The Mollusca are one of the most successful animal phyla — ubiquitous, varied in body plan and with a long fossil record. Their interrelationships have been a matter of debate, but phylogenomic methods are beginning to resolve the issue. A new study answers some questions about the base of the molluscan tree, showing that, contrary to the traditional view, bivalves and gastropods are members of sister taxa. This finding also raises the possibility that centralization of neural and sensory organs in the head region, and the development of protective shells (shell-less Chaetoderma nitidulum,pictaied) may have occurred on several occasions in the evolutionary history of the molluscs.
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