Updated: Mar 25
For millions of years, reptiles were the dominant forms of life. The first reptiles evolved from early amphibia ans, and walked on the Earth about 340 million years ago. They differed from their ancestors in two ways, a hard scaly outer skin that protected their body, and the shelled amniotic egg that do not need water. These features helped the reptiles to move beyond the boundaries of water bodies to settle on the land.
Reptiles flourished, and diversified into a wide variety of types, and be came the dominant animals. The first birds developed from certain species of these reptiles. Flying reptiles, pte-dinosaurs, dominated the air for over one hundred million years. Dinosaurs, the giants, evolved from one of the reptile families during the great age of reptiles. They ruled the world for more than one hundred million years. The fossil records say that, once there were about twenty groups of reptiles. However, only four groups survive today. This issue of Tell Me Why takes you to the amazing world of reptiles.
The World of Reptiles
What is reptile?
Reptiles are creatures with many interesting features. Like us, they need a backbone however they crawl or swim on. They own scales, breathe air and lay eggs with shells. They're cold full-blood, they rely upon out aspect sources for body heat.
Sixteen groups of reptiles have lived on the face of the earth. only four groups survive that time.
The largest cluster is that the Squamata. Squamata includes liz rats and snakes. There square measure 5700 living species within the Squamata cluster.
The second group is that the crocodilians, which has crocodiles, alligators, and caimans. There are twenty three species of crocodilians. They're the biggest of the reptiles.
Tortoises and turtles kind the third group, that has regarding 294 species. They're the oldest of all living reptiles. The primary appeared concerning two hundred million years quality. Their most dignity is that the exhausting shell that encloses the soft elements of their body, professional viding protection from preda tors.
The smallest of the four groups has only 1 quite animal, the Sphenodon punctatum. The tuataras go on a bunch of remote islands off the New Seeland coast. they give the impression of being like lizards.
Reptiles square measure found on each continent except Antarctic continent.
Why is it saying that snakes evolved from lizards?
The lizard is a nice grand father of the snake. Snakes evolved from lizards lots of years ago. There's confusion concerning the cluster of lizards from which the snake evolved. Scientists depend upon fossils to review evolution. A snake doesn't create a decent fossil. Only pieces of backbone, and also the odd bone in poor condition are found. The most primitive living snakes are bur rowers. Therefore, some scientists believe that snakes arose from burrowing lizards which had a lot of reduced limbs. Others assume that snakes evolved within the ocean.
There is an excellent family of non burrowing lizards called platynota, and lots of scientists believe that lizards rose from this super family. The Gila monster, beaded lizard and a poisonous lizard called lanthanotus belong to this family. Members of this family do have some characteristic in common with snakes. The backbone, the tongue of these lizards, the snakes are similar in form. The 2 halves of the mandible don't seem to be firmly joined. However, the eye of the snake is specialised, quite unlike the eye of a non burrowing lizard. Scientists point out that the primitive platynota may themselves have been burrowers. So, lizards belonging to the superfamily platynota are regarded as the 'great grandfathers' of snakes.
Why is that the place Nova Scotia thought-about to be necessary within the study of ancient reptiles?
Ancient reptiles were unfree within the hollow stumps of primitive plants known as lycopsids. Nova Scotia house to such hollow lycopsid plants. Three genera or groups of reptiles were trapped in these type of tree stumps. Take a deep breath and read the names of the three groups Apollotyres, Hylonomus, and Proto clepsydrops. This kind assembly of reptiles was lucky for scientists always because the ancestors of all the primitive reptilian groups were represented in this assembly.
What we realized about the evolution of reptiles?
Once there were no reptiles on land. The earliest reptiles lived in the sea. More than two hundred fifty million years ago, reptiles travelled to the shore in search of food. Forests of ferns and other vegetation covered the land that time. Plant eating insects appeared in the early reptiles moved to the land in search for these insects. The competition for life in the sea can also have forced them to form the shore their home, and to hunt food there. They developed legs for walking around, lungs for respiratory air, and scales for defense, Gradually, they evolved into reptiles totally alter for life in land.
No one was truly present to observe the evolution of reptiles because the fossils of the remnants of prehistoric animals and plants helped the scientists. Scientists argue regarding the order during which separate diversifications like the legs and also the lungs appeared. However, they agree that the most important ad adaptation was the reptilian egg.
Why is it saying that reptiles are very near to amphibians?
Have you seen a lizard's egg? It has a white shell. Reptile eggs have a shell, whereas amphibian eggs don't have one. The shell prevents the egg from dehydration. In fact, evolution of such type of egg was the key to the evolution of reptiles. Unlike am amphibian eggs, such eggs could be laid on land. Amphibians were the ancestors of reptiles. Some scientists believed that the amphibian ancestors spent plenty of time on the land, and therefore the evolution of the egg with a shell followed other scientists like Alfred S. Romer believe that the earliest reptiles came ashore main- to lay eggs, just as turtles and today.
Between 63 and 245 million years ago at the time of Mesozoic Era was the golden age of the reptiles. The ancestors of all later day reptiles known as stem reptiles or cotylosaurs dominated the world. Stem reptiles or cotylosaurs were like lizard and hopped like frogs. Turtles might have arisen directly from stem reptiles. Turtles are re regarded as the oldest among modern day reptiles.
How did the evolution of Lizards occur?
Lizards evolved from the stem reptiles. This evolution began within the Permian period, that's between 299 and 251 million years before. The cotylosaurs (stem reptiles), which had solid box, which like skulls with openings just only for the eyes and nostrils. Lepidosaurs evolved from cotylosaurs. That they had a lighter skull with a addi tional gap. Eosuchians were the first of the Lepidosaurs. Lizards evolved from the Eosuchians two hundred fifty to two hundred million years before within the Triassic period. Some early lizards had ribs rather just like the ribs of a umbrella. They supported a folding membrane that, once expanded allowed the animal to glide through the air. In Southern England Kuehneosaurus and icarosaurus that lived in recent United Sates, had these special ribs. Mosasaurs were giant sea lizards. They ate fish. They reached a length of twelve metres, and swam with the assistance of paddle formed limbs. These early lizards died out. The flying lizards of South East Asia, Draco has ribs similar like the icarosaurus.
What are pterosaurs?
Pterosaurs were flying reptiles. About 150 million years ago, this group of reptiles were flies in air. Pterosaurs were light bodied creatures with leathery membranes stretched between their arms and forefinger to form wings for flying in air. The first pterodactyls may have been gliders. Later, Pterosaurs were developed the ability to fly by flapping their wings up and down in air and some even fed on the wing. Pterosaurs were plucked fish out of the sea like modern sea birds. Pteranodon was the largest of them. It had a wingspan of six meters. Pterosaurs are also known as pterodactyls.
What is an archaeopteryx?
The archaeopteryx was part of reptile and part of bird. Archaeopteryx is an wonderful example of an in-between creature an several fossils of this reptile bird have been found in fine grained stone. The skeleton looks like that of a dinosaur but it shows the presence of feathers evolved from the scales of reptiles are the most important feature of birds. The archaeoteryx had a toothed jaw, they have a long tail and a weak breast bone unlike the bones of birds. All the bones of archaeaopteryx were solid and the feathers of the archaeaopteryx tell us that the crocodile is related to the cuckoo.
What is Euryapsida?
Once upon a time, reptiles were the kings of the Earth and they were the most dominant animals in Earth. However in an unexpected way thousands of reptiles became extinct or died out completely wipe out from Earth. Euryapsida is a subclass of extinct reptiles and these reptiles had a single opening on the upper part of the skull behind the eye socket. Therapsids are further divided into four orders or groups. Araeocelidia had long necks. They were lived on the land. Sauropterygians had long necks, a small head, short wide bodies and they swam using flipper like limbs and ate fish.
A small group of reptiles are snails, other molluscs and they heavy bodied with long tails. They had broad flat teeth for crushing shells. This order is known as Placodontia. The final order were fish eaters is Icthyosaurs and they had paddle like limbs, a fin on the back and a fish like tail. Scientists have found an ichthyosaur fossil. It containing a baby ichthyosaur. So, we know that icthyosaurs gave birth to young ones.
What are synapsids?
Synapsids are reptiles that look like mammals. We all know that mammals animals which give milk to their young arose from reptiles. Synapsids have a single opening on the side of the skull behind the eye socket and primitive synapsids are called pelicosaur. They were more advanced mammal like therapsids. Several sub groups of peli-dinosaurs exist. Some ate fish. Dimetrodon was a pelicosaur. Dimetrodon preyed on other animals and it reached a length of about three metres. Edaphosaurus was a vegetarian pelicosaur. It had strange long spines on its back and this could have supported a large sail rich in blood vessels. The edaphosaurus turned the sail towards the sun to them warm up in the cold. They keep away from the sun to keep them cool.
299 to 251 million years ago in the Permian period Pelicosaurs were replaced by therapsids and these therapsids ate plants, some others preyed on animals. Therapsids in turn, gave rise to the mammals, 250 to 200 million years ago in the Triassic Age. Like mammals, some therapsids had different types of teeth, and limbs pulled beneath the body, lifting it off the ground. However, we are yet to find out exactly when the reptiles became mammals.
Why Did reptilian extinction occur?
Reptilian extinction is a puzzle. Thousands of reptiles died out at the end of the Cretaceous Period, about 65 million years ago. Scientists have put forth several theories to account for this mass extinction. At the end of the Cretaceous Period, cli mate changes occurred. Seas disappeared, and mountain ranges appeared. However, these changes happened quite slowly. They were not quick enough to wipe out reptiles.
The climatic changes may have slowly affected the larger reptiles of the time. Reptiles are cold blooded. So, they were un able to survive long periods of cold or heat, but reptiles could have moved out to warmer or cooler areas and escaped ex tinction. So some scientists be lieve that climate changes may not have caused reptilian ex tinction. Another theory has to do with over specialization-the reptiles may have had features well suited for a particular envi ronment. When the environ mental conditions changed, they failed to adapt and they died out. Some scientists blame the change in vegetation for the extinction. The reptiles that fed on plants could not adjust to the new vegetation. As they died out, the reptiles that preyed on them also met their end.
Why do we say that an ancient reptiles were carnivorous?
Early reptiles like the dimetrodon were meat eaters, Many ate insects. Insects are small packages of energy, and for many reptiles, it is still the basic food. Most young rep tiles start out as insect eaters. The young need plenty of energy for growing up, and the insects provide just that. Older lizards continue to eat insects. However, older snakes eat frogs, mice, birds, and eggs.
How are reptiles distributed geographically?
Reptiles are found almost everywhere in the world, except in Antarctic. Crocodiles and alligators are found in the warm tropics. However, the American and the Chinese alligators can tolerate the cold, and are found in the cooler temper ate regions. There are some lizard like creatures, which burrow into the earth and eat flesh. They are called amphisbaenians. These amphisbaenians are mainly seen in the tropical regions of the world. The tuatara which belongs to the order Rhynchocephalia, is found only on a few remote islands off New Zealand.
Turtles, lizards and snakes are seen throughout the world. Though all of them occur in the tropics, some are seen in the temperate regions as well. The painted turtle is seen in North America. Fresh water and land turtles are seen in Afri ca, Australia and Northern Argentina In South America. Lizards are the most widely distributed of all reptiles.
Snakes such as the com mon viper and the com mon water snake, cross the Arctic Circle. Lizards and snakes reach the end of the land in Africa, and Australia. Snakes are not seen in the far South of South America, but lizards reach Tierra del Fuego, the southern tip of South America. There are no land snakes in New Zealand, but two families of lizards are found there. There are no snakes in Ireland also.
How is a reptile adapted for under ground life?
Some snakes swim in the sand. The Australian Sandfish, the nearly legless Neoseps of Central Florida, several other lizards and some snakes are known for swimming in the sand. They go underground by wriggling in through the loose soil or sand. The sand viper of the African desert swims into the sand and sticks the black tip of its tail out to attract prey. Sand swimmers are mainly desert animals.
Monitors, some other lizards and some tortoises live in permanent bur rows. The burrows serve to beat the heat and the cold and for hiding from enemies. These reptiles come out of their burrows to eat. Another group of reptiles spent their entire lives under the ground. Blind Legless lizard fall into this group. They tunnel great distances in search of worms and insects. These strange creatures have lived in the soil, since the days of the dinosaurs.
How do reptiles survive in the desert?
Snakes live under rocks, in burrows, or they may be sand swimmers. A few snakes live in holes in the ground. There is very little food underground. Therefore, they crawl out of their hiding places at night, and hunt for their food. A well made bur- row of one animal often attracts other animals. The burrow of the gopher tortoise in the South Eastern United States is inhabited regularly by rattle snakes, indigo snakes, two kinds of lizard, the gopher frog, various small mammals, and a number of insects.
Anthills and the nests of termites also have snake and lizard guests. The reptiles of Central America occasionally shelter in the burrows of leaf cutting ants, armadillos, and those of poisonous spiders called tarantulas.
and lies there like a dead twig. Other snakes also try this trick. Coral snakes and some other snakes move their tails. so they look like their heads. Some reptiles are able to change their colour to match their surrounding. A reptile may be dark coloured when it lives on dark soil, and light coloured on light soil. The green lizard is a great example. Three kinds of old world geckos combine colour and form to escape the eyes of their enemies. They have greatly flattened bodies and tails, and bark like colour patterns. Natural protective colouring is known as camouflage.
Why is it said that some reptiles are expert mimics?
Have you seen a mimic imitate some one else and make people laugh? Some reptiles are professional mimics, however they are doing it for a serious reason -to save their lives.
The harmless milk snake, has the banded look of the toxic coral snake. This mimicry happens in areas where the two live together. Outside these areas, the milk snake does not look much like a coral snake.
The non toxic Mexican king snake seems like the coral snake, when young. A harmless snake may look like a poisonous snake. This is Batesian mimicry. So, enemies mistake the harm less reptile for the poisonous one, and leave it alone. The scientist H.W. Bates discovered this mimicry overtone hundred years ago
Blind legless lizards that live under the ground trick their enemies by displaying their tail. The underside of their tails usually red or yellow colour, and looks like an open mouth. The enemy attacks the tail, misunderstanding it for the head. The tail will face up to injury higher than the head, and therefore the lifetime of the lizard is saved.
Lizards may have a tail differently coloured from the rest of their body. When the enemy attacks them, they break off their tail. The tail jumps concering on the bottom, confusing the enemy, and helps the lizard to form smart its escape.
Why is it said that the sense of smell is very important to reptiles?
Like our nostrils, reptiles have nasal passages. The nasal pas sage is lined with tiny hairs. These hairs can sense very small units of substances that are to be smelled. The nasal passages f of most reptiles have an opening into the mouth. An organ f called the Jacobson's organs opens into the nasal passages of snakes and lizards. This organ o helps snakes and lizards to smell. The sense of smell is very important to reptiles. The sense of taste is closely related to the sense of smell, but it is not as important as the sense of smell, for reptiles. Pit vipers, rattle snakes, and pythons have a special organ for sensing heat called the pit organ. The pit organ is located on the sides of the head between the eyes and the nose. The pit organs can sense even tiny changes in temperature. The snake senses the body heat of mammals and birds with the help of its pit organ, and it goes for the kill. A rattle snake can Y strike accurately at a mouse or a man in total darkness, with the aid of its pit organ.
Why did some reptiles return to water during the process of evolution?
Millions of years ago, reptiles left water for dry land, but they did not leave water for good. Many reptiles went back to the water, not once, but many times. Reptiles left water in the first place to increase their chances for survival. They went back to water for the same reason. Most of the animal body is made of water. The temperature of lakes, rivers, and seas do not change much. This is an advantage for reptiles as they cannot keep up their body temperature by themselves. Land animals need big bones to support their weight. On the other hand, water can hold animals up. That is why the whale is bigger than the elephant.
However, big water animals find it difficult to move quickly. Water reptiles like the long dead ichthyosaurs solved this problem by swimming like fish. Snakes, crocodilians, and lizards move their body up and down in waves, or they paddled. Breathing is also a problem for reptiles. The oxy gen for breathing is dissolved in the water. Fish breathe by means of gills. Reptiles have lungs which are not suited for making use of the dissolved oxygen. Therefore, some reptiles have modified their body surfaces to make use of small amount of oxygen dissolved in the water.
Long History of Reptiles
Around 280 million years ago, three orders were in existence. The most important was the cotylosaurs- ria or the stem reptiles. The other two were mesosauria and pelycosauria. The mesosaurus gave rise to the ichthyosaur. Pelycosauria gave rise to therap sida which in turn gave rise to the mammals. Cotylosauria gave rise to saurischia, protosauria, chelonia, theco dontia and eosuchia. Eunuchia gave rise to rain rhynchocephalia and squamata. Thecodontia gave rise to pte rosaria, crocodilia, ornithosischia and sauropterygia.
All living reptiles and many dead ones arose from cotyledon saurs or stem reptiles. All but five died out suddenly in the late Cretaceous period. Therefore, the Cretaceous Period was called the 'great time of dying'.
Why are ichthyosaurs important?
Ichthyosaurus appeared 225 million years ago. They were fully adapted for life in water. They probably lived like the small toothed whales and porpoises of today. They had a fish like body adapted for swimming. The ichthyosaur had a short body shaped like an underwater missile, and it had a high fin on the back. The ichthyosaur tail was like a shark's tail, and sweeps of the tail powered it forward. Many lived out their lives in the sea. On the land, they would have been like fish out of water. Icthyosaurs died out mysteriously about 150 million years ago.