What (if anything) can be inferred about whether the common ancestor of each of the three major bilaterian clades had a true coelom? What (if anything) can be inferred about whether the common ancestor of each of the three major bilaterian clades had a true coelom? We cannot infer anything about the status of the ancestor of the Lophotrochozoa, Ecdysozoa, or Deuterostomia. The common ancestor of each of the three clades -- Lophotrochozoa, Deuterostomia, and Ecdysozoa -- had a true coelom. The common ancestor of the Lophotrochozoa and the Deuterostomia had a true coelom, but we cannot infer anything about the ancestor of the Ecdysozoa. The common ancestor of the Deuterostomia had a true coelom, but we cannot infer anything about the ancestor of the Lophotrochozoa or the Ecdysozoa.