When you hear the word animal, what comes to mind? Perhaps the word causes you to think of marine life, such as the whales, dolphins, and seals that call the oceans home. Maybe it brings to mind the jaguars, sloths, and toucans that reside in the Amazon rainforest. Or perhaps it makes you think of a furry companion who shares your home and is truly your best friend.
Nonetheless, one thing is for certain—the animal kingdom is full of variety. Aside from their classification as mammals, reptiles, birds, fish, or amphibians, each species also has unique physical characteristics, habitats, and reproductive methods that allow the animals to thrive based on their own individual needs. However, some animals seem to be anomalies and do not fit into any of the traditional classifications or categories.
While some animals, such as the apex predators, venomous snakes, and poisonous insects, seem to naturally stand out among the crowd, this list takes a glimpse into some of the lesser-known animals that are not only incredible but unlike any other animal, either within their own species or within the entire world.
These one-of-a-kind animals include an independent group of all female lizards who do not need a male “to get the job done,” a pea-sized insect that can not only survive the harsh Antarctic climate but is also the continent’s largest terrestrial animal, as well as a mollusk that is covered in medieval-like armor which is known as the “RoboCop of the ocean world.”
Here are ten animals that have proven to be in a class all their own.
Related: Top 10 Animals You Thought Were Extinct But Aren’t
10 Pangolin: The Only Mammal Covered in Scales
Pangolins, which are also referred to as scaly anteaters, are solitary, nocturnal mammals that make their homes on the continents of Africa and Asia. They are 1-3 feet (30-90 cm) long (excluding the tail) and weigh 10-60 pounds (5-27 kg). Pangolins have no teeth but instead use their sticky tongues, which can be up to 16 inches (40 cm) long, to reach ants, termites, and larvae that are buried underground.
However, what sets the pangolin apart from any other mammal is the fact that their bodies are covered with overlapping brownish scales. In fact, they are the only mammals wholly covered in scales.
The name pangolin actually comes from the Malay word “penggulung,” which means “one that rolls up.” The name is quite fitting given that when threatened, they emit an odorous secretion from their anal glands, curl up into a ball, and expose their tough scales as a means of self-defense. The pangolin will even perform a cutting motion with the scales, should anything be inserted between them.
Sadly, given that the pangolin’s scales are made of keratin (the same material that is found in fingernails, hair, and rhino horns), they are also the most trafficked mammal in the world. Their meat is considered a delicacy, and their scales are used in traditional medicine as well as folk remedies, with the belief that they can assist with ailments such as lactation difficulties, arthritis, asthma, and rheumatism. Their skins are also used to make fashion accessories and leather products such as boots, bags, and belts.
Thankfully, in 2016, 186 countries that are party to the Convention on International Trade in Endangered Species (CITES) announced an agreement to ban the commercial trade of pangolins in an attempt to protect the species from extinction. Additionally, in June 2020, China increased protection for the native Chinese pangolin species to the highest level, which also banned the use of pangolin scales in traditional medicine. Unfortunately, the illegal trade of this one-of-a-kind mammal continues.
Due to its threatened status, the third Saturday in February is observed as World Pangolin Day—a day dedicated to not only celebrating but raising awareness about this truly unique mammal.[1]
9 Antarctic Midge: The Only Insect Native to Antarctica
While midges are tiny insects that typically fly and bite their hosts in order to feed on blood, the Antarctic midge, or Belgica antarctica, does neither. Instead, these tiny insects, which measure only 0.07-0.2 inches (2-6 mm) in length, are wingless and choose to feed on terrestrial algae, mosses, bacteria, and even nitrogen-rich penguin droppings.
Despite the fact that they are smaller than a pea, this wingless adaptation prevents the Antarctic midge from being blown away and has essentially allowed it to survive in Antarctica’s extreme conditions. Therefore, the Antarctic midge is the only known insect species native to Antarctica, making it also the largest terrestrial animal on the icy continent, given that all of Antarctica’s other fauna are either smaller or live in the ocean.
So, how exactly do these insects survive on the world’s coldest continent? During the brief Antarctic summer, adult flies mate in large swarms. When the females begin to lay eggs, they secrete a clear jelly around the eggs, which acts like antifreeze and protects the larvae from extreme temperature swings and dryness. The newborn flies will then spend the next two years developing as larvae, entombed in a “deep freeze.”
During this time, in order to prevent internal tissue damage caused by ice crystals, the larvae will “overwinter” and lose up to 70% of their bodily fluids, essentially dehydrating themselves. Once their bodies are frozen, the larvae will spend approximately six months of the year in a suspended state called diapause, where they will not eat or move. Essentially, the midges will remain in a type of hibernation for two winters.
For a few short weeks during the summer, the Antarctic midge larvae will emerge in order to seek out meager amounts of nutrition from tiny terrestrial algae, mosses, and sparse grasses in an attempt to continue to develop during their life cycle. However, they are quickly encased in ice once again for the second winter.
Finally, after two years, the “brown, wormlike juveniles” have developed into black, ant-like adults. As fully formed adults, the midges will then spend the last seven to ten days of their life eating and mating but will die just days after mating, and the process will start all over.[2]
8 Kiwi: The Only Bird with Nostrils at the Tip of its Bill
Kiwis are small, pear-shaped, flightless birds that resemble a large, hairy pear and are found only in New Zealand. Given their inability to fly, kiwis are classified as ratites—birds whose sternum is smooth or raftlike because it lacks a keel where flight muscles attach—like their larger cousins: the cassowary, emu, ostrich, and rhea.
They have small heads and no tail, and their bodies are covered in long, loose, hair-like feathers that are reddish-brown and streaked with darker brown and black. The kiwi also has modified feathers around the base of its elongated beak that are cat-like.
Kiwis do have wings, which are approximately 1 inch (3 cm) long with a cat-like claw at the tip, but these wings are completely hidden under their feathers and utterly useless. Yet don’t let the kiwi’s awkward appearance, inability to fly, and small stature fool you, because these birds can outrun a human.
However, aside from their odd appearance, kiwis are the only birds in the world that have nostrils at the tip of their beaks, giving them a highly developed sense of smell. Given that the kiwi’s eyes are small and do not see well at night, this heightened sense of smell, along with sensor pads at the tip of the bill, allows the kiwis to seek out grubs, worms, bugs, berries, and seeds as they forage from dusk to dawn. Not to worry, though, if the kiwi sniffs any dirt into its nostrils in the process, it can simply sneeze it out![3]
7 Whiptail Lizard: The Only All-Female Lizard Species
Whiptail lizards are slender-bodied, diurnal lizards with long tails that range in size from 8 to 20 inches (20-50 cm) long. These lizards are also often called racerunners due to the fact that some species can run up to 17 mph (28 km/h) over short distances.
However, given that there are approximately 60 different species that make up this lizard family, which stretches across North America, Central America, and South America, their colors, patterns, and markings vary greatly. For example, the New Mexico whiptail has a brown to black body, which is marked with seven yellow or cream-colored stripes, numerous light spots, and a blue or gray-green tipped tail. In contrast, the Belding’s orange-throated whiptail can be spotted, brown, gray, or striped but has an orange chest and throat as well as a tail that changes from blue to gray as it ages.
However, it is not the lizards’ physical characteristics, their high-speed run, or their wide-ranging habitats that make this species so special. As many as one-third of all whiptail species of the Aspidoscelis genus, which are found in Mexico and the Southwestern United States, are the sole female-only species that are parthenogenetic, meaning their eggs develop into embryos without any fertilization.
So, how is this possible? While whiptail lizards don’t require a male partner, they do engage in “mating behaviors” with other females. This process, which is known as pseudocopulation, involves individual lizards switching between typical male and female sexual behaviors, which then results in enhanced ovulation. Whiptail lizards are then able to start the reproductive process with twice the number of chromosomes to create eight copies of each during meiosis (cell division). This results in a standard pair of chromosomes that is derived from two sets of pairs.
So, how did this all-female species come to be? Scientists believe that at some point in their history, lizards of the Aspidoscelis genus had a “hybridization event” in which females of one species broke form and mated with males of another species. This offspring of hybrids contained two different sets of chromosomes from two uniquely different species, providing the lizards with not only genetic variation but an evolutionary advantage.[4]
6 Henneguya Salminicola: The Only Animal That Doesn’t Need Oxygen to Survive
Henneguya salminicola is a lollipop-shaped white parasite that is 0.3 inches (8 mm) long and has less than 10 cells. The multicellular organism is part of a group of animals closely related to the jellyfish known as Myxozoa.
This parasite grows in annelid worms and the skeletal muscles of salmon off the Pacific coasts of Oregon, Canada, Alaska, and Japan, causing “milky flesh” or “tapioca” disease in the salmon > This results in unsightly cysts on the salmon’s flesh. While the parasite does not harm its host, and the cysts are harmless to humans, it does affect the fisheries as the unsightly appearance makes the fish harder to sell.
However, what makes this parasite truly remarkable is that it is the only known animal that does not need oxygen to breathe.
A research study was conducted by scientists at Tel Aviv University, and on February 25, 2020, the results were published in the scientific journal Proceedings of the National Academy of Sciences, which revealed that the mitochondrial genome was missing from the animal. Mitochondria are subcellular structures that are fundamental for collecting oxygen and converting it into energy. Therefore, the tiny parasite has “lost the ability to perform aerobic cellular respiration.”
How is this possible? Researchers found that because Henneguya salminicola lives inside both the annelid worms and skeletal muscles of salmon, it has adapted and evolved by eliminating many of the traits associated with multicellular species—tissue, nerve cells, and now, their ability to breathe—in order to survive without an adequate oxygen supply.
So, where does this tiny parasite get its energy? It is believed that the parasite may simply steal it from hosts, relieving it of the need to manufacture energy on its own.[5]
5 King Cobra: The Only Snakes That Build Nests for Their Eggs
While 21 species of cobra exist, the king cobra is the sole member of its genus—Ophiophagus—and its name stems from its ability to kill and eat other cobras.
King cobras mainly live in the rainforests and plains of India, Southern China, and Southeast Asia. Although their color varies from region to region, the main physical feature that distinguishes the king cobra from other cobras is the 11 large scales on the crown of its head.
On average, the king cobra measures 10-12 feet (3-3.6 meters) long but can reach up to 18 feet (5.4 meters) in length, making them the largest of all venomous snakes. They are also one of the most venomous snakes on the planet. In fact, the amount of neurotoxin they deliver in a single bite—up to two-tenths of a fluid ounce (5.9 mL)—is enough to kill 20 people or even an elephant.
Even though they are generally not aggressive to humans, king cobras do become hostile during the breeding season and when cornered or startled. When confronted, the king cobra will flare its hood, emit a hiss, and lift up to a third of its body off the ground, in some cases, making it taller than an average man.
However, this fierce and venomous snake is also the only snake in the world that builds a nest for its eggs.
In April, the female king cobra will choose a well-drained spot below a tree or clumps of bamboo and begin constructing her nest. She will spend the next several days sweeping leaves together with her body and gathering them into a pile. Once she has enough leaves, the female will compact the leaves into a “waterproof chamber” and then burrow into the heap to create a cup-like hollow. This process results in a completed nest that stands nearly 3.2 feet (1 meter) tall, where she will lay 15-50 eggs and ferociously guard them until the hatchlings emerge.[6]
4 Scaly-Foot Snail: The Only Animal with Iron in Its Exoskeleton
The scaly-foot snail (Chrysomallon squamiferum) is also known as the sea pangolin or the scaly-foot gastropod, given that the soft, fleshy underside of the snail’s foot looks like overlapping fish scales.
The scaly-foot snail lives in three different hydrothermal vents in the Indian Ocean at depths of 1.4-1.8 miles (2,400-2,900 meters). These fissures in the seafloor are often found near volcanically active places, which eject warm water that has been heated by molten rock deep below the ocean crust, making the snail’s habitat quite extreme.
The scaly-foot snail is subject to water temperatures up to 752°F(400°), high pressure, and high acidity levels, which not only bathe them in toxic chemicals but threaten to dissolve their protective shell. The snail’s shell is necessary as a means of protection from its two biggest predators: cone snails and crabs. While fist-sized crabs will squeeze the snail’s shell until it cracks, cone snails will attempt to kill the mollusk by using a hypodermic needle to spear the scaly-foot snail, injecting a deadly toxin.
Thankfully, it has an iron-plated shell “unlike any other known mollusk or any other known natural armor,” which protects it from predators as well as its harsh environment. In fact, it is the only animal in the world known to incorporate iron into its exoskeleton.
So, how exactly did this “RoboCop of the ocean world” acquire its protective armor? Essentially, the scaly-foot snail doesn’t require typical feeding because it has a food factory within its body. They have bacteria that grow inside of their throat, which convert the chemicals coming out of the vents into energy and food for the snail. Sulfur is then released as a waste product, as it is deadly to snails, and the internal structure of their scales acts as tiny exhaust pipes, filtering the sulfur away. The secreted sulfur then reacts with the iron ions from the hydrothermal vents in a process known as biomineralization, where organisms use minerals to produce hard tissues.
While scientists aren’t exactly sure how the snail “constructs” its armor, they have adapted to their harsh environment. They are able to take the iron-sulfide compounds from the water in order to incorporate an additional layer of iron onto its shell and the hundreds of external scales that cover its foot. Aside from the iron-sulfide compounds, the scaly-foot snail also uses chemicals such as pyrite (fool’s gold) and gregite, which makes them magnetic.[7]
3 Praying Mantis: The Only Invertebrate That Can See in 3D
Praying mantises are predatory insects that appear to be “praying” when their front legs are held at rest. However, these ferocious carnivores do more “preying” than “praying.”
These insects are typically found among vegetation and can camouflage themselves to resemble foliage, dried leaves, twigs, or even brightly colored flowers. This camouflage allows a praying mantis to stalk or ambush prey before launching a calculated attack that takes only milliseconds. They then use their raptorial legs (forelegs) to seize their prey in a viselike grip that is impossible to escape.
While they typically eat moths, crickets, grasshoppers, and flies, they also do not discriminate and will also eat beneficial insects such as bees, butterflies, and their own siblings, and in some cases, the females will eat their mate.
These insects are also the only invertebrates that can see in 3D, although it is different from the way humans and other animals see in three dimensions. Scientists at New Castle University conducted a study in which they used beeswax to attach a tiny pair of 3D glasses to the praying mantis’ eyes while they were suspended upside down in front of a computer screen that displayed 3D footage of prey. The mantises then tried to catch the digital prey.
The insects were also given vision tests and shown complex 2-dot patterns. However, the mantises mostly ignored these as well as the still images and, instead, focused on scanning for changes. The results revealed that not only do they have the ability to see in 3D, but that in certain circumstances, their visual technique for detecting the distance to a moving object is better than humans.[8]
2 Turritopsis Dohrnii: The Only Biologically Immortal Animal
Turritopsis dohrnii is a species of jellyfish that was first discovered in the Mediterranean Sea in the 1800s. However, this tiny jellyfish, which measures just 0.18 inches (4.5 mm) across, is not only an extraordinary survivor but also has a remarkable ability that sets it apart from any other animal on the planet. It is the one and only biologically immortal animal—otherwise known as the immortal jellyfish.
These small, transparent animals hang out in oceans around the world and, like all jellyfish, begin their life cycle as larvae called planulae. The planula will first swim and then settle on the seafloor before growing into a cylindrical colony of polyps. Multiple young will then bud off from the polyp, which will spawn into the medusae (adult) we know as jellyfish.
What sets these jellyfish apart is that anytime they are faced with environmental stress, aging, physical damage, or starvation, Turritopsis dohrnii can “take a leap back in their development process” by activating a series of genetic switches, which then initiates a reversal of its cells, causing the jellyfish to go back to the polyp stage, essentially rewinding time.
This phenomenon is due to a process known as transdifferentiation in which one mature adult cell that is specialized for a particular tissue is converted into an entirely different type of specialized cell.[9]
1 Yellow Spotted Salamander: The Only Known Solar-Powered Vertebrate
The spotted salamander is bluish-black in color and distinctively marked with two rows of bright yellow or orange spots. It measures approximately 7 inches (18 cm) long. They can be found throughout forests in the eastern United States and Canada, yet despite their bright markings, these salamanders are not easy to locate as they are only active at night.
The yellow-spotted salamander, however, is completely unique because its embryos use the sun for energy, making them the only known solar-powered vertebrate.
Near the beginning of each spring, adults go to pools of water where there are no fish in order to mate and breed and ensure their larvae won’t be eaten by any potential predators. Unfortunately, fishless ponds don’t contain very much oxygen. Thankfully, the yellow-spotted salamander eggs have formed a symbiotic relationship with the algae in the pools.
Females will lay two to four masses of up to 250 eggs, affixing them to submerged twigs and plants in gelatinous capsules approximately the size of a tennis ball. The eggs and embryos will then be colonized by tiny green algae, which invade the baby salamanders’ tissues and cells. Once there, the algae will stay near the mitochondria, which creates energy for the cells and provides a metabolic form of glucose.
During this process, the algae provides oxygen and carbohydrates to the salamanders’ cells, raising the oxygen content of the egg, removing waste, and allowing for normal embryonic development. In turn, the ammonia waste from the embryos provides a nitrogen-rich environment for the algae to feed on.[10]
