Dating dinosaur bones how stop settlers 4 updating
Higher up come creatures like bony fishes, then land plants and animals, then birds and larger land animals.
Of course, this is a very general pattern and does not explain why certain creatures that lived on the bottoms of oceans, like trilobites, make their first appearance in the Cambrian (505-540 Ma) while other creatures that live on ocean bottoms, like crabs and lobsters, don't appear until the beginning of the Cretaceous (65-145 Ma).
The nested subset pattern arises because species differ in their distributions across space.
Some species use a wider range of resources or persist across a wider range of habitats than others (Brown, 1984; Brown et al., 1996; Hanski and Gyllenberg, 1997).
Why would creatures that would seem to share the same general environment while alive be so widely separated in the fossil record if they did indeed live at the same time and in pretty much the same location?
For most scientists all of this seems so obvious that it is difficult to question.
The CRSQ study authors tested seven dinosaur bones, including a from Montana, hadrosaurids, a cartilaginous paddlefish, a bony fish, and fresh-looking wood and lizard bones from Permian layers in Canada and Oklahoma.
Five different commercial and academic laboratories detected carbon-14 in all the samples, whether from Cenozoic, Mesozoic, or Paleozoic source rocks. The team also compared the results to several dozen published carbon-14 results for fossils, wood, and coal from all over the world and throughout the geologic column.
Comparable amounts of radiocarbon showed up in almost 50 total samples.
Defenders of evolutionary time scales will have to assert that the radiocarbon all came from some sort of contamination, where recent or modern carbon somehow crept into all these samples.
Therefore, the best thing to do in science is to continually question and test previous hypothesis and theories to see if they continue to hold up under scrutiny.