Difference Between Tetrapods and Amphibians

The key difference between tetrapods and amphibians is that tetrapods are vertebrates with four limbs while amphibians are a group of chordates that live in both aquatic and terrestrial habitats.

Some amphibians are tetrapods; some reptiles also fall under the realm of tetrapods, but not all reptiles or amphibians could be categorized as tetrapods. A proper understanding of the difference between tetrapods and amphibians would pave the way to identify these two types well.

CONTENTS

1. Overview and Key Difference
2. What are Tetrapods 
3. What are Amphibians
4. Similarities Between Tetrapods and Amphibians
5. Side by Side Comparison – Tetrapods vs Amphibians in Tabular Form
6. Summary

What are Tetrapods?

Tetrapods are mainly vertebrates with four limbs. Many reptiles, many amphibians, all mammals, and all birds fall under this group. This means most vertebrates are tetrapods, but not all. Tetrapods started to evolve on the Earth before 400 million years from today.

As the theories of the evolution of tetrapods describe, the earliest tetrapods were Panderichthys (a genus having aquatic animals), Ichthyostega and Tiktaalik. From there on, the land living amphibians and the reptiles have been evolved up to mammals. However, tetrapods have two forelimbs known as hands and two hind limbs known as legs. Except in primates, all four limbs aid in walking. In addition, they developed lungs, padded or hoofed feet, ears and nostrils, fur or feathers and keratinized skins as adaptations for terrestrial life. However, some animals decided to go back to water (whale, dolphin, penguin). Among amphibians and reptiles without limbs, some still have rudimentary limbs; python is an example of this.

What are Amphibians?

Amphibians evolved from fish, before 400 million years from today. Presently, there are over 6,500 species living on the Earth, and they are distributed through all continents. Amphibians can inhabit both aquatic and terrestrial ecosystems, but most of them go to the water to mate and lay their eggs. Usually, amphibian hatchlings start their lives in water and migrate to land, if it is a terrestrial species. That means, they spend at least one stage of their life cycle in water. During their aquatic life as a larva or tadpole, amphibians take the appearance of small fishes. Tadpoles undergo the process of metamorphosis from larvae into adults.

Amphibians have lungs for air-breathing in addition to their skin, oral cavity, and/or gills. Amphibians are of three body forms as anurans, caudate and gymnophions. Anurans have a typical frog-like body. Frogs and toads are examples of anurans. Caudates have a tail. Salamanders and Newts are examples of caudates. Gymnophions have no limbs (Caecilians). Therefore, except for caecilians, all other amphibians are tetrapods. They do not have scales on their skins. But their skin is a moistened body cover that facilitates gas exchange.

Usually, amphibians are rarely found in the desert climate, but very common in damp and wet environments. In addition, they inhabit freshwaters than saltwater environments. Since they are extremely sensitive to environmental changes, amphibians are important as bioindicators. However, environmental pollution usually affects amphibians more than other life forms.

What are the Similarities Between Tetrapods and Amphibians?

• Tetrapods and amphibians include vertebrates.
• Tetrapods and some amphibians have four limbs. Hence, some amphibians are tetrapods.
• It is believed that tetrapods have evolved from amphibians.

What is the Difference Between Tetrapods and Amphibians?

Tetrapods are four-limbed vertebrates while amphibians are a group of animals that inhabit in both aquatic and terrestrial environments. Thus, this is the key difference between tetrapods and amphibians. Tetrapods include many more species than amphibians. Moreover, tetrapods are larger in body sizes than amphibians. So, these facts also highlight the difference between tetrapods and amphibians.

The below infographic summarizes more information on the difference between tetrapods and amphibians.

Summary – Tetrapods vs Amphibians

Tetrapods are vertebrates that have four limbs. Amphibians are a group of chordates that lives in both aquatic and terrestrial habitats. Some amphibians are tetrapods, but not all amphibians are tetrapods. This summarizes the difference between tetrapods and amphibians.

Reference:

1. “Tetrapod.” Wikipedia, Wikimedia Foundation, 17 June 2019, Available here.
2. Zug, George R. “Tetrapod.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 8 Jan. 2010, Available here.

Image Courtesy:

1. “Extant tetrapoda” By Petter Bøckman – Own work (Public Domain) via Commons Wikimedia
2. “Amphibians” – this is a collage from four different works already in Wikimedia Commons: File: Litoria phyllochroa.JPG, File:Seymouria1.jpg, File:Notophthalmus viridescensPCCA20040816-3983A.jpg, File: Dermophis mexicanus.jpg (CC BY-SA 3.0) via Commons Wikimedia