"Kimberella" had a dorsal integument that has been described as a non-mineralized "shell"; in the larger specimens this reached up to 15 cm in length, 5 to 7 cm in width, and was 3 to 4 cm high; the smallest specimens are only about 2–3 mm long. The shell was stiff but flexible, and appears to have been non-mineralized, becoming tougher as it grew larger (and presumably thicker) in more mature specimens. The deformation observed in elongated and folded specimens illustrates that the shell was highly malleable; perhaps, rather than a single integument, it consisted of an aggregation of (mineralized?) sclerites. At its highest point was a hood-like structure, forming what is thought to be the front. In some specimens, the inner surface of the shell bears stripes spanning the width of the creature; these may represent the attachment sites of muscles. Similar stripes around the edge of the shell may have been connected to muscles involved in retracting the muscular foot into the shell.