What is "spiralia"

The Spiralia are a morphologically diverse clade of animals, including within their number of molluscs, annelids, platyhelminths and other phyla. The Spiralian clade of animals are more commonly referred to as the Lophotrochozoa, although whether these two terms are equivalent is debated, as noted further below. More uncontroversially, the term Spiralia is applied to those phyla that exhibit canonical spiralian cleavage.

Spiral cleavage, from which this group draws its name, is a pattern of early development found in most (but not all) members of the Lophotrochozoa.