Many vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s have evolved limbless forms. Reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s have on a number of occasions evolved into limbless forms - snake

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s, amphisbaenia

Amphisbaenia

The Amphisbaenia are a usually legless suborder of squamates closely related to lizards and snakes. As many species possess a pink body coloration and scales arranged in rings, they have a superficial resemblance to earthworms. They are very poorly understood, due to their burrowing lifestyle...

, and legless lizard

Legless lizard

Legless lizard may refer to any of several groups of lizards which have independently lost limbs or reduced them to the point of being of no use in locomotion. It is the common name for the family Pygopodidae, but often refers to other groups, such as limbless anguids, depending upon the region of...

s (limb loss in lizards has evolved independently several times, examples include Isopachys

Isopachys

-Classification:Genus Isopachys*Isopachys anguinoides*Isopachys borealis*Isopachys gyldenstolpei*Isopachys roulei...

, Pygopodidae

Pygopodidae

Pygopodidae is a family of squamates that have reduced or absent limbs and are related to the geckos. There are at least 35 species in two subfamilies and eight genera. They have unusually long, slender, bodies, giving them a strong resemblance to snakes...

, Anguis

Anguis

Anguis, or the slow worm, is a small genus of lizard in the family Anguidae. It has two described species.Although they are lizards, slow worms have lost their limbs completely and are often mistaken as snakes. Slow-worms typically grow to between , with the females slightly larger than the males...

, and Ophisaurus). The same is true of amphibian

Amphibian

Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s - caecilian

Caecilian

The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly...

s, Sirenidae (a clade of salamander

Salamander

Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...

s that are limbless except for atrophied front limbs), Amphiumidae (a clade of salamander with extremely atrophied limbs that appear non-functional) and at least two extinct groups (Aïstopoda

Aïstopoda

Aïstopoda is an order of highly specialised snake-like amphibians known from the Carboniferous and Early Permian of Europe and North America, ranging from tiny forms only , to nearly in length...

 and Lysorophia

Lysorophia

Lysorophia is an order of aquatic Carboniferous and Permian amphibians within the extinct subclass Lepospondyli. Lysorophians resembled small snakes, as their bodies are extremely elongate. There is a single family, the Lysorophidae...

). Legless forms of reptiles and amphibians probably evolved so as to be able to move underground or in water more easily.

There are also a number of fish with elongated bodies that have no or reduced appendage-like fins, for example eel

Eel

Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...

s and swamp eel

Swamp eel

The swamp eels are a family of freshwater eel-like fishes of the worldwide tropics.-Description:...

s. Hagfish

Hagfish

Hagfish, the clade Myxini , are eel-shaped slime-producing marine animals . They are the only living animals that have a skull but not a vertebral column. Along with lampreys, hagfish are jawless and are living fossils whose next nearest relatives include all vertebrates...

 and lamprey

Lamprey

Lampreys are a family of jawless fish, whose adults are characterized by a toothed, funnel-like sucking mouth. Translated from an admixture of Latin and Greek, lamprey means stone lickers...

also do not have appendage-like fins, they may not have lost them, but simply retained the form that vertebrates had before they evolved limbs.

There are no known limbless species of mammal or bird.