a iguana vs an iguana

Some examples from the web:

• We got a nest against, by a iguana... Budzo named, was attacked.
• If I like a woman, I dream about her in a symbolic fashion, she's a penguin bearing the mythological baggage of penguins, or she's a iguana, that's a mature dream.
• Your breath smells worse than a dead iguana.
• You fed me to a giant iguana.
• We have a Green Iguana Park with more than 100 iguanas you will be able to watch, touch and enjoy.
• In 1985 the Cuban government issued a commemorative peso depicting a Cuban iguana on the head side of the coin in an attempt to raise awareness for this animal.
• An unusual incident occurred when a detainee in the prison assaulted a guard with a bloody tail torn from a Cuban iguana in May 2005.
• She also sautés up a mean iguana, if you're ever in the mood.
• A cafe downstairs and a cozy restaurant Iguana are at your disposal.
• They're a type of iguana, I should think.
• In close proximity is also a stylish restaurant iguanas, offering modern cuisine and exotic atmosphere.
• Animators studied comets and nebulae at the Mount Wilson Observatory, and observed a herd of iguanas and a baby alligator that were brought into the studio.
• I saw an iguana and a dwarf Indian.
• It is a subspecies of Cuban iguana.
• Zoologists Thomas Barbour and Gladwyn Kingsley Noble first described the Lesser Caymans iguana as a species in 1916.
• The rhinoceros iguana is a species of lizard belonging to the genus Cyclura.
• The rhinoceros iguana is a diurnal species living primarily in rocky outcroppings with little vegetation for cover.
• I cannot delay for the sake of an iguana or a giant peccary.
• Someone thought it was appropriate to bring an iguana into a hospital?
• If you want a pet, you can have something expensive, like an iguana with a silver necklace.

Some examples from the web:

• I saw an iguana and a dwarf Indian.
• I have an iguana that eats crickets.
• We came across a nest under attack, by an iguana named Budzo.
• When I asked to connect the Gibson SG to a Leslie cabinet he looked at me like he had seen an iguana on his bath mat!
• I cannot delay for the sake of an iguana or a giant peccary.
• Someone thought it was appropriate to bring an iguana into a hospital?
• If you want a pet, you can have something expensive, like an iguana with a silver necklace.
• Wilner argued, Anyone, including a federal official, who violates the Endangered Species Act by harming an iguana at Guantanamo, can be fined and prosecuted.
• If he's getting an iguana, I want a snake.
• How does holding an iguana make you a street performer?
• Are you aware that you have an iguana on your shoulder?
• Are you aware that you have an iguana on your shoulder?
• And what do you want, an iguana?
• When I decided to add an iguana to our long list of pets, who would have thought it would require such dedication and commitment?
• An iguana can lose his tail and grow it back.
• An Iguana walking into the ocean at the Galapagos Islands.
• It's an iguana.
• Maybe it was an iguana.
• They're chasing an iguana.
• Nobody but an iguana.