Hello and welcome to "JackFast.ucoz.com". Here you will be learning about dinosaurs. If you do not even know what a dinosaur is, then I'll teach you about them.
First lets’ start off with what a dinosaur is. From www.dictionary.com, the meaning of dinosaur is: any chiefly terrestrial, herbivorous or carnivorous reptile of the extinct orders Saurischia and Ornithischia, from the Mesozoic Era, certain species of which are the largest known land animals. The first dinosaurs appeared around 225 million years ago (mya) in a time known as the Mesozoic Era. The first dinosaurs were in the Triassic Era. Scientists divide the Mesozoic Era into 3 time periods: the Triassic, Jurassic and Cretaceous.
Lets’ talk about the Triassic Era of dinosaurs. At the beginning of the Triassic, most of the continents were concentrated in a supercontinent known as Pangaea. The climate was generally very dry over much of Pangaea, with very hot summers and cold winters in the Pangaea interior. Late in the Triassic, the seafloor spreading in the Tethys Sea led to rifting between the northern and southern portions of Pangaea, which began the separation of Pangaea into two continents. The two continents were named Laurasia and Gondwana, which would be completed in the Jurassic Period.
Now I’m going to tell you about the Marine life of the dinosaurs in the Triassic Era. The oceans Marine life had been massively becoming highly endangered by the Permian Extinction, when as many as 95 percent of the extant marine genera were wiped out by high carbon dioxide levels. Fossil from fish in the Triassic Period are very uniform, which indicates that at least a few families of Marine life survived the extinction. The mid- to late time of the Triassic Period shows the first development of the modern stony corals and a time of modest reef building activity in the shallower waters of the Tethys, near the coasts of Pangaea.
Now it’s time for the Plants and Insects section of the Triassic Era of the dinosaurs. Plants and insects did not go through any extensive evolutionary advances during the Triassic Era. Due to the dry climate, the interior of Pangaea was mostly desert. In higher latitudes, the gymnosperms survived and conifer forests began to recover from the Permian Extinction. Mosses and ferns survived in coastal regions. Spiders, scorpions, millipedes and centipedes survived, as well as the newer groups of beetles. The only new insect group of the Triassic was the grasshoppers.
Now I am going to talk about the Reptiles during the Triassic Era of the dinosaurs. The Mesozoic Era can be recognized as the Age of Reptiles. Two groups of animals survived the Permian Extinction were the: Therapsids, which were mammal-like reptiles, and the more reptilian Archosaurs. In the early Triassic, it appeared that the Therapsids would rule the new Era. One genus, Lystrosaurus, has been called the Permian/Triassic “Noah,” as fossils of this animal predate the mass extinction but are also commonly found in early Triassic strata. However, by the mid-Triassic, most of the Therapsids had become extinct and the Archosaurs were clearly dominant.
Archosaurs had two openings in the skull and teeth that were more firmly set in the jaw than the Therapsid contemporaries. The terrestrial apex predators of the Triassic were the Rauisuchians, an extinct group of Archosaurs. In 2010, scientist found a fossilized skeleton of a newly discovered species, Prestosuchus chiniquensis, measured more than 20 feet (6 meters) in length. Unlike their close relatives the crocodilians, Rauisuchians had an upright stance but are differentiated from true dinosaurs by the way that the pelvis and femur were arranged.
Another lineage of Archosaurs evolved into true dinosaurs by the mid-Triassic. One genus, Coelophysis, was bipedal. Although they are smaller than the Rauisuchians, they were probably faster because they had a more flexibly jointed hip. Coelophysis also picked up speed by having lightweight hollow bones. They had long sinuous necks, sharp teeth, clawed hands and a long bony tail. Coelophysis fossils are found in large numbers in New Mexico witch indicated the animal hunted in packs. Some of the individuals found had remains of smaller members of the species inside the larger animals. Scientists are unclear as to whether this indicates internal gestation or possibly cannibalistic behavior.
By the late Triassic, a third group of Archosaurs had branched into the first pterosaurs. Sharovipteryx was a glider about the size of a modern crow with wing membranes attached to long hind legs. It was obviously bipedal with tiny, clawed front limbs that were probably used to grasp prey as it jumped and glided from tree to tree. Another flying reptile, Icarosaurus, was much smaller, only the size of a hummingbird, with wing membranes sprouting from modified ribs.
Now it’s time for the Jurassic Period. The Jurassic Period was the second segment of the Mesozoic Era. It occurred from 199.6 to 145.5 million years ago, following the Triassic Period and continuing to the Cretaceous Period.
During the Jurassic Period, the world supercontinent “Pangaea” split apart. The northern half, known as Laurentia, was splitting into a landmasses that would eventually form into North America and Eurasia, opening basins for the central Atlantic and the Gulf of Mexico. On the other hand, the southern half, Gondwana, was drifting into an eastern segment that would form Antarctica, Madagascar, India, Australia, and a western portion that would eventually form Africa and South America. This rifting, along with generally warmer global temperatures, allowed for diversification and dominance of the power reptiles, known as dinosaurs.
Know lets’ talk about the plant life. By the Mesozoic Era, living things had evolved into the capability of living on the land rather than being confined to the oceans. By the beginning of the Jurassic Era, plant life had evolved from Bryophytes, the low-growing mosses and liverworts that lacked vascular tissue and were confined to swampy moist areas.
Ferns and gingkoes, complete with roots, vascular tissue to move water, nutrients, and a spore system of reproduction, were the dominant plants of the early Jurassic. During the Jurassic, a new method of plant reproduction evolved. Gymnosperms, cone-bearing plants such as conifers, allowed for wind distribution of pollen. This bisexual reproduction allowed for greater genetic combination and by the end of the Jurassic, the gymnosperms were widespread. True flowering plants did not evolve until the Cretaceous.
Know it’s time for the moment that you’ve been waiting for, the DINOSAURS!!! As Steven Spielberg’s 1993 film "Jurassic Park" asserts, reptiles were the one of the most dominant animal life forms during the Jurassic Period. Reptiles had overcome the evolutionary hurdles of support and reproduction that limited the amphibians. Reptiles have strong ossified skeletons supported by advanced muscular systems for body support and locomotion. Some of the largest animals ever to live were dinosaurs of the Jurassic Period. Reptiles were also capable of laying amniotic eggs, which kept the developing young moist and nourished during the gestation. This allowed the first fully terrestrial animal life cycles.
Sauropods, which were called the “lizard hipped” dinosaurs, were herbivorous quadrupeds with long necks balanced by heavy tails. Many, such as Brachiosaurus, were huge. Some genera obtained lengths greater than 100 feet and weights over 100 tons, making them the largest land animals ever to walk the earth. Their skulls were relatively small, with nostrils carried high near their eyes. Such small skulls meant that they had very small brains as well. Despite the small brains, this group was very successful during the Jurassic Period and had a wide geographic distribution. Sauropod fossils have been found on every continent except Antarctica. Other well-known dinosaurs of the Jurassic include the plated Stegosaurus and the flying Pterosaurs.
Carnosaurus means “meat-eating dinosaur.” With such large herbivorous prey animals, it makes sense that large predators were also common. Allosaurus was one of the most common Carnosaurs in North America; numerous intact skeletons have been found in the fossil beds of Utah. Allosaurus was superficially similar to the later evolving Tyrannosaurus rex, although cladistics analysis shows them to be only distantly related. Allosaurus was a bit smaller with a longer jaw and heavier forelimbs. They relied on the stronger hind limbs for a running gait, but it is unclear how fast they could move.
It is unlikely to have been common for an Allosaurus to take on a healthy large adult herbivore like a Brachiosaurus or even a Stegosaurus. They were most likely opportunistic, consuming young, sick, aged or injured prey. They were probably able to grasp such prey with their heavily muscled forelimbs, tearing it to pieces with large claws and then swallowing the pieces whole.
Now it’s time for the finale period of the dinosaurs, the Cretaceous. For the first topic about the Cretaceous. The Cretaceous Period was the last and longest segment of the Mesozoic Era. It lasted approximately 79 million years, from the minor extinction event that closed the Jurassic Period about 145.5 million years ago to the Cretaceous-Paleogene (K-Pg) extinction event dated at 65.5 million years ago.
In the early Period of Cretaceous, the continents were in very different positions than they are today. Sections of the world supercontinent, Pangaea was drifting apart. The Tethys Ocean still separated the northern Laurasia continent from southern Gondwana. The North and South Atlantic were still closed, although the Central Atlantic had begun to open up in the late Jurassic Period. By the middle of the period, ocean levels were much higher than normal; most of the landmass we are familiar with was underwater. By the end of the period, the continents were much closer to modern configuration. Africa and South America had assumed their distinctive shapes; but India had not yet collided with Asia and Australia was still part of Antarctica. Now it’s time for the Cretaceous plant life. One of the hallmarks of the Cretaceous Period was the development and radiation of the flowering plants. The oldest angiosperm fossil that has been found to date is Archaefructus liaoningensis, found by Ge Sun and David Dilcher in China. It seems to have been most similar to the modern black pepper plant and is thought to be at least 122 million years old.
It used to be thought that the pollinating insects, such as bees and wasps, evolved at about the same time as the angiosperms. It was frequently cited as an example of co-evolution. New research, however, indicates that insect pollination was probably well-established before the first flowers. While the oldest bee fossil was trapped in its amber prison only about 80 million years ago, evidence has been found that bee- or wasp-like insects built hive-like nests in what is now called the Petrified Forest.
These nests, ( that were found by Stephen T. Hasiotis and his team from the University of Colorado), are at least 207 million years old. It is now thought that competition for insect attention probably facilitated the relatively rapid success and diversification if the flowering plants. As diverse flower forms lured insects to pollinate them, insects adapted to differing ways of gathering nectar and moving pollen thus setting up the intricate co-evolutionary systems we are familiar with today. Now it’s time for the animals of the Cretaceous Period. During the Cretaceous Period, birds replaced the Pterosaurs in the air. The origin of flight is debated by many experts. In the “trees down” theory, it is thought that small reptiles may have evolved flight from gliding behaviors. In the “ground up” hypothesis flight may have evolved from the ability of small Theropods to leap high to grasp prey. Feathers probably evolved from early body coverings whose primary function, at least at first, was thermoregulation.
Confuciusornis, avian ancestors, flying dinosaurs, feathered dinosaurs
About the size of a crow, Confuciusornis is the earliest known bird to have a true beak. It lived about 10 to 15 million years after Archaeopteryx, but like its early ancestor, it still had clawed fingers. Males were typically larger than females and sported long, narrow tail feathers that they may have used to attract mates. Some scientists question whether Confuciusornis was a direct ancestor of modern birds. They propose instead that it was a cousin that early on went its own separate way.
At any rate it is clear that Avians were highly successful and became widely diversified during the Cretaceous. Confuciusornis (125 to 140 million years) was a crow-sized bird with a modern beak, but enormous claws at the tips of the wings. Iberomesornis, a contemporary, only the size of a sparrow, was capable of flight and was probably an insectivore. [Image Gallery: Avian Ancestors: Dinosaurs That Learned to Fly]
By the end of the Jurassic, the giant Sauropods, such as Apatosaurus, were becoming extinct. Evidence suggests that by the early Cretaceous they were being replaced by large herds of herbivorous Ornithischians such as Stegosaurus, Iguanodon and the Ceratopsians. Theropods, including Tyrannosaurus rex, continued as apex predators until the end of the Cretaceous.
K-Pg extinction event
About 65 million years ago, nearly all large vertebrates and many tropical invertebrates became extinct in what was clearly a geological, climatic and biological event with worldwide consequences. Geologists call it the K-Pg extinction event because it marks the boundary between the Cretaceous and Paleogene periods. The event was formally known as the Cretaceous-Tertiary (K-T) event, but the International Commission on Stratigraphy, which sets standards and boundaries for the geologic time scale, now discourages the use of the term Tertiary. The "K" is from the German word for Cretaceous, Kreide.
The Chicxulub crater in the Yucatan dates precisely to this time. The crater site is more than 1,000 feet across and chemical analysis shows that the sedimentary rock of the area was melted and mixed together by temperatures consistent with the blast impact of an asteroid about 6 miles (10 km) across striking the Earth at this point.
There is also evidence of a series of huge volcanic eruptions along the tectonic border between India and Africa that began just before the K-Pg event boundary. It is likely that these regional catastrophes combined to precipitate climatic change. Now we will review the Cretaceous Period because the dinosaurs are about to come to a end. All over North America, the highest of the Cretaceous fossils are found directly beneath a thin layer of sediments that contain an unusual amount of iridium, an element otherwise uncommon in Earth’s crust. Also within this layer are indications of “shocked quartz” and tiny glass-like globes called “tektites” that form when rock is suddenly vaporized then immediately cooled, as happens when an extraterrestrial object strikes the Earth with great force. These remains are found as far north as Colorado. Temperatures would have reached levels high enough to cause flash fires in many locations and a tsunami inundated much of the Eastern United States.
It is hypothesized that debris aerosols from the asteroid impact and the resulting fires may have combined with the ash and smoke from the continuing volcanic activity to significantly reduce global temperatures for a few decades. As a result of suddenly lowered temperatures, there may have been a global disruption in the numbers of both land plants and plankton in the oceans, evidence of which is part of the K-Pg fossil record. With such a crisis in the photosynthetic communities a cascading crisis would have toppled the food/energy pyramids extant at the time. This hypothesis accounts for the extinction of the largest animals of the time, the dinosaurs and giant marine reptiles. I am going to now talk about sharks. If you do not know what a shark even is; from http://dictionary.reference.com/ any of a group of elongate elasmobranch, mostly marine fishes, certain species of which are large, voracious, and sometimes dangerous to humans.
Now I am going to talk about the parts of a shark. As you can see, there are many parts of a shark. If you don’t know what any of these parts mean, than I will tell you. The first dorsal fin (also referred to the cranial dorsal fin), has a conical spine that can secrete a glandularly produced poison for defensive purposes. The second dorsal fin (also referred to the caudal fin), also has a spine. The spines grow throughout the animals life and are considered to be modified dermal scales (denticles). The spine is supported basally by a rod of cartilage just above the vertebrae. Now the eye. The eye is where the the shark see's through. For the snout, the snout is where they sense their prey. The mouth is where the sharks eat there prey. They have multiple rows of teeth. Fun fact, sharks lose over 30,000 teeth in their lifetime. That's why there are so many shark teeth. Their gill slits is where they breath through on both sides of their body. The nostril is on the snout and they have the same jobs. The pectoral fin the helps go to the direction the shark wants to go. Either of a pair of lateral hind of fishes, attached to the pelvic gir.
