Lizard Facts: 8,003 Species, Venom and Sticky Feet

• The biggest lizard alive is over three metres long. The largest Komodo dragon ever verified measured 10.3 feet (3.13 m) and weighed 366 pounds (166 kg), according to Smithsonian's National Zoo.
• Komodo dragons are genuinely venomous. Researchers have documented a venom gland in the dragon's lower jaw. The venom is real anatomy, not a figure of speech for a dirty bite.
• A Komodo dragon produced 25 eggs with no male involved. A female named Flora at Chester Zoo laid a clutch of 25 eggs despite never having been kept with a male. Because Komodo dragons use ZW sex chromosomes, such fatherless hatchlings are always male.
• Chameleon colour is structural, not pigment. The lizard physically re-spaces a lattice of guanine nanocrystals inside skin cells called iridophores, and the new spacing reflects a different colour. Nothing is being repainted.
• The fastest tongue belongs to one of the smallest chameleons. The tongue of Rhampholeon spinosus, a chameleon that would fit on your thumb, hits a peak acceleration 264 times the acceleration due to gravity — in car terms, 0 to 60 mph in a hundredth of a second.
• Gila monsters have to hang on to envenomate. They have no hollow fangs. Venom travels along grooved teeth set in the lower jaw, which is why the lizard must keep its grip to deliver a dose.
• Gila venom is rattlesnake-grade in a test tube and rarely dangerous in the field. Drop for drop it is about as toxic as a western diamondback rattlesnake's, but lab toxicity is not field danger: only small amounts enter through a bite, because the Gila has to chew venom in through grooved teeth rather than inject it, and these lizards spend most of their lives hidden below ground, so encounters are rare. The genuinely uncomfortable detail is the opposite of the usual scare story — there is no antivenin for Gila bites, so hospitals treat symptoms rather than neutralising the venom.
• A Gila monster peptide became a diabetes drug. Exendin-4, found in Gila monster venom, became exenatide — the first of the GLP-1 receptor agonist class.
• Geckos climb by intermolecular attraction. Geckos climb using van der Waals forces between millions of hair-like setae and the surface. Autumn et al. (2002) tested capillary/hydrophilicity against van der Waals on hydrophobic and hydrophilic surfaces and rejected capillary adhesion; suction and glue had been ruled out by earlier work.
• The species count only means something with a date on it. There are 8,003 described lizard species out of 12,650 reptile species worldwide, as of the Reptile Database update of 16 June 2026, and the number climbs every year. Almost every lizard count you will read is out of date: the San Diego Zoo's own lizard page still says "over 4,675 lizard species," barely half the current figure. Because roughly 200 new reptiles are described annually, a species count is only meaningful with a date attached to it.
• Lizards taste the air. They live on every continent except Antarctica, and most of them smell with their tongues — flicking scent particles onto sensory cells in the roof of the mouth, the same way snakes do.
• The smallest one is 13.5 mm. The nano-chameleon Brookesia nana, described in 2021 from the Sorata massif in northern Madagascar, has a male holotype just 13.5 mm from snout to vent — apparently the smallest mature male amniote ever recorded.
• Marine iguanas shrink and regrow. After El Niño events, surviving Galápagos adults lost over 20% of their body length by resorbing tissue, including cartilage and bone, then regrew when food returned.
• The thorny devil's plumbing needs help from gravity. The thorny devil moves water to its mouth through capillary channels between overlapping scales. Filling that system takes water equal to 3.19% of body mass. Standing in water fills it and the lizard drinks; standing on wet sand fills it only to 59% and the lizard does not drink — to use damp sand it appears to shovel sand onto its own back so gravity helps.
• The lizard lineage is 240 million years old. Megachirella wachtleri, from the Dolomites of northern Italy, is the oldest known relative of all lizards and snakes — 75 million years older than the previous record holder.
• Some skinks have lime-green blood. Green-blooded skinks of the New Guinea genus Prasinohaema carry biliverdin at about 40 times the concentration that is lethal in humans, staining muscles, bones and tongues lime-green. Phylogenetic reconstruction suggests the trait arose independently about four times from red-blooded ancestors.
• The third eye is real anatomy. Many lizards have a parietal eye on top of the head, with a primitive retina and photoreceptor cells. It does not form images; it detects changes in light and dark and helps regulate the production of certain hormones.
• Blood-squirting is real but uncommon. Horned lizards (Phrynosoma) can squirt blood from the sinuses around their eyes as a defence, and the behaviour occurs across much of the genus. It is not a trick they perform on demand: in one field study of the Mexican plateau horned lizard, researchers handled 47 animals and only three squirted blood, all of them males. Most horned lizards you meet will simply flatten themselves and sit still.

"Komodo dragons kill by infecting prey with septic bacteria in their filthy saliva." When microbiologists actually cultured Komodo mouths, they found ordinary bacteria — nothing uniquely lethal. All the microbes they found were common in the skin and guts of the dragons' recent meals. The dragon kills with huge tearing wounds from serrated teeth plus venom that thins blood and drops blood pressure, and the Smithsonian's National Zoo confirms a documented venom gland in the lower jaw.

"Chameleons change colour to blend into whatever they are sitting on." Chameleons do not match arbitrary backgrounds like a cartoon. The fast, dramatic shifts are social signalling — male contests and courtship. The same nanocrystal system serves three ends at once: camouflage, display, and a deeper iridophore layer that screens about 45% of near-infrared radiation energy, a passive sunshade.

"A lizard that drops its tail grows an identical replacement." In the green anole, the regrown tail is supported by a single unsegmented cartilage tube around the regenerated spinal cord instead of a chain of vertebrae. The widely reported consequence — that the regenerate lacks the vertebral fracture planes needed to shed again — is not in that paper and needs its own citation.

"Gila monsters and beaded lizards are the only venomous lizards in the world." Gila monsters and beaded lizards are not the only lizards with venom-type toxins. Fry et al. (2006, Nature) recovered venom toxins from monitor lizards, including the Komodo dragon, and from an agamid, and argued on that basis for a single ancient origin of the venom system shared by snakes, anguimorphs and iguanians. Whether individual iguanas and chameleons secrete functional venom was not demonstrated — the grouping is phylogenetic inference.

"If it is long, legless and slithering, it is a snake." Several lizard families dropped their legs independently. The California legless lizard looks exactly like a small snake but has moveable eyelids, which no snake has, and it can shed its tail to escape a predator — something snakes cannot do. Watch for a blink.

Lizards have had a strange career on screen, usually playing something else. In Jurassic Park (1993), the Dilophosaurus was given the fictional abilities to spit venom and expand a neck frill — a frilled-lizard flourish invented for the film and attached to an animal that had neither.

Holes (2003), directed by Andrew Davis for Walt Disney Pictures, went the other way and cast real lizards as the deadly yellow-spotted variety. Production notes record that fourteen bearded dragons were used, four of which were used for the main parts, and the rest used as "background atmosphere lizards".

Comics supplied the best-known human-lizard hybrid: Marvel's Lizard, alias Dr. Curt Connors, debuted in The Amazing Spider-Man #6 (November 1963) from Stan Lee and Steve Ditko, and was played by Rhys Ifans in The Amazing Spider-Man (2012). Chameleons carry the animated end. Pascal, created by screenwriter Dan Fogelman, never speaks a line in Tangled (2010).

The lizards with names tend to be specimens rather than personalities, and the most famous of them is Flora, a female Komodo dragon at Chester Zoo. Flora laid a clutch of 25 eggs despite never having been kept with a male. Komodo dragons use ZW sex chromosomes, so hatchlings produced this way are always male — which makes Flora's clutch a working demonstration of parthenogenesis in a large vertebrate rather than a zoo curiosity.

The size records belong to individuals too. The largest Komodo dragon ever verified reached 10.3 feet (3.13 m) and 366 pounds (166 kg). At the opposite end sits the male holotype of Brookesia nana, collected on the Sorata massif in northern Madagascar and described in 2021 at 13.5 mm snout to vent — apparently the smallest mature male amniote ever recorded.

The oldest famous lizard is a fossil. Megachirella wachtleri, from the Dolomites of northern Italy, is the oldest known relative of all lizards and snakes at 240 million years, pushing the origin of the group back 75 million years past the previous record holder.