Structures, reminiscent of the lattice organs in thecostracan crustaceans, are described from the carapace cuticle of Cretaceous thylacocephalans. The new lattice organ like structures occur in pairs along the dorsal midline. While these have a similar outline to true lattice organs, they seem to lack pores and do not occur in the highly apomorphic pattern found in thecostracans. These discrepancies do not easily support earlier ideas of a position of the thylacocephalans within the thecostracans.
The significance of the possible lattice organs for inferring a relationship between thylacocephalans and thecostracans is discussed.