Geoscience Reference
In-Depth Information
andwhattheyweredoinginwhateverenvironmenttheytraversed.Conversely,very
few dinosaur bones were buried where a dinosaur lived; that is, most bones were
likely moved some distance from their original habitats. As a result, I like to argue
that dinosaur tracks constitute the “real” fossil record of dinosaurs rather than their
bones, which are nice but, well, just a little too
dead
. Tracks breathe life back into
dinosaurs.
Dinosaur Feet and Footprints through Time
Before jumping into a more detailed discussion of dinosaur tracks, it's probably a
good idea to learn about the main groups of dinosaurs and their feet, which helps to
identifydinosaurtrackmakers.Paleontologistsclassifydinosaursthroughanatomic-
altraits,andthesetraitsarenearlyalwaysrelatedtodinosaurs'evolutionaryhistory,
or their shared ancestry. Ideally, then, each recognizable dinosaur bone can be cor-
related with about six broad groups of dinosaurs: theropods, pro-sauropods, saur-
opods, ornithopods, thyreophorans (stegosaurs, ankylosaurs, and nodosaurs), and
marginocephalians(pachycephalosaursandceratopsians).Thesegroupingsofdino-
saurs that share a common ancestor—called
clades
—are best expressed graphically
through a branching diagram called a
cladogram
.
In the simplest cladogram for dinosaurs, theropods are more closely related
to prosauropods and sauropods than they are to ornithopods, whereas stegosaurs,
ankylosaurs, and nodosaurs are more closely related to one another than they are
to marginocephalians. Also, because birds descended from theropod ancestors and
thus qualify as dinosaurs, these are included on any self-respecting dinosaur clado-
gram. But if you want to be even more of a “lumper” with classifying dinosaurs,
youcouldgobacktotheirinitialsplitinto
saurischians
(“lizard-hipped”dinosaurs),
which includes all theropods (birds too), prosauropods, sauropods, and
ornithischi-
ans
(“bird-hipped” dinosaurs), which are all ornithopods, thyreophorans, and mar-
ginocephalians.
Dinosaur feet can be roughly correlated with the evolutionary history of di-
nosaurs, based on the appearance and disappearance of these clades in the fossil
