Heliacus d’Orbigny, 1842

Harzhauser, Mathias & Landau, Bernard, 2023, The Architectonicidae and Mathildidae (Gastropoda, Heterobranchia) of the Miocene Paratethys Sea-victims of the Miocene Climatic Transition, Zootaxa 5370 (1), pp. 1-74 : 27

Genus Heliacus d’Orbigny, 1842

Type species. Solarium herberti Deshayes, 1830 [= Heliacus cylindricus ( Gmelin, 1791) ]; by monotypy. Present-day, Atlantic.

Original diagnosis. “ Testa orbiculato-conica, trochiformi, transversim costata, longitudinaliter striata , nigrofusca; spira elevata, anfractibus quinis subconvexis; umbilico angusto, crenato, intus tricostate; apertura subrotunda” [Shell orbicular-conical, trochiform, transversely ribbed, longitudinally striated, black-brown; a raised spiral, subconvex with bends; umbilicus narrow, crenate, tricostate inside; aperture sub-rounded] (d’Orbigny 1842: 68).

Revised description. “ Teleoconch: small to medium-sized (usually 6-13 mm, rarely over 20 mm}, depressed to tall roundly cone-shaped, with narrow to very wide umbilicus (ca. 8-40% of shell diameter); whorls weakly to distinctly bulging; sculpture: spiral ribs with relatively large nodules on entire surface; number of ribs constant, only between lower peripheral and infraperipheral ribs occasionally with 1 ± strong additional rib; apical side: subsutural rib, single midrib (or two narrow ones) and upper peripheral rib usually equally developed, rarely upper peripheral rib somewhat stronger; periphery formed by lower peripheral rib and only slightly weaker infraperipheral rib (occasionally with additional rib between them); upper point of whorl attachment at or below lower peripheral rib; base usually with 5 spiral ribs, increasing in width towards umbilicus; umbilical wall usually with 1-2 strong, narrow spiral ribs ” ( Bieler 1993: 184) ( Fig. 2 ).

Synonyms. Torinia J. E. Gray, 1842, type species Trochus cylindraceus Dillwyn, 1817 [= Heliacus cylindricus ( Gmelin, 1791) ]. Present-day, Atlantic.

Figures

FIGURE 2. Whorl cross-sections of Architectonicidae genera. All modified after Bieler (1993) except for Simplexollata, Basisulcata and Ammotectonica. Solatisonax? refers to Solatisonax? kostejana (Boettger, 1907), Bold genera are represented in the Paratethys Sea. SSC: subsutural cord, MC: mid cord(s), UPC: upper peripheral cord, LPC: lower peripheral cord, IPC: infraperipheral cord; UC: umbilical crenae; PUC: proxumbilical cord.