What is Waukesha butterfly animal?

The butterfly animal is an enigmatic arthropod from the middle Silurian Waukesha Lagerstätte in Wisconsin. Very few papers have been published on the creature, and it seems to have no scientific description or name given to it. The current consensus is that it is an arthropod of unknown affinities, with a bivalve-like carapace. According to a paper on the biota, the animal has some resemblance to Phyllocarid crustaceans, but the resemblance may be only superficial.