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At first instance it looks like an iguana and since this photo was taken near the coast of Pernambuco, Brazil it could only be the green iguana, but as you can see from the photo the reptile is black. Perhaps green iguanas can be black under strict circumstances, but I could not find any instances concerning that from a reputable source, only from some dubious pet blogs and it was due to the lighting, temperature and overall cage conditions. It's worth noting that there were multiple animals and they were all black. In response to tyersome comment, the picture was taken in summer so I'm gonna assume it was hot at the time, regarding the size it seems to have almost 2 meters. This has to definitely be from the Iguanidae family and it appears to share similarities with the green iguana but the color is off.

enter image description here enter image description here

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    $\begingroup$ Welcome to Biology.SE. You've done a good job of providing information, but it would be helpful if you could add: 1) an estimate of the iguana's size; and 2) as much environmental, habitat and behavioral information you can. In particular, was it cool/cold when the picture was taken? $\endgroup$
    – tyersome
    Commented Apr 10, 2022 at 23:46
  • $\begingroup$ Okay thanks for the heads up. I've updated the post. Also added another photo that I've found. $\endgroup$ Commented Apr 11, 2022 at 1:56
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    $\begingroup$ Could be a hybrid or simply a melanistic green iguana. $\endgroup$
    – bob1
    Commented Apr 11, 2022 at 21:52
  • $\begingroup$ Never heard of this melanistic phenomenon before, very interesting. That might be it, many thanks. $\endgroup$ Commented Apr 12, 2022 at 1:32
  • $\begingroup$ You might find the following interesting as it discusses the phylogenetics / splitting of I. iguana and descriptions of melanistic iguanas in/around S. America: zookeys.pensoft.net/article/48679 $\endgroup$ Commented May 15 at 18:22

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This is a Green Iguana (Iguana iguana) of the genus Typical Iguanas (Iguana)

The green iguana (Iguana iguana), also known as the American iguana or the common green iguana, is a large, arboreal, mostly herbivorous species of lizard of the genus Iguana. Usually, this animal is simply called the iguana. The green iguana ranges over a large geographic area; it is native from southern Brazil and Paraguay as far north as Mexico.
Source: https://en.wikipedia.org/wiki/Green_iguana

How to identify

The iguana is of the genus Iguana due to its defining characteristics:

Iguanas are large lizards that can range from 1.2 to 2.0 m (4 to 6.5 ft) in length, including their tails. They possess a dewlap and a row of elongated scales running from the midline of their necks down to their tails.
Source: https://en.wikipedia.org/wiki/Iguana

After identifying the genus, the rest is straightforward. There are two iguanas that live in Brazil: The Brazilian Steppe Iguana (Urostrophus vautieri) and the Green Iguana (Iguana iguana). The species is easily determined as not being Urostrophus vautieri because the Steppe Iguana has a distinguishing stripped pattern along its back. Therefore this must be Iguana iguana.

The Reason for the Black Color

The black coloration on the Green Iguana is not at all unusual, in fact the US Fish and Wildlife service describes the lizard as:

large, typically green lizards, though they can sometimes be brown or almost black in color. Some adults can take on an orange or pink coloration during certain times of the year. Hatchling and young green iguanas usually have bright green coloration.

And this wikipedia article notes that green iguanas are often found in many different varying shades of colors:

Despite their name, green iguanas occur in different colours and types. In southern countries of their range, such as Peru, green iguanas appear bluish in colour, with bold blue markings. On islands such as Bonaire, Curaçao, Aruba, and Grenada, a green iguana's colour may vary from green to lavender, black, and even reddish brown. Green iguanas from the western region of Costa Rica are red, and animals of the northern ranges, such as Mexico, appear orange.Juvenile green iguanas from El Salvador are often bright blue, but lose this color as they get older.

So what is the reason for this color change? This scientific article on iguanas provides the answer. Stating that:

Body colour of the green iguana changes depending on its mood and is a good form of visual communication. Highly aroused green iguanas usually lighten their typical brownish green hue, within five minutes of arousal. Males who have been ousted from their territory during mating season also display a visual form of defeat in the form of a colour change from the reddish orange colour displayed during mating season to a dull brown.

The speed of the color change is quite remarkable, taking place within hours:

This colour change can take place in a matter of hours and the iguana remains this way until it regains control of its territory

The color of the iguana will also change during the mating season:

Mating season for the green iguana occurs just before the start of the rainy season in the tropics. Males usually experience intensification of colour at the start of the mating season with larger males changing colour to bright red or golden hues of orange along with this change in colour was an increase in the number of displays occurred with males becoming well spaced apart and conspicuous. This reduced the number of incidences of males meeting each other and reduced the occurrence of antagonistic encounters

The reason for the black color is more normal. The green iguana turns color with age, becoming black or brown as it becomes older:

The adults become more uniform in color with age, whereas the young may appear more blotchy or banded between green and brown. Color of an individual may also vary based upon its mood, temperature, health, or social status.
Source: https://animaldiversity.org/accounts/Iguana_iguana/

Examples of the green iguana (Iguana iguana): enter image description here enter image description here

First Image Reference: https://www.inaturalist.org/photos/21169473, Photo 21169473, (c) Andrés Mauricio Forero Cano, all rights reserved, uploaded by Andrés Mauricio Forero Cano

Second Image Reference: https://www.inaturalist.org/photos/187564945, Photo 187564945, (c) Luiz Carlos Ramassotti, all rights reserved, uploaded by Luiz Carlos Ramassotti

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