[1] Like the echinoderms, they are covered in armour plates, each of which comprises a single crystal of calcite.

[2] However, they do not display the familiar fivefold symmetry that more recent echinoderms possess, instead being close to (but not fully) bilaterally symmetrical.

[1] Their tails were long and segmented, resembling the stalk of a crinoid or the arm of a brittlestar.

[1] They also bear features reminiscent of pharyngeal slits,[4] a character lost in other echinoderms but present in hemichordates,[1] causing R.P.S.

[5][6] Their interpretation requires an understanding of how the animal was oriented in life; it's not agreed whether the convex side of the head was up or down, or indeed whether the "tail" was at the front or back of the organism.