Аннотация:Brachiopods are a phylum of bilaterally symmetrical animals whose direct ancestors are unknownin the fossil record. As a result, the origin of their body plan can only be reconstructed based on indirect evidence. Currently, there are two conflicting hypotheses developed by paleontologists and zoologists. Thepaleontological hypothesis is based on fossil remains of small-shelled organisms known as tommotiids, thesoft body morphology of which remains unknown. However, their skeletal remains (sclerites) bear similaritiesto the valves of brachiopod shells. According to paleontological hypotheses, the ancestor of brachiopods wasa tube-dwelling. Zoologists, on the other hand, base their conclusions on the soft-body structure and ontogeny of modern brachiopods. They identify morphological features suggesting that the ancestor of brachiopodshad a worm-like body and underwent ventral folding. This paper compares and analyzes both hypotheses,concluding in favor of the folding hypothesis.
