MARY Continued

and therizinosaurs, may have been herbivorous or insectivorous. Hypotheses about theropod feeding habits, based on functional morphology, tracks, toothmarks, gastroliths, and coprolites, are still unclear as to whether most meat-eaters were primarily predators or scavengers. Reproductive behavior is well documented for two tetanuran species, Oviraptor and Troodon, which show evidence of both nest-building and brooding behavior, but is poorly known for other theropods. Some theropod juveniles were apparently precocial, and rapid growth rates are inferred for a few species of theropods, which may relate to thermoregulatory modes similar to endothermy.

Some evidence from both monospecific assemblages of theropod bones and closely spaced (and possibly contemporaneous) trackways suggests social behavior in some theropods, such as pack hunting. In contrast, individual trackways suggest that they sometimes roamed alone. Theropods were typically healthy animals but occasionally were injured or suffered from infections. Their general healthiness would have contributed to the evolution of some long-lived theropod lineages.

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1. What would have been the evolutionary advantage of a reduction of digit in a theropod manus, such as that shown by the Early Cretaceous ceratosaur Carnotaurus and the

Late Cretaceous tetanurans (and coelurosaurs) Albertosaurus and Tyrannosaurus? If you cannot think of any advantage for it, then how could it have become a vestigial organ, like a human appendix?

2. While working as a summer volunteer on a dinosaur dig, you and several other lucky participants uncover skulls from three new theropod species. Three years later, when you read the scientific papers reporting on the skulls, you notice the following endocranial volumes estimated for each species. The reconstructed original body volumes are given in parentheses following the endocranial volumes. Calculate the brain/body volume ratios for the three. Use your three calculations to determine which one is the "brainiest" in comparison to body size. How do they compare with the brain/body ratio calculated for Tyrannosaurus in the chapter?

3. One hypothesis proposed for why some theropods had feathers is that they served as a sexual display for potential mates. What is an alternative hypothesis for a function of feathers in theropods that

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