Geoscience Reference
In-Depth Information
shifted them onto the land. Once paleontologists had the right search images for
sauropod trackways, they started finding them outside of Texas. In the U.S., saur-
opod tracks are also in Colorado, New Mexico, and Utah, as well as in Argentina,
Australia, China, France, Korea, Mexico, Morocco, Switzerland, the United King-
dom, and Zimbabwe, among other places. These tracks are also in rocks from near
the start of sauropods in the fossil record (Late Triassic) to their very end (Late
Cretaceous).Somethingnoteworthyaboutthesesauropodtrackwaysfoundthusfar,
though, is that nearly all show these massive animals walked on emergent surfaces,
such as along coastlines, lakeshores, or river floodplains.
Still, paleontologists wondered: What if dinosaurs other than hadrosaurs or
sauropods went for a swim? How would we know from looking at their bones? For
example, even the most skilled anatomists would be hard pressed to demonstrate
from an elephant's skeleton that these multi-ton animals are capable of swimming
longdistances.YetIndianelephants(
Elephas maximus
)canswimasfaras25miles
(40 km), a feat far better than most humans are capable of. In fact, elephant swim-
ming abilities show one of the probable ways mammoths dispersed to islands dur-
ing the Pleistocene Epoch, where some isolated populations lasted until only about
4,000 years ago. (These elephants also became much smaller after generations of
living on these islands, leading to the oxymoronic condition of becoming “dwarf
mammoths.” But that's another story.)
Justincaseyouwerewonderingwhethertracefossilsmightcometotherescue
again to solve this dinosaurian mystery, you would be right (again). First, as early
as 1980, a paleontologist interpreted swim tracks from Early Jurassic rocks of Con-
necticut as made by theropods, and provided a fine argument as to how such di-
nosaurs would have made these tracks while partially buoyed by water. More than
twenty years later, in 2001, paleontologists working in separate studies and places
(Wyoming and the U.K.) interpreted Middle Jurassic tracks as possible dinosaur
swim tracks. Soon after that (2006), hundreds of much better examples were dis-
coveredanddocumentedbyAndrewMilnerinEarlyJurassicrocksofsouthwestern