Siphogonuchitidae
Siphogonuchitidae is a family of sachitids known mostly from isolated sclerites and shells.
Description
The siphogonuchitid scleritome consists of two main kinds of sclerites, as well as dabashanitid arrays of fused sclerites and a maikhanellid shell. Siphogonuchitid sclerites are hollow and bear prominent ridges.Lopochitid sclerites are elongate, narrow, helically twisted by up to 90 degrees, and gently bent longitudinally, while palaeosulcachitid sclerites are flattened and curved in one plane. Dabashanitid sclerites are composed of multiple sclerites sharing a common base. They are likely derived from the fusion of paleosulcachitid sclerites and may serve as central branched sclerites of the siphogonuchitid scleritome.
Besides these basic types of sclerites, there are several other kinds that are much less common.
The maikhanellid shell is patelliform and bears a distinct pattern of scales. These scales are embedded siphogonuchitid sclerites.
Calvapilosa is the sole siphogonuchitid not known from isolated shells or sclerites, and bears a single anterior shell, a dorsoventrally flattened body, and a dorsal mantle coated in sclerites.