Paedophryne amauensis is the smallest amphibian, growing only 7.7 millimeters (0.3 inch). This species boasts a wide head and short tail.

Amphibians’ permeable skin allows oxygen and water to pass through, so they can breathe both on land and underwater. Unfortunately, however, their bodies cannot regulate temperature on land; hence the need to return to water in order to breed successfully.

Caecilians

Caecilians resemble an amalgamation between a worm and snake in appearance and lack any limbs; their sizes range from three inches to five feet in length, depending on species, but all have no legs. Most are brown-black-gray-orange in hue; although more colorful species do exist. They inhabit tropical environments where they burrow underground to burrow sand, leaf litter or soil; in Amazonia exhibit one particular caecilian is known as rubber eel which thrives in rivers and streams of Colombia and Venezuela.

Scientists still know relatively little about caecilians. Some species consume their eggs while others lay them either underwater or on land, with those known to be viviparous scraping secretions from walls of their oviducts to feed the young as part of parental care known as histophagy.

Caecilians have left only fragmentary fossil records behind; we know their ancestors had short limbs and stronger eyes; their present characteristics result from many genetic mutations; scientists continue to gain more insights into their evolutionary history.

There are currently 189 species of caecilians known to science. Most live in fossorial soil surrounding streams, lakes, swamps or ponds; exceptions being the Gymnophiona blind cave caecilian found near tropical streams as well as Madagascar’s lungless Emerald caecilians (Gymnophiona).

Anura

Frogs and toads belong to the order Anura, with over 4,500 living species distributed across terrestrial habitats. Frogs can reach sizes larger than humans; Conraua goliath was recorded reaching 32 cm (12 inches). Their bodies feature long and thin shapes with short forelimbs for jumping as well as hind legs with long hind legs specialized for this action. Their wide eyes let in light while eggs are laid into water bodies internally to reproduce.

Anura stands out among amphibians by possessing several distinguishing features, such as lacking tails in adulthood and possessing aquatic larvae with gills; walking on land using hind limbs for support; and using vocalization known as pulmonic gurgle to communicate with other animals or predators.

Frogs and toads possess unique physical features that set them apart, including large eyes located atop their heads, squat posture, long hind legs designed for jumping, as well as possessing a special pectoral girdle in which two halves overlap ventrally or fuse midventrally – this condition was present in their common ancestor Anura among other amphibian classes, yet still persists today in several species that live varying lifestyles and diets.

Urodela

Urodela, comprising all living salamander species (Order: Salamandroidea) as well as some extinct ones, stands out among amphibian orders with its distinctive lizard-like appearance, featuring long, slender bodies with blunt snouts and short limbs that project at right angles to their bodies; additionally all salamanders possess visible tails which give rise to its Latin name “Urodela”, signifying that feature.

Eat small aquatic plants and animals while breathing through their gill pouches at first before evolving lungs that rise up from below the water’s surface to breathe air. Similar to other limniforms, their gills are lined with mucus for easier breathing while their excretory system removes waste products from their blood.

Frogs are generally herbivorous creatures; however, some are carnivorous. Most spawn in shallow ponds and rivers where their larvae reside as aquatic larvae; however, some species can adapt to dry climates without reproducing.

Frogs, despite their adaptions, are among the most threatened vertebrates, with many species facing extinction due to factors like loss of wetlands and small ponds, pollution, habitat fragmentation and pesticide usage – which all play a part in their decline.

Apoda

Caecilians are limbless amphibians characterized by vermiform (worm-shaped) or serpentine (snake-shaped) bodies that look similar to large earthworms. Living hidden away in soil or streambeds, they feed on subterranean creatures like earthworms for sustenance. As their lifestyle remains hidden from most people’s view, most are unfamiliar with these amphibians – yet many unique characteristics such as fused cranial and jaw bones, two-part jaw muscles, toxic glands on skin as well as using cloacal copulatory organs instead of gills as sources for oxygen and mineral intake from their surroundings – which allows them to remain ectothermic during dry summertimes while ectothermics use body heat as heat sources despite using no water source to find food.

Apoda (caecilians), or more accurately Apoda Podlin/, is one of three living amphibian groups alongside Anura (frogs) and Urodela (salamanders). There are over 200 caecilian species living across 10 families, and while they resemble snakes they are not true reptiles but instead closely related to stem-group amphibians that existed prior to modern amphibians’ evolution that also shared many traits similar to their contemporary relatives – modern amphibians share in common with snakes.

The three groups differ significantly, including body shape (tailless frogs, tailed salamanders and limbless caecilians); life cycle stages retained through adulthood; reproductive modes (oviparous frogs, paedomorphic uranium viviparous salamanders); overall geographic distribution (caecilians are mostly tropical; Anura mostly temperate; Salamandra worldwide). They also differ with regards to whether species have aquatic larvae, terrestrial forms or both forms as well as relative abundance among different phylogenetic groupings.