The Subphylum Homalozoa is divided into four classes, which while having similar morphological features, are at best distantly related. All classes exhibit flattened thecae, are bilateral to relatively asymmetrical and apparently were surface detritus feeders or low level suspension feeders. Many homalozoans display thick marginal plates with smaller central plates on dorsal and ventral surfaces, possibly to augment gut and/or cloacal pumping.