Parvamussium mordsdrum Schneider, Crampton & Lukeneder, 2013
SCHNEIDER, S., J. S. CRAMPTON & A. LUKENEDER. 2013. Propeamussiidae, Inoceramidae, and other Bivalvia from the Lower Cretaceous Puez Formation (Valanginian–Cenomanian; Dolomites, South Tyrol, Italy). Cretaceous Research, 46: 216-231, figs. 1-12. [p. 225, figs. 10A-10E]
2013 Parvamussium mordsdrum Schneider, Crampton & Lukeneder, 2013
S. Schneider, J. S. Crampton & A. Lukeneder, 2013, figure 10.
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«Diagnosis. Extraordinarily large Parvamussium species (L > 90 mm) with 13 internal costae extending fromumbo to approximately 70% of shell height.
Material. Holotype, a large articulated specimen from the upper Lower Barremian of the Puez Limestone Member at Piz de Puez (NHMW 2013/0292/0037). Paratype, a medium-sized left valve from the same unit at Ra Stua, north of Cortina d’Ampezzo, Belluno Province, Veneto (Museo Paleontologico “Rinaldo Zardini”; no. 1868 RS-Z).
Measurements. Holotype: L = 92 mm; H = 87 mm; Paratype: L = c. 65 mm; H = c. 63 mm [paratype measurements based on photograph].
Type locality. Piz de Puez, Dolomites, South Tyrol, Italy and Ra Stua, north of Cortina d’Ampezzo, Province of Belluno, Veneto, Italy.
Type stratum. Puez Limestone Member, Puez Formation; late Early Barremian.
Derivation of name. Derived from the Bavariane-Austrian vernacular words ‘mords Drum’, meaning ‘very large specimen’.
Description. Shell exceptionally large (L (max) = 92 mm), semitranslucent; slightly longer than high; anterior, ventral and posterior shell margins well rounded, forming a subcircular segment; dorsal shell margin straight. Anterior-dorsal and posterior-dorsal disc margins almost straight. Apical angle c. 115°. Auricles comparably large, almost perfectly trigonal; posterior auricle significantly larger than anterior one. Posterior auricle ornamented with growth lines, becoming more prominent, almost plicate, just below the dorsal margin. Prodissoconch not preserved.
Shell interior ornamented with initially seven (?) and finally up to 11 near-straight radial internal costae in adulthood. New costae inserted across anterior and posterior parts of shell during ontogeny. Outside of left valve ornamented with up to c. 120 slightly irregular, sinuous, radial costellae. Earlier growth stage ornamented with c. 60 costellae only; additional set of costellae gradually but almost simultaneously emerging from shell surface at shell height of c. 55 mm. No commarginal lirae present; growth lines irregular, faint. Marginal apron broken and largely dissolved. Posterior and central portions of dissolved apron removed during preparation. Outside of right valve, including potential byssal notch, unknown. Remarks. The unique combination of the most conspicuous features of Parvamussium mordsdrum n. sp., i.e. its extraordinary size and the ornamentation of c. 120 costellae, clearly distinguish this species from all other Jurassic and Cretaceous species of the genus.»
SIMON SCHNEIDER, JAMES S. CRAMPTON & ALEXANDER LUKENEDER, 2013
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