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Amphibian Classification

Amphibians are classified into three subclasses based on their appearance and reproduction.

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Amphibian Classification

Frog, toad, or salamander. What's the difference?

Look closely at the face of this salamander. It is strikingly similar to that of a frog or toad. As the first vertebrates to evolve from life in the sea to life on land, amphibians share a number of important evolutionary adaptations.

Classification of Amphibians

There are about 6,200 known species of living amphibians. They are placed in three different orders:

  1. Frogs and toads
  2. Salamanders and newts
  3. Caecilians

Frogs and Toads

One feature that distinguishes frogs and toads from other amphibians is lack of a tail in adulthood. Frogs and toads also have much longer back legs than other amphibians. Their back legs are modified for jumping. Frogs can jump up to 20 times their own body length. That’s the same as you jumping at least 100 feet, or more than the length of a basketball court. Think how fast you could move if you could travel that far on one jump!

Frogs and toads are closely related, but they differ in several ways. Generally, frogs spend more time in water, and toads spend more time on land. As you can see from Figure below, frogs also have smoother, moister skin than toads, as well as longer hind legs.

Frogs and toads

Frog and Toad. Frogs (a) and toads (b) are placed in the same amphibian order. What traits do they share?

Salamanders and Newts

Unlike frogs and toads, salamanders and newts keep their tails as adults (see Figure below). They also have a long body with short legs, and all their legs are about the same length. This is because they are adapted for walking and swimming rather than jumping. An unusual characteristic of salamanders is their ability to regenerate, or regrow, legs that have been lost to predators.

Salamander and newt

Salamander and Newt. Salamanders and newts can walk or swim. Salamander on a leaf (left), newt swimming in the water (right).

Caecilians

Caecilians are most closely related to salamanders. As you can see from Figure below, they have a long, worm-like body without legs. Caecilians evolved from a tetrapod ancestor, but they lost their legs during the course of their evolution.

Swimming caecilian

Swimming Caecilian. Caecilians are the only amphibians without legs.

Summary

  • There are about 6,200 known species of living amphibians. They are classified into three orders: frogs and toads, salamanders and newts, and caecilians.
  • Frogs and toads are adapted for jumping. Salamanders and newts may walk or swim. Caecilians live in the water or soil and are the only amphibians without legs.

Explore More

Use this resource to answer the question that follows.

  • http://www.hippocampus.org/Biology \begin{align*}\rightarrow\end{align*} Non-Majors Biology \begin{align*}\rightarrow\end{align*} Search: Amphibians
  1. Create a table/chart comparing frogs, toads, salamanders, and caecilians.

Review

  1. Distinguish frogs from toads.
  2. What is an unusual characteristic of salamanders.
  3. Compare and contrast the three orders of living amphibians.

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Vocabulary

caecilian

Order of amphibians that resemble earthworms or snakes; mostly live hidden in the ground.

frog

Order of amphibians characterized by a short body, webbed digits, protruding eyes, bifid tongue and the absence of a tail; known as exceptional jumpers; classified in the same order as toads.

newt

Subfamily of amphibians with lizard-like bodies; may be either fully aquatic, living permanently in the water, or semi-aquatic, living on land but returning to the water each year to breed.

salamander

Order of amphibians characterized by a lizard-like appearance, with slender bodies, short noses, and long tails.

toad

Order of amphibians characterized by dry, leathery skin, short legs, and snout-like parotid glands on the back, neck, and shoulder, which secrete a milky substance to deter predators; classified in the same order as frogs.

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