But the fossils are often damaged, because pterosaurs had light, hollow bones similar to birds. Birds Hesperornis resembled modern loons, which are considered among the most primitive birds. Like loons, Hesperornis had heavy bones and probably walked poorly on land, if at all, because its legs were set so far back. Unlike loons, Hesperornis couldn t fly. Like other toothed birds, Hesperornis and Ichthyornis died out with the dinosaurs.
Scientists think they left no descendants, as modern birds evolved from other prehistoric birds.
What appear to be wheat grains are actually fusulinids. Fusulinids were in turn types of foraminifera that became extinct during the Triassic Period, around 200 million years ago. But thousands of other types of Foraminifera still float in sea, growing to amazing sizes for one-celled organisms. Rivers or floods occasionally washed dinosaurs out into Cretaceous seas. The only known skeleton of a duck-billed dinosaur called Claosaurus was found in Kansas chalk.