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guana is a genus of herbivorous lizards native to tropical areas of Mexico, Central America, several islands in Polynesia such as Fiji and Tonga, and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena. Two species are included in the genus Iguana: the green iguana, which is widespread throughout its range and a popular pet, and the Lesser Antillean iguana, which is native to the Lesser Antilles and endangered due to habitat destruction.

The word "iguana" is derived from a Spanish form of the original Taino name for the species, iwana.

In addition to the two species in the genus Iguana, several other related genera in the same family have common names of the species including the word "iguana".

Iguana can range from 4 to 6 feet (1.2 to 1.8 m) including their tail. The two species of lizard within the genus Iguana possess a dewlap, a row of spines running down their backs to their tails, and a third "eye" on their heads. This eye is known as the parietal eye, visible as a pale scale on the top of the head. Behind their necks are small scales which resemble spokes, known as tuberculate scales. These scales may be a variety of colors and are not always visible from close distances. They have a large round scale on their cheeks known as a subtympanic shield.

Iguanas have excellent vision and can see shapes, shadows, colors, and movement at long distances. Iguanas use their eyes to navigate through crowded forests, as well as for finding food. They use visual signals to communicate with other members of the same species.

The tympanum, the iguana's ear drum, is located above the subtympanic shield and behind the eye. Iguanas are often hard to spot, as they tend to blend into their surroundings. Their scale colors are a mode of hiding from larger predators.

Male iguanas, as well as other male members of the order Squamata, have three hemipenes.

NASA's OSIRIS-REx Spacecraft Arrives at Asteroid Bennu by NASA's Marshall Space Flight Center

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NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft completed its 1.2 billion-mile (2 billion-kilometer) journey to arrive at the asteroid Bennu Monday. The spacecraft executed a maneuver that transitioned it from flying toward Bennu to operating around the asteroid.

Now, at about 11.8 miles (19 kilometers) from Bennu’s Sun-facing surface, OSIRIS-REx will begin a preliminary survey of the asteroid. The spacecraft will commence flyovers of Bennu’s north pole, equatorial region, and south pole, getting as close as nearly 4 miles (7 kilometers) above Bennu during each flyover.

The primary science goals of this survey are to refine estimates of Bennu’s mass and spin rate, and to generate a more precise model of its shape. The data will help determine potential sites for later sample collection.

This image of Bennu was taken by the OSIRIS-REx spacecraft from a distance of around 50 miles (80 km).

Image credit: NASA/Goddard/University of Arizona

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