The early platycopine dynasty (Ostracoda; Palaeozoic)

Abstract

The kloedenellid-type domiciliar dimorphism, showing the brood pouch separated from the proper domicilium, and the either continuously developed, as shown in cytherellids, or dorsally interrupted contact groove, as demonstrated in kloedenellids, are the most essential characters determining platycopine shell attributes. The Suborder PlatycopinaSars, 1866 has probably originated from palaeocopine (leperditellid) roots. Accordingly, palaeocopines and platycopines are closely related groups and are classified into the same Order PalaeocopidaHenningsmoen, 1953, an assumption quite different from conventional views. Depending on opposing attitudes, taken either by Palaeozoic or post-Palaeozoic workers, distinct superfamily, family and subfamily units are used in different ways. The unusual, domatial dimorphic features, recently described in archaic (Ordovician) forms are not homologous to the kloedenellid-type brood pouch. Speaking in terms of phylogeny, such ancient features are considered to be pseudo-advanced patterns (“evolutionary dead-ends”), only ephemeral in appearance. In contrast, the kloedenellid-type domiciliar dimorphism has persisted, practically unchanged, from early Silurian times to Recent.