Questions that we should consider about dinosaur biology include the following: What do we know? What can we know? How can we find out?
Inferences about dinosaur biology range from those with fairly robust amounts of evidence to those that include vast amounts of speculation.
Questions: Why were carnivorous dinosaurs (a significant number) so large? Why are there no elephant-sized carnivorous mammals today?
The numbers and sizes of species of the "modern" meat-eating mammals were compared with the numbers and sizes of species of meat-eating dinosaurs. Most mammalian carnivores are about the size of domestic cats (the largest carnivore being the bear). In general, carnivorous dinosaurs were two magnitudes of order larger than todayıs mammalian predators (about the size of elephants). Such factors as pre-predator population density, the amount of prey mass required to support a predator, and predator-prey distribution ranges should be considered as part of any hypotheses that might help answer these questions.
Generalization: a large continental area makes it easier for organisms to reach a large size: thus, large continents (or land masses) tend to have larger predators than smaller land masses.
Enough prey must be present to support the predator. Large predator organisms require a very low population density of predators to assure that enough prey can be caught. If they were "elephant sized" today, mammalian carnivores would require even larger ranges than they presently have. It would be very difficult for large warm-blooded carnivores to maintain low population density and still have enough organisms to likely find a mate needed to maintain the species.
In the late Cretaceous period, the carnivorous dinosaurs were attaining sizes ten times larger than the largest carnivores existing today AND they were doing so on smaller land masses that were divided into even smaller habitats. How is this possible?
Dr. Farlow hypothesized these reason for the larger size of carnivorous dinosaurs:
Questions and Answers (following the lecture):
|Increased Size of Animals||->||Decreased Rate of Food Passing||->||Increased Time for Fermentation of Food|