Article: Microstructure and growth of the conulariid test: implications for conulariid affinities

The conulariid test has been interpreted as homologous to the theca of coronatid scyphozoans, but recently it has been claimed that the conulariid test and coronatid theca are fundamentally dissimilar. This claim is based largely on putative microstructural characteristics of conulariid tests. Examination of sectioned conulariids using scanning electron microscopy reveals that their microstructure is similar to that of the coronatid theca. Analysis of the microstructure and patterns of malformation of healed injuries and growth abnormalities in conulariids indicates that the conulariid test and coronatid theca were also similar in mode(s) of growth and injury repair. Werner's (1966a, 1967) suggestion that the ornamentary (outer) layer of the conulariid test is homologous to the outer layer of the coronatid theca is problematic. Nevertheless, the conulariid test and coronatid theca can be interpreted as homologous at a more general level of comparison.