This is cool! Science Daily is reporting on the discovery of 330 million year old fossil imprints discovered in Pennsylvania. The imprints are not actually fossils in the sense of being mineralized bone, rather they seem to be natural molds of the animals in question.
Here is a picture:
The finds were presented earlier today at annual meeting of the Geological Society of America in Denver. Paleontologists will be able to learn some interesting things about the amphibians in the early Mississippian:
Without the imprints of the webbed four-toed feet, for instance, it would be virtually impossible to say they were truly amphibians. The imprints also provide body proportions and important clues to the kind of outer skin the little beasts had. The skin is smooth, not armor plated as many would have expected, Lucas said.
There were other finds as well, including footprints of large animals, fossil plants, fossil insects and, most interesting:
There is even a saucer-sized footprint of an unknown vertebrate that suggests larger four-footed beasts lived far earlier than ever before suspected.