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The earliest creatures to crawl out of the water onto land may have concocted antacids out of their own bones, a clever innovation that would’ve let the animals breathe, researchers now find.

The earliest tetrapods, or four-limbed creatures, made their first evolutionary forays onto land about 370 million years ago. Breathing air came with challenges, though. A major one was getting rid of the air’s carbon dioxide, which, when it builds up, reacts with water in the body and forms an acid.

Now, growing evidence in modern reptiles suggests that bones that grew within the skin of early tetrapods may have acted as a natural antacid by releasing their neutralizing chemicals into the bloodstream. The result would have bought the creatures time to spend on land before they had to head back to the water to rid themselves of excess carbon dioxide.

“Now we know that dermal bone can do this and it’s something we didn’t know before, that gives us a basis that maybe this is why tetrapods had this feature, which previously we didn’t have a good explanation for,” study researcher Christine Janis, a paleontologist at Brown University, told LiveScience. “It’s the discovery of this new feature of the physiology of these living animals that lets us go back [in time].”

First on land

So let’s rewind the clock: The first tetrapods evolved from fish in the Devonian period, which spanned from about 416 million years ago to 359 million years ago. These early tetrapods had broad faces, not unlike frogs, and rather immobile ribcages. That means they wouldn’t have been able to get rid of extra carbon dioxide by breathing quickly, as humans and other mammals do with their longer snouts and flexible ribcages. Nor were the tetrapods small enough to exchange carbon dioxide and oxygen via their skin, as modern amphibians do.

What tetrapods did have was complex “dermal bone,” or bone that forms from connective tissue in the skin instead of from cartilage like the long bones of the arm or leg. The concept of skin bone may seem strange, but it’s very common: The human skull, for example, is a dermal bone.

Early tetrapod bone showed many pits and furrows, indicating lots of blood supply, Janis said. Her colleagues, including paper co-author and biologist Daniel Warren of Saint Louis University, had found another piece of the puzzle: In modern turtles and alligators, this dermal bone helps the reptiles tolerate carbon dioxide buildup when they’re under water, unable to breathe.

Bone breathing

Tetrapods would have the opposite problem, Janis realized: They’d be able to release carbon dioxide through their skin while in the water, since their skin was more permeable than an alligator’s tough hide. But out on land, they’d need another means of release. It seemed very possible that tetrapods could have used their complex dermal bones as a storage unit for calcium and other acid-neutralizing minerals, releasing them as needed when body acid levels got too high, Janis said.

To test the idea, the researchers analyzed the skeletons of tetrapods. As you might expect, the tetrapods known by the skeletons to spend more time out of the water had the most complex dermal bones. The evolutionary history of the animal supports the hypothesis, as well.

“When [the dermal bone] gets lost, it gets lost in the lineage leading to modern reptiles when they start getting more mobile ribs,” Janis said.

She and her colleagues reported their work Tuesday (April 24) in the journal Proceedings of the Royal Society B.

End of the early tetrapods

While the evidence is consistent with Janis’ theory, there’s no proof yet that tetrapods really used their bones in this way. The next step, Janis said, will be to look for chemical or other clues in modern reptiles who use their bones as antacid. If any telltale signs are established, researchers can then hunt for the same signals in ancient tetrapods.

The terrestrial tetrapods studied by Janis and her colleagues went extinct during the Permian period 299 million to 251 million years ago. It was a changing world, Janis said, and atmospheric carbon dioxide was increasing. It’s possible that tetrapods’ bone-dependent breathing wasn’t as effective in this new atmosphere.

“Who knows?” Janis asked. “I think the point to make is that this was probably a perfectly good way to live for awhile — millions of years — but in the end, there were things that had figured out better ways of how to get rid of carbon dioxide.”

Source: www.livescience.com/19876-bone-antacid-early-land-animals.html

Trilobites are distant relatives of lobsters, spiders and insects that died off more than 250 million years ago, before the dinosaurs even came into existence. They prowled the seas for roughly 270 million years, longer than the Age of Dinosaurs, and new species of trilobites are unearthed every year, making them the single most diverse class of extinct life known.

Tiny Orgy: Billions of Beasts Fossilized in Act of ‘Naked’ Sex

Orgies of sometimes billions of trilobites have been discovered, ones captured in a torrent of mud right after these extinct creatures ditched their hard shells to get up close and personal.

These findings, which will be presented March 20 at the Geological Society of America regional meeting in Pittsburgh, help show how social these ancient beasts were.

A key problem when it comes to investigating any extinct creature is deducing how it might have once behaved. Now scientists are unearthing mass graves of trilobites, revealing details regarding how they acted in groups.

Mating madness

Trilobites, like other arthropods, shed their hard exoskeletons from time to time in order to grow larger. They appeared to have gathered in large groups for safety in numbers when they molted their armor, just like modern crabs and lobsters.

Moreover, trilobites seem to have used these gatherings as opportunities to mate, just like many of their distant living relatives do. Preserved together are large groups of similar-sized and therefore similarly aged trilobites, separated by species; they may have reproduced essentially “naked” after molting.

“It’s an orgy,” said researcher Carlton Brett, an invertebrate paleontologist and sedimentary geologist at the University of Cincinnati.

The first hints that Brett and his then-graduate student Stephen Speyer had that such orgies took place were actually discovered about two decades ago in 385-million-year-old rocks in New York. Since then, a lot of new material has come into light that strengthened those claims — in 390-million-year-old rocks in Germany, 400-million-year-old sites in Morocco, 450-million-year-old groups near Cincinnati, and up to 470-million-year-old areas holding remains of trilobite orgies in Oklahoma.

“The fact that you can find this in many different places and ages among many different species of trilobites suggests that this behavior might have been pretty general to the entire group, and that it likely began fairly early on in the evolution of trilobites,” Brett told LiveScience.

“There were different groups segregated by species at these sites, yet they all seemed to be molting in synchrony — this is something we see today in modern marine animals as well,” Brett said. “They may have spawned in response to some external trigger from the environment, such as a new moon tide in a particular season of the year.”

Head to tail

Graduate student Adrian Kin of Jagiellonian University in Krakow, Poland, also recently discovered long chains of more than a dozen trilobites arranged head to tail in 360-million-year-old rocks in the Holy Cross Mountains of Poland. This seems to be evidence of another behavior seen in their living relatives — migration.

“The recent discovery of rows of more than a dozen specimens provides the oldest evidence of migratory queues similar to those seen in modern crustaceans,” Brett said.

“These trilobites were blind, eyeless,” Brett added. “They lived in relatively deep and probably no-light zones. They were probably relying on their tactile senses to literally keep in touch with each other as they migrated.”

These cases of mass burials may have occurred when runoff from hurricanes propelled tons of mud over the trilobites. These catastrophic deposits smothered the creatures so rapidly that they were delicately preserved in the last positions they held when they were alive, essentially recording snapshots of their behavior much the way ancient Roman life was recorded at Pompeii by volcanic ash.

“We find trilobite beds that we can trace across distances of 80 miles (130 kilometers), all the effect of a single event,” Brett said. “The numbers of individuals caught in those must easily be in the billions. These were probably extraordinarily rare events in terms of human scales, but on the grand scale of geological time, you can have a number of these extraordinarily bad days that record these amazing glimpses into what the lives of ancient organisms were like.”

Source: www.LiveScience.com

The Cambrian Period is the first geological time period of the Paleozoic Era (the “time of ancient life”). This period lasted about 53 million years and marked a dramatic burst of evolutionary changes in life on Earth, known as the “Cambrian Explosion.” Among the animals that evolved during this period were the chordates — animals with a dorsal nerve cord; hard-bodied brachiopods, which resembled clams; and arthropods — ancestors of spiders, insects and crustaceans.

Though there is some scientific debate about what fossil strata should mark the beginning of the period, the International Geological Congress places the lower boundary of the period at 543 million years ago with the first appearance in the fossil record of worms that made horizontal burrows. The end of the Cambrian Period is marked by evidence in the fossil record of a mass extinction event about 490 million years ago. The Cambrian Period was followed by the Ordovician Period.

The period gets its name from Cambria, the Roman name for Wales, where Adam Sedgwick, one of the pioneers of geology, studied rock strata. Charles Darwin was one of his students. (Sedgwick, however, never accepted Darwin’s theory of evolution and natural selection.)

Climate of the Cambrian Period

In the early Cambrian, Earth was generally cold but was gradually warming as the glaciers of the late Proterozoic Eon receded. Tectonic evidence suggests that the single supercontinent Rodinia broke apart and by the early to mid-Cambrian there were two continents. Gondwana, near the South Pole, was a supercontinent that later formed much of the land area of modern Africa, Australia, South America, Antarctica and parts of Asia. Laurentia, nearer the equator, was composed of landmasses that currently make up much of North America and part of Europe. Increased coastal area and flooding due to glacial retreat created more shallow sea environments.

At this point, no life yet existed on land; all life was aquatic. Very early in the Cambrian the sea floor was covered by a “mat” of microbial life above a thick layer of oxygen-free mud. The first multicellular life forms had evolved in the late Proterozoic to “graze” on the microbes. These multicellular organisms were the first to show evidence of a bilateral body plan. These near-microscopic “worms” began to burrow, mixing and oxygenating the mud of the ocean floor. During this time, dissolved oxygen was increasing in the water because of the presence of cyanobacteria. The first animals to develop calcium carbonate exoskeletons built coral reefs.

The largest predator was Anomalocaris, a free-swimming animal that undulated through the water by flexing its lobed body. It had true compound eyes and two claw-tipped appendages in front of its mouth. It was the largest most fearsome predator of the Cambrian Period, but did not survive into the Ordovician. The earliest known chordate animal, the Pikaia, was about 1.5 inches (4 centimeters) long. Pikaia had a nerve cord that was visible as a ridge starting behind its head and extending almost to the tip of the body. The fine detail preserved in the Burgess Shale clearly shows that Pikaia had the segmented muscle structure of later chordates and vertebrates. Haikouichythes, thought by some to be the earliest jawless fish, were also found in the Burgess Shale.

A mass extinction event closed the Cambrian Period. Early Ordovician sediments found in South America are of glacial origin. James F. Miller of Southwest Missouri State University suggests that glaciers and a colder climate may have been the cause of the mass extinction of the fauna that evolved in the warm Cambrian oceans. Glacial ice would have also locked up much of the free ocean water, reducing both the oxygen in the water and the area available for shallow water species.

The Paleozoic Era, which ran from about 542 million years ago to 251 million years ago, was a time of great change on Earth. The era began with the breakup of one supercontinent and the formation of another. Plants became widespread. And the first vertebrate animals colonized land.

Life in the Paleozoic

The Paleozoic began with the Cambrian Period, 53 million years best known for ushering in an explosion of life on Earth. This “Cambrian explosion” included the evolution of arthropods (ancestors of today’s insects and crustaceans) and chordates (animals with rudimentary spinal cords).

In the Paleozoic Era, life flourished in the seas. After the Cambrian Period came the 45-million-year Ordovician Period, which is marked in the fossil record by an abundance of marine invertebrates. Perhaps the most famous of these invertebrates was the trilobite, an armored arthropod that scuttled around the seafloor for about 270 million years before going extinct.

After the Ordovician Period came the Silurian Period (443 million years ago to 416 million years ago), which saw the spread of jawless fish throughout the seas. Mollusks and corals also thrived in the oceans, but the big news was what was happening on land: the first undisputed evidence of terrestrial life.

This was the time when plants evolved, though they most likely did not yet have leaves or the vascular tissue that allows modern plants to siphon up water and nutrients. Those developments would appear in the Devonian Period, the next geological period of the Paleozoic. Ferns appeared, as did the first trees. At the same time, the first vertebrates were colonizing the land. These vertebrates were called tetrapods, and they were widely diverse: Their appearance ranged from lizardlike to snakelike, and their size ranged from 4 inches (10 cm) long to 16 feet (5 meters) long, according to a study released in 2009 in the Journal of Anatomy.

As the tetrapods took over, they had company: The Devonian Period saw the rise of the first land-living arthropods, including the earliest ancestors of spiders.

Paleozoic evolution

Life continued its march in the late Paleozoic. The Carboniferous Period, which lasted from about 359 million years ago to 299 million years ago, answered the question, “Which came first — the chicken or the egg?” definitively. Long before birds evolved, tetrapods began laying eggs on land for the first time during this period, allowing them to break away from an amphibious lifestyle.

Trilobites were fading as fish became more diverse. The ancestors of conifers appeared, and dragonflies ruled the skies. Tetrapods were becoming more specialized, and two new groups of animals evolved. The first were marine reptiles, including lizards and snakes. The second were the archosaurs, which would give rise to crocodiles, dinosaurs and birds. Most creepily, this era is sometimes referred to as the “Age of the Cockroaches,” because roaches’ ancient ancestor (Archimylacris eggintoni) was found all across the globe during the Carboniferous.

The last period of the Paleozoic was the Permian Period, which began 299 million years ago and wrapped up 251 million years ago. This period would end with the largest mass extinction ever: the Permian extinction.

Before the Permian mass extinction, though, the warm seas teemed with life. Coral reefs flourished, providing shelter for fish and shelled creatures, such as nautiloids and ammonoids. Modern conifers and ginkgo trees evolved on land. Terrestrial vertebrates evolved to become herbivores, taking advantage of the new plant life that had colonized the land.

Paleozoic geology and climate

All this evolution took place against the backdrop of shifting continents and a changing climate. During the Cambrian Period of the Paleozoic, the continents underwent a change. They had been joined as one supercontinent, Rodinia, but during the Cambrian Period, Rodinia fragmented into Gondwana (consisting of what would eventually become the modern continents of the Southern Hemisphere) and smaller continents made up of bits and pieces of the land that would eventually make up today’s northern continents.

The Cambrian was warm worldwide, but would be followed by an ice age in the Ordovician, which caused glaciers to form, sending sea levels downward. Gondwana moved further south during the Ordovician, while the smaller continents started to move closer together. In the Silurian Period, the land masses that would become North America, central and northern Europe, and western Europe moved even closer together. Sea levels rose again, creating shallow inland seas.

In the Devonian, the northern land masses continued merging, and they finally joined together into the supercontinent Euramerica. Gondwana still existed, but the rest of the planet was ocean. By the last period of the Paleozoic, the Permian, Euramerica and Gondwana became one, forming perhaps the most famous supercontinent of them all: Pangaea. The giant ocean surrounding Pangaea was called Panthalassa. Pangaea’s interior was likely very dry, because its massive size prevented water-bearing rain clouds from penetrating far beyond the coasts.

Source: www.livescience.com

Synapsids (Greek, ‘fused arch’), synonymous with theropsids (Greek, ‘beast-face’), are a group of animals that includes mammals and every animal more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having a temporal fenestra, an opening low in the skull roof behind each eye, leaving a bony arch beneath each; this accounts for their name. Primitive synapsids are usually called pelycosaurs or pelycosaur-grade synapsids; more advanced mammal-like ones, therapsids. The non-mammalian members are described as mammal-like reptiles in classical systematics; they can also be called stem mammals or proto-mammals. Synapsids evolved from basal amniotes and are one of the two major groups of the later amniotes; the other is the sauropsids, a group that includes modern reptiles and birds. The distinctive temporal fenestra developed in the ancestral synapsid about 312 million years ago, during the Late Carboniferous period.

Synapsids were the largest terrestrial vertebrates in the Permian period, 299 to 251 million years ago, although some of the larger pareiasaurs at the end of Permian could match them in size. As with other groups then extant, their numbers and variety were severely reduced by the Permian–Triassic extinction. By the time of the extinction at the end of Permian, all the older forms of synapsids (known as pelycosaurs) were already gone, having been replaced by the more advanced therapsids. Though the dicynodonts and Eutheriodontia, the latter consisting of Eutherocephalia (Therocephalia) and Epicynodontia (Cynodontia), continued into the Triassic period as the only known surviving therapsids, archosaurs became the largest and most numerous land vertebrates in the course of this period. The cynodont group Probainognathia, which includes Mammaliaformes, were the only synapsids who outlasted the Triassic. After the Cretaceous–Paleogene extinction event, the synapsids (in the form of mammals) again became the largest land animals.

Synapsids as a reptilian subclass

Synapsids were originally defined at the turn of the 20th century as one of the four main subclasses of reptiles, on the basis of their distinctive temporal openings. These openings in the cheek bones allowed the attachment of larger jaw muscles, hence a more efficient bite. Synapsids were considered to be the reptilian lineage that led to mammals; they gradually evolved increasingly mammalian features, hence the name “mammal-like reptiles”, which became a broad, traditional description for all Paleozoic synapsids.

The “mammal-like reptiles”

The traditional classification of synapsids as reptiles is continued by some palaeontologists (Colbert & Morales 2001). In the 1990s, this approach was complemented by a cladistic one, according to which the only valid groups are those that include common ancestors and all of their descendants: these are known as monophyletic groups, or clades.

Phylogenetically, synapsids are the entire synapsid/mammal branch of the tree of life, though in practice the term is most often used when referring to the reptile-grade synapsids. The term “mammal-like reptiles” represents a paraphyletic grade, but is commonly used both colloquially and in the technical literature to refer to all non-mammalian synapsids. The actual monophyly of Synapsida is not in doubt, however, and the expressions “Synapsida contains the mammals” and “synapsids gave rise to the mammals” both express the same phylogenetic hypothesis.

Primitive and advanced synapsids

The synapsids are traditionally divided into a primitive group and an advanced group, known respectively as pelycosaurs and therapsids. ‘Pelycosaurs’ make up the six most primitive families of synapsids. They were all rather lizard-like, with sprawling gait and possibly horny scutes. The therapsids contain the more advanced synapsids, having a more erect pose and possibly hair, at least in some forms. In traditional taxonomy, the Synapsida encompasses two distinct grades successively closer to mammals: the low-slung pelycosaurs have given rise to the more erect therapsids, who in their turn have given rise to the mammals. In traditional vertebrate classification, the Pelycosauria and Therapsida were both considered orders of the subclass Synapsida.

In phylogenetic nomenclature, the terms are used somewhat differently, as the daughter clades are included. Most papers published during the 21st century have treated “Pelycosauria” as an informal grouping of primitive members. Therapsida has remained in use as a clade containing both the traditional therapsid families and mammals. However, in practical usage, the terms are used almost exclusively when referring to the more basal members that lie outside of Mammaliaformes.

The Permian Period was the final period of the Paleozoic Era. Lasting from 299 million to 251 million years ago, it followed the Carboniferous Period and preceded the Triassic Period. By the early Permian, the two great continents of the Paleozoic, Gondwana and Euramerica, had collided to form the supercontinent Pangaea. Pangaea was shaped like a thickened letter “C.” The top curve of the “C” consisted of landmasses that would later become modern Europe and Asia. North and South America formed the curved back of the “C” with Africa inside the curve. India, Australia and Antarctica made up the low curve. Inside the “C” was the Tethys Ocean, and most of the rest of Earth was the Panthalassic Ocean. Because Pangaea was so immense, the interior portions of the continent had a much cooler, drier climate than had existed in the Carboniferous.

Marine life

Little is known about the huge Panthalassic Ocean, as there is little exposed fossil evidence available. Fossils of the shallower coastal waters around the Pangaea continental shelf indicate that reefs were large and diverse ecosystems with numerous sponge and coral species. Ammonites, similar to the modern nautilus, were common, as were brachiopods. The lobe-finned and spiny fishes that gave rise to the amphibians of the Carboniferous were being replaced by true bony fish. Sharks and rays continued in abundance.

Plants

On land, the giant swamp forests of the Carboniferous began to dry out. The mossy plants that depended on spores for reproduction were being replaced by the first seed-bearing plants, the gymnosperms. Gymnosperms are vascular plants, able to transport water internally. Gymnosperms have exposed seeds that develop on the scales of cones and are fertilized when pollen sifts down and lands directly on the seed. Today’s conifers are gymnosperms, as are the short palm like cycads and the gingko.

Insects

Arthropods continued to diversify during the Permian Period to fill the niches opened up by the more variable climate. True bugs, with mouthparts modified for piercing and sucking plant materials, evolved during the Permian. Other new groups included the cicadas and beetles.

Land animals

Two important groups of animals dominated the Permian landscape: Synapsids and Sauropsids. Synapsids had skulls with a single temporal opening and are thought to be the lineage that eventually led to mammals. Sauropsids had two skull openings and were the ancestors of the reptiles, including dinosaurs and birds.

In the early Permian, it appeared that the Synapsids were to be the dominant group of land animals. The group was highly diversified. The earliest, most primitive Synapsids were the Pelycosaurs, which included an apex predator, a genus known as Dimetrodon. This animal had a lizard-like body and a large bony “sail” fin on its back that was probably used for thermoregulation. Despite its lizard-like appearance, recent discoveries have concluded that Dimetrodon skulls, jaws and teeth are closer to mammal skulls than to reptiles. Another genus of Synapsids, Lystrosaurus, was a small herbivore — about 3 feet long (almost 1 meter) — that looked something like a cross between a lizard and a hippopotamus. It had a flat face with two tusks and the typical reptilian stance with legs angled away from the body.

In the late Permian, Pelycosaurs were succeeded by a new lineage known as Therapsids. These animals were much closer to mammals. Their legs were under their bodies, giving them the more upright stance typical of quadruped mammals. They had more powerful jaws and more tooth differentiation. Fossil skulls show evidence of whiskers, which indicates that some species had fur and were endothermic. The Cynodont (“dog-toothed”) group included species that hunted in organized packs. Cynodonts are considered to be the ancestors of all modern mammals.

At the end of the Permian, the largest Synapsids became extinct, leaving many ecological niches open. The second group of land animals, the Sauropsid group, weathered the Permian Extinction more successfully and rapidly diversified to fill them. The Sauropsid lineage gave rise to the dinosaurs that would dominate the Mesozoic Era.

The Great Dying

The Permian Period ended with the greatest mass extinction event in Earth’s history. In a blink of Geologic Time — in as little as 100,000 years — the majority of living species on the planet were wiped out of existence.  Scientists estimate that more than 95 percent of marine species became extinct and more than 70 percent of land animals. Fossil beds in the Italian Alps show that plants were hit just as hard as animal species. Fossils from the late Permian show that huge conifer forests blanketed the region. These strata are followed by early Triassic fossils that show few signs of plants being present but instead are filled with fossil remnants of fungi that probably proliferated on a glut of decaying trees.

Scientists are unclear about what caused the mass extinction. Some point to evidence of catastrophic volcanic activity in Siberia and China (areas in the northern part of the “C” shaped Pangaea). This series of massive eruptions would have initially caused a rapid cooling of global temperatures leading to increased glaciations. This “nuclear winter” would have led to the demise of photosynthetic organisms, the basis of most food chains. Lowered sea levels and volcanic fallout would account for the evidence of much higher levels of carbon dioxide in the oceans, which may have led to the collapse of marine ecosystems. Other scientists point to indications of a massive asteroid impacting the southernmost tip of the “C” in what is now Australia. Whatever the cause, the Great Dying closed the Paleozoic Era.

Original source: www.LiveScience.com

With its snout bones drawn up into a giant snorkel-like structure, Parasaurolophus was one of the most bizarre of all the hadrosaurs. It lacked a hole in its apex, and because of this it is clear that this bony structure was not used as a breathing apparatus while the animal was swimming or feeding underwater. It seems more likely that it helped Parasaurolophus produce noises for signaling to mates or, if it was colored, for courtship displays. We know from the specimens that have been discovered that soft tissues adorned the bony crest.

As a hadrosaurid, Parasaurolophus was a large bipedal/quadrupedal herbivore, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing. Its teeth were continually being replaced; they were packed into dental batteries containing hundreds of teeth, only a relative handful of which were in use at any time. It used its beak to crop plant material, which was held in the jaws by a cheek-like organ. Vegetation could have been taken from the ground up to a height of around 4 m (13 ft). As noted by Bob Bakker, lambeosaurines have narrower beaks than hadrosaurines, implying that Parasaurolophus and its relatives could feed more selectively than their broad-beaked, crestless counterparts.

Source: www.natgeo.com

Nearly all Pachycephalosaurus fossils have been recovered from the Lance Formation and Hell Creek Formation of the western United States. Pachycephalosaurus possibly co-existed alongside additional pachycephalosaur species of the genera Sphaerotholus, Dracorex and Stygimoloch, though these may represent juveniles of Pachycephalosaurus itself, though Sphaerotholus is regarded as a valid species. Other dinosaurs that shared its time and place include Thescelosaurus, the hadrosaurid Edmontosaurus and a possible species of Parasaurolophus, ceratopsids like Triceratops, Torosaurus, Nedoceratops, Tatankaceratops and Leptoceratops, 

ankylosaurids Ankylosaurus, nodosaurids Denversaurus and Edmontonia, and the theropods Acheroraptor, Dakotaraptor, Ornithomimus, Struthiomimus, Anzu, Leptorhynchos, Troodon, 

Pectinodon, Paronychodon, Richardoestesia and Tyrannosaurus.

Could you outrun a T. rex? Research on the rare Wyoming discovery has determined that the tyrannosaur was traveling roughly 2.8 to 5 miles per hour, slower than an average human runs. But, the researchers warn that these footprints aren’t nearly representative of a T. rex’s peak speed.

• Fossilized footprints reveal a tyrannosaur traveling between 2.8 to 5 mph

• This is slower than an average human runs, at 11 mph over short distance

• Still, researchers assert prints only represent walk through mud, not a run 

• Decades of debate reveal estimates between 10 and 45 mph for top speed

QUICK ANSWER

A T. rex could have run faster than an average human at top speed, but there is a chance that a human could outrun a T. rex. We can never fully know how fast the Tyrannosaurus rex ran, but scientists at the University of Manchester in England have come up with animated computer models based on fossils and estimated muscle mass that have helped them compute the probable top speeds of many dinosaurs. The Tyrannosaurus rex is nowhere near the fastest, topping out at around 18 mph. The fastest dinosaur they computed was the Compsognathus, which ran about 40 mph.

FULL ANSWER

Usain Bolt, the fastest man on Earth, set a world record for running 27.79 mph in the 100 meter sprint in 2009. He is not likely to get eaten by a Tyrannosaurus rex in the near future, but let’s look at a more average human. Running a four minute mile is the standard of all male professional middle distance runners, and translates to a speed of 15 mph. That’s perhaps a little faster than some of us would run a mile, but if we were running for our life it’s a pretty decent estimate.

If speed alone was a factor, a T. rex would win. However, it would take time for a dinosaur of that mass to get started, and it would not reach its top speed of 18 mph as soon as it would take a human to reach their top speed. Additionally, a Tyrannosaurus Rex is not as agile as a human and would likely get exhausted quickly. So your chances of outrunning a Tyrannosaurus rex are good if the distance to safety is short, or if you could weave and avoid him until he gets exhausted.

If I’d list down all their species then that would be more than a hundred thousand, so diverse was the kingdom of this terrestrial reptile. Since quite enough we have been conjured up by the aura of that one mosquito bite which could bring that vogue extinct race back to the world’s terrene. So what if it actually happens? would we risk it or not i don’t know so avoiding that dispute  and taking you to those ten esteemed dinosaurs out of way so many that people fancy and would like to have in that kind of park.

10. Sinosauropteryx (The Most Colorful Dinosaur)

There have been a number of dinosaurs with feathers but some were not even recognizable. Sinosauropteryx is the first genus of non-avian dinosaur found with the fossilized impressions of feathers, as well as the first non-avian dinosaur where coloration has been determined. It lived in China during the early Cretaceous period and was a close relative of Compsognathus (the smallest dinosaurs ever). The remarkably well-preserved fossils show that Sinosauropteryx was covered with a furry down of very simple feathers — though some contention arose with an alternative interpretation of the filamentous impression as collagen fiber remains. These filaments consisted of a simple two-branched structure, roughly similar to the secondarily primitive feathers of the modern kiwi. Sinosauropteryx is distinguished from other small dinosaurs by several features, including having a skull longer than its upper leg bone (femur) and very short, stout forelimbs, with the arms being only 30% the length of the legs.

9. Liopleurodon (Marine Dinosaur)

Liopleurodon is only on this list which is not scientifically classified as a dinosaur but in popular culture, it is referred to as so because of their co-existence with dinosaurs in the Jurassic era. Liopleurodon fossils have been found mainly in England and France, with one younger species known from Russia. Four strong paddle-like limbs suggest that Liopleurodon was a powerful swimmer. It provides very good acceleration – a desirable trait in an ambush predator by  scanning the water with its nostrils to ascertain the source of certain smells. It’s size was around  34 ft long. In 1999, Liopleurodon was featured in an episode the BBC television series Walking with Dinosaurs. In the programme, Liopleurodon was depicted attacking and devouring the theropod dinosaur, before becoming beached during a typhoon and suffocating under its own weight. The depiction of Liopleurodon leaping onto the land in order to catch land-based prey is entirely speculative.

8. Ankylosaurus (The Armored Dinosaur)

Ankylosaurus is often considered the archetypal armored dinosaur. Its well-known features are – the heavily-armored body and massive bony tail club – but Ankylosaurus was the largest known member of the family. In comparison with modern land animals the adult Ankylosaurus was very large. Some scientists have estimated a length of 30 ft. The body shape was low-slung and quite wide. Ankylosaurus was quadrupedal, with the hind limbs longer than the forelimbs. Ankylosaurus was herbivorous, with small, leaf-shaped teeth suitable for cropping vegetation. These teeth were smaller, relative to the body size. Bones in the skull and other parts of the body were fused to increase their strength. The most obvious feature of Ankylosaurus is its armor, consisting of massive knobs and plates of bone, known as osteoderms or scutes, embedded in the skin. The plates were aligned in regular horizontal rows down the animal’s neck, back, and hips, with the many smaller nodules protecting the areas between the large plates. The famous tail club of Ankylosaurus was also composed of several large osteoderms, which were fused. It allowed great force to be transmitted to the end of the tail when it was swung. It seems to have been an active defensive weapon, capable of producing enough of a devastating impact to break the bones of an assailant.

7. Triceratops (Last Dinosaur before Mass Extinction)

It was one of the last dinosaur genera to appear before the great extinction. Bearing a large bony frill and three horns on its large four-legged body, and conjuring similarities with the modern rhinoceros, Triceratops is one of the most recognizable of all dinosaurs. Although it shared the landscape with and was preyed upon by the fearsome Tyrannosaurus, it is unclear whether the two did battle in the manner often depicted in museum displays and popular images. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories claim that it is more probable that these features were used in courtship and dominance displays, much like the antlers and horns of modern reindeer, mountain goats, or rhinoceros beetles.

6. Stegosaurus (Spiky Dinosaur)

Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs. They lived some 150 to 145 million years ago, in an environment and time dominated by the giants. A large, heavily built, herbivorous quadruped, Stegosaurus had a distinctive and unusual posture, with a heavily rounded back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Its array of plates and spikes has been the subject of much speculation. The spikes were most likely used for defense, while the plates have also been proposed as a defensive mechanism, as well as having display and thermoregulatory (heat control) functions. Stegosaurus was the largest of all the stegosaurians but still roughly bus-sized. Averaging around 30 ft long and 14 fttall, the quadrupedal Stegosaurus is one of the most easily identifiable dinosaurs, due to the distinctive double row of kite-shaped plates rising vertically along its rounded back and the two pairs of long spikes extending horizontally near the end of its tail. Although a large animal, it was dwarfed by its contemporaries, the giant sauropods. Some form of armor appears to have been necessary, as it coexisted with large predatory dinosaurs.

5. Archaeopteryx (Only Avian Dinosaur)

Archaeopteryx, from the late Jurassic Period, may be the earliest known theropod dinosaur which may have had the capability of powered flight. If Archaeopteryx is defined as an avian, then there are few non-avian avialans. Avialae is the only clade of dinosaurs containing their only living representatives, birds, and the most immediate extinct relatives of birds.  Similar in size and shape to a European Magpie, Archaeopteryx could grow to about 1 metre  in length. Despite its small size, broad wings, and inferred ability to fly or glide, Archaeopteryx has more in common with small theropod dinosaurs than it does with modern birds. In particular, it shares the following features with the deinonychosaurs (dromaeosaurs and troodontids): jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes (“killing claw”), feathers (which also suggest homeothermy), and various skeletal features. The features above make Archaeopteryx a clear candidate for a transitional fossil between dinosaurs and birds. Thus, Archaeopteryx also plays an important role not only in the study of the origin of birds but in the study of dinosaurs.

4. Compsognathus (Smallest Known Dinosaur)

The animal was the size of a turkey and could weigh as less as 0.26g and lived around 150 million years ago in what is now Europe. It is the smallest known dinosaur. Compsognathus is one of the few dinosaurs for which the diet is known with certainty: the remains of small, agile lizards were found preserved in the bellies of  specimens. Although not recognized as such at the time of its discovery, Compsognathus is the first dinosaur known from a reasonably complete skeleton and the smallest and the closest supposed relative of the early bird Archaeopteryx. Thus, the genus is one of the few dinosaur genera to be well known outside of paleontological circles.

3. Amphicoelias fragillimus (Largest Known Dinosaur)

A. fragillimus is the largest and heaviest dinosaur ever discovered. A. fragillimus may have been the longest known vertebrate at 40–60 meters (131–196 ft) in length, and may have had a mass of up to 122 metric tons. Whatever evolutionary pressure caused large size was present from the early origins of the group. Carpenter cited several studies of giant mammalian herbivores, such as elephants and rhinoceros, which showed that larger size in plant-eating animals leads to greater efficiency in digesting food. Since larger animals have longer digestive systems, food is kept in digestion for significantly longer periods of time, allowing large animals to survive on lower-quality food sources. This is especially true of animals with a large number of ‘fermentation chambers’ along the intestine which allow microbes to accumulate and ferment plant material, aiding digestion.

2. Velociraptor (Raptor)

Velociraptor (commonly shortened to ‘raptor’) is one of the dinosaur genera most familiar to the general public that existed approximately 75 to 71 million years ago. Velociraptor was a mid-sized dromaeosaurid, with adults measuring up to 6.8 ft long, 1.6 ft high at the hip, and weighing up to 15 kg. The skull, which grew up to 9.8 in long, was uniquely up-curved, concave on the upper surface and convex on the lower. The jaws were lined with 26–28 widely spaced teeth on each side, each more strongly serrated on the back edge than the front—possibly an adaptation that improved its ability to catch and hold fast-moving prey. It was a bipedal, feathered carnivore with a long, stiffened tail and an enlarged sickle-shaped claw on each hindfoot, which is thought to have been used to kill its prey. Velociraptor can be distinguished from other dromaeosaurids by its long and low skull, with an upturned snout.

1. Tyrannosaurus rex

T-Rex, yes we can’t forget the dinosaur king for obvious reasons. It was among the last non-avian dinosaurs to exist. It lived throughout what is now western North America, 7 to 65.5 million years ago. Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two clawed digits. Although other theropods (a dinosaur subclassification) rivaled or exceeded Tyrannosaurus rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to 42 ft in length, up to 13 ft tall at the hips, and up to 6.8 metric tons (7.5 short tons) in weight. By far the largest carnivore in its environment, Tyrannosaurus rex was an apex predator.

Runner Ups:

Brachiosaurus (a well known specie known for it’s largest size but new discoveries negated that claim and we had to chose only 1 for our zoo for the big size)
Parasaurolophus (Duck Billed Dinosaur)
Pentaceratops (Triceratops cousin with 5 horns and largest dino skull)

Source: www.SmashingLists.com