Mussau Island, a small, partly volcanic stretch in Papua New Guinea's St. Matthias chain, has been harboring for up to 2 million years a previously unknown species of blue-tailed monitor lizard.
The new species (Varanus semotus) can grow to well over 3 feet long and has a black body marked with yellow and orange. Its yellow tongue is a feature possessed by only three other monitor lizards in the Pacific. Adult tails take on a bluish or turquoise hue.
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The creature is isolated from any other monitor lizard species, separated by several hundred kilometers of water from others of its kind. But, things could be worse. Islands as isolated as Mussau don't tend to have colonizing, predatory mammals on scene.
That leaves smart, active lizards like V. semotus as the island's top predator and general scavenger. It will eat other reptiles and their eggs, crabs, and small birds.
The team that discovered the lizard, led by University of Turku, Finland graduate student Valter Weijola, called the animal a "biogeographical oddity." Genetic analysis showed the animal to have been isolated on the island for a whopping 1 to 2 million years.
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"Isolation is the keyword here," said Weijola. "It is what has driven speciation and made the South-Pacific region one of the World's biodiversity hotspots."
"For anything to arrive on Mussau (from New Guinea or New Britain) it would need to cross 250-350 kilometers of open sea, and this doesn't happen frequently," Weijola added. "So, once the ancestor arrived, perhaps in the form of a gravid female, the population must have been completely isolated."
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"These islands are full of unique creatures often restricted in distribution to just one island or island group," Weijola said. "Yet, we know relatively little about them. Even large species of reptiles and mammals are regularly being discovered, not to mention amphibians and invertebrates. This is what makes it such a biologically valuable and fascinating region."
Details about the new species have been published by Weijola, Stephen Donnellan, and Christer Lindqvist in the open-access journal ZooKeys.