Reasons of micromorphism in modern or fossil brachiopods

Mass samples of the micromorphic recent (Hemithyris psittacea, Eucalathis murrayi, Macandrevia cranium, Megathyris detruncate, Argyrotheca cuneata, Argyrotheca cordata) and fossil Silurian (Microsphaeridiorhynchus sp.) brachiopods were studied. New location of Eucalathis murrayi on the Kitovyi Ridge in the Atlantic Ocean is described. Rates of growth of shells were revealed by the study of the sizes and age of brachiopods. Reasons of dwarfism in brachiopods are discussed. Three strategies of growth of the micromorphic brachiopods are distinguished. Appearance of micromorphic brachiopods is connected with the changes in the rates of shell growth and life expectancy.