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Tyrannosaurus

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Manetho
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« Reply #15 on: July 23, 2007, 01:51:44 pm »

The most recent research on Tyrannosaurus locomotion does not specify how fast Tyrannosaurus may have run, but admits that there is little capacity to narrow down speeds further than a range from 17 km/h (11 mph), which would be only walking or slow running, to 40 km/h (25 mph), which would be moderate-speed running. For example, a paper in Nature[71] used a mathematical model (validated by applying it to two living animals, alligators and chickens) to gauge the leg muscle mass needed for fast running (over 25 mph / 40 km/h). They found that proposed top speeds in excess of 40 km/h (25 mph) were unfeasible, because they would require very large leg muscles (more than approximately 40–86% of total body mass.)[73] Even moderately fast speeds would have required large leg muscles. This discussion is difficult to resolve, as it is unknown how large the leg muscles were. If they were smaller, only ~11 mph (18 km/h) walking/jogging might have been possible.[67]

According to Thomas R. Holtz Jr however, it is notable that in terms of any animal as massive as it was (5-7 tons), the tibia/femur and metatarsus/femur ratio of tyrannosaurs are the most gracile known of any animal in the Mesozoic or Cenozoic fossil record.

At the typical size of an adult Tyrannosaurus, gracile limb proportions appear bulky. However, when compared to the hindlimbs of other similarly sized animals, like an elephant (as a modern example), a Triceratops, or Edmontosaurus, the legs of Tyrannosaurus rex are more slender and have relatively longer tibiae and metatarsi.

In relation to other large theropod families, tyrannosaurids had limb proportions that are more gracile. The smaller tyrannosaurids were even more gracile, and the smallest had the same limb proportions to the largest ornithomimids: in terms of measurement, the legs of Alectrosaurus and Gallimimus are identical (Holtz).

Additionally, tyrannosaurids had ornithomimid-like feet, which were smaller and more slender than that of other large theropod families, which would equate to more efficient locomotion as the leg was articulated while the animal was moving.

According to Holtz, with functional morphology as a guide, tyrannosaurids would be better adapted for speed than any other family of large theropod, including allosauroids, megalosauroids and neoceratosaurs. This may not mean that T. rex was capable of the more fantastic speed figures estimated for it, but that it was, for an animal for its size, optimised for speed, and in relevance to the predator/scavenger debate, faster than its prey.[74]

New evidence based on biomechanic computer models suggests Tyrannosaurus had a poor turning circle. According to John Hutchinson, expert on biomechanics at the University of London's Royal Veterinary College in England, Tyrannosaurus would probably have taken one to two seconds to turn only 45° – an amount that humans, being vertically oriented and tail-less, can spin in just a fraction of a second.
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