Content
- what are tetrapods
- Origin and evolution of tetrapods
- Characteristics of tetrapods
- Examples of tetrapods
- Amphibian tetrapods
- sauropsid tetrapods
- Synapsid tetrapods
When talking about tetrapods, it is important to know that they are one of the vertebrate groups evolutionarily most successful on Earth. They are present in all types of habitats as, thanks to the fact that their members have evolved in different ways, they have adapted to life in the aquatic, terrestrial and even air environments. Its most significant feature is found in the origin of its members, but do you know the definition of the word tetrapod? And do you know where this vertebrate group comes from?
We'll tell you about the origin and evolution of these animals, their most striking and important characteristics, and we'll show you examples of each of them. If you want to know all these aspects of tetrapods, keep reading this article that we present to you here on PeritoAnimal.
what are tetrapods
The most evident characteristic of this group of animals is the presence of four members (hence the name, tetra = four and podos = feet). It is a monophyletic group, that is, all its representatives share a common ancestor, as well as the presence of those members, who constitute a "evolutionary novelty" (ie, a synapomorphy) present in all members of this group.
Here are included the amphibians and amniotes (reptiles, birds and mammals) which, in turn, are characterized by having pendactyl limbs (with 5 fingers) formed by a series of articulated segments that allow the movement of the limb and the displacement of the body, and that evolved from the fleshy fins of the fish that preceded them (Sarcopterygium). Based on this basic pattern of limbs, several adaptations for flying, swimming, or running took place.
Origin and evolution of tetrapods
The conquest of Earth was a very long and important evolutionary process that involved morphological and physiological changes in almost all organic systems, which evolved in the context of Devonian ecosystems (about 408-360 million years ago), period in which the Tiktaalik, already considered a terrestrial vertebrate.
The transition from water to land is almost certainly an example of "adaptive radiation".In this process, animals that acquire certain characteristics (such as primitive limbs for walking or the ability to breathe air) colonize new habitats more conducive to their survival (with new food sources, less danger from predators, less competition with other species, etc. .). These modifications are related to the differences between the aquatic and terrestrial environment:
With the passage from water to land, tetrapods had to face problems such as sustaining their bodies on dry land, which are much denser than air, and also gravity in the terrestrial environment. For this reason, your skeletal system is structured in a different from fish, as in tetrapods it is possible to observe that the vertebrae are interconnected through vertebral extensions (zygapophysis) that allow the spine to flex and, at the same time, act as a suspension bridge to support the weight of the organs below it.
On the other hand, there is a tendency to differentiate the spine into four or five regions, from the skull to the tail region:
- cervical region: that increases the mobility of the head.
- Trunk or dorsal region: with ribs.
- sacral region: is related to the pelvis and transfers the strength of the legs to locomotion of the skeleton.
- Caudal or tail region: with simpler vertebrae than those of the trunk.
Characteristics of tetrapods
The main characteristics of tetrapods are as follows:
- ribs: They have ribs that help protect the organs and, in primitive tetrapods, they extend throughout the entire spine. Modern amphibians, for example, have virtually lost their ribs, and in mammals they are limited only to the front of the trunk.
- Lungs: in turn, the lungs (which existed before the appearance of tetrapods and which we associate with life on Earth) evolved into aquatic individuals, such as amphibians, in which the lungs are simply sacs. However, in reptiles, birds and mammals, they are divided in different ways.
- Cells with keratin: on the other hand, one of the most important characteristics of this group is the way they avoid the dehydration of their bodies, with scales, hair and feathers formed by dead and keratinized cells, that is, impregnated with a fibrous protein, keratin.
- reproduction: Another issue faced by tetrapods when they arrived on land was to make their reproduction independent of the aquatic environment, which was possible through the amniotic egg, in the case of reptiles, birds and mammals. This egg has different embryonic layers: amnion, chorion, allantoid and yolk sac.
- larvae: amphibians, in turn, exhibit a variety of reproductive modes with a larval state (for example, frog tadpoles) with external gills, and part of their reproductive cycle develops in water, unlike other amphibians, such as some salamanders .
- salivary glands and others: among other tetrapod characteristics, we can mention the development of salivary glands to lubricate food, the production of digestive enzymes, the presence of a large, muscular tongue that serves to capture food, as in the case of some reptiles, protection and lubrication of the eyes through the eyelids and lacrimal glands, and the capture of sound and its transmission to the inner ear.
Examples of tetrapods
As it is a megadiverse group, let us mention the most curious and striking examples of each lineage that we can find today:
Amphibian tetrapods
Include the frogs (frogs and toads), urodes (salamanders and newts) and gymnophions or caecilians. Some examples are:
- poisonous golden frog (Phyllobates terribilis): so peculiar due to its eye-catching coloring.
- fire salamander (salamander salamander): with its brilliant design.
- Cecilias (amphibians that have lost their legs, that is, they are apods): their appearance resembles that of worms, with large representatives, such as cecilia-thompson (Caecilia Thompson), which can reach up to 1.5 m in length.
To better understand these particular tetrapods, you might also be interested in this other article on amphibian breathing.
sauropsid tetrapods
They include modern reptiles, turtles and birds. Some examples are:
- brazilian choir (Micrurus brasiliensis): with its potent poison.
- Kill Kill (Chelus fimbriatus): curious for its spectacular mimicry.
- birds of paradise: as rare and fascinating as Wilson's bird of paradise, which has an incredible combination of colors.
Synapsid tetrapods
Current mammals such as:
- Platypus (Ornithorhynchus anatinus): an extremely curious semi-aquatic representative.
- flying fox bat (Acerodon jubatus): one of the most impressive flying mammals.
- star-nosed mole (Crystal condylure): with very unique underground habits.
If you want to read more articles similar to Tetrapods - Definition, evolution, characteristics and examples, we recommend that you enter our Curiosities section of the animal world.