Metamorphosis of the loop in Cenozoic dallinacean brachiopods and its developmental constraint

Gunji, Yukio 1987 07 15: Metamorphosis of the loop in Cenozoic dallinacean brachiopods and its developmental constraint. The well‐known metamorphosis of loop development in select species of Dallinacea is investigated by numerical analysis. It is shown how loop transformation depends on the location of the ‘loop center’, that stage forms are determined by the position of the center, and that there may be two ‘shift directions’. The succession found in Campages, Laqueur and Dallina can be explained by a posterior shift, while the succession found in Terebratalia and Coptothyris is explained by an anterior shift. These two directions may be linked, because both are found in a single species Nipponithyris afra. Loop development in species of Dallinacea can therefore be transformed through variation of a specific constraint; this is regarded as an example of developmental constraint. Developmental constraints as common features are useful in studying comparative morphology during ontogeny and phylogeny.