Article: Bifida and Kayseria (Brachiopoda) and their affinity

The internal morphology of the European Middle Devonian brachiopods Bifida and Kayseria is truly athyridid in every character, especially with regard to the structure of the spiralia. Several previously unknown internal structures and two new species, Kayseria alvea, and K. nohnensis are described. One species of Kayseria is also shown to have an unusual external shell cover consisting of bushy frills located in rib troughs. It is proposed that both genera, as well as other known dayiacean brachiopods, be removed entirely from the order Atrypida and be reassigned to the suborder Athyridina (order Spiriferida).