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During Mesozoic era there are three specific periods of time in which dinosaurs ruled the Earth, the Triassic, the Jurassic and the Cretaceous periods. These eras were labeled by geologists as a way to distinguish between geologic strata and the periods in which they occurred. The most well-known and publicized period of the three dinosaur times is the Jurassic. Why is this so?
Why Is The Jurassic Period so Famous?
Well, the Jurassic period, which ran from 199 million years ago to 145 million years ago, saw the large dinosaurs that we are so familiar with. Of the dinosaurs that roamed the earth during the Jurassic period there were the Sauropods, the Theropods, and the Ornithopods.
It is a common misconception that during the Jurassic period that the Tyrannosaurus and Velociraptors roamed the land alongside the dinosaurs listed above. However, it was not until long after the Jurassic period ended that these two dinosaurs made their mark on the planet. A few of the individual dinosaurs that are the most recognized Jurassic period dinosaurs include the Brachiosaurus, the Diplodocus, the Iguanodon, the Megalosaurus, and the Stegosaurus.
Sauropods made their appearance during the early to middle Jurassic period. The Sauropods that graced the Earth during the Jurassic period include all of the dinosaurs which had long necks as well as long tails. Sauropods were the largest creatures to ever walk the Earth and have been dug up on every continent including Antarctica! Sauropods branched out in to so many species over 100 million years, however, that the majority of them still managed to follow the “blueprint” for Sauropods. Sauropod families during the Jurassic period included the Diplodocids, Brachiosaurids, Camarasaurids, Titanosaurids, and Cetiosaurids.
The Diplodocids were known for their whip-like tails and their long necks but small heads. Diplodocids had nostrils above their eyes and had teeth only in the front of their mouths. Diplodocids also had hollows in their vertebrae. Examples of the Diplodocids include the Diplodocus, Apatosaurus, Seismosaurus and Supersaurus.
The Braciosaurids were known for their giraffe type stance and for their front legs being longer than their rear legs. Braciosaurids also had short and thick tails and nostrils above their eyes. Examples of the Braciosaurids include Brachiosaurus and Ultrasauros.
The Camarasaurids were known for their short neck and tail. For dinosaurs in the Sauropod family, they also had hollows in their vertebrae and large box-shaped heads and nostrils ahead of their eyes. Examples of the Camarasaurids include Camarasaurus, Aragosaurus, and Parrosaurus.
The Titanosaurids were known for their armor coverings, wide heads and solid vertebrae. Examples of the Titanosaurids include Titanosaurus, Laplatasaurus, and Paralititan.
The Cetiosaurids were known for their almost solid vertebrae and their shorter tails. Examples of the Cetiosaurids include the Amygdalodon, Dystrophaeus, Protognathus and Shunosaurus.
The Theropods that graced the Earth during the Jurassic period include dinosaurs that hunted on two legs and they were nearly all carnivores. The Theropods were much more vicious than the long-necked Sauropods and were considerably faster being that they hunted on two legs. It is believed that most of the Theropods evolved from Archosaurs in the late Triassic period and continued to evolve through to the end of the Cretaceous period when the end came to the dinosaurs.
Paleontologists often have trouble distinguishing between the various Theropods due to the fact that there are so many varieties of them and many of them look similar after millions of years of wear and tear in the ground. It is believed by paleontologists that Theropods were opportunistic hunters who, being carnivorous, learned to hunt in small groups to increase their chances at feeding on meat. There were four distinct lines of Theropods during the Jurassic period: the Ceratosaurs, Megalosaurs, Allosaurs and Coelurosaurs.
The Ceratosaurs appeared during the early Jurassic period and were known for their horns. Unlike other classifications of Theropods the Ceratosaurs have no set group of characteristics that can be agreed upon by paleontologists and they seem to be a subject of contention among varying schools of thought. Some examples of Jurassic Ceratosaurs include the Ceratosaurus and the Dilophosaurus.
The Megalosaurs are the oldest group of Theropods and unfortunately due to sloppy classification during the early 19th century the majority of carnivorous dinosaurs discovered were classified as Megalosaurs. Many paleontologists these days see Megalosaurs as the junk basket of carnivorous dinosaurs as it contains large, meat-eating dinosaurs that have been found on every continent. There are no complete Megalosaur remains to go from in any of the individual specimens. Some examples of Megalosaurs include Megalosaurus, Torvosaurus, and Magnosaurus.
The Allosaurs are considered to include any dinosaur that is related to the Allosaurus. Allosaurs had large and ornate heads, large forearms and three-fingered hands. Some examples of the Allosaur include Gigantosaurus, Spinosaurus and Carcharodontosaurus.
The Coelurosaurs were the group of Theropods that resembled birds more so than other Theropods. The majority of feathered dinosaurs that have been discovered fell in to the Caelurosaur category. The sacrum of the Caelurosaur is longer than other dinosaurs and the tail stiffens towards the hip, the lower arm bone is bowed and the lower leg bone is longer than the femur. Some examples of the Caelurosaurs include Archaeopteryx, Pedopenna, Omitholestes and Epidendrosaurus.
The Ornithopods that graced the Earth during the Jurassic period are recognized as dinosaurs that ate only plants and had hips that were structured more like birds than other dinosaurs. Unlike some dinosaurs and dinosaur classifications Ornithopods were strictly plant eaters. Ornithopods had a beak and they had a two or two and four-legged walk. Ornithopods existed from the late Triassic period through the Cretaceous period. The Ornithopods had pelvises where the long pubis pointed backwards and ran parallel to the ischium, extending farther forward than the ilium. Examples of the Jurassic Ornithopods include the Agilisaurus, Iguanodon, Dryosaurus and Phyllodon.
Within all of the dinosaur classifications within the Jurassic period a select few dinosaurs stand out as the big names of the era. Some of these dinosaurs include the Brachiosaurus, the Diplodocus, the Iguanodon, the Megalosaurus, and the Stegosaurus. These ‘big wigs’ of the Jurassic period are well-recognized from their exposure in the media as well as through their skeletal discovery by paleontologists. It is far easier to give more recognition to the dinosaurs we know far more about from scientific discovery rather than those dinosaurs that have been recognized by only a singular tooth!
The Brachiosaurus (long neck like Brontosaurus)
The Brachiosaurus is the dinosaur that most children recognize as the “long neck”. This Sauropod lived during the late Jurassic period in to the early Cretaceous period. The Brachiosaurus is one of the largest animals to ever walk the face of the Earth weighing in at twenty-eight and a half tons. Brachiosaurus had four thick and relatively short legs and a smaller brain than would be expected for its size. The very first Brachiosaurus remains were found in 1900 by Elmer Riggs in Western Colorado and in 1903 he named the Brachiosaurus. The Brachiosaurus lived on the prairies and fed on vegetation. Contrary to some beliefs the Brachiosaurus did not use its nasal openings on the top of its head as snorkeling apparatus and it is now understood that the Brachiosaurus was a strictly terrestrial animal.
The Diplodocus was first discovered in 1877 by S.W. Williston. This large Sauropod made its home in the Western area of North America towards the end of the Jurassic period. For a long time it was believed that the Diplodocus was the longest dinosaur in existence measuring in at 54 meters (177 feet!) long. Paleontologists believe that carnivorous predators of the time avoided hunting these massive beasts because of their sheer size; they measured in at 17 tons. The Diplodocus is so named for two beam-like bones which run under the dinosaur’s tail which are thought to have provided support for the 80 vertebrae as well as to protect the blood vessels which ran through the tail when the large appendage was laid on the floor. As with the Brachiosaurus the Diplodocus was a terrestrial animal but due to variations in the Diplodocus’ teeth it is thought that it fed by stripping branches for vegetation rather than grazing.
The Iguanodon is an ornithopod that lived from the late Jurassic period through to the late Cretaceous period and dwelled within Asia, Europe and North America. The Iguanodon was first discovered in 1822 and named three years later by Gideon Matell; it is one of the first dinosaurs to have been named. The Iguanodon was a rather large herbivore that could move from two to four feet and is believed to have weighed three and a half tons and measured 10 meters (33 feet) long. The Iguanodon had a tall but slender skull and a toothless beak; however, they carried small teeth within their mouths. Iguanodons are known for having a large spiked thumb which is believed to have been used for defense or food foraging; they also had three fingers on each hand which bore the dinosaurs weight when walking on all fours. Unlike many dinosaurs whose diet can be inferred from teeth, the Iguanodon’s strange small teeth and toothless beak lead to some confusion as to what, and how, this herbivorous dinosaur ate.
The Megalosaurus is the first genus of dinosaur to be described and named. The large meat-eater thrived in the middle Jurassic period in Southern England, France and Portugal. The first Megalosaurus bone was a section of bone found in a limestone quarry in Cornwall, England in 1676. It was Robert Plot of the University of Oxford who believed it to be the bone of a giant human being. It was not until 1824 when William Buckland classified the bone segment and other similar remains as that of a giant lizard in the new genus Megalosaurus. To date no complete skeleton of the Megalosaurus has been discovered making it difficult to get an accurate picture of the Megalosaurus; however, modern-day recreations of the dinosaur portray it as a bipedal carnivore. It is believed that the Megalosaurus measured 9 meters (30 feet) in length and fed off Sauropods. While the Megalosaurus was a perfectly able hunter it is believed that it may also have fed by scavenging.
The Stegosaurus is another one of the most widely recognized dinosaurs by children today. The Stegosaurus is mostly recognized by the line of plates which ran down the dinosaurs back in two columns. This dinosaur is also recognized for its two large spikes which protrude horizontally at the end of its tail, it is widely held that these two spikes were used in battle for defense and weaponry after skeletal remains displayed damage to the spikes. The Stegosaurus lived during the late Jurassic period in Western North America and Europe. This large quadruped had a heavily rounded back, short front legs and it held its head low to the ground while its tail was held up high in the air. It is believed that the large armored plates which ran up and down the dinosaurs back played a part in defense, sexual display as well as thermoregulation.
The Stegosaurus measured around 9 meters (30 feet) long and stood around 12 meters (39 feet) tall. Due to the posture of the Stegosaurus (it walked with its head low to the ground) it is believed that this dinosaur was a low grazer and fed off vegetation that grew low on the ground. Paleontologists believe that due to the small brain casing of the Stegosaurus meant that the dinosaur had a brain no larger than a dog despite its large size; however, it is now understood that a smaller brain did not result in a lack of intelligence. The first example of the Stegosaurus was discovered and named by Othniel Charles Marsh in 1877 when remains were found just north of Morrison, Colorado.
The End of the Jurassic Period Dinosaurs
Of all of the three classifications of Jurassic period dinosaurs, the Sauropods, the Theropods, and the Ornithopods and of all of the most recognized dinosaurs of the Jurassic era, each had their own distinguishing characteristics which set them apart from each other. Despite all of these classifications of dinosaurs having their own characteristics and evolving from their ancestors primitive forms, not one of them managed to survive the final event which brought the end of the dinosaurs. It was up to the sea-faring and flying prehistoric creatures to carry on life as the dinosaurs knew it.
There Are Many More Jurassic Period Dinosaurs to Cover – Update Published on January 16, 2012
In addition to some of the more popular Jurassic period dinosaurs that have already been covered there is many more that played a large role in the Jurassic era. We will now discuss a few more of these Jurassic period beasts including: the Plesiosaurus, the Archaeopteryx, the Allosaurus, the Rhamphorhynchus and the Dilophosaurus.
The plesiosaurus is a genus of marine reptile that is believed to have existed during the early Jurassic period some 199.6 to 175.6 million years ago. The plesiosaurus is recognized for having a particularly small head with an incredibly long neck and a body that resembles a turtle with a short tail and two pairs of paddle shaped fins. The plesiosaurus is definitely not the longest of marine dinosaur species measuring in at approximately 15 feet long. It is not believed that this large reptile fed on other marine dinosaurs like some of the Cretaceous period marine reptiles, rather the plesiosaurus likely fed on fish and belemnites. There is currently only one species of plesiosaurus known to have existed: Plesiosaurus dolichodeirus.
The archaeopteryx is one of the more well-known of the Jurassic period dinosaurs. While many people claim that this birdlike dinosaur was the first bird to ever exist, much disagreement exists as many other believe that archaeopteryx was simply a link between dinosaurs and birds. This bird like dinosaur is believed to have flown the skies of Earth in the late Jurassic period somewhere between 150.8 and 148.5 million years ago. Most reports of the archaeopteryx state that this high-flying reptile was native to what is now southern Germany. The archaeopteryx was not a particularly large dinosaur in comparison to other dinosaurs of the Jurassic period and measured in at around 1.6 feet long. Since the archaeopteryx had many more physical characteristics in common with reptilian dinosaurs than with birds yet it was still able to fly, it plays an important role in the development of the bird from dinosaurs. The most important factor implicating the archaeopteryx in the link between dinosaurs and birds is the presence of feathers in many of the archaeopteryx fossils that have been recovered to date. The raven sized archaeopteryx is believed to have weighed in at roughly 1.8 to 2.2 lbs.
The Allosaurus was a large theropod dinosaur that roamed the Earth during the late Jurassic period some 155 to 150 million years ago. Allosaurus is important because it was one of the first well-known theropod dinosaurs. Like other well-known theropods, Allosaurus is a large and bipedal predator with large muscular hind legs and particularly short forearms. The Allosaurus had particularly large teeth that had saw-like edges and curved towards the back of the mouth to facilitate the movement of food to the back of the throat. The skull of the Allosaurus is like that of many theropods and is extremely large sitting on a smaller neck. The weight of such a large skull is counterbalanced by the long tail that theropods are known for. The largest known specimen of the Allosaurus measured in at around 32 feet long, however, it is stated that the average size for this carnivore is more likely to be around 28 feet. This large theropod is shockingly small when compared to theropod Tyrannosaurus Rex, Allosaurus weighs in at a small 2.3 metric tons. Allosaurus may not have been as large as the Tyrannosaurus but that did not stop this theropod from feeding on large dinosaur species.
The Rhamphorhynchus is another flying dinosaur that flew the skies of the Earth during the late Jurassic period some 150 to 148 million years ago. Rhamphorhynchus is recognized for having a long tail in addition to a beak-like snout that had many needle like teeth. The presence of teeth in the beak of Rhamphorhynchus suggests that this reptile fed on a diet of mainly fish and small insects. There is one species of Rhamphorhynchus currently known to date: Rhamphorhynchus muensteri. The largest Rhamphorhynchus specimen recovered to date measures 4.1 feet long and has a wingspan of 5.9 feet. Unlike many of the other flying reptiles of the Jurassic period, Rhamphorhynchus is not recognized for having a cranial crest. A number of fossilized Rhamphorhynchus specimens have been found but the most complete show a presence of not only bones but they also show impressions of the wing membranes and the soft tissues of individual dinosaurs as well. This intricate type of fossil allows for paleontologists to find out much more about this late Jurassic high flyer.
The Dilophosaurus was a small theropod dinosaur that roamed the Earth some 193 million years ago during the early Jurassic period. Ironically while Dilophosaurus is noted as being one of the first Jurassic theropods it is not very well understood by paleontologists. It is believed that Dilophosaurus measured in at around 20 feet long and weighed around half a ton. The most distinguishing feature of this theropod was the presence of two round crests that were found on the skull. Most paleontologists believe that the cranial crests of Dilophosaurus were utilized for display purposes perhaps in attracting a mate and scaring off predators or other males from mating with “claimed” females. Like the other theropods covered in this article, Dilophosaurus had longer more muscular back legs that supported the body and shorter forelimbs. The long tail of Dilophosaurus would have served to balance out the dinosaur as it ran on its back legs. The teeth of Dilophosaurus are particularly unique in their lay out with a notch that sits behind the front teeth which indicates that rather than capturing its own prey Dilophosaurus was most likely a scavenger feeding off dead carcasses that had already been picked over by other dinosaurs. The biggest misconception about Dilophosaurus that has been attributed to this Jurassic beast through modern media (specifically the Hollywood film Jurassic Park) is that this dinosaur spat poison to incapacitate enemies. There is no indication that the Dilophosaurus was ever capable of spitting poison.
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