Read Dinosaurs Without Bones for Free Online Page B

wasn’t supposed to run.
    Speaking of sauropod trackways, their patterns can be further placed into two categories based on their widths: narrow gauge and wide gauge . These terms are borrowed from railroads, in which the rails are either narrowly spaced (light rail) or widely spaced (freight trains). For bipedal dinosaurs like theropods and most ornithopods, their normal trackway patterns show they were walking, although some have been interpreted as slow walking, fast walking, or running. Their trackways have an alternating right–left–right pattern, and most are probably narrower than the body width of the dinosaur that made them, especially for theropods. They did this by rotating their legs inward with each step forward, as if they were fashion models sashaying down a runway.
    To figure out the approximate size of a dinosaur from its footprint, you’ll need to use a formula. No worries, it’s an easy one. Take the length of a theropod or ornithopod track and then multiply it by four. The resulting number gives the approximate hip height of the dinosaur:
H = 4 l
    where H = hip height and l = footprint length.
    For example, let’s say you find a definite theropod track—longer than it is wide, relatively thin toes, with sharp claw marks—and it is about 35 centimeters (14 inches) long. Let’s see: 35 cm 3 4 = 1.4 m, which translates to about 55 inches, or four and a half feet off the ground. That’s an intimidating height, especially if you think about it in human-meets-dinosaur terms, as a horizontally oriented predatory theropod would be staring directly in the faces of most people, and with the rest of its body behind it.
    Okay, now for a more complicated formula:
V = 0.25 g –0.5 s 1.67 h –1.17
    In this, V is velocity, g is the acceleration of a free-falling object, s is stride length, and h is hip height, which you’ve already tackled. Originally devised in 1976 by a paleontologically enthused physicist, R. M. Alexander, this formula took into account the size (mass) of an animal as part of its forward momentum (the “ g ” in the equation relates to gravity), while also expressing the common-sense principle that, all other things being equal, short strides between tracks means an animal was moving slower, and longer strides means it was moving faster.
    But not all things are equal in this relationship, either. For instance, if a chicken were forced to race against an elephant, it has a decided disadvantage of its leg length being much shorter than that of a typical elephant. Chicken leg lengths are more or less proportional to their foot lengths, which can be readily seen in their growth from a small chick to a full-sized roaster. In other words, relatively long strides measured between tracks made by a small-footed and short-legged animal implies it was moving faster. Alexander’s formula was also based on modern animals, in which he used measured speeds, body masses, and stride lengths of many two- and four-legged animals to establish a baseline for comparing these to dinosaur trackways.
    Fortunately, there is a simpler way to express this equation and get a quick-and-dirty sense of whether a dinosaur was walking slowly, trotting, or running. This is to look at stride length versus hip height as a ratio, called relative stride length . As an example, let’s take our previously mentioned theropod with the 35-cm long footprint and 1.4 m hip height. Let’s say its stride was measured as 2.8 m (about 9 feet). So its relative stride length is 2.8 m/1.4 m, which = 2.0. Basically, Alexander proposed that relative stride lengths of 2.0 or less reflect walking, 2.0–2.9 trotting, and >2.9 running. This means our hypothetical theropod was likely walking. Using the fullformula, this corresponds to a calculated speed of about 3 m/s, or 10.6 kph (6.6 mph).
    How fast is that in practical everyday terms? Olympic racewalkers regularly exceed 15 kph, which they can keep up for 20 km (12.4 mi). However amusing it