The group ancestral to dinosaurs, the predatory thecodonts, have intermediate predator/prey ratios of 4 to 20 percent. Animatronic dinosaur costume This is right in line with the tenrec-like metabolic rates that their intermediate morphology indicates. As for the birdlike theropods, Bakker and others found that in a dozen faunas they make up 0.7 to 6 percent of the herbivore biomass, just like the fossil mammal carnivores. Again there are exceptions. Animatronic dinosaur The predatorpacked Cleveland-Lloyd, Ghost Ranch, and Chitake quarries are obvious predator kill sites. But overall the evidence is conclusive that predatory dinosaur populations are structured like those of fossil mammals, and are very different from those of lowermetabolic- rate vertebrate fossils. Bulk endothermy could explain the low predator/prey ratios of big theropods, but not the equally low ratios of small Velociraptor. Predator/prey ratios offer firm evidence that theropods had mammal-like metabolic systems.
This argument has not been accepted by the “biomass” of dinosaurologists, however. walking dinosaur costume Some skeptics say that since we do not fully understand how animals get preserved in the fossil record, we cannot yet trust the reliability of what predator/prey ratios tell us. This sounds wise and prudent, but if it were really true we would have been seeing chaos. The Pf ratios of the various conununities would fluctuate widely and show no particular pattern. But as we just saw, this is not the case. With few exceptions, the archaic sprawling reptiles show just the sort of high ratios we would expect them to have, the intermediatedesign mammal-like reptiles and thecodonts exhibit the intermediate ratios that best fit them, and erect-legged dinosaurs and mammals share the lowest figures. This is just too much consistenry to be mere coincidence-PP ratios must be reflections of physiology.