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end of the Middle Triassic Period. Sure enough, three- and four-toed tracks similar to those predicted for primitive dinosaurs are fairly common in some Middle Triassic rocks. Because these tracks were so similar to those of known dinosaur tracks, their discoverers excitedly pronounced them as “dinosaur-like” and hinted that these footprints extended dinosaur lineages to well before their skeletal record. Unfortunately, such claims were thoroughly trounced, flogged, ridiculed, and otherwise treated as unworthy of any encouragement whatsoever. The bulk of this disdain, of course, came from paleontologists who studied dinosaur bones, not tracks. As a result, advocates of trace fossil evidence for dinosaur ancestry were stymied, as they also somehow had to connect tracks to feet foretold—but not yet found—for animals that heralded the arrival of true dinosaurs in the Late Triassic Period.
    Some of this disrespect for all things ichnological was allayed in 2010 when a team of paleontologists, led by Stephen Brussatte, published a paper in which they proposed the oldest “dinosauromorph” tracks from the fossil record. Dinosauromorph refers to the clade Dinosauromorpha, which includes all animals more closely related to dinosaurs than other non-dinosaurs, such as pterosaurs and crocodilians. This means that ancestral dinosauromorph tracks almost look like dinosaur tracks, but not quite: sort of how a primitive human’s tracks would differ from those of a same-sized modern human. Some of these tracks, which were from Early Triassic (about 245 mya ) rocks in Poland, precede Eoraptor by more than 15 million years. These paleontologists also pointed out, somewhat indignantly, that “… footprints are often ignored or largely dismissed by workers focusing on body fossils, and are rarely marshaled as evidence in macroevolutionary studies of the dinosaur radiation.” Yes, indeed. Knowing they would face resistance from their body-fossil-focused brethren, they carefully linked the tracks to likely anatomical features of dinosauromorphs. They also pointed out that the oldest probable dinosaur tracks were from the end of the Middle Triassic Period, about 235 mya , which were geologically younger than their tracks, but still before the earliest dinosaur body fossils by about 5 to 7 million years. Dinosaurs later became much more abundant and diverse by the end of the Triassic Period, at about 200 mya . Accordingly, their tracks were common and varied by then, too, and became much larger. Within only about 50 million years, dinosaurs began making the largest footprints of any animals that ever lived.
    These Triassic dinosauromorph tracks point toward what paleontologists call, intriguingly enough, a ghost lineage . A ghost lineage is one for which we have evidence that ancestral members of a clade and their descendants lived at a certain time in the geologic past, but we so far lack corporeal evidence for its existence. Given these dinosauromorph tracks, somehow this phrase seems even more appropriate as we consider these ethereal, disembodied traces as evidence of the first proto-dinosaurs.
    Four Legs Good, Two Legs Better, or Does It Matter? Trackway Patterns and Dinosaur Gaits
    Thus armed with all of this knowledge about dinosaur tracks and how they record when dinosaurs first evolved, it’s tempting to think that you can just identify a dinosaur by looking at one track, state confidently “theropod,” “ornithopod,” “sauropod,” or whatever other dinosaur clade you think it belongs to, identify the geologic age of the rocks hosting this track, take a photograph, and be done with it. But that would be a sad state of affairs, utterly lacking a sense of adventure and curiosity, living in a bland world filled with beige tones and unseasoned instant grits. In other words, you don’t want to do that.
    Instead, you want to know more about how this theropod, ornithopod, sauropod, prosauropod, stegosaur, ankylosaur, or