Class Gastropoda
Family Muricidae Rafinesque, 1815
Genus Hexaplex Perry, 1810
species Hexaplex praeduplex Landau, Houart & Marques Da Silva, 2007
Hexaplex praeduplex Landau et al., 2007, (Mollusca – Gastropoda – muricidae) is a rare species in the Tuscan Pliocene (Zanclean / Piacenzian). Is found in sandy sediment in Val d’Elsa Basin (Siena).
Hexaplex praeduplex Landau et al., 2007, (Mollusca – Gastropoda – muricidae) nel pliocene toscano è una rara specie che è possibile trovare con maggiori probabilità nei sedimenti sabbiosi fini della Val d’Elsa. Pliocene (Zanclean / Piacenzian).
Hexaplex praeduplex Landau, Houart & Marques Da Silva, 2007. (Mollusca – Gastropoda – Muricidae). Località Lupignano (Siena). Pliocene, height 66 mm. Oral view.
Original Description / Descrizione Originale:
Shell large, relatively fragile, globose, spire scalate, relatively high, weakly spinose. Protoconch unknown. Teleoconch consisting of seven angulate whorls; surface of first whorl almost eroded. Suture impressed, irregular. Spire whorl with a broad, shallow sloping infrasutural platform, roundly angulate at shoulder, convex below, with periphery just below mid-whorl. Axial sculpture consisting of nine rounded ribs on first two teleoconch whorls, on third whorl every other rib disappears, leaving six varices, rounded and high on middle teleoconch whorls, weakening abapically, very high, with the occasional weak, irregular intervarical ridge on penultimate and last whorls. Spiral sculpture consisting of narrow, rounded cords, with a single secondary cord developed in interspaces; cords and interspaces overlain by numerous fine spiral threads. Spiral cords forming small, short, open spines where they cross the varices, most prominently developed at shoulder. Last whorl globose, with a relatively broad, almost horizontal infrasutural ramp, angulate at shoulder, convex below, strongly constricted at base. Spiral sculpture; IP developed; P1, P3-P6 similar in strenght, P2 similar to oper spiral cords on first whorls but becoming narrower and lower on fifth, s3-s6 developed. Spiral sculpture forming short, open spines on apertural varix. Aperture roundly ovate, broad; outer lip erect, with crenulated edge, weakly denticulate within with six split denticles; labral spine indistinct. Anal notch marked by a small, shallow adapical notch, bordered medially by a ridge of parietal callus. Columellar lip concave, smooth, narrow, erect abapically, forming medial border of a narrow pseudo-umbilicus. Siphonal canal narrow or relatively broad, long, open, recurved. Siphonal fasciole narrow; ADP obsolete, MP and ABP prominent, subequal in strength. (Landau et al, 2007).
Landau B., Houart R. & Da Silva C.M. (2007). The early Pliocene Gastropoda (Mollusca) of Estepona Southern Spain. Part 7: Muricidae. Palaeontos, 11: 1-87. (pp. 11-12).
Distribution
Italian and Spanish Pliocene (Ciuciano, Poggibonsi (Siena), Altavilla (Palermo) and Estepona (Malaga)
” Sulla base dei dati disponibili, Hexaplex praeduplex, può essere considerata una specie di ambienti sabbiosi infracircalitorali. Per la malacofuana associata si rimanda a Forli & Dell’Angelo (2000), Brunetti & Forli (2010), Brunetti & Della Bella (2010). La presenza della specie nel Pliocene italiano è al momento accertata per Altavilla (Palermo), e per le località toscane precedentemente citate. La distribuzione è presumibilmente limitata allo Zancleano, o fino alla base del Piacenziano anche se, nei depositi di Altavilla, non è chiara la presenza di livelli attribuibili al Pliocene inferiore.” (Forli et al., 2013)
Bibliographic references and some more common synonyms
2000 Hexaplex brevicanthos (Sismonda, 1847) – Chirli, p. 11, pl. 5, figs 7-9.
2007 Hexaplex (Trunculariopsis) brevicanthos (Sismonda, 1847) – Landau et al., p. 8, Text fig. 2, pl. 2, fig. 1.
2007 Hexaplex (Trunculariopsis) praeduplex – Landau et al., p. 11, Text fig. 3, pl. 2, figs 5-6.
2013 Hexaplex praeduplex Landau et al, 2007 − Forli et al., p. 52, figs 3A-F, 4A-F, 6.
References
Brunetti M.M.& Forli M., 2010. Murexsul zezae n. sp. del Pliocene italiano (Gastropoda: Muricidae). Bollettino Malacologico, 46 (1): 4-8.
Brunetti M.M. & Della Bella G., 2010. Tellina (Moerella) ciucianensis n. sp. un nuovo bivalve per il Pliocene toscano. Bollettino Malacologico, 46 (1): 39-43.
Forli M. & Dell’Angelo B., 2000. A new species of Marginella (Mollusca, Gastropoda) from the Italian Pliocene. Bollettino Malacologico, 36 (5-8): 93-98.
Forli M., M. Mauro Brunetti & Reitano A. (2013). Due specie del Pliocene italiano a confronto: Hexaplex dumosus (de Stefani, 1875) ed Hexaplex praeduplex Landau, Houart & da Silva, 2007 (Gastropoda: Muricidae). Bollettino Malacologico, 49: 49-57.
Landau B., Houart R. & Da Silva C.M. (2007). The early Pliocene Gastropoda (Mollusca) of Estepona Southern Spain. Part 7: Muricidae. Palaeontos, 11: 1-87.
We thank our friend Massimo Cresti for the execution and use of the photos.
Ringraziamo per l’esecuzione e l’uso delle foto, l’amico Massimo Cresti.
