Dinosaurs Without Bones Read Free

young for later dinosaurs. Wasps, beetles, and other insects likewise were attracted to the well-drained soils in between the Troodon nests. These insects burrowed into the sand and made brooding cells, which were later occupied by their larvae and cocoons. The former nesting horizons of the sauropods also restricted the burrowing of small mammals, which brought them closer to the surface and made things a little easier for the Dromaeosaurus and other predators to find them.
    Yet another trace left by the sauropods was an evolutionary one, evident in the plant communities. The hadrosaurs had been grazing on vegetation that was the result of intense selection pressures placed on past plants by sauropods through both stomping and eating. These changes in plant communities consequently shiftedevolution in the animal communities that used them, reinventing entire ecosystems.
    Thus the stage for this Cretaceous drama was constructed and its actors were unwittingly directed by the lasting marks of these vanished sauropods and other dinosaurs. In this sense, traces begat traces, and the dinosaur vestiges of the past influenced those of the present, an expansive canvas gently suggesting where the next brushstrokes should go.
    Tracing Dinosaur Lives
    Most of the scientists I know try hard not to write fiction. After all, our primary goal each day is to understand just a bit more about whatever we study and clearly communicate our newly realized comprehensions to others. Even so, as a practicing paleontologist, I thought that a fictional scenario would best encapsulate much of what this book is about, while also introducing its main topic in a way that engages and encourages our imaginations.
    Perhaps more than any other part of paleontology, the research specialty of ichnology —the study of trace fossils (tracks, trails, burrows, feces, and other traces of behavior, including fossil examples)—is about that exciting intersection between science and flights of fancy. When applied to dinosaurs, ichnology becomes even more stimulating. In fact, I like to argue that for us to truly grasp how dinosaurs behaved, to really know how they lived as animals and interacted with one another and their environments, we absolutely must study their trace fossils, and not just their bones, in order to paint the most vivid picture imaginable of their world.
    In the story above, I placed together dinosaurs that may not have been in the same time and place, although most are from near the end of the Cretaceous Period (about 70 million years ago) and in an area defined approximately by Montana and Alberta, Canada. Furthermore, even those dinosaurs overlapping in both respects still may not have encountered or affected one another. However, in this deliberate mash-up of dinosaurs and their behaviors, real dinosaur trace fossils inspired nearly every element of this story.
    Even better, many of these trace fossils have been discovered or studied just recently. Because of these finds, paleontologists are reconsidering some of what we thought we knew for sure about dinosaurs, either confirming long-suspected behaviors or revealing astonishing new insights into their lives. In other words, dinosaur trace fossils very often fulfill or exceed our expectations of these most celebrated of fossil animals.
    Let’s start with the Triceratops fight as an example. It turns out a good number of Triceratops head shields, which are composed of paired parietal and squamosal bones, bear deformities in the squamosals. These look like former healed wounds and are consistent with injuries caused by Triceratops horns. Ceratopsians, a group of dinosaurs that includes Triceratops and related horned dinosaurs, also made tracks, which are preserved in Cretaceous rocks from about 70 million years ago in the western U.S. and Canada. Ceratopsian tracks can be identified from their size, numbers of digits—five on the front foot and four on the rear—and are preserved in rocks the