A Cambrian rock layer is considered to be "Cambrian" because of the particular fossils it contains. But what does it mean when a rock layer designated as "Ordovician" contains distinctly Cambrian fossils? Paleontologists are facing that question after a recent find in North Africa.

According to evolution, dinosaurs lived during an age when birds and non-reptile land creatures were either present in just a few "primitive" forms or not at all. But a recent National Geographic online interview offered a summary of fossil discoveries made in a dinosaur-bearing deposit in Madagascar.

A piece of oxygen-darkened amber was said to hold a particular arachnid, but it wasn't clearly visible. Scientists made a surprising discovery when a computed tomography scan was able to produce a finely detailed three-dimensional image of a hunting spider. But if the amber is actually 49 million years old, as is claimed, why hadn't it completely darkened long ago?

A massive fossilized spider has set a new size record. It looks like today's golden orb-weavers, which are large enough to dine on small birds. This discovery, in conjunction with similar ones, presents problems for evolutionary origins, and also shows how a name choice can be misleading. What did scientists decide to name this fossil, and why?

The skull of a previously unknown dinosaur with interesting teeth and a unique head shape was uncovered in Ghost Ranch, New Mexico.