Change in Predominant Growth Trajectories in the Ontogeny of Recent Brachiopods

The study of the size and age parameters of the brachiopod shell revealed changes in the predominant growth trajectories in the species Macandrevia cranium (Müller, 1776) , Laqueus californianus (Koch, 1843) , Diestothyris frontalis (Middendorf, 1849) , Megathyris detruncata (Gmelin, 1790) and, possibly, in Eohemithyris grayi (Woodward, 1955) , Argyrotheca cuneata (Risso, 1826) , and Joania cordata (Risso, 1826). The change is associated with the stages of development of the brachydial loop and reaching puberty. In the species Hemithiris psittacea (Gmelin, 1790) , Terebratulina retusa retusa (Linnaeus, 1758) , Terebratulina retusa septentrionalis (Couthouy, 1838) , Terebratulina unguicula (Carpenter, 1864) , Eucalathis murrayi (Davidson, 1878) , Terebratella enzenspergeri Blochmann, 1906, changes in the predominant growth trajectories were not observed. The appearance of hypothetical descendants of brachiopods with growth changes formed as a result of paedomorphosis is proposed. The genus Eucalathis Fischer et Oehlert, 1890 and Nanacalathis Zezina, 1981 emerged from an evolutionary process of fetalization.