Trilobites dominate the Cambrian fossil record, and these arthropods actually attained their peak number of families near the end of the Cambrian. It is believed there were some 15,000 species that evolved during the Paleozoic. Hence, the Paleozoic is sometimes called the age of trilobites. Modern times are sometimes called the age of insects (that are also arthropods), and it is believed there may be some 10,000,000 species of insects on Earth today (with beetles predominating).
The first detailed record of vertebrates appears during the Cambrian as fossils of jawless fish. These bottom-dwellers, some of which had skeletons made of cartilage rather than bone, first appeared some 500 million years ago. Many were covered in plate-like armour.
When one thinks of the migration of animals from the marine environment to land, Devonian-time comes to mind. But, in fact, the fossil record has substantial evidence that this critical adaptation had already begun in the Cambrian. One of these fossils, Climactichnites is almost as enigmatic today as it was during the time of Darwin.
The first detailed record of vertebrates appears during the Cambrian as fossils of jawless fish. These bottom-dwellers, some of which had skeletons made of cartilage rather than bone, first appeared some 500 million years ago. Many were covered in plate-like armour.
When one thinks of the migration of animals from the marine environment to land, Devonian-time comes to mind. But, in fact, the fossil record has substantial evidence that this critical adaptation had already begun in the Cambrian. One of these fossils, Climactichnites is almost as enigmatic today as it was during the time of Darwin.
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