Revision of Late Devonian Lunulacardiidae (Bivalvia) from the German Hercynian Facies

Taxa of the Lunulacardiidae were characteristic members of the Hercynian or Bohemian deeper water bivalve faunas of the Devonian. Most of them show peculiar and uncommon morphologies, but paleobiology, taxonomy, systematics and ecology of these bivalves, which are known for more than 150 years and often assigned to the Cryptodonta, are poorly understood. Our current revision of these taxa tries to interprete their paleobiology, stabilize their taxonomy, regroup them systematically and make them available for paleoecological interpretations. In the course of this study all the species erected by MÜNSTER and HOLZAPFEL originally assigned to Lunulacardium are re-studied. Lectotypes are selected where appropriate, and a neotype is chosen for L. semistriatum MÜNSTER, the type species of Lunulacardium. Several species are either transferred to the genus Prosochasma BEUSHAUSEN or their systematic position is confififi rmed (P. pyriforme MÜNSTER, P. muelleri HOLZAPFEL,
P. mytiloides BEUSHAUSEN, and P. bickense HOLZAPFEL). The third genus belonging to the lunulacardiids is Chaenocardiola HOLZAPFEL, which crossed the Devonian-Carboniferous transition. This study concentrates on the review of the Devonian chaenocardiolid taxa C. canalife rMÜNSTER, C. tetragona MÜNSTER, C. koeneni BEUSHAUSEN, C. denckmanni BEUSHAUSEN, and C. carinata BEUSHAUSEN. Lectotype selection and designation for all the studied species intends to stabilize the systematic situation of the family Lunulacardiidae FISCHER. Several nominative species are regarded as junior subjective synonyms of other taxa or isolated as nomina dubia. Biostratigraphic data according to modern stratigraphy are compiled, but here limited to Upper Devonian occurrences. Finally, paleoecological interpretations and hypotheses are presented for the studied lunulacardiids according to their morphology and paleobiological constraints.