Geoscience Reference
In-Depth Information
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 or-
nithopod track and then multiply it by four. The resulting number gives the approx-
imate 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,relativelythintoes,withsharpclawmarks—anditisabout35centimeters(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 ac-
count 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,
allotherthingsbeingequal,shortstridesbetweentracksmeansananimalwasmov-
ing slower, and longer strides means it was moving faster.
Butnotallthingsareequalinthisrelationship,either.Forinstance,ifachicken
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
