LIZARDS: CHARACTERISTICS, SENSES, ODDITIES

LIZARDS

anatomy of lizard

Lizards and snakes are regarded as members of the same order (Squamata, meaning “scaly skins”) within the reptile class of animals because of anatomical similarities. Some creatures such as the glass snake are actually legless lizards and some snakes have rudimentary legs with their bodies. What distinguishes a lizard from a snake is that snakes have a flexible skull to swallow prey larger than they are. Lizards don’t have this.

Lizards evolved about 200 million years ago during the Jurassic Period. Their scaly skins helped protect their bodies from desiccation. The adaption allowed the move away from water into a drier environment. The lizard and snake branches are thought to have diverged about a 100 million years ago when a group of reptiles that evolved into snakes began adopting a burrowing lifestyle.

There are about 4,500 species of lizard, compared to about 4,000 mammals. Most lizards are predators with smaller species feeding on spiders, worms, larvae pill-bugs and various ground-dwelling insects. Large ones eat small mammals, eggs. Some even eat other lizards and their own kinds.

Websites and Resources on Animals: Reptile Database reptile-database.org ; Reptileweb reptilesweb.com ; Reptile Phylogeny whozoo.org/herps/herpphylogeny ; Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org

Lizard Characteristics

Lizards have long tails and wide mouths. They differ from similar animals such salamanders in that they have scales, claws, movable eyelids and ear openings.

Most lizards run by alternately moving the front right and rear left legs together and then the front left and rear right legs. This motion gives lizards a distinctive “wriggling” motion. Lizards can’t breath and run at the same time. The lack a diaphragm muscle to push their lungs. Their rib muscles which expand the chest during each breath also brace the forelimbs during locomotion, especially running. This means that lizards can run for only a short time and need to pant afterwards to restore depleted oxygen.

Many species are able to discard their tails to distract predators. They do his by squeezing special muscles, causing the still-wriggling tail to pops off while muscles pinch close the blood vessels, minimizing blood loss. Lizards can regenerate a new tail but it takes a lot of energy to do this. Some lizards have blue tails designed to attract predators and break off, allowing the lizard to escape.

Scientist that catch lizards work in teams. One man approaches the lizards and drives it towards a catcher hidden behind the bushes. As the lizard approaches the catchers snags with fishing lines fashioned into a noose.

Lizard Senses

Lizards have movable eyelids (snakes don't have these) and most species have excellent eyesight. Some species of lizard even have a "third eye." on top of their head. This eye does not form an image but may help a lizard distinguish between light and dark. Lizards also have external eardrums and can hear very well.

Lizards and snakes are both very good at sensing and analyzing smells and message-carrying chemicals Many have a vomeronasal organ embedded in the roof of their mouth that detects heavy non-airborne molecules taken in through the mouth. It supplements olfaction which is the ability to smell airborne molecules that enter the nostrils and is distinct from taste, which analyzes chemicals that come into contact with taste buds on the tongue. These senses help reptiles locate prey and help warn them or potential prey that might be toxic. It also frees up the eyes to locate prey and find mates.

The vomeronasal organ is sometimes called the Jacobsen's organs. Lizards and snakes with forked tongues have these on either side of the roof of their mouth. Chemicals are picked up from the environment with their forked tongues then transfer to these organs.

Lizards with Forked Tongues

Some lizards have forked tongues, which helps them smell in "three dimensions," meaning that the two tips can pick up the same odor and then distinguish the chemical gradients in the air, which, in turn, helps the reptile determine the location of the smell's source, Andrew Durso, a herpetologist at Florida Gulf Coast University, wrote in The Conversation. [Source Laura Geggel, Live Science, July 11, 2024]

When the lizard gets hungry, it flicks its sensitive tongue in and out, picking up chemical information about its surroundings. Then, the lizard’s Jacobson's organ, a part of the olfactory (smelling) system in its nasal chamber, analyzes this information, letting the lizard know whether potential prey, such as small mammals, frogs, lizards, rodents and insects, are nearby.

Lizards and snakes with forked tongues constantly flick their tongues in and out of their mouths, bringing in new samples of chemicals on either side of the tongue through the chemical equivalent of stereoscopic vision. Not only can they determine the presence of chemicals and where they are coming from they can also detect edges and dimensions of the sources.

Lizards and snakes use their forked tongues and sense organs in their mouth to locate food, enemies and mates. And this they can do without even opening their mouths. Predators rely on smells and message-carrying chemicals to locate their prey and use their eyes to determine the location of the prey for the final lunge.

Lizard Mating

The males of some lizard species mate by clamping their jaws onto the rear leg of a female and then slide their bodies underneath to copulate. The eggs are fertilized in the bodies. The females of some species will mate several time over a period of several months. The eggs hatch in a month to a month and half, with the lizards emerging fully-formed and ready to fend for themselves.

Most lizards lay eggs with tough, leathery shells warmed by the sun. Some bring forth live young from eggs hatched in their bodies. The young are generally not taken care of by adults after they hatch and have to fend for themselves.

At least 27 species in seven different families exist mostly or entirely as females and produce eggs that develop without sperm and produce clones of the single parent. None of these females can reproduce by themselves. They need the stimulation of with the help of pseudo-male female

Legless Lizards and Skinks

Legless lizards refer members of several groups of lizards that have independently lost limbs or have limbs so small you can barely see and can not be used to move around. Ones belonging to the family Pygopodidae look just like snakes except they have eyelids and external ear openings which snakes don’t have and lack broad belly scales which snakes have. Legless lizards also often have a notched rather than forked tongue, two more-or-less-equal lungs (most snakes have one) and have a very long tail (by contrast snakes have a long body and short tail). [Source: Wikipedia]

Most legless lizards are either long-tailed surface dwellers that “swim” through grass or short-tailed burrowers. The surface dwellers have long tails that can be bitten off by predators without causing serious harm to the lizard. Burrowers that live underground don’t need this defense. Every stage of reduction of the shoulder girdle — including complete loss — occurs among limbless squamates, but the pelvic girdle is never completely lost regardless of the degree of limb reduction or loss. At least the ilium is retained in limbless lizards.

Many families of lizards have independently evolved limblessness or greatly reduced limbs including the following examples: 1) Anguinae, an entirely legless subfamily native to Europe, Asia, North America and North Africa, that contains well-known species such as slowworms, glass snakes and glass lizards; 2) Cordylidae, an African family of 66 species, with one virtually legless genus Chamaesaura, containing five species with hindlimbs reduced to small scaly protuberances; 3) Pygopodidae, with 44 species, almost all of which are endemic to Australia. Pygopodids are not strictly legless since, although they lack forelimbs, they possess hindlimbs that are greatly reduced to small digitless flaps, hence the often used common names of "flap-footed lizards" or "scaly-foot".The pygopodids are considered an advanced evolutionary clade of the Gekkota, which also contains six families of geckos.

Skinks are kinds of lizards with small legs and bodies that can squirm like a snake. They are quick and their tails break off and will grow back. They often have stripes. Some are bluish in color. Skinks and rattlesnakes give birth to live young. Sometimes when the skinks tail comes off it keeps moving. Skins perform this dramatic form of self-amputation by suddenly contracting it muscles, which it turn causes a fragile vertebrae to break. The new tail often looks different from the original. Instead of bonding to vertebrae it has a tube of cartilage.

moving detached skink tail

All-Female Lizard Species

According to Smithsonian.org: Somewhere along the meandering path of evolution, a branch of the reptilian tree decided it was fed up with males and their worthless sperm. So it got rid of them entirely. Today’s New Mexico whiptail lizards (Aspidoscelis neomexicanus) are one of several all-female species that reproduce without male input. Instead, these lizard ladies clone themselves in perpetuity, producing eggs with twice the typical number of chromosomes that can develop into embryos without being fertilized by sperm. (They do, however, still show some proclivities for mating behaviors, with females mounting females — an act that might boost fertility.) [Source: Katherine J. Wu, Rachael Lallensack, Smithsonianmag.com, February 14, 2020]

“New Mexico whiptails actually represent a remarable evolutionary feat: Their lineage came about via the union of two separate species, the little striped whiptail and the western whiptail. Hybrids like these are often unable to reproduce (think mules), but in blending the traits of their parents, New Mexico whiptails inherited a diverse genome, and are able to carbon copy it over and over. Should their environment change, though, they could someday be in trouble: Without another genetic pool to dip into, these lookalike ladies risk dying out in one fell swoop.

Entire 110-Million-Year-Old Lizard Found in a Chunk of Amber

A 110 million-year-old lizard was found in a piece a amber — which is essentially fossilized tree sap — in Myanmar. The creature was so well preserved you could make out the double eyelids of the left eye. SYFY reported: Rhetinosaurus hkamentiensis is a new extinct species of lizard that was unexpectedly found trapped in Burmese amber. No one expected an entire reptile to be preserved so well, from its scaly skin down to its skeleton. [Source: Elizabeth Rayne, SYFY, February 19, 2022]

“What are now the empty eyes of Rhetinosaurus may have once seen dinosaurs or giant ferns or dragonflies the size of your head. It was determined to be a juvenile that ran into a sticky situation when it ran into a glob of tree amber that it couldn’t escape. It was so well preserved that paleontologist Andrej Čerňanský of Comenius University and his team, who recently published a study in Nature, approached the prehistoric lizard almost as if it were alive.

““Its vertebrae are mostly cartilaginous, so we were able to study not only a skeleton, but even the external appearance (scalation) of the lizard,” Čerňanský told SYFY WIRE. "In fact, we can study the animal in the same way that herpetologists study modern species.” Its organs didn’t survive, but its trachea and bronchi are preserved. By taking a closer look at the skeleton and patterns of the scales, they were able to make out that it was not yet mature.

“This tiny lizard could have huge implications for how its successors ended up where they are now. Morphological comparisons were used to find its closest surviving relatives, as well as phylogenetic analysis, which finds out evolutionary connections through genetic sequencing. What the researchers found from physical studies of the specimen and its fragmented DNA were that it is a scincoid (meaning it resembles a skink) that echoes the features of some xantusiids, which are endemic to North America. So how did the fossil end up in Myanmar? It is possible that Rhetinosaurus spawned somewhere else when its territory moved elsewhere.

““This is complicated, because other hypotheses about the origin and paleoposition of the Burma Terrane microplate exist,” Čerňanský said. “It is still rather controversial and leaves room for further interpretations regarding the origin of the animal lineages occurring there during the Cretaceous.”

Falling Iguanas and Healing Gila Monsters

Jennifer S. Holland wrote in National Geographic: “Gila monsters, pebbly-skinned lizards found in the deserts of the U.S. Southwest, eat as few as three big meals a year (storing fat in their tails for the long wait), but their blood sugar remains stable. In 1992 an endocrinologist named John Eng at the Bronx/James J. Peters VA Medical Center in New York identified a component in Gila venom that controls blood sugar and even reduces appetite. Exenatide, a drug derived from the venom in their saliva, works like a natural hormone, stimulating cells to deal with sugar overload but remaining inactive when sugar levels are normal. It even helps diabetics produce their own insulin and lose weight. With almost 25 million people suffering from type 2 diabetes in the U.S. alone, the Gila monster is nothing short of a medical superhero. [Source: Jennifer S. Holland, National Geographic, February 2013]

In January 2024, Doyle Rice wrote in USA TODAY: Yes, falling iguanas are in the forecast once again in Florida. Here's why: Some of the brutal cold that's enveloped most of the nation recently will finally make its way to south Florida this weekend, where temperatures could dip into the low 40s — a chilly reading in that subtropical climate. The cold blast could immobilize iguanas and cause them to fall out of trees. The lizards start getting sluggish in temperatures below 50 degrees and are known to "freeze" when temperatures dip into the 30s and 40s, according to the Florida Fish and Wildlife Conservation Commission. [Source: Doyle Rice, USA TODAY, January 20, 2024]

WINKNews meteorologist Matt Devitt said on X, that "FALLING IGUANAS are possible this weekend in Southwest Florida as the coldest air of the season moves in Sunday morning." "We have a pretty sizable iguana population from Sanibel to Cape Coral to Naples," he said. "Locally, lows will dip into the 40s, wind chills in the 30s by sunrise."

National Weather Service stations in Florida have issued unofficial "falling iguana" advisories before to warn residents of the threat of severe cold and advise that the lizards they might find on the ground are usually temporarily immobilized, not dead. "Iguanas are cold blooded. They slow down or become immobile when temps drop into the 40s. They may fall from trees, but they are not dead," the weather service said.

During a similar cold snap and iguana warning five years ago, well-meaning residents finding stiffened iguanas were advised to leave them alone, as they may feel threatened and bite once they warm up. “Don’t assume that they’re dead,” Kristen Sommers, who at the time oversaw the nonnative fish and wildlife program for the Florida Fish and Wildlife Conservation Commission, said during the January 2018 cold spell.

Iguanas are an invasive species in Florida known for eating through landscaping and digging burrows that undermine infrastructure. There are businesses in south Florida that focus on iguana removal: Michael Ronquillo, owner of Humane Iguana Control in Miami, said it's important to get iguanas removed. "Falling iguanas can actually cause bodily harm to humans, pets, and damage personal property," he told USA TODAY. "We also highly advise not bringing iguanas inside to warm up if you find them non-responsive due to cold weather, as when they wake up, it can become a nightmare in your home."

Image Sources: Wikimedia Commons

Text Sources: Mostly National Geographic articles. Also David Attenborough books; Live Science, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

Last updated February 2025