Revision der Familie HippocardiidaePojeta & Runnegar, 1976 (Mollusca; Rostroconchia)

Shallow marine Rostroconchia (Mollusca) from the latest Devonian (Strunian) and their significance for rostroconch life style and evolution

“…Internal details of the hood's shell microstructure have as yet not been described adequately, as the shell material in most of the fossils is recrystallized. However, as can be observed in several specimens from different localities and stratigraphic levels, a radial structure crossed by comarginal elements of micro-to mesoscopic scale is often preserved (Rogalla & Amler, 2006b). In steinkerns and moulds, these rather quadratic to trapezoidal elements can be seen as equivalent dots (Figs 4,5A,C,6).…”

“…Whereas the widely known type species of the genus Conocardium Bronn, 1835, Conocardium aliforme (J. de C. Sowerby, 1827), as such also the type of the Conocardiidae and the Conocardioidea, is still under revision, the members of the Hippocardioidea are well studied (e.g. Amler, 1996b;Rogalla & Amler, 2006a, 2006b, 2006c, 2006d. Although morphological differences between Hippocardioidea and Conocardioidea are as yet not precisely defined (recent studies by M. Amler, K. Pfennings, University of Cologne), they are basically distinguished till present by the presence (Hippocardioidea) or absence (Conocardioidea) of the characteristic hood (see below).…”

“…All these features apply to the few studied specimens, hence, combination of steinkerns, external moulds and incomplete shelly specimens requires detailed and proper knowledge of the hippocardiid anatomy (see Rogalla & Amler, 2006b). The very complex shell architecture relative to the shell microstructure (Amler, 1996b;Rogalla et al, 2002Rogalla et al, , 2003 does not allow direct comparison of internal rib ornamentation as displayed by the steinkern with probable external or medial layer ornamentation as seen in shelly specimens.…”

“…Undoubtedly, based on the presence of a wide hood, the specimens -albeit their specific determination -are typical members of the Hippocardiidae (see Rogalla & Amler, 2006b). …”

“…In the Devonian siliciclastic and calcareous shallow shelf environments, specimen size grew up to 5-8 cm conch length (see e.g. Hall, 1884Hall, -1885Rogalla & Amler, 2006b, 2006cBeushausen, 1895;Halfar, 1882;Whidborne 1892Whidborne -1907 with an equivalent hood -conch ratio. This tendency is also mirrored in the Velbert specimens.…”