This week's memo arrives courtesy Dr. Meg Daly, Directory of OSU's Museum of Biological Diversity.
Just as in good fiction, the alternative universe of dinosaurs shares foundational principles with our universe. We can see that the anatomies of dinosaurs and their contemporaries were shaped by physical forces like gravity, that organisms that inhabit similar environments have similar anatomies, that organisms change over time through development and that species change over time through evolution. These shared principles make it possible for us to use comparisons with modern organisms to understand and interpret the seemingly peculiar morphologies of dinosaurs.
Through this lens of comparative biology, we can fill in gaps in the fossil record and flesh out our understanding of fossil animals. For example, the structure of dinosaur eggs and the way in which adult dinosaurs sit on them is identical to what we see in birds, allowing us to interpret dinosaurs as providing care for their young. Similarly, we can understand the flight mechanics of pterosaurs by comparing them to bats, which are distantly related to them but which also have a wing comprised of a membrane stretched across hand bones.
However, some unique aspects of dinosaur biology remain a puzzle, like the spines, spikes, and armor of ceratopsian dinosaurs. We can see that the elaborations on the skulls of these dinosaurs changed over the life of the animal, typically becoming more pronounced and larger as the animal grew. This is a pattern that has echoes in the horns of modern mammals. Nonetheless, the ways in which the spikes and spines functioned is elusive--were these used in male-on-male combat, as are antlers and horns in modern hoofed mammals? Or did these ridges and frills enable muscle attachment and augment the power of grinding jaws, as do the crests on the skulls of modern gorillas? Were they part of a mating display, highlighting the physicality and foraging prowess of a male, like long tail feathers of birds or the antlers of extinct Irish elk? Did these horns dissipate heat, or increase hearing range, functions demonstrated for antlers and horns in mammals? Because these functions are not mutually exclusive and at least some act in concert in modern animals, comparative biology is silent on the probability of each of the possibilities leaving room for a little mystery.