Why did the major groups of animals suddenly appear in the fossil record, known as the Cambrian Explosion?
This question seriously misleads students about the actual natural history of this planet. The term “major group” lacks scientific meaning. Many students, for example, might regard the mammals as a major group. Mammals, however, did not appear during the Cambrian explosion, but rather in the Triassic, nearly 300 million years later. The same can be said of birds, insects, reptiles, and amphibians, each of which are major groups in the ordinary meaning of the term, and none of which appeared in the Cambrian period. Clearly, the authors of the statement could have prevented such confusion by referring only to the animal phyla instead of “major groups”. Unfortunately, even if they had done so, the question would still be misleading. Not all animal phyla originated during the Cambrian. Compounding this serious mistake, the authors of the disclaimer seem to be unaware that the first multicellular animals appeared on earth during the Ediacaran Period, and many predate the Cambrian by more th
