The vetulícolas, old inhabitants of the seas.

Some five hundred million years ago, in the middle of the Cambrian, many of today’s groups of multicellular animals had already appeared, such as molluscs, arthropods, echinoderms, and chordates. The great diversification of animal forms at that time also produced many fossils that were difficult to classify, such as those of vetulícolas. So difficult in this case, that even its name, vetulícolas, does not commit to anything; It simply means “old inhabitant” or “inhabitant of antiquity” in Latin. The vetulícolas are marine animals; its body is vaguely reminiscent of a tadpole, it is made up of a voluminous head, with a mouth at the anterior end and five round or oval openings aligned on each side, which have been identified with gills; and a long and generally flattened tail that ends in the anus and that in the most primitive vetulícolas is formed by seven segments