Geoscience Reference
In-Depth Information
The first discovered running-dinosaur trackways were from a site in Texas,
where at least three theropods moved at high speed. These dinosaurs had footprints
ranging from 29 to 37 cm (11.4-14.5 in) long, which are not much longer than
many people's shoe sizes. Yet they were taking strides that measured 5.4 to 6.6 m
(17-22 ft)! Once these numbers were crunched through Alexander's formula, the
tracks spoke of speeds of 8.3 to 11.9 m/s (27-39 ft/s), or 30 to 43 kph (19-27 mph).
To put it into a bipedal-human perspective, the top speed recorded by Usain Bolt
over200m(656ft)duringthe 2012Olympics was also 27mph,meaning that these
dinosaurs and he would have had a very good race, perhaps with an outcome only
affected by who was pursuing whom. But we also have no idea if these running di-
nosaurs were actually reaching their top speeds or not on whatever day their tracks
happened to get preserved for us to see millions of years later. Theropods and hu-
mans alike, though, would be humbled by the top speed recorded for a cheetah
(
Acinonyx jubatus
), which from a standing start and over 100 m (328 ft) has been
clocked at 98 kph (61 mph).
Nonetheless, a dinosaur tracksite in Queensland, Australia out-does the Texas
tracksite for sheer numbers of running dinosaurs. This tracksite is worth its own
chapter,becauseitwasn'tjustonedinosaurtrackwaybutnearlyahundred,suggest-
ingdinosaursall withrelatively small footprints skedaddling, scampering, booking,
bolting, or otherwise traveling quickly (for them), which was at about 12 to 16 kph
(7.5-10 mph). Even more significant, it was a mixed group of small ornithopods
and theropods all moving in the same direction. However, this interpretation has
undergone some recent scrutiny and reinterpretations, which we'll take up in detail
later.
To better understand what running-dinosaur tracks look like, we often turn to
modern examples that can serve as search images for finding these, and not look-
ing to cheetahs. Instead, we observe large bipedal flightless birds. For example,
the fastest bipedal land animals today are ostriches (
Struthio camelus
), which have
maximum speeds of 45 mph (72 kph). Less speedy—but still much quicker than
