20 Different Animals with No Legs in the World

Animals with no legs include snakes, glass lizards, caecilians, earthworms, leeches, roundworms, snails, slugs, clams, octopuses, jellyfish, sponges and many other groups. But “no legs” is not always the same as “no limbs”: whales and dolphins have forelimbs modified into flippers, while seals, sea lions and walruses have four flippered limbs.

That distinction matters because the same leg-free appearance can come from very different body plans. Some vertebrate lineages lost functional limbs. Many invertebrates never shared the four-limbed vertebrate body plan. Fish use fins, and marine mammals reshaped ancestral limbs for swimming.

What counts as an animal with no legs?

In everyday language, an animal has no legs if it cannot stand or walk on legs. Biology needs a little more precision. A limbless vertebrate, such as a snake or caecilian, has no functional external limbs. An invertebrate such as a jellyfish or sponge has a different body plan and may never have had anything comparable to vertebrate legs.

Other animals sit in a gray area. A snail has a muscular structure called a foot, but it is not a leg. A sea cucumber has hydraulic tube feet, not jointed walking legs. Whales have no external hind legs, yet their pectoral flippers are modified forelimbs. The table below keeps those distinctions visible instead of treating every fin, foot, arm and flipper as the same structure.

20 animals with no legs at a glance

Animal	Group	How it moves	What “no legs” means here
1. Snake	Reptile	Body waves, belly scales and muscular contractions	No functional legs; some lineages retain vestigial hind-limb structures
2. Glass lizard	Reptile	Serpentine body movement	A genuinely limbless lizard
3. Caecilian	Amphibian	Muscular undulation and burrowing	A genuinely limbless amphibian
4. Earthworm	Annelid	Peristaltic contractions and tiny bristles	No legs; the bristles are anchors, not limbs
5. Leech	Annelid	Sucker-assisted looping or body undulation	No legs
6. Tapeworm	Flatworm	Limited contractions inside a host	No legs or locomotor limbs
7. Roundworm	Nematode	Side-to-side undulation	No legs
8. Snail	Gastropod mollusk	Muscular foot and mucus	No legs, despite the anatomical term “foot”
9. Slug	Gastropod mollusk	Muscular foot and mucus	No legs, despite the anatomical term “foot”
10. Clam	Bivalve mollusk	A muscular foot in many species	No legs; the single “foot” is a burrowing organ
11. Octopus	Cephalopod mollusk	Eight arms and jet propulsion	No legs in standard anatomical terminology
12. Jellyfish	Cnidarian	Bell pulses and water currents	No legs
13. Sea anemone	Cnidarian	Usually attached; some creep on a pedal disc	No legs
14. Sponge	Poriferan	Adults generally remain attached	No legs or other locomotor limbs
15. Sea cucumber	Echinoderm	Tube feet and body-wall contractions	No jointed legs, but it does have tube feet
16. Hagfish	Jawless fish	Whole-body undulation	No legs and no paired fins
17. Lamprey	Jawless fish	Body and tail undulation	No legs and no paired fins
18. Eel	Ray-finned fish	Body waves and fins	No legs; it has fins
19. Whale	Mammal	Tail flukes and pectoral flippers	No external hind legs; forelimbs remain as flippers
20. Dolphin	Mammal	Tail flukes and pectoral flippers	No external hind legs; forelimbs remain as flippers

Twenty examples commonly described as animals without legs, with the anatomical qualification that applies to each one.

Truly limbless vertebrates

1. Snakes (Serpentes)

Snakes are limbless reptiles in the suborder Serpentes. They descend from four-limbed ancestors, and a few groups—including boas and pythons—retain vestigial pelvic or hind-limb structures. No living snake has functional walking legs.

Instead, snakes coordinate their ribs, muscles, scales and flexible spines. Depending on the surface and species, they use lateral undulation, concertina movement, rectilinear movement or sidewinding. The Smithsonian’s explanation of snake locomotion shows why “slithering” is not a single movement.

2. Glass lizards (Anguidae)

Glass lizards are lizards, not snakes. These limbless reptiles move with side-to-side waves, but many retain traits associated with other lizards. The National Park Service notes that glass lizards have movable eyelids and external ear openings—two useful differences from snakes.

The “glass” name refers to their ability to shed a fragile tail when threatened. That defense can make an individual appear to break apart, although the animal is not made of glass.

3. Caecilians (Gymnophiona)

Caecilians are limbless amphibians, not worms or snakes. Most species spend much of their lives burrowing in humid tropical soil, although some are aquatic. Their compact skulls help them push through substrate, while a pair of sensory tentacles helps compensate for reduced vision.

The Smithsonian’s caecilian profile describes the group’s long bodies, small eyes and chemosensory tentacles. Their underground habits also explain why caecilians remain less familiar—and less thoroughly studied—than frogs and salamanders.

Invertebrates without legs

Most described animal species are invertebrates, and many invertebrate lineages have no legs. Their movement depends on structures such as bristles, suckers, muscular feet, arms, bells, tube feet or fluid-filled body cavities rather than a vertebrate skeleton.

4. Earthworms (Annelida)

Earthworms are segmented annelids. Circular muscles lengthen sections of the body, longitudinal muscles shorten them, and repeated contractions create a peristaltic wave. Tiny bristles called setae grip the soil so the worm can push one region forward without the rest sliding backward.

Those setae are not legs. They act more like temporary anchors, giving the worm traction as its fluid-supported body changes shape.

5. Leeches (Hirudinea)

Leeches are also annelids, but they move differently from earthworms. Many crawl by alternately attaching their posterior and anterior suckers, stretching forward and pulling the rest of the body along. Aquatic species may also swim with eel-like body waves. The Australian Museum’s leech guide describes both forms of locomotion.

Not every leech drinks blood. The group also includes predators and scavengers that eat small invertebrates.

6. Tapeworms (Cestoda)

Tapeworms are parasitic flatworms with ribbon-like, segmented bodies. An attachment structure called a scolex anchors an adult to its host, while nutrients pass across the worm’s outer surface. Adult tapeworms do not need legs to search for food because they live inside a host that supplies both habitat and nutrients.

Once established in the intestine, an adult remains attached rather than roaming through the environment in search of food. The CDC’s tapeworm life-cycle overview illustrates how different this lifestyle is from that of a free-living worm.

7. Roundworms (Nematoda)

Roundworms, or nematodes, are unsegmented worms found in soil, water, plants and animals. They lack limbs and mainly have longitudinal muscles. Alternating muscle contractions bend the body from side to side, producing the undulating gait used for crawling, swimming or moving through a host.

The group includes microscopic free-living species as well as plant and animal parasites. A legless body plan is therefore not tied to one habitat or feeding strategy.

8. Snails (Gastropoda)

Snails belong to the mollusk class Gastropoda. They glide on a broad muscular foot while waves of contraction travel along its underside. Mucus can improve adhesion, protect the tissues and help the animal cross rough surfaces.

The term “foot” can be confusing, but a gastropod foot is one continuous muscular organ, not a leg. The British Geological Survey’s gastropod overview also notes that the shell may be reduced or lost entirely in some members of the class.

9. Slugs (Gastropoda)

Slugs are gastropods in which the shell is greatly reduced, internal or absent. Like snails, they move on a muscular foot and secrete mucus. Slugs live in marine, freshwater and terrestrial habitats; they are not restricted to tropical forests or gardens.

Because “slug” describes a body form that evolved in several gastropod lineages, it does not refer to one single taxonomic group.

10. Clams (Bivalvia)

Clams are bivalve mollusks protected by two hinged shell valves. Many species extend a wedge-shaped muscular foot into sand or mud, expand it, and pull the shell deeper into the sediment. Other bivalves use different strategies: mussels attach with byssal threads, oysters cement themselves in place, and scallops can swim by clapping their shells.

The clam’s foot is not a leg, and its shell does not open so it can “breathe air.” Aquatic bivalves exchange gases and collect food as water passes across their gills. See the British Geological Survey’s bivalve guide for the relationship between shell, muscles and burrowing.

11. Octopuses (Octopoda)

An octopus has eight arms, not eight tentacles. Each flexible arm contains muscles, nerves and suckers that help the animal crawl, grip surfaces, handle prey and explore its surroundings. The body is supported largely by muscular hydrostats rather than rigid bones.

Octopuses can also draw water into the mantle and force it through a funnel, producing jet propulsion. The Smithsonian’s cephalopod anatomy guide explains the distinction between octopus arms and the specialized feeding tentacles found in squid and cuttlefish.

12. Jellyfish (Cnidaria)

Jellyfish have no legs, bones or fins. A medusa swims by contracting its bell and pushing water behind it, then gains another small boost as the bell refills. Currents still influence where many jellyfish travel, but they are not simply passive drifters.

Their tentacles and oral arms help capture and move prey. Stinging cells called cnidocytes belong to the cnidarian body plan; they are not limbs. The Smithsonian’s jellyfish overview describes their pulsating bells, tentacles and distinctive cnidarian body plan.

13. Sea anemones (Actiniaria)

Sea anemones are cnidarian polyps related to corals and jellyfish. Most attach their base, or pedal disc, to rock, reef, shell or another surface. Their tentacles surround the mouth and contain stinging cells used for prey capture and defense; the tentacles are not what normally hold the animal in place.

“Sessile” does not always mean permanently immobile. Some anemones can creep slowly on the pedal disc, while a few species detach, drift or swim when disturbed. Most, however, spend long periods anchored in one location. The Smithsonian’s sea-anemone overview describes the typical sessile polyp body plan and its ring of prey-catching tentacles.

14. Sponges (Porifera)

Sponges are multicellular animals in the phylum Porifera. Most adults remain attached to a surface and draw water through pores in the body. The water current delivers oxygen and food particles and carries waste away.

They have no legs and do not need to chase food. Their stationary filter-feeding lifestyle is an entirely different solution from the muscular locomotion of a snake or worm. NOAA’s overview of sponge biology explains how pores, flagella and water flow support this body plan.

15. Sea cucumbers (Holothuroidea)

Sea cucumbers are elongated echinoderms related to sea stars and sea urchins. Many crawl over the seafloor using rows of tube feet powered by a water vascular system, often with help from body-wall contractions. Modified tube feet around the mouth act as feeding tentacles.

Tube feet are genuine appendages, but they are hydraulic structures rather than jointed legs. That makes sea cucumbers a useful reminder that the word “foot” does not always mean the same anatomical structure. The Smithsonian’s echinoderm guide explains how water pressure extends and coordinates tube feet.

Fish with no legs

Fish do not have legs in the ordinary sense, but most have fins. Paired fins and tetrapod limbs share an evolutionary history, which is why questions such as whether sharks are tetrapods require more than counting visible appendages. The three elongated fish below are especially likely to be mistaken for snakes or worms.

16. Hagfish (Myxini)

Hagfish are eel-shaped jawless marine animals with no paired fins. They propel themselves with waves that pass along the body and tail. Despite the resemblance, hagfish are not true eels and belong to a much older jawless lineage.

They are best known for producing defensive slime, but the feature that matters here is their elongated swimming form: no legs and no paired fins. Whole-body movement supplies propulsion without weight-bearing appendages.

17. Lampreys (Petromyzontiformes)

Lampreys are another jawless fish lineage. They have long, cylindrical bodies, dorsal and tail fins, but no paired fins or legs. Waves travel down the body to generate thrust.

Some adult lampreys attach to fish with a circular oral disc, while other species do not feed as adults. Lampreys are not eels, despite the common phrase “lamprey eel.” The National Park Service’s jawless-fish overview compares lampreys with hagfish.

18. Eels (Anguilliformes)

True eels are ray-finned fish in the order Anguilliformes. Their elongated bodies bend into traveling waves, while long dorsal and anal fins contribute to propulsion and control. They have no legs, but they are not limbless tetrapods.

Eels occupy freshwater, coastal and deep-sea habitats, and their life histories vary widely. See our guide to the different types of eels for examples beyond the familiar freshwater and moray forms.

Marine mammals often described as legless

Whales and dolphins have no external hind legs and cannot walk on land. Still, calling them completely limbless erases an important anatomical fact: their pectoral flippers are modified forelimbs, with bones corresponding to the upper arm, forearm, wrist and digits.

19. Whales (Cetacea)

Whales swim primarily by moving their tail flukes up and down. Pectoral flippers help with steering, stability and maneuvering. Modern whales lack external hind legs but retain small pelvic remnants inherited from land-dwelling ancestors.

That history makes whales legless in an everyday, locomotor sense—not fully limbless in strict comparative anatomy. The Natural History Museum’s cetacean anatomy overview explains how forelimbs became pectoral flippers while hind limbs disappeared externally.

20. Dolphins (Cetacea)

Dolphins are toothed whales and share the same basic limb pattern. Tail flukes provide most of the thrust, while pectoral flippers steer and stabilize the body. They have no external hind legs, but their flippers remain modified forelimbs.

This distinction applies to river dolphins, oceanic dolphins, porpoises and other cetaceans. Our overview of different dolphin types explains how body form and habitat vary within the group.

Why walruses, seals and sea lions are not truly legless

Walruses, seals and sea lions are pinnipeds. Unlike whales, they retain all four limbs as flippers. Walruses can rotate their rear flippers beneath the body and walk on all fours, and their tusks can help them haul onto ice. The Smithsonian’s pinniped overview makes clear why they should not appear on a strict list of limbless animals.

Sea lions use large foreflippers for propulsion in water and rotate their hind flippers under the body to walk on land. True seals have a different gait and often undulate across land on the belly, but they still possess four flippers. NOAA’s seal and sea lion comparison makes the limb differences clear.

How do animals without legs move?

There is no single form of “legless movement.” The method depends on the animal’s body structure and the resistance offered by soil, rock, water or a host.

Movement method	Examples	How it works
Lateral undulation	Snakes, caecilians, eels, lampreys and hagfish	Traveling body waves push against the ground, tunnel walls or water.
Peristalsis and anchoring	Earthworms	Muscle layers alternately lengthen and shorten segments while setae grip the substrate.
Sucker-assisted looping	Leeches	The front and rear suckers take turns anchoring as the body stretches and contracts.
Muscular-foot movement	Snails, slugs and many clams	Muscular waves move across a broad foot; mucus or sediment anchoring provides traction.
Arm crawling or jet propulsion	Octopuses	Arms pull across a surface, or water expelled through the funnel produces thrust.
Bell pulsing	Jellyfish	Bell contractions push water backward and move the animal forward.
Hydraulic tube feet	Sea cucumbers	A water vascular system extends and coordinates many small tube feet.
Fins, flippers and flukes	Eels, whales, dolphins and pinnipeds	Specialized appendages and tails generate thrust, steering and stability in water.
Mostly sessile or host-assisted life	Sponges, sea anemones and tapeworms	The adult remains attached or lives within a host, so long-distance locomotion is limited.

Why does leglessness evolve?

Losing legs—or never developing them in the first place—can work well in several ecological settings. A narrow body can pass through soil, leaf litter, reef crevices or a host without projecting limbs catching on the surroundings. In water, whole-body waves can generate thrust, while fully aquatic mammals can transform weight-bearing limbs into flippers.

Other animals do not need active travel at all. Sponges filter food from moving water, anemones wait for prey to reach their tentacles, and tapeworms live inside a food-rich host. Each body plan reflects a different answer to the same basic challenge: surviving and reproducing in a particular environment.

Leglessness is therefore not a sign that an animal is “primitive” or incomplete. It is one of many ways animals adapt to their environment. These species serve as predators, prey, filter feeders, parasites, scavengers and soil engineers across ecosystems on land and in water.

Frequently asked questions

Related wildlife guides

• What is an invertebrate?
• Endangered amphibians and the threats they face
• Different types of eels
• Different types of dolphins
• How animals adapt to their environment