Paleontologists and molecular biologists have searched for a couple of decades to find and replicate DNA from some non-avian dinosaur fossil. But to date, no results have been obtained, either from fossil bones or teeth preserved in sediments or from a fossil preserved in amber, as was done in the film, Jurassic Park.
The extinction of non-avian dinosaurs except birds at the end of the Cretaceous has intrigued paleontologists for more than a century. One theory is that an asteroid impact 65 million years ago off the coast of Mexico generated massive tsunamis, with impact debris cutting off sunlight for months, stopping photosynthesis and causing freezing temperatures. Chemical reactions in the atmosphere caused acid rain and long-term global warming, all of which extinguished non-avian dinosaurs. However, at the same time, massive lava flows erupted across what is now southwest India. The eruptions probably caused many of the same effects as the asteroid impact. Although most scientists believe that the impact was the final blow for non-avian dinosaurs, both events could well have played a role. Created by American Museum of Natural History.
Understanding questions of dinosaur behavior and biology depends on a firm understanding of their evolutionary relationships. To reconstruct the evolutionary relationships between different groups of dinosaurs, one must carefully study and analyze the anatomy, essentially searching for characteristics that are shared among different kinds of dinosaurs. These characteristics are then interpreted to have been present in the common ancestor and inherited by its descendants. This analysis produces a branching diagram, called a cladogram, on which different kinds of dinosaurs are shown at the endpoints of the branches. Created by American Museum of Natural History.
Were dinosaurs already undergoing a long-term decline before an asteroid hit at the end of the Cretaceous about 65.5 million years ago? A study led by Museum scientists gives a multifaceted answer. The findings, published in May, 2012, in the journal Nature Communications, suggest that in general, large-bodied, ƒ??bulk-feedingƒ?� herbivores were declining during the last 12 million years of the Cretaceous Period. But carnivorous dinosaurs and mid-sized herbivores were not. Created by American Museum of Natural History.