When we talk about bipedalism or bipedalism, we immediately think of the human being, and many times we forget that there are other animals that are transported by this form. On the one hand, there are the apes, the animals evolutionarily closest to our species, but the reality is that there are other bipedal animals that are not related to each other or to humans, do you want to know what they are?
In this article on our site we tell you what bipedal animals are, what their origins were like, what characteristics they share, some examples and other curiosities.
What are bipedal animals? - Characteristic
Animals can be classified in many ways, one of them is based on their mode of locomotion. In the case of land animals, they can move from one place to another by flying, crawling or using their legs. Bipedal animals are those that use only two of their legs to move Throughout evolutionary history, numerous species, including mammals, birds, and reptiles, have evolved until adopting that form of locomotion, among them are dinosaurs and human beings.
Bipedalism can be used when walking, running or jumping. The different species of bipedal animals may have this form of locomotion as the only possibility or they may use it in specific cases.
Difference between bipedal and quadrupedal animals
Quadrupeds are those animals that move using four limbslocomotives, while bipeds move using only their two hind limbs. In the case of terrestrial vertebrates, they are all tetrapods, that is, their common ancestor had four locomotive limbs. However, in some groups of tetrapods, such as birds, two of their limbs have undergone evolutionary modifications resulting in bipedal locomotion.
The main differences between bipeds and quadrupeds are based on the extensor and flexor muscles of their limbs. In quadrupeds, the mass of the flexor muscles of the legs is almost twice that of the extensors. In bipeds, this situation is reversed, facilitating the upright posture.
Bipedal locomotion has several advantages over quadrupedal locomotion. On the one hand, it increases the visual field, which allows bipedal animals to detect dangers or possible prey in advance. On the other hand, it gives rise to the release of the front limbs, leaving them available to perform different maneuvers. Lastly, this type of locomotion involves an upright position, which allows for greater expansion of the lungs and rib cage when running or jumping, generating greater oxygen consumption.
Origins and evolution of bipedalism
Locomotive extremities have evolved in a convergent way in two large groups of animals: arthropods and tetrapods. Among tetrapods, the quadrupedal condition is the most common. However, bipedal locomotion, for its part, has also arisen more than once in animal evolution, in different groups, and not necessarily in a related way. This type of locomotion is present in primates, dinosaurs, birds, jumping marsupials, jumping mammals, insects, and lizards.
There are three main causes considered to be responsible for the appearance of bipedalism and, consequently, of bipedal animals:
- The need for speed.
- The advantage of having two of the extremities free.
- Adaptation to flight.
Increasing speed tends to increase the size of the hind limbs compared to the front limbs, causing the steps produced by the hind limbs to be longer than those of the front limbs. In this sense, at high speeds, the front ends can even become an obstacle to speed.
Bipedal dinosaurs
In the case of dinosaurs, it is believed that the common character is bipedalism and that quadrupedal locomotion reappeared later in some of the species. All tetrapods, a group to which predatory dinosaurs and also birds belong, were bipedal. In this way, we can say that the dinosaurs were the first bipedal animals.
Evolution of bipedalism
Bipedalism has also arisen optionally in some lizards. In these species, the movement that produces the elevation of the head and trunk is a consequence of forward acceleration combined with a retreat of the center of body mass, due, for example, to an elongation of the tail.
On the other hand, it is believed that among primates bipedalism arose 11.6 million years ago as an adaptation to life in the trees According to this theory, this characteristic would arise in the Danuviusguggenmosi species, which, unlike orangutans and gibbons that use great help from their arms for locomotion, had hind limbs that were kept straight and were their main locomotive structure.
Finally, jumping is a fast and energy-efficient mode of locomotion and has arisen more than once among mammals, linked to bipedalism. Jumping on large hindlimbs provides an energy advantage through elastic storage of energy.
Because of all of the above, bipedalism or standing arose as a form of evolution in certain species in order to guarantee their survival.
Examples of bipedal animals and their characteristics
After reviewing the definition of bipedal animals, seeing the differences with quadrupedal animals and how this form of locomotion arose, the time has come to learn about some of the examples of bipeds most outstanding:
Human Being (Homo sapiens)
In the case of humans it is believed that bipedalism was selected primarily as an adaptation to leave the hands completely free to get food. Having hands free the tool creation behavior took place.
The human body, totally vertical and with completely bipedal locomotion, has undergone abrupt evolutionary renovations until reaching its current condition. The feet went from being parts of the body with possibilities of manipulation to being completely stable structures. This happened from the fusion of some bones, changes in the size ratios of others, and the appearance of muscles and tendons. In addition, the pelvis widened and the knees and ankles aligned below the body's center of gravity. On the other hand, the knee joints now have the ability to twist and lock completely allowing the legs to stand erect for long periods of time without causing too much stress on the postural muscles. Finally, the chest shortened from front to back and widened to the sides.
Cape Jumping Hare (Pedetes capensis)
This furry rodent 40 cm long has a long tail and ears, features that remind us of hares, although in reality they do not is related to them. Its front legs are very short but the hind legs are long and robust and it moves through jumps. In a pinch, he can jump two to three meters in a single jump.
Red Kangaroo (Macropus rufus)
It is the largest existing marsupial and another example of bipedal animals. These animals are not capable of walking and can only do so by jumping. They perform the jumps using their two hind legs at the same time. They can reach a speed of up to 50 km/h.
Discover the different types of marsupials in this other article.
Eudibamus cursoris
It is the first reptile known to have bipedal locomotion. It is currently extinct. It lived in the late Paleozoic. It was about 25 cm long and walked on the toes of its hind limbs.
Jesus Christ Lizard (Basiliscus basiliscus)
Some lizards, such as the Jesus Christ lizard or common basilisk, have developed the ability to use bipedalism in times of need (facultative bipedalism). In these species the morphological changes are subtle. The body of these animals continues to maintain a horizontal and quadrupedal balance Among lizards, bipedal locomotion is performed mostly when moving towards a small object, where it is advantageous have a wide field of vision, and not so much when aiming at an object that is too wide for which it is not necessary to keep it in the crosshairs.
The Basiliscus basiliscus is capable of running using only its hind limbs and reaching speeds so high that it can run through water without sinking.
African Ostrich (Struthio camelus)
This bird is the fastest bipedal animal in the world, being able to reach 70 km/h. Not only is it the largest bird in existence, but it has the longest legs relative to its size and has the longest stride length when running: 5 meters. The large size of its legs in proportion to its body and the arrangement of its bones, muscles and tendons are the characteristics that generate in this animal a long step and a high frequency of step, resulting in its high maximum speed.
Magellanic Penguin (Spheniscus magellanicus)
This bird has interdigital webs on its legs and its terrestrial locomotion is slow and inefficient. However, the morphology of its body presents a hydrodynamic design and when swimming it can reach up to 45 km/h.
American cockroach (Periplaneta americana)
The American Periplaneta is an insect and therefore has six legs (it belongs to the Hexápoda group). This species is especially adapted to high-speed locomotion. It has developed the adaptation of being able to move on two legs reaching a speed of 1.3 m/s, which is equivalent to 40 times the length of its body per second.
It has been discovered that this species has different patterns of locomotion depending on the speed at which it is being transported. At slow speeds it uses a tripod gait, using three of its legs. At high speeds (greater than 1 m/s) it runs with its body raised off the ground and its front end raised relative to the rear. In this posture, its body is powered primarily by the long hind legs
Other bipedal animals
As we say, there are many animals that walk on two legs that exist, and below we show a list with more examples:
- Meerkats
- Chimps
- Hens
- Penguins
- Ducks
- Kangaroos
- Gorillas
- Baboons
- Gibbons
