Prehistoric Animal That Looks Like a Ppant

Introduction

Because the era known equally prehistoric covers the hundreds of millions of years before the first hominids, or humanlike creatures, existed, most prehistoric animals have never been seen past humans. Prehistoric animals evolved in 2 ways. Early, very simple kinds of animals gradually inverse into new and more complex kinds; and the process of adaptation enabled some animals to survive in all parts of the Earth.

While some prehistoric animals died out completely, condign extinct, the descendants of others are notwithstanding living on Globe. The all-time-known extinct animals are dinosaurs, huge animals that disappeared about 65 million years ago. Sponges, corals, bounding main stars (starfish), snails, and clams—all familiar creatures today—tin can be traced back 500 million years or more. Spiders originated virtually 400 million years ago. Insects and sharks as well have long histories.

Dinosaurs dominated the Earth for more 150 million years and and so vanished. Scientists have many theories to explain this fact. Some say that when flowering plants appeared on World about 200 million years ago, they increased the amount of oxygen in the atmosphere, causing dinosaur breathing rates and heartbeats to increase to the extent that the creatures burned themselves out. Other theorists suggest that the dinosaurs were poisoned by plants they ate. However others say that the huge animals began to die off after the World's continents, which had originally been a single landmass, broke apart, causing tremendous environmental changes, submerging huge areas, and radically irresolute the climate. A more recent theory states that a giant falling star struck the Globe, exploded, and filled the atmosphere with debris for many years. This debris darkened the skies and blocked out the sunlight. The resulting lower temperatures on Earth caused the extinction of many animals.

Scientists have learned a great deal nigh prehistoric life by studying animal skeletons or shells. At times they have found bones and pieced them together. Often the remains were petrified (turned to a stony hardness) and discovered every bit fossils.

Early Sea Life

The earliest fossils date from about 570 1000000 years ago. In those days, shallow seas covered many places that accept since become dry out land. Jellyfish drifted about in the water; vase-shaped sponges grew on the lesser of the sea; pocket-size shellfish and worms crawled about under seaweed. Brachiopods—a large family of beat-covered animals with a kind of arm used to stir up the sandy bottom and to crusade nutrient to float most them—were common in ancient seas. Trilobites 6 to 7 inches (15 to 18 centimeters) long were the largest animals in those early on seas. Some were oval and shine while others had goggle optics and spiny shells fabricated upwardly of several sections. These creatures had feathery legs and used jointed feelers to find nutrient.

Echinoderms, or echinoids, named for the modest plates that make up their outer coverings, are one of the nearly numerous creature groups to have lived in ancient seas. Sea stars, ocean urchins, and sea cucumbers survive today. The closely related crinoids, besides a living species, are fastened to the seafloor by stalks and resemble flowers somewhat; hence they are oftentimes chosen ocean lilies. 2 extinct kinds of echinoderms are cystoids, which had complex breathing organs, and blastoids, which resembled ocean plants.

Also common were ammonites, some of which had ridged shells in the form of apartment spirals. Others had cone-shaped hard coverings and bodies with long feelers that made them look like octopuses coming out of cones. Nautiloids, some species of which survive today as the nautilus of the Southward Pacific, were members of the ammonite family.

Fishes appeared nigh 450 one thousand thousand years agone, evolving peradventure from ancient soft-bodied organisms. Moving slowly forth the sea bottom, they ate by straining food from water drawn through their gills. They did non look much like modern fishes: they had no jaws (and thus no mouth to open and close), no fins, and probably no head in the usual sense. Scientists imagine that their bodies were hose-shaped with simple digestive organs and a nervus cord running from front end to back supported by a notochord, a kind of stiff supporting material. The notochord was extremely important considering much later information technology was to evolve into a spine.

The first fish that resembled the present-day fishes was the ostracoderm, which lived almost 400 million years ago. The creature had no jaws, a bony skull, and a thick shell-like armor on its back. A spinal cord ran from neck to tail, and it had two stumpy fins.

The numbers and species of fishes increased rapidly from the beginning of the Devonian period, some 395 million years ago. Fishes evolved jaws, which freed them to hunt nutrient throughout the sea, and pairs of fins, which stabilized their bodies and made them faster swimmers. With mobility they lost their heavy dorsum armor, growing scales as a replacement. Sharks appeared in Devonian times, with some species growing up to 50 anxiety (15 meters) long.

The lungfish is thought to stand for a transitional stage between the fish (which lives entirely in the h2o) and the amphibian (which can survive on land or in water). Lungfish have existent lungs, which means that they can rise to the water surface to breathe. They have pairs of fins at the fronts and backs of their bodies that they use similar legs to crawl across the mud of river and lake bottoms. Although they live their entire lives in h2o, lungfish can survive long dry out spells by slowing down their body functions (estivating) and by burrowing into the mud.

The Showtime Land Animals

At the beginning of the Devonian menstruation, the Earth's surface changed as the continents drifted into new arrangements. Deep seas replaced shallow ones, and there was more than dry state. Early on forms of plants were algae, lichens, and probably mosses.

Past that time, the structure and habitats of fishes were changing. Some forms, ii to three feet (0.6 to 0.9 meter) long, also lived in pools on country. Called crossopterygians, or lobe-fins, they had bony heads, sharp teeth, and simple lungs equally well as gills. If the pools were fouled by decaying vegetation, these fish raised their heads to breathe air. If the pools stale upwards, the fish used their thick, short fins to crawl over strips of state that still contained minor pools of water.

Amphibians, the descendants of sure itch fishes, developed legs from fins and could move more easily. The first amphibians probably looked like salamanders, 3 to four feet (0.9 to 1.2 meters) in length, with sharp teeth and wide heads.

During the next l million years, plants and animals changed greatly. About 280 1000000 years ago, at the finish of the Coal Age (Carboniferous, or Pennsylvanian, menstruum), trees as much equally 100 feet (30 meters) in meridian and vi feet (1.8 meters) in diameter grew in swampy forests. Cockroaches grew four inches (10 centimeters) long, and dragonflies were enormous.

Labyrinthodonts also lived during the Coal Historic period. They were amphibians that may well have been the ancestors of all state vertebrates (animals with spines), including human being beings. Some had body structures like those of reptiles. Many labyrinthodonts were as big equally alligators, while some were every bit small equally salamanders.

Reptiles represented the side by side stride in creature evolution. On the evolutionary scale, they stand between the amphibians and the birds and mammals. Reptiles are vertebrates that breathe air and are covered with scales rather than hair or feathers. Cotylosaurs, extinct today, were probably the first reptiles, dating perhaps from well-nigh 300 million years ago. They were nearly 3ⁱ/₃ anxiety (one meter) long with stumpy legs, brusk necks, and long tails.

Reptiles made the final suspension with life in the water. They lived entirely on land and thus could movement to areas that lay far from seas and rivers. Reptiles also developed difficult-shelled eggs that they could lay about anywhere on the ground.

Insects began to evolve about 325 million years ago. Fossils bespeak that they adult from land-dwelling arthropods—invertebrate (spineless) creatures with shells and jointed legs. The primeval insects crawled but did non fly. Winged insects appeared nigh 300 million years ago.

Dinosaurs and Other Reptiles

When prehistoric reptiles are mentioned, many people recollect of huge dinosaurs. But the first dinosaurs—chosen thecodonts—were no larger than turkeys. Living from most 230 one thousand thousand to 190 million years agone, thecodonts walked or ran upon their hind legs and used their long tails to balance their bodies. Every bit millions of years went by, the descendants of these first dinosaurs grew larger and larger. Some of these dinosaurs began to walk on 4 legs while others remained on 2; dinosaurs became some of the biggest animals that ever lived on land.

The giant dinosaurs dwelt in deep swamps surrounded by forests about 150 million years ago. Apatosaurus (formerly called Brontosaurus) was an herbivore with a very minor brain; information technology stood most 30 feet (9 meters) loftier and measured ninety feet (27 meters) from head to tail. Apatosaurus and smaller herbivorous (plant-eating) dinosaurs had massive bodies and legs, long necks, and even longer tails. When they were hungry, they pulled upward water plants and swallowed them without chewing. When danger threatened, they waded into deep water. They could stand on the bottom of a bounding main for hours with but their nostrils above the surface to exhale.

Dinosaurs lived all over the world except in the very coldest areas. At that place was a tremendous diverseness of species with a wide range of sizes and with scaly or heavily armored bodies. Some had ducklike bills full of sharp teeth. One blazon of dinosaur had 2 rows of bony plates on its dorsum and long, bony spikes on its tail. Instead of running from danger, this creature swung its tail to and fro. The spikes delivered terrible blows against annihilation they struck.

The simply animals that could damage the giant herbivorous dinosaurs were the carnivorous, or meat-eating, dinosaurs. These were savage creatures thirty to 50 feet (9 to 15 meters) long, with big heads and wide mouths set with daggerlike teeth. They stood on long, powerful hind legs, and their toes were armed with sharp, curved claws. They oftentimes attacked swamp-home dinosaurs that had strayed too near the shore.

Advances in research techniques and many new excavations have resulted in the identification of more than fifty additional kinds of dinosaurs in recent years. Some scientists believe they have discovered the bones of two previously unknown, very large vegetarian dinosaurs—commonly chosen Supersaurus and Ultrasaurus. Supersaurus may take been 100 to 120 feet (thirty to 37 meters) in length, and it is believed Ultrasaurus was even larger. Other discoveries take included very well-preserved baby dinosaur skeletons in nests.

Dinosaurs became extinct at the end of the Cretaceous period, about 65 meg years ago. The mass extinction may have been caused by whatsoever number of events, every bit stated earlier, but a heavily favored theory is that a huge meteor struck the Earth, concealment the sky and blocking the sun with its droppings. The subsequent cold temperatures may then have caused the extinctions on Earth. Paleontologists believe that a behemothic crater institute in Mexico may be the site at which the meteor hit Earth.

Although dinosaurs were the most spectacular animals of their day, they were by no ways alone on the World. Other reptiles walked the country, flew through the air, and swam in the h2o. At that place were birds, mammals, and some odd creatures that were halfway between the reptile and the mammal.

Mosasaurs, giant lizards that ranged from xvi to 33 feet (five to 10 meters) in length, never left the body of water. They had brusque paddles instead of legs and propelled themselves through the h2o by swinging their long tails from side to side. Icthyosaurs (meaning "fish-lizards"), smaller reptiles that lived entirely in the ocean, looked very much like sharks. Fossil testify indicates that, like mammals, they gave birth to live young instead of laying eggs, as reptiles exercise.

Plesiosaurs were ocean-dwelling reptiles, well-nigh of which were about 15 feet (5 meters) long, though some later forms were as long as 43 feet (xiii meters). Some species had very long necks and had flippers instead of legs.

Pterosaurs, flying reptiles, ranged from types the size of a sparrow to giant flesh-eating types with wingspans of up to 25 feet (8 meters). They had no feathers. To motility through the air, they flapped large winglike webs of peel that stretched from their elongated front legs to their hind legs.

Theriodonts (meaning "mammal-toothed") were members of a reptile family that died out nearly 190 meg years agone. They had skeletal features that suggest an evolutionary midpoint betwixt the reptile and the mammal.

Birds and Mammals

The slap-up difference between the reptiles and the birds and mammals that followed them is warm blood. Reptiles are cold-blooded, which ways that they must seek warmth for their bodies from an external source. Birds and mammals are warm-blooded; they can create their own trunk oestrus and accept coverings of feathers or hair to conserve information technology.

Birds with teeth lived from virtually 150 one thousand thousand to 65 meg years ago. These creatures might have evolved from flying reptiles, replacing their pare flaps with feathers. The earliest known bird, named archaeopteryx (meaning "ancient wing"), was virtually the size of a crow.

Mammals represent an advance from birds because of their method of reproduction. Birds lay eggs that must be protected until they hatch. Mammals, the largest course of animals, develop their young within the mother's body.

Many of the early on mammals were ancestors of familiar animals of today. Ancient horses had iii toes and were not much larger than sheep. There were besides petty camels that had no humps and modest rhinoceroses without horns. Mammoths and mastodons resembled elephants but were larger. The ground sloth was as big as an ox. Cannibal mammals were common simply non very large.

Several herbivorous creatures accept no living relatives. Among these were the and so-chosen "giant pigs", 5 to 6 feet (ane.5 to 1.8 meters) in top. They had bony lumps on the sides of their heads and potent tusks, which they used for digging roots and for fighting. Even larger were plains-habitation titanotheres. The biggest of these looked similar a rhinoceros 8 feet (2.4 meters) high. On its olfactory organ it had two long, blunt horns of bone covered with difficult skin.

It was during the Pleistocene epoch, or Smashing Ice Historic period, which began about 2 one thousand thousand years ago, that about of the recent fauna extinctions took identify. Since this epoch coincides with the appearance of humans on Earth, information technology is probable that some of the extinctions can be attributed to early on humans.