Anatomy is a fascinating subject because of the complex characteristics of each living creature, whether plant, human, or animal. The common iguanas (Iguana iguana) are no exception. Let’s look at the visible anatomy of a typical green iguana and what makes each body part important.

1,2,3 eyes?!

Iguanas, like most lizards, possess movable eyelids that can help clean, protect, and shield their eyes from the harsh sun and from foreign particles like dust or sand. Their eyes have incredible vision that can detect color and movement at long distances and they also have something known as a parietal eye, also referred to as their “third eye”.

Found in the middle of the head usually as a pale transparent-to-white scale, this organ helps iguanas and other reptiles stay alert at all times, especially for predators who strike from above, such as birds. Although it does not look like the typical eyeball, it can detect light and movement quickly to alert the brain when there is a need to run or hide to evade threat.

Tuberculate scales and armor

Tuberculate scales are tiny, pointy bits scattered around an iguana’s neck.

Scales, in general, are made up of hard keratin used to protect the reptile from injury and harmful elements, a built-in suit of armor that they get as soon as they’re born. It is also said to help them retain water.

Subtympanic shield?

The subtympanic shield is the large scale found on the jowl of a common iguana. It is one of the characteristics found only within their species and, although it serves almost no purpose other than it being a physical trait, it is theorized that it could be used to fool possible predators into thinking there’s a large eye staring back at them.

Cheeky jowls

Jowls are found at either side of an iguana’s head around the lower cheek area. These muscle-filled areas help people determine an iguana’s sex: Males’ jowls are typically larger and more prominent, whereas females’ are smaller or even flat.

Buff limbs and sharp claws

Green iguanas are arboreal reptiles that live on top of trees and have therefore developed strong upper and lower limbs that help them climb different surfaces in their environment. Pair that together with a good set of claws and they can latch onto almost any rough surface.

Although they have sharp claws, they do not use these as a primary means of defense. It is extremely unlikely to see an iguana raising his arms like a cat ready to scratch.

Salt out the nose

Iguanas use their noses to smell and detect things around them. However, iguanas also display a unique characteristic of dispelling snalts (as some people would like to call it) through sneezing.

The word snalt is not the official term, but it’s said to be a combination of both snot and excess salt from their system. Snalt is a normal and healthy byproduct of digestion, so white clumps around their nostrils and on anything else they sneeze on can sometimes be noticed.

Sneezing is normal once in a while and is due to whatever diet the iguanas have previously consumed. However, it shouldn’t be confused with signs of respiratory infection which may be caused by bacteria.

The bigger the dewlap, the better

The dewlap is the large, loose skin hanging around the jaw of a common iguana. Although not all species of iguana have dewlaps, this flap of skin serves multiple purposes, such as helping with thermoregulation, showing dominance among peer iguanas, attracting potential mates, or warding off predators by giving the appearance of a large physique or even flat.

Pointy teeth, curious tongue

Iguanas are mostly herbivorous and have a row of small pointy teeth similar to the sharp edges of a tape dispenser. However, don’t let those tiny chompers fool you! An iguana’s bite, especially one from an agitated adult, can leave a nasty wound that will need multiple stitches to fully patch up — they can even take a chunk of flesh right off you.

Similar to other reptiles, iguanas would regularly flick their tongue when in a new environment. Although some people would think that this is a threatening behavior, they are simply gathering more information about their surroundings by tasting all the new things presented to them.

Tail whip

Besides their sharp teeth, an iguana’s main defense is their powerful tail whip.

Their tails cover the majority of their length, often stretching to double the size of their main body. As babies and juveniles, it is common for them to be skittish and for them to constantly tail whip anything and everything that makes them feel unsafe. These attacks can be compared to light flicks on your skin; however, be wary of an adult’s tail whip for it will literally feel like an actual whip, leaving a nasty sting.

Similar to other reptiles, like geckos and bearded dragons, an iguana’s tail can easily fall off. This is called autotomy or self-amputation. This can be caused by whipping on a particularly hard surface, having it forcibly pulled, or being held or stepped on. The good news is that they can grow their tails back. However, it is extremely difficult and painful that some stop growing during the healing process since it requires a lot of energy, protein, and nutrients. Even if the tail does grow back, they’re never the same as before.

Nuchal, dorsal, and caudal spines

An iguana has lots of spikes around their body and they are divided into three sections: the nuchal spine found on the base of their neck as tiny little spikes, the dorsal spines that run across their back, and the caudal spines on its tail.

Spike characteristics also help in determining an iguana’s sex. Females typically have curved spines, while males have pointy and straight ones, especially around the mid-neck region.

Femoral pores

Femoral pores can be found near the underside of the base of their tail and particularly on their back legs. They contain several unique glands that emit pheromones and look distinctly different depending on the sex. Checking out an iguana’s femoral pores is one of the best ways to determine their sex at an early age, especially since they don’t have external genitalia.

Males would have a waxy object protruding from the pores which forms a comb-like shape, whereas female femoral pores are plain flat. These characteristics usually start appearing after around 12 months.


Some people think that reptiles rely solely on the vibrations around them to hear since they don’t have external ears. However, that isn’t the case with many lizards.

The tympanum is a thin, clear to yellowish membrane at the side of an iguana’s head that enables them to transmit sounds from the air into their internal ear.

Not created equal

Iguanas are great! But it’s important to remember that not all iguanas possess all the characteristics mentioned here. Each species has unique features that set them apart from one another, and each has its own use.

Remember: It’s important to continuously learn about them in order to not just care for them better, but also appreciate and respect them in general.

This appeared in Animal Scene magazine’s June 2019 issue.

Related stories:
– 10 myths about iguanas
– Iggies 101: What you need to know before welcoming an iguana into your home
– By any other name – Meet the green iguana and its albino mutation