#I’m not using Amphibia because it’s paraphyletic btw

[bestanimal]

Round 2 - Chordata - Lissamphibia

(Sources - 1, 2, 3, 4)

Lissamphibia is a subclass of tetrapods that includes all modern amphibians, including the orders Anura (“frogs”), Urodela (“salamanders”), and Gymnophiona (“caecilians). There are roughly 8,000 species of lissamphibians, of which nearly 90% are frogs.

Lissamphibians use their skin as a secondary respiratory interface. Some small terrestrial salamanders and frogs even lack lungs, relying entirely on their skin to breathe. To compensate for their thin and delicate skin, amphibians have evolved mucous glands, primarily on their heads, backs and tails, to keep their skin from drying out. Most species of amphibian have parotoid glands that secrete the neurotoxin bufotoxin as a defense mechanism. These are located behind the ears of toads, along the backs of frogs, behind the eyes of salamanders, and on the upper surface of caecilians. Some amphibian toxins can be lethal to humans while others have little effect. Some salamanders and caecilians have Ampullae of Lorenzini: pores able to detect electric fields.

Young lissamphibians generally undergo metamorphosis from an aquatic larval form with gills to an air-breathing adult form with lungs. Some amphibians pass through the larval stage while in the egg, hatching as a miniature version of the adult. Most amphibians will require fresh water to lay their eggs, though some lay their eggs on land and have developed various means of keeping them moist, after which the newly hatched larvae wriggle or are transported to water bodies. Frogs and salamanders that hatch from the egg as larvae are called tadpoles. They have thick bodies, muscular tails, cartilaginous skeletons, and external gills. Most tadpoles are filter feeders or grazers, feeding on algae, bacteria, and/or diatoms, though some are carnivorous, eating insects, smaller tadpoles, and fish. Metamorphosis involves an intensive change of the body, as the animal loses its gills and grows lungs, eyes, legs, jaws, and a tongue, and sometimes switches to a carnivorous diet, all in just about a day. In frogs, the tail can take more time to reabsorb. In caecilians, the metamorphosis is more gradual.

The earliest known lissamphibians are Triadobatrachus and Czatkobatrachus from the Early Triassic, though animals from the more diverse paraphyletic class Amphibia are known from the Carboniferous.

Propaganda under the cut:

Some amphibians can grow back limbs, and even organs, with stem cells that form at the site of injury. Scientists are studying this ability to hopefully one day apply it to human medicine.

While most amphibians are dependent on a watery environment for survival, some frogs are able to survive in deserts. They do this by burrowing underground and aestivating during the dry season, sometimes waiting for many months until it rains. Some will even secrete a layer of mucous around their burrow to keep themselves moist. In areas like this, frogs often depend on the burrowing, digging, and wallowing behaviors of other animals to create suitable temporary ponds for breeding use.

While not as long as that of chameleons, some frogs and salamanders use long, sticky tongues to draw prey into their mouth. As many species lack teeth, they must then swallow their prey whole. Some even use their eyeballs to push prey down their throat. Most frog tongues are only an inch long or less, about 1/3 the length of the frog’s body. However, salamanders of the family Plethontidae have tongues that reach up to 80% of their body length, are attached to their skeleton, and fire ballistically at prey in less than 20 milliseconds!

While most amphibians do not exhibit parental care for their young, some are very caring parents. Some poison frogs carry their young to place in individual water-filled bromeliads, periodically returning to each individual tadpole to deposit unfertilized eggs for them to eat. Male Darwin Frogs (Rhinoderma darwinii) carry their young in their vocal sac, keeping them safe from predators. Suriname Toads (Pipa pipa) incubate their eggs in pits on their back (if you have trypophobia you probably already know about this, but if not, don’t look it up). Slimy Salamanders (Plethodon glutinosis) do not lay their eggs in water, so they stay near them to keep them from drying out, as well as to defend them from predators. All caecilians care for their young. Some caecilians even “nurse” their young, growing a special layer of fatty, nutritious skin for them to feed on. As it does in nursing mammals, this also helps transfer microbes from the mother to her young, promoting a healthy microbiome.

The smallest amphibian, and vertebrate, in the world is the Brazilian Flea Toad (Brachycephalus pulex), at 8���8.4 mm long from snout to vent. Brachycephalus species (called “Saddleback Toads”) are so tiny that their vestibular systems are too small for dependable locomotion, and their balance is lost mid-air when jumping.

The largest living lissamphibian is the South China Giant Salamander (Andrias sligoi), with the largest known individual having been 1.8 m (5.9 ft) long. It is critically endangered due to habitat loss, pollution, and overcollection, and its use in traditional medicine and status as a delicacy has led to it being farmed for meat. It is hoped that this will take the heat off the wild salamanders, though wild salamanders are still often caught to bolster breeding populations in meat farms. It is unknown if any South China Giant Salamanders still exist in the wild, and those on farms are likely hybridized, as Andrias species are often caught indiscriminately and are able to interbreed. Of the known individuals that survive in zoos, all are males, and are nearing the end of their natural lifespans.

Amphibians are the canaries in the coal mine. With their complex reproductive needs and permeable skins, lissamphibians are often ecological indicators to habitat conditions. In recent decades there has been a dramatic decline in amphibian populations for many species around the globe, indicating an upcoming extinction crisis.