Allosaurus fragilis:A Paleobiological Analysis
Taxonomy of Allosaurus fragilis
Allosaurus fragilis
Kingdom:Animalia
Phylum:Chordata
Class:Sauropsida
Superorder: Dinosauria
Order:Saurischia
Suborder:Theropoda
Infraorder:Carnosauria
Family:Allosauridae
Genus:Allosaurus
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Period:Late Jurassic
Ages:Kimmeridgian,Tithonian
Time Span:199.6 - 145.5 MYA
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Anatomy
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Length:8.5 meters(30ft) some specimens 12 meters(40ft)
Height:5.2 meters(17ft)
Weight:2.3 t(2.5 S/T)
Diet:Carnivorous
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Allosaurus fragilis has typical Carnosaur characteristics. A large skull,short neck,reduced forelimbs and sharp teeth.Like many other dinosaurs, it most likely had pebbly leathery scales. Allosaurus had three fingers and three toes. It's feet have been described as "hoof like" by Paleontologist Gregory S. Paul. The skull of Allosaurus , like the skull of Tyrannosaurus, contained large openings (fenestrae) which reduced the weight of the skull and provided a place to attach the powerful jaw muscles needed for an apex predator. Like the bones of modern birds and other theropods, Allosaurus bones contained a "honeycomb" structure which lightened their weight even further.
As we can see from the skull,Allosaurus had binocular vision,meaning it's eyes faced forward,It's brain case shows that it had large olfactory bulbs which indicates it had a good sense of smell.This is seen in many predatory animals,even today. The skull is light, yet strong. This allowed Allosaurus to go after large Sauropod dinosaurs like Diplodocus and still be able to hunt smaller dinosaurs. The dental structure is similar to that of Allosaurus' Archosaurian cousins crocodilians. The teeth were socketed in the jaw and were routinely replaced when they fell out. This is in stark contrast with reptiles like lizards who have their teeth fused to their jaw. The animal also had two small horns on top of it's head.The purpose of these horns still remains unclear, but scientists estimate they could have been used for fighting off other Allosaurus for mating or other ritualsand for display purposes.
Unlike the small arms of Tyrannosaurus,Allosaurus' forearms were not nearly as useless. Skeletal remains show the arms had great muscular power. This is true of all Allosaurids, which never evolved the degree of specialization the Tyrannosaurids achieved. The legs and feet of Allosaurus were not suited for speeds comparable to what members of the Tyrannosauridae family, but scientists estimate Allosaurus could still reach speeds of 30 to 55 kilometers per hour(19-34 MPH).
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Predatory Behavior
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Allosaurus was a vicious and efficient predator. Discoveries of a Stegosaurus neck plate with a U-shaped wound that fits an Allosaurus snout,and scrapes on Sauropod bones that fit Allosaurus teeth show that it hunted large prey in addition to young and sick animals. There are two competing theories on how Allosaurus hunted it's prey. Allosaurus was unusual among large predators in that it had relatively small teeth and a relatively weak bite force. Renowned paleontologist Robert Bakker theorizes that since Allosaurus had the same characteristics as Saber toothed cats (ability to open jaws extremely wide and weakening of the jaw but strengthening of the neck muscles) it hunted in a similar manner. Instead of using "saber teeth" to bite down on the prey, Allosaurus jumped at it's prey with jaws wide open,sinking it's mouth and slashing it's prey's flesh like an axe. While Allosaurus was attacking in this manner,it's powerful forearms would hold fast to it's hapless victim. By using such an attack method, the animal would minimize the risk to itself and maximize the damage done to it's prey. It is postulated, but not known for certain, that Allosaurus may have harbored bacteria in it's saliva, aiding in it's prey's demise.
Another explanation as to how Allosaurus hunted is that it preferred to hunt juvenile or small animals. This view has generally fallen out of favor in recent times. Paleontologists have also theorized that Allosaurus hunted in groups to bring down large prey.Although no concrete evidence of this has been found. Allosaurus was most likely an ambush predator,which snuck up on it's unwary prey. Using the technique proposed by Bakker,Allosaurus could have sheared off chunks of flesh and waited for it's unfortunate quarry to bleed to death or possibly die of infection.
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Social Behavior
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Paleontologist Robert Bakker has postulated,from finds of chewed Sauropod bones and associated Allosaurus teeth,that Allosaurus brought food to their young in "lairs" where the young would wait for the parents to come back. Although there is no other proof for this hypothesis, in fact, evidence has been found that shows wounds on Allosaurus specimens caused by members of the same species. This indicates that encounters with members of the same species could have been anything but loving. Paleontologists have long said that Allosaurus may have hunted in packs to bring down large Sauropod dinosaurs,as doing it alone would have been next to impossible. It is worth noting however that studies of Theropod dinosaurs and modern Crocodilians and birds show that these creatures could have been very territorial. In fact,some paleontologists postulate that the reason Allosaurus skeletons have been found close together is that individuals were feasting on the remains of already dead or cannibalized Allosaurus. This has also been given as an explanation of Bakker's "lairs". The debate is still raging as to which interpretation is true.
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Conclusion
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Allosaurus was the king of the Jurassic world,the image of it's large head,sharp teeth and claws and large stature continue to terrify and delight us. It was a merciless hunter and could even have been a cannibal,but it may also have been a caring parent. Allosaurus fragilis, truly a master of it's role.
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Sources
http://www.dinodata.org/index.php?option=com_content&task=view&id=6026&Itemid=67
http://www.uwyo.edu/GeoMuseum/tour/allosaurus.asp
http://en.wikipedia.org/wiki/Allosaurus
"The Dinosaur heresies", Dr. Robert T. Bakker
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Originally Posted by Bernem
