Geoscience Reference
In-Depth Information
first recognized example of herding behavior shown by dinosaur tracks, and still
one of the best, stems from a series of Early Cretaceous sauropod tracks at Daven-
portRanchinTexas,foundbyRolandBirdin1941.Thissitehastrackwaysofmore
than twenty sauropods walking in the same direction and apparently made at about
the same time. A Late Jurassic sauropod tracksite near La Junta, Colorado, also
shows the tracks of five sauropods moving in the same direction, spaced at regu-
lar intervals, and turning in harmony along the length of their trackways. One time,
when visiting this site with students, I asked them to walk alongside the tracks. By
observing them this way, the lesson became much more visceral for these students
as they could experience the subtle changes in movement made by the sauropods,
rather than just gazing at them from afar or listening to me babble on about them.
Sauropodtracks,infact,providethebestevidencethatthesedinosaursherded.
So far, sauropod trackways indicating group behaviors are documented from Jur-
assic-Cretaceous rocks of the U.S. (Arkansas, Colorado, Texas, Utah), Brazil,
Bolivia, China, Portugal, and the U.K. The tracksite in the U.K., preserved in
Middle Jurassic (about 165
mya
) rocks, was likely made by dozens of sauropods
moving together, a truly awesome spectacle to imagine. Even better, some of the
same sauropod tracksites show smaller tracks along with larger ones, suggesting
that sauropods of different ages were traveling with one another, perhaps with mul-
tiple families.
For ornithopods, similar sorts of trackways also point toward their herding.
TheseincludeseveralsitesfromtheCretaceousofKorea,oneofwhichhastracksof
about twenty large ornithopods heading in the same direction, and another from the
CretaceousofCanada,whichhad10to12ornithopods.Afewankylosaurtracksites
have parallel trackways, suggesting that at least two ankylosaurs were traveling to-
gether at the same time. So far, stegosaur tracks are so rare we don't know if these
animals were social or not. Ceratopsian tracks are also uncommon enough to with-
hold judgment on that aspect of their lives too, although rocks bearing hundreds of
