Diacalymene is closely related to Calymene, to the point where some palaeontologists have suggested that they should be regarded as the same genus.
However, there are some differences between the two.
For a start, Diacalymene has a distinct ridge along the anterior of the cephalon, as well as a narrower glabella (central head region) than Calymene.
In addition, Diaca/ymene also has a slightly more triangular-shaped cephalon (head
shield), and it also tended to live in muddier sediments than did Calymene.
Like Calymene, however, Diacalymene could roll up tightly for protection against th rea ts, such as predators and storms.