which is part of the Jaragua National Park in the Dominican Republic.

"Our discovery illustrates that we still don't know everything about the Earth's species, even in areas that are very close to the United States, " Hedges says. "The island home of this tiny lizard is closer to Miami than Miami is to Puerto Rico, and we did not even know the species existed, although the area has been studied by biologists for several hundred years." Hedges says the habitat that this species needs to survive is disappearing rapidly. "People are cutting down trees even within the national parks and, if they take the forest away, these lizards and other species will disappear."

Economic and law-enforcement difficulties are contributing to deforestation of the Caribbean forests, which are even more fragile and more threatened than those in the Amazon of South America because they are so small. "In the Caribbean, forests that used to cover all of the land now typically cover less than 5 percent-and they are being cut down at an increasing rate, mainly for subsistence farming and fuel, " Hedges says. "Although there are laws against cutting down trees in the national parks, the enforcement of the laws is not enough to protect the forests, for a variety of reasons."

Jaragua lizard (adult female), from Beata Island, on Dominican Republic one peso coin (approximately size of U.S. quarter).

Hedges and Thomas went to the remote Isla Beata specifically with the goal of discovering previously unknown species that might be living there. "We tend to explore more rugged and hard-to-reach areas than other scientists, " Hedges says.

The "smallest" and "largest" species of animals tend to be found on islands, the researchers say, because species can evolve there over time to fill ecological niches in the habitat left vacant by other organisms that never reached the remote locations. If a species of spider is missing from an island, for example, the lizards there might evolve into a very small species to "fill" the missing spider's ecological niche.

"Habitat destruction is the major threat to biodiversity throughout the world, " says Hedges, who has studied Caribbean species for many years, and has long recognized it as a "hot spot" of threats to biodiversity. "The Caribbean is now widely recognized by conservationists and biologists as an ecological hot spot because it clearly is an area that has an unusually high percentage of endangered species that occur nowhere else in the world, " Hedges says. "Most land species on Earth have evolved to live in forested regions, and now humans are destroying the forests-which is a big problem, especially on islands, where species have restricted ranges."

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