The extinct Aenigmacaris are classified in the Arthropoda phylum and their closest relatives are the mantis shrimp.
Aenigmacaris is an extinct genus of malacostracan crustacean, which includes the species Aenigmacaris cornigerum and Aenigmacaris minima. Arthropoda Phylum: Their closest extant relatives are the mantis shrimp. 
