Ecological theory explains that in order for more than one predator species to thrive in an ecosystem, the different species must occupy different niches, or roles, in the ecosystem.
Paleontologists have discovered an example of niche partitioning among different types of carnivorous dinosaurs: tyrannosaurs--the group that includes T. rex--and their sail-back cousins, the spinosaurs. Researchers analyzed the isotopic signature of spinosaur and tyrannosaur teeth and found that the oxygen isotope ratio of spinosaurs is lower than that of other theropods living in the same area at the same time.
The lower spinosaur ratio is a closer match to that of fossilized crocodiles and turtles from the same area. This match suggests that spinosaurs spent most of their time in or around aquatic habitats, a niche not occupied by the tyrannosaurs.
Source: Science News March 13, 2010, p. 18
Amiot, R., et al., Geology February, 2010
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