Was T.rex The King of the Dinosaurs

By Cara Patel

Heathfield School

Centre Number: 12728

Candidate Number: 3680

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ContentsIntroduction...........................................................................................................................................3

Teeth and Jaws......................................................................................................................................4

Shape:................................................................................................................................................4

Teeth Marks on Bones:......................................................................................................................5

Big Brain................................................................................................................................................7

Arms....................................................................................................................................................10

Strength...........................................................................................................................................10

Protection........................................................................................................................................10

Leg Bones and Speed...........................................................................................................................12

Modern Fast Animals:......................................................................................................................12

Studies Done To Estimate T.rex Speed............................................................................................12

My Own Study.................................................................................................................................14

Prediction:...................................................................................................................................15

Data:............................................................................................................................................15

Graph:..........................................................................................................................................15

Statistical Analysis:..........................................................................................................................16

Evaluation:.......................................................................................................................................16

Conclusion:......................................................................................................................................17

Miscellaneous......................................................................................................................................18

Tyrannosaurus Sue..........................................................................................................................18

Ecosystem........................................................................................................................................18

Conclusion...........................................................................................................................................19

Appendix 1 – Statistical Analysis..........................................................................................................20

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IntroductionThe Tyrannosaurus Rex (T.rex) was first discovered by Barnum Brown in 1902 (despite the

mix up described by Jack Horner as “He didn’t realise that ... T.rex had already been discovered, twice, one of those times by himself” i). Archaeologists and scientists assumed that it was a fearsome predator. Just at a glance, features like the massive jaw with serrated teeth and sharp claws lead to this conclusion.

Henry Osborn named the skeleton that Barnum Brown had excavated Tyrannosaurus Rex meaning “Tyrant Lizard King” in Latin. There have been several variations of this: “The King of the Dinosaurs” i, “The King” ii, “Dinosaur King” iii and “King Lizard” iv.

The T.rex is the most famous dinosaur known to man with its appearance in films i.e., “King Kong”, “The Land Before Time”, “King Dinosaurs” and “Jurassic Park”, in books and even in the theatre – “Walking With Dinosaurs, The Arena Spectacular” at Wembley Arena.

To earn the title of “The King of the Dinosaurs”, the T.rex would have had to have been a successful hunter and a deadly killer. In the present day, there are many aspects that make a successful predator the most important being a means of killing prey, such as, claws/sharp teeth/tool etc. Some animals rush at prey with a burst of speed, like the cheetah, some lay in the shadows before pouncing, such as, snakes and others use camouflage to surprise their prey, i.e., the great white shark with a white belly to blend in with the water when prey look up and a dark back to blend in with the water when prey look down.

Recently several scientists have started to challenge the idea of the T.rex being a predator. In this paper I aim to examine the evidence looking at the different parts of the T.rex’s predatory weaponry separately including teeth, arms, legs, speed and brain, and come to my own conclusions.

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Teeth and Jaws

Shape:When the first T.rex skeleton was found, the archaeologists saw that the teeth were sharp

and assumed that the T.rex was a predator. This view was shared by the scientists who studied the fossil. However, since that time, scientists have realised that how sharp a tooth’s edge is, is not the only factor affecting the position of an animal on the food chain. Even in prehistoric animals, there is a huge range in variation of tooth size and shape within the carnivores each having an individual function.

As a predator, the T.rex would have needed thin, dagger-like teeth similar to those found on contemporary predatory dinosaurs such as Velociraptor, as the killers tend to get the best of the kill i.e., the muscle and organs. Kevin Padien – an Evolutionary Biologist of the Padien Lab at the University of California describe the teeth of the T.rex as being “like lethal bananas”v. Shorter sturdier teeth would have still packed a lethal punch with the power of the T.rex’s bite which was “eight times as powerful as a lion’s”vi . Such a powerful bite was caused by “wide cheeks and deep jaws supported bigger, more powerful jaw muscles than those of any other dinosaur we know” says Jack Horner i. Horner – the curator of palaeontology at Montana State University – thinks that the reason for this is that the teeth were not designed for slicing but for bone crushing. If the T.rex had been a scavenger, thick teeth would have been useful as what would be left of a carcass when a predator had finished with it would be the bones and gristle.

Some scientists insist that the teeth were large for such a large carnivore. However, research done by Jim Farlow – a palaeontologist at the Indiana-Purdue University – contradicts this belief. Looking into the proportions between the size of the teeth to the size of the T.rex, he found that “its teeth were oversized” i.

T.rex’s teeth are also serrated. Some scientists for example Phil Currie – a museum curator and a professor at the University of Alberta, Canada, say that the serrated teeth are “beautifully adapted to saw bone and meat” i. There is a general agreement with this view as demonstrated by the fact that The Natural History Museum say “their dagger-like shape and serrated edges were designed to kill, slash and tear”. Another idea (proposed by Bill Abler – a researcher of dinosaur tooth structure in Chicago) is that the serrations provided a home for bacterial colonies in were if pray was bitten, the bacteria would weaken or kill the victim. However this view has little evidence to support it. It is unlikely that bacteria could have survived continual chewing and there are too few living animals that have serrated teeth to make a clear comparison (Komodo Dragon and Sharks).

Some scientists’ ideas contradict the view of the serrations being useful for hunting, one example being Jim Farlow who thinks that the serrations allowed the T.rex to get “a better grip on the victim” i.

From this evidence I conclude that the shape and size of the T.rex’s teeth indicates that the T.rex was indeed a scavenger as the bone crushing power would not have been needed if it was a predator eating the best parts of a kill.

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Teeth Marks on Bones:Until now, teeth marks left on the bones of dinosaurs were a useful tool in the identification

of the position of animals in the food web. Once the animal was identified from the teeth marks, if vaguely resembling a predator, it was assumed that it was responsible for killing the prey. However, in the case of the T.rex, new evidence and re-examination of old evidence suggests differently.

An online article says “bones have been found with tyrannosaurus embedded in them or scratched by them, but so far no study has shown that tyrannosaurus killed other dinosaurs for food” v. There have been a growing number of cases where the teeth marks of the T.rex have been found on the bones of other dinosaurs and, from perspective of the T.rex being a predator, the facts don’t add up.

One interesting example documented in Dinosaurs by Dougal Dixon is of a Triceratops pelvic bone, which raises two issues. The first being that the scrape marks are on the underside of the bone, “from these marks, scientists could tell that a tyrannosaurus bit down ... when the triceratops was already dead”vii. This leads onto the next issue which is that, for a predator, to go for the pelvis of a carcass is an oddity in itself. When a pray animal is killed in the present day, the predator that kills it normally has first pick at the carcass. This is unless a larger predator scares away the first from the carcass or in a pack environment where superiors eat first. Predators typically start with areas that are predominantly muscle for example the underbelly or thigh leaving scavengers to scrape scraps off bones. It is highly likely that ancient animals also exhibited the same behaviour. As a predator it would not be expected for the T.rex bone marks to be left on the underside of the pelvis; this only makes it more likely for the T.rex to have been a scavenger.

There has been one find of a prey animal with T.rex bite marks on the spine, which many believe proves that the T.rex was a predator. An article documenting this find says “because this injury shows subsequent re-growth of bone, this wound was inflicted on a living animal rather than a carcass”viii. One conclusion to draw is that the T.rex was indeed a predator, however as this is a rare find, different scenarios must be considered. There have been skeletons of prey animals where they have been caught by more than one carnivore and due to external factors were able to escape. One example is shown on a BBC documentary – “Planet Dinosaur”. In North Africa 90 million years ago, a juvenile Paralititan got caught in a “deadly game of tug of war” ix says John Hurst (narrator) between a Sarcosuchus and a Carcharodontosaurus. There were tooth marks on the neck and hind leg from the two different predators which showed bone re-growth. Sarcosuchus was an 8 ton crocodilian. However being no match for the 6-15 ton Carcharodontosaurus, it stood down. It is believed that the baby Paralititan was able to escape as members of the heard moved in to protect it. Despite being one of the more fearsome predators in North Africa, an adult Carcharodontosaurus would never pick a fight with a herd of 60 ton Paralititans and the baby was able to escape.

In terms of the T.rex, even an obligate scavenger would not miss up an opportunity to take advantage of another predator’s hunt. Jack Horner says “T.rex was simply the greatest opportunist of them all”i. Despite the attack in North Africa involving different dinosaurs at a different time I believe they can be compared as to find a bite mark from a T.rex showing subsequent bone re-growth is such a rare event when compared to the number of fossils found with T.rex bite marks. It is a possibility that the T.rex took advantage of a predator’s hunt and got a hold on the prey but due to other factors it was able to escape.

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In conclusion, I believe that this evidence strongly supports the T.rex being a scavenger due to the proportion of bite marks found being when an animal was already dead.

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Big BrainIt is said that “carnivorous dinosaurs had the biggest brains for their body size”x. “They

needed such big brains, together with keen senses to track down their prey”x says Firth. However making assumptions on the senses of a dinosaur by simply looking at the overall brain size does not provide any information about the individual senses. To do this, scientists have found ways to measure the brain cavity and to create computer generated images of the brain.

With today’s technology, a T.rex skull can be put through a CAT scan where high quality images and in-depth analysis can be carried out. It is a preferable method as the skull is not damaged but this is costly as no hospital CAT scanner in the world is large enough to fit such a mammoth head. However, in America there has been one built that is large enough and through this new light has been shed on the brain cast of T.rex.

Before the CAT scanner, the only method to analyse the brain cavity was by eye. From data collected by visual examination, scientists believed that the T.rex possessed an acute sense of smell and average eyesight with the possibility of depth perception “it’s likely that T.rex had superior eyesight for a dinosaur”i. By looking at the brain cavity estimates could be made on the proportion of different sections of the brain. From these estimates it was found that the optic lobes were of moderate size whereas “Tyrannosaurus had very large olfactory lobes (the area in the brain used for processing odours)” says Henry F. Osbornxi.

Based on these estimates, scientists drew together theories about the eyesight of Tyrannosaurus. “T.rex had a narrow eye socket” i says Jack Horner which he believed could have produced a sharper image while forward facing eyes caused the belief that the image received by each eye overlapped and created the possibility of judging distances. This would be an extremely useful tool in hunting and provide an advantage over other predators.

It was seen that “there were also many holes for nerves in the snout of the T.rex” i. This coupled with enlarged olfactory lobes created the potential for an immense sense of smell, which would be advantageous to both predators (tracking prey) and scavengers - “a keen sense of smell would help find rotting meat”i.

With the recent CAT scan data, exact values rather than estimates have been possible. The first images of the T.rex brain were shown to be wrong by Lawrence M. Witmer and Ryan C. Ridgely who found that a “portion of the olfactory region of the nasal cavity is the sight of sensory epithelium”xii. The revised image of a brain cast shown on the next page with the relative positions and sizes of the olfactory and optic lobes labelled showing that even with the reduction from original estimates of the olfactory lobes are still large. From this, scientists are now forced to admit that the T.rex had “small, weak, beady eyes”xiii.

The brain cast was compared to that of a scavenger (vulture) and the T.rex brain was proportionally similar to that of a vulturexiv. Jack Horner calls it “the vulture of its day”i.

The new CAT scan data suggests that Tyrannosaurus possessed a keen sense of smell and only average eyesight it has been shown in the modern scavenging species that smell was more

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important than eyesight. The most recent evidence suggests the T.rex was more likely to have been a scavenger.

Cast of the T.rex Brain

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Optic Lobe

Olfactory Lobe

Arms

StrengthIt was originally thought that the arms of the T.rex were unnecessary for survival and so over

time became smaller and weak. Scientists are now starting to think differently, the only question left unanswered is why?

“The arm bones are only three feet long”i which is about the same as the arm length of the average adult human but on a thirteen meter long animal; “in evolution it’s an amazing reduction over earlier tyrannosaurs” i says Jack Horner.

There is a dent left where muscles attach to bone and from the depth, length and shape, an accurate approximation of the size of the muscle can be derived. Scientists Matt Smith and Ken Carpenter used this technique to reconstruct the muscle and tendons of the T.rex. If it is to be assumed that the T.rex had little arm strength, the scars would be shallow and small, however “the arm bones have very distinct muscle scars”i. It was found that although flexibility was not something that Tyrannosaurus could boast of, its strength was immense. Whereas our biceps are around 2 inches in diameter, the T.rex’s were 6 inches. This allowed the T.rex to “hoist four hundred pounds towards its body at one time”i : the same as an adult male lion.

Palaeontologists have been unable to identify a purpose for this strength as the arms could not reach its mouth, they could not help in feeding. Some suggest that they could be used in combat but in close quarters with another dinosaur, the teeth would be a more useful weapon. Tony Gibbons and Robert Shedelon say “It is possible that they were used to lift tyrannosaurs up from resting position”xv which is a reasonable assumption as the animal weighed 4.5-6 tonnes. However due to the length, there is a limit to how much the arms could help.

This evidence supports both the predator and scavenger theories until a more reliable argument is put forward.

ProtectionIn humans, our arms protect us when we fall over. Reflexes mean that we raise our arms as

we fall so that our head is protected. I conducted an experiment to test this by getting someone to push me over. Although not a completely fair test as I was expecting it, to push an unsuspecting victim over without warning or consent would not have been possible for ethical reasons.

Shown on the next page is a freeze frame from the video taken.

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A seen above, I raised my arms so that my head did not hit the ground.

To do this would be impossible for the T.rex as the arms were so small. “Drop a skull from that height and there’s a chance of causing a nasty injury, even a fatal one” i says Jack Horner. This is more likely to be taken into account if the T.rex is considered a predator. To be running at top speed and to fall over would cause more damage than a scavenger, not needing to rely on speed. Even if it did survive such a fall, it is unlikely to survive for very long. Open to infection and possibly unable to eat, there would be very grim prospects for this Tyrannosaur.

I believe its small arms suggest the T.rex was a scavenger and even if the T.rex was capable of great speed (as I discuss in the next section), to do so would have been too much of a risk if it were to fall over.

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Leg Bones and SpeedOne of the most important attributes of predators throughout history is speed. Most if not

all methods of predation require the predatory animal to have a high speed; ambush predation, the use of poison or tracking prey over long distances all require prey to be first caught. As Gregory S.Paul says, “there are no slow predators” (Limb design, function and running…).

Henry Osborn was of the opinion that the “tyrannosaurus was unquestionably fleet of foot” (the complete T.rex) a view that was held by The New York Times that advertised the find calling it a “swift two-footed tyrant”.

Modern Fast Animals:P. David Polly conducted a study in which he compared many modern animals comparing

their category and their speed. He found that the graviportal animals (animals with large body mass) were the low speed animals as opposed to the cursorial animals (fast running animals)xvi.

The fastest land mammal is the cheetah which has many adaptations enabling it to reach maximum speeds of 70-75 mph. When looking at these adaptations, it is seen that some are shared with the T.rex and some aren’t.

Both the T.rex and the cheetah have “long legs”xvii for propulsion and “rigid paws”xvii - or feet in the case of the T.rex - for traction. They both have a long tail (in the cheetah, “the tail adds 60-84 extra cm to the length”xvii). It is also indicated by fossils that the T.rex had large lungs and nostrils, a trait shared with the cheetah. If the T.rex was a scavenger, each of these characteristics could be useful if used for different functions. Long legs and rigid feet would be useful for distance walking, long tail would counterbalance the T.rex’s large head and large nostrils would allow for better detection of the smell of a carcass from a further distance.

There are many traits that the cheetah has that the T.rex lacks. The cheetah has a “flexible spine: acting as a spring” xvii while hitting high speeds. The T.rex had a very rigid spine to the extent that simply maintaining the upright position would cause possible “dislocation of several joints, including the articulation between the head and the spinal column”xviii. The cheetah is “small with a slender streamline body” while the T.rex weighing 6-8 tonnes, was not.

One of the most noticeable differences is that the cheetah has a “small aerodynamic head”xvii which is extremely different to the T.rex where Lawrence Witmer and Rian Ridgely claim that their estimate of the weight of the T.rex head of 515.5kgxix is the most accurate to date. This is more than the weight of a pregnant polar bear.

Simply comparing traits of the two species, this indicates that the ability of the T.rex to reach high speeds is highly unlikely.

Studies Done To Estimate T.rex SpeedThere have been many experiments conducted and estimates of speed for the T.rex

calculated have been over a huge range. For example, Bob Bakker estimates the T.rex to have reached speeds of 40-42 mph while Jim Farlow argues that it could only reach a maximum speed of

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25mph. Some scientists even insist that the top speed was merely 10 mphxiii. Each test looks at a different aspect of the Tyrannosaurus leg functions and bases speed assumptions from this.

Some of the studies conducted look at the structure and shape of the actual leg bones. Jack Horner and Don Lesson look at the thickness of the leg bones compared with smaller predators. They said that “T.rex’s bones were far stouter than those of mid-sized predators … designed to compensate for the stress associated with fast running”i. However they then make reference to several other studies done about T.rex speed and say that no definite conclusion could come from this data.

Studies of the bones have also revealed extensive muscle scarring. The evidence for the T.rex having a considerable mass of leg muscle supports both the scavenger and predator argument as “if it were a scavenger, it would have had to roam around looking for carrion. If it were a hunter, it would have had to track down pray”i. The extensive leg muscle is also what fuelled the idea that the T.rex stood up on its hind legs: “Tyrannosaurus ran upright on its powerful hind legs”xx.

Gregory S. Paul also looked at the structure of the leg bones, his main focus being on the flexibility of the joints as the size of the animal increased looking at the T.rex compared to several other species some being fast runners and some slow. His main argument was that “animals designed in a similar, manner function and perform in a similar manner”xxi. From looking at the flexibility of the ankle bones in particular, he found that “they maintained remarkably uniform, flexed jointed limbs suited for running at high speeds”xxi. He estimated that the T.rex could have reached speeds of 37 mph. This is assuming that structures that are the same are used in the same way in different organisms. An example where this is not the case is described by R. McNeill Alexander where he says “Humming birds hover, vultures cannot. Vultures soar and humming birds do not”xxii.At the time the paper by Gregory S. Paul was written (1998), he admits that “a comprehensive scaling study has not been performed”xxi which might provide a greater degree of accuracy into this debate.

Since then, many scaling models have been done. One of the most recent models was done by a US team who looked at the most up to date estimates of T.rex weight and used this to find flexibility while running at speeds. Despite some scientists putting forward the idea that the T.rex could have weighed 3-4 tonnes, they say that the most recent estimates show that 6-8 tonnes would be a more accurate measurement. Predators also need to possess the ability to turn quickly during hunting to be able to out-manoeuvre prey and avoid dangers as is the case for modern predators. However, the results from this test state the opposite with regards to the T.rex. They claim that tyrannosaurus “hardly reached 25 mph and required a couple of seconds to turn 45o”xxiii indicating that chasing and hunting its prey to obtain food would be unlikely if not impossible.

Other models have been created by using a combination of scaling and muscle mass. John R. Hutchinson and Marlano Garcla constructed a model that estimated the mass of extensor muscle required in the legs required for running. The models predicted that “in order to be a good runner it required 80% of its weight to be in its leg muscles, which is next to impossible”xxiv. The results from this study indicate that the T.rex could have never reached high speeds. This study concluded that a T.rex running at 11-20 m/s would have “been near or above its maximum muscular capacity”xxv.

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A similar model was done by another team by scaling up modern animals to T.rex size. The test they conducted was to see what proportion of the overall weight of the T.rex would need to be in its legs to be able to run. They used the chicken as birds are the dinosaurs’ closest living relatives and a chicken walks on its two hind legs. Their research showed that although “a chicken could run with only about 9% of its mass in its legs”xxvi as a minimum (most having approximately 11-15%), “a tyrannosaurus sized chicken would need an impossible 99% of its body mass in each leg to run” xxvi.

Calculations of speed have also been drawn from fossilised dinosaur tracks. Adam Hibbert says “study of fossil foot prints suggests that T.rex walked at about human speed” iv and from this, scientists then scaled up speeds of running. However some scientists, for example Jack Horner i, remain sceptical about conclusions drawn from fossilised tracks for several reasons:

It is hard to positively identify the species that left the footprints. Footprints are only fossilised if they are made in areas of soft ground. If this is so, the

animal would not be travelling at top speed on such terrain. Running at full speed, there is a large distance between each footprint, David Burnie

saying “it took paces nearly 5m long”xxvii. It is possible that only a few footprints were made on ground suitable for them to be fossilised.

More than one individual of the same species may have walked the same pathway or the same individual repeatedly using the pathway which may distort a single track.

Other tests have included a group that conducted tests to measure the distance nerve impulses could travel in a given time. From their calculations, nerve impulses travelled at a “basic speed limit of 180 feet per second”xxviii. Calculating the time it would take for nerve impulses in a T.rex to travel from the foot, up the leg and along the spinal cord to the brain, they found that if a T.rex were to injure its foot, then it would not realise it until several seconds afterwards where it could potentially do irreversible damage while continuing to run. During the study, the T.rex is compared to the elephant which they state “can’t run too fast or they’re effectively running blind”xxviii. The study concluded that “the mighty Tyrannosaurus Rex was no quick, agile killing machine … it would have needed to move slowly to feel with its feet”xxviii. The test does not however suggest that higher speeds in T.rex were impossible.

Some scientists now believe that dinosaurs were evolving beyond the limits of modern reptiles and becoming warm blooded. Fossil evidence suggests that “T.rex had little internal body temperature variation”i . Although the ability to regulate body temperature is considered a trait of animals with high metabolic activity, “it does not mean that T.rex was a fast runner” i.

There is a range of different estimates for T.rex but the evidence suggests that it was simply too slow and inflexible to catch prey.

My Own StudyI decided to conduct my own study and to make my own estimate on the speed of the T.rex.

It is thought that faster animals have a longer tibia compared to their femur. I plotted a scatter graph of the ratio of Tibia over Femur to speed of modern animals to test for a correlation and then plotted the T.rex with regards to the bone ratios to estimate the speed.

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Prediction:The ratios were determined by calculating the tibia length over the femur length. Assuming

that faster animals have a longer tibia, slower animals have a ratio of <1 and faster animals have a ratio of >1.

Data:* lengths of the leg bones of the T.rex were from the documentary “Valley of the T.rex”xiv.

** taken from the paper “limb designs and functions ...”xxi. (All other measurements were made by me using the bones at Heathfield School and Roehampton University)

***(calculated as assumed to be 60% of a race horse)

For sources of average speeds, refer to bibliography.

Species Femur /mm Tibia /mm Ratio (Tibia/Femur) Average Speed /mph

T.rex* 1270.0 1168.4 0.92 ?Race Horse** - - 0.88 42.50Rhino** - - 0.65 15.53Elephant** - - 0.55 25.00Human 441.0 340.0 0.77 22.00Rabbit 105.0 105.0 1.00 35.00Pony 275.0 380.0 1.38 25.50 ***Sheep 200.0 120.0 0.60 25.00Giant Anteater 230.0 204.0 0.87 31.00Platypus 38.0 67.0 1.76 22.00White Ruffed Lemur 145.0 132.0 0.91 12.00Rhesus Macaque 147.0 130.0 0.88 35.00Striped Skunk 61.0 62.0 1.02 10.00Mara (in the rodent family) 120.0 149.0 1.24 10.00Rat 29.5 32.9 1.12 8.00Cat 110.1 113.7 1.03 30.00Gibbon 209.0 184.0 0.88 35.00Chimp 288.0 250.0 0.87 25.00Wallaby 124.9 130.0 1.04 30.00Small Antelope 125.0 130.0 1.04 43.00Penguin 78.7 72.3 0.92 2.05 (on land)Pig 234.0 206.0 0.88 11.00Ostrich 280.0 500.0 1.79 40.00

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Graph:

0.5 0.75 1 1.25 1.5 1.75 210

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20

25

30

35

40

45

Bone Ratio

Anim

al S

peed

/m

ph

Figure 1: Scatter Graph Showing Animal Speed /mph Plotted Against Bone Ratio

Statistical Analysis:(See Appendix 1)

Regression line equation y = a + bx

a = 19.25269 b = 11.99857

y = 19.25269 + 11.99857x

when x = 0.92

y = 30.29

Estimated Speed: 30.29mph

Evaluation:The data is less accurate than if the average bone lengths for each species were used but as

this information was not available, it is assumed that the ratios are the same. My sample size was small decreasing the accuracy of my results however the accuracy of the bone lengths was to a tenth of a mm.

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Regression Line

Conclusion:The top speed of a Triceratops is estimated at 35mph. From my calculations a T.rex could

not outrun a Triceratops at top speed. A T.rex did not have the speed or the manoeuvrability needed to take down prey and therefore it is more likely to have been a scavenger.

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Miscellaneous

Tyrannosaurus SueSue was the name given to the T.rex found by Sue Hendrickson in South Dakota. The

skeleton is particularly important because it is over 90% complete i but what intrigued scientists was her sheer size – “Sue’s thigh bone (femur) measures fifty-four inches long” i. Few dinosaurs reached old age because of the dangers they faced on a daily basis.

Sue sustained several injuries throughout her life which showed re-growth of bone, one of these injuries being of particular importance. Sue had broken foot bones which were most likely caused by the foot being stepped on by another T.rex if a few were “battling over a corpse” i.

With this injury, as a predator, it would have been impossible for a T.rex to hunt for food. It is possible that a T.rex could have changed from predation to scavenging to obtain food but this is unlikely. Sue would have had the best chance for survival if she had been an obligate scavenger.

EcosystemChris Carbone and team (at the Zoological Society of London) conducted a study calculating

“the range in which T.rex could roam on a daily basis, how many dead dinosaurs it was likely to come across and what other foragers might be around”xxix.

His research concluded that “it is extremely unlikely that an adult T.rex could use scavenging as a long-term sustainable foraging strategy”xxix as “fossil records show that the ecosystem at the time would have been overwhelmingly populated by smaller dinosaurs”xxix.

This research supports the T.rex being a predator assuming that the proportions of dinosaurs of different sizes will not change as new dinosaurs are discovered. “There is a new species described every seven weeks on average”i says Jack Horner. In time, the proportion of larger dinosaurs that were in the population may increase as more fossils are uncovered.

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ConclusionThere are two types of science. One is where you look at the evidence and draw conclusions

from it. The other is where you have a pre-decided conclusion and find evidence to support it. I believe the first is better as it avoids bias. However many scientists use the second with regard to the predator/scavenger argument.

As with many aspects of science, there is no definite answer. We can only give the best estimate with the evidence we have at the time.

As a result of my research I have concluded the following:

The teeth were the wrong shape and size to have been used to kill. Teeth marks left on bones were left by that of a scavenger. Brain proportions follow the pattern of modern scavengers. The arms were of little use both in combat and if the T.rex were to fall over. Reaching high speeds would have been impossible.

I believe it is near impossible for the T.rex to have used predation as the main source of its food. The vast majority of evidence supports this view with a few exceptions that could be applicable to either predator or scavenger. Many arguments supporting the T.rex being a predator have now been disproved due to improvement in analytical techniques or simply by taking another look at the fossils.

I am not suggesting however, that it is impossible that if a T.rex were to encounter an animal on its last legs that it wouldn’t have been able to kill it.

I would love to believe that the T.rex had been the diabolical murderer that it is made out to be in the media and scientific studies but the evidence does not support this hypothesis.

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Appendix 1 – Statistical AnalysisFrom the statistical analysis, I have removed the platypus because its speed was measured

as it moves through water; the lemur, rat, penguin, skunk and mara as their small size limits the speed at which they travel and the pig as it has been breed to be so overweight that this affects how fast it can move.

x(ratio)

y(speed)

X2 Y2 xy

0.88 42.50 0.7744 1806.2500 37.4000

0.65 15.53 0.4225 241.1809 10.0945

0.55 25.00 0.3025 625.0000 13.7500

0.77 22.00 0.5925 484.0000 16.9400

1.00 35.00 1.0000 1225.0000 35.0000

1.38 25.50 1.9044 650.2500 35.1900

0.60 25.00 0.3600 625.0000 15.0000

0.87 31.00 0.7569 961.0000 26.9700

0.88 35.00 0.7744 1225.0000 30.8000

1.03 30.00 1.0609 900.0000 30.9000

0.88 35.00 0.7744 1225.0000 30.8000

0.87 25.00 0.7569 625.0000 21.7500

1.04 30.00 1.0816 900.0000 31.2000

1.04 43.00 1.0816 1849.0000 44.7200

1.79 40.00 3.2041 1600.0000 71.6000

Σx14.23

Σy459.53

Σx2

14.8475Σy2

14941.6800Σxy

452.1145

Total Sample Size (n) = 15

Sxx= Σx2 – ( (Σx)2/n )

= 14.8475 – (14.232/15)

= 1.34797

19

Syy= Σy2 – ( (Σy)2/n )

= 14941.68 – (459.532/15)

= 863.82527

Sxy= Σxy – ( (ΣxΣy)/n )

= 452.1145 – ((14.23x459.53)/15)

= 16.17371

PMCC (r)

r = Sxy/ [√(Sxx x Syy)]

= 16.17371/ [√(1.3497 x 863.82527)]

= 0.4743...

= 0.47

0<r<1 therefore positive correlation

Regression Line

b = Sxy/Sxx

= 16.17371 / 1.34797

= 11.99857

a = (Σy/n) – [b x (Σx/n)]

= (459.53/15) – [11.99857 x (14.23/15)]

= 19.25269

y = a + bx

y = 19.25269 + 11.99857x

when x = 0.92

y = 30.29

this is interpolation as 0.92 is between 0.55 and 1.79

Estimated Speed: 30.29mph

20

iReference and Bibliography

The Complete T.Rex by Jack Horne and Don Lesson - Souvenir Press (1993)ii Dinosaur by Dr David Norman and Dr Angela Milner – HarperCollins (1992)iii Dinosaurs by Stephanie Turnbull – Usborne (2003)iv Dangerous Dinosaurs by Adam Hibbert – Ticktock Media Ldt. (1999)v http://www.ucmp.berkeley.edu/diapsids/saurischia/tyrannosauridae.htmlvi London’s Natural History Museumvii Dinosaurs by Dougal Dixon – Hamlyn (1988)viii http://www.dinosaur-world.com/tyrannosaurs/0_tyrannosaurs.htmix BBC Documentary – Planet Dinosaur (2011)x Dinosaurs by Rachel Firth – Usborne (2001)xi Dinosaurs and Prehistoric Life by Hazel Richardson – Dorling Kindersley Publishers (2003)xii New Insights into the Brain, Braincase, and Ear Region of Tyrannosaurus (Dinosauria, Theropoda), with Implications for Sensory Organisation and Behaviour by Lawrence M. Witmer and Ryan C. Ridgely – paper published in The Anatomical Record (2009)xiii http://dinosaurs.about.com/od/dinosaur controversies/a/trexhunter.htmxiv Discovery Channel Documentary – Valley of the T.rex (2001)xv Dinosaur Atlas by Tony Gibbons and Robert Shedelon – Parragon (2002)xvi Principles of Locomotion: Functional Morphology and Artistic Reconstructions by David Polly – Department of Geological Sciences at Indiana University (2011)xviihttp://www.bio.davidson.edu/people/midorcas/animalphysiology/websites/2011/Ptaschinski/Builtforspeed.htmxviii http://en.wikipedia.org/wiki/Tyrannosaurusxix Paper by Lawrence M. Witmer and Ryan C. Ridgely – The Anatomical Record vol. 291 no.11 (2008)xx The age of the dinosaurs by David Lambert – Kingfisher Books (1987)xxi Limb Design, Function and Running Performance in Ostrich – Mimics and Tyrannosaurus by Gregory S. Paul – Paper published in GAIA (1998)xxii Principles of Animal Locomotion by R. McNeill Alexander – Princeton University Press (2006)xxiii http://news.softpedia.com/news/T-rex-was-slow-and-clumsy-56469.shtmlxxiv http://www.rvc.ac.uk/SML/Projects/TRex/Summary.cfmxxv Tyrannosaurus Was Not a Fast Runner by John R. Hutchinson and Marlano Garcla – http://www.rvc.ac.uk/aboutus/staff/jhutchinson/files/JRH5.pdfxxvi http://www.nature.com/news/2002/020228/full/news020225-5.htmlxxvii The Kingfisher Illustrated Dinosaur Encyclopedia by David Burnie – Kingfisher (2001)xxviii http://news.nationalgeographic.com/news/2010/06/100629-science-dinosaurs-t-rex-nerves-elephants/xxix http://news.discovery.com/animals/dinosaurs/tyrnnosaurus-rex-hunter-scavenger-110126.htm

Other Sources A Dinosaur Life by Dr Brian Knapp First Encyclopaedia of Dinosaurs and Prehistoric Life by Sam Taplin – Usborne (2004) Teratophoneus Curriei article by BLM http://news.nationalgeographic.com/news/2009/08/090811-t-rex-dinosaurs.bully.html http://news.bbc.co.uk/l/hi/sci/tech/3112527.stm The American Museum of Natural History’s Book of Dinosaurs: and Other Ancient Creatures by Joseph

Wallace Dinosaurs: The Textbook by Spencer G. Lucas The Dinosaur Heresies by Robert Bakker T. Kuhn Meets T.rex: Critical Conversations and New Directions in Science Centres and Science Museums –

Paper in Studies in Science Education vol. 37 (2002) Encyclopedia of Dinosaurs Edited by Philip J. Currie and Kevin Padion The Great Dinosaur Controversy by Keith M. Parsons The evolution and Extinction of the Dinosaurs by David E. Fastovsky and David B. Weishampel Muscle Moment Arms of Pelvic Limb Muscles of the Ostrich by N. C. Smith, R. C. Payne, K. Jesper and A. M.

Wilson – Paper published in Journal of Anatomy (2007)

http://www.montana.edu/wwwes/facstaff/horner.htm http://videos.howstuffworks.com/discovery/7172-t-rex-brain-clues-video.htm http://australianmuseum.net.au/Uploads/Images/8200/T.%252520rex%252520brain%252520cast

%252520F.112624_.jpg&w=526&h=395&ei=l0xcUJ6TNKO70QXx0oCIBA&zoom=1&iact=rc&dur=70&sig=109815355484716038217&page=1&tbnh=145&tbnw=258&start=0&ndsp=14&ved=1t:429,r:0,s:0,i:71&tx=202&ty=84

http://www.google.co.uk/imgres?q=T.rex+brain&num=10&hl=en&safe=active&biw=1024&bih=673&tbm=isch&tbnid=PCtPzW6IJlQ6OM:&imgrefurl=http://australianmuseum.net.au/image/Tyrannosaurus-rex-brain/&docid=60jklhtxsK2lAM&imgurl

http://www.ucmp.berkeley.edu/people/padian/home.php http://en.wikipedia.org/wiki/Polar_bear http://en.wikipedia.org/wiki/Sue_(dinosaur)

Sources of Animal Speeds:

http://wiki.answers.com/Q/What_is_the_speed_of_a_rhino http://wiki.answers.com/Q/What_is_the_speed_of_a_penguin http://www.saczoo.org/document.doc?id=270 http://en.wikipedia.org/wiki/Talk%3AAntelope http://a-z-animals.com/animals/platypus/ http://a-z-animals.com/animals/lemur/ http://a-z-animals.com/animals/skunk/ http://a-z-animals.com/animals/rat/ http://a-z-animals.com/animals/gibbon/ http://a-z-animals.com/animals/sheep/ http://a-z-animals.com/animals/chimpanzee/ http://a-z-animals.com/animals/wallaby/ http://www.fossilguy.com/articles/montana_tric/tric_topic.htm