Possible Directions For Future Research

Although progress in understanding predator-prey interactions in dinosaur communities will depend in large part on fortuitous discoveries of particularly informative specimens or assemblages, we can suggest some approaches that might prove fruitful. One matter worth exploring is the incidence of bite marks in dinosaur bones, or teeth embedded in bone. Such fossils have already been noted for the Late Cretaceous of western North America (Jacobsen, 1997, 1998, 2001), but older formations could also be surveyed. Similarly, paleontologists should keep their eyes open for potential theropod coprolites. With sufficiently large sample sizes of tooth-marked bone and coprolites, it might be possible to determine which species of herbivorous dinosaurs, and which size classes within those species, were preferentially eaten by which predator species. If we were really lucky, we might even find, say, a bite mark unambiguously made by a Tyrannosaurus that had healed, which would establish beyond doubt that these predatory dinosaurs at least sometimes attacked live prey. Unfortunately, distinguishing successful predation events from scavenging on the basis of tooth-marked bones is probably impossible, because the victim cannot recover from either.

Structural analysis (including computer modeling) of a variety of theropod skulls in particular faunas (cf. Henderson, 2000; Rayfield et al., 2001) could be used to test whether reconstructions of different biting and/or feeding styles in sympatric theropod species are mechanically feasible, and thus ways in which coexisting species could have subdivided the resource base. Such approaches could be combined with analyses of tooth shape, tooth cutting edges, and wear and breakage patterns, in both in situ and shed theropod teeth (Farlow et al., 1991; Farlow and Brinkman, 1994; Abler, 1997). The degree of size and shape overlap of the skulls and teeth of different species of potentially sympatric theropods could be compared with that in modern communities of predatory lizards (e.g., the varanids of Australia) and crocodylians.

With a better understanding of the systematic composition of dinosaur faunas, we could see how the different composition of the prey base in sauropod-dominated and ornithischian-dominated

FIGURE 4—Right lateral view of the pelvis of a moa (Canterbury Museum Av 8317, Emeus crassus) showing an elliptical gouge (arrow) dug by the hind toe talon of Harpagornis, a huge, extinct eagle. The paper label is 102 mm long. Photograph courtesy of Richard Holdaway.

faunas affected the structure of predatory dinosaur guilds. Do the two kinds of faunas consistently differ in the ratio of the number of herbivore species to carnivore species, or might they differ in the ratio of individual herbivorous animals to carnivorous animals? And can any such differences be related to the mechanisms by which sympatric carnivorous dinosaur species reduced potential niche overlap?

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