Kiel and Taviani—Miocene methane-seep bivalves from Italy
Meganodontia acetabulum. Therefore we consider “Lucina” hoernea as belonging to Meganodontia, but as distinct from M. acetabulum. In addition to the differences mentioned above, Meganodontia hoernea has a less distinctive posterior adductor muscle scar than Meganodontia acetabulum. Moroni (1966) provided an extensive synonymy for Meganodontia
hoernea.In the Meganodontia species from the early Miocene of Cuba (Kiel and Hansen, 2015), the anterior adductor muscle scar deviates from the pallial line at a broader angle, as in M. hoernea. Examination of Sacco’s type material showed that his “variations” L. globulosa var. alta Sacco, 1901 and L. globulosa var. perinaequilatera Sacco, 1901 represent deformed specimens of Meganodontia hoernea and should therefore be considered as synonyms. Taylor et al. (2011) tentatively assigned Meganodontia to
their new subfamily Pegophyseminae, whose species are united by some unusual morphological characters, including thin, globular, smooth shells, a narrow edentulous hinge with an internal and laterally extended ligament in most species (Taylor et al., 2011). Meganodontia hoernea is a common and widespread species in the Miocene of Italy, associated with ‘Calcari a Lucina’ limestones and reducing deep-sea marly sediments.
Genus Lucinoma Dall, 1901
Type species.—Lucina filosa Stimpson, 1851 (by original designation); Recent, northwest Atlantic.
Lucinoma perusina (Sacco, 1901) Figures 8, 9
1901 Dentilucina perusina Sacco, p. 83, pl. 19, figs. 12–14.
1901 Dentilucina perusina var. pseudorotunda Sacco, pl. 21, fig. 15.
1966 Phacoides (Lucinoma) perusinus (Sacco); Moroni, p. 82, pl. 5, figs. 1, 3, pl. 6, figs. 1, 2.
1996 Lucinidae Taviani, fig. 4b.
Description.—Medium- to large-sized Lucinoma, outline of shell oval in small specimens, becoming more round in large ones; umbones central, prosogyrate, elevated; surface sculptured by fine, irregular growth increments or commarginal ribs, posterior sulcus only weakly developed; lunule elongate, heart-shaped, moderately excavated, bordered by distinct angulation; escutcheon lanceolate, wide; anterior adductor muscle scar thin, elongate, reaching well below midline of shell, detached from pallial line for more than three-quarters of its length, deviates from pallial line by ~10°; posterior adductor muscle scar oval, dorsally pointed; hinge plate broad, two strong, radiating cardinal teeth in each valve, one anterior lateral tooth in each valve, posterior lateral teeth not seen.
Materials.—Ten specimens from Ca’ Piantè and six specimens from Santa Sofia; six shells from Montepetra, all articulated; one specimen on block with articulated Archivesica sp. (MSF 2111); four articulated shells (MSF 2114–2117) and a cluster (MSF 2118) from erratic blocks in Sintria Creek, near Ca’ Fornace; 26 articu- lated shells from Deruta (as Dentilucina cf perusina Deshayes,
453
Bellardi and Sacco collection in the Turin Museum, PU 40604); ten articulated shells from Deruta (as Lucina globulosa Deshayes, Bellardi and Sacco collection in the Turin Museum, PU 40602); one articulated shell from Deruta (Bellardi and Sacco collection in the Turin Museum, as Dentilucina perusina Sacco pseudorotunda Sacco, 1901, BS.154.03.034) ; see Table 5 for measurements and specimen numbers.
Occurrence.—Middle to late Miocene seep carbonates, from northern Italy to Sicily.
Remarks.—There is no formal description of Dentilucina perusina in Sacco (1901); he used this name in the discussion of Dentilucina barrandei (Mayer, 1871), and illustrated three specimens as D. perusina, including one as Dentilucina perusina var. pseudorotunda Sacco, 1901; all specimens are from Deruta. The figured specimens ofD. perusina sensu strictu are not present at MRSN and are presumably lost; here, we illustrate the specimen previously illustrated as Dentilucina perusina var. pseudorotunda Sacco (1901, pl. 21, fig. 15) and designate it as lectotype for Dentilucina perusina. Sacco’s illustrated specimens of D. perusina sensu strictu are more oval than the rather round D. p. pseudorotunda; however, virtually all of the 37 specimens of Bellardi and Sacco collection from Deruta (housed in MRSN) are of the round shape of D. p. pseudorotunda. Hence, we consider this as the typical shape of D. perusina. Moroni (1966) provided an extensive synonymy for this species. Externally similar is the Miocene “Dentilucina” barrandei
from the Turin Hills, but its cardinal teeth are smaller than in L. perusina and they are nearly parallel, in contrast to the radiating teeth in D. perusina. Among the extant species, Lucinoma kazani Salas and Woodside, 2002 living at seeps in the Mediterranean Sea, has a similar shell but less inflated, a similarly short and well-defined lunule, and similar fine commarginal ribs, whereas the North Atlantic-Mediterranean L. borealis has a broader and more elongate lunule, and its ribs are more lamellar than in L. perusina and L. kazani (Salas and Woodside, 2002). None of the Lucinoma species known from Japan are particularly similar to L. perusina (Okutani, 2000).
Family Vesicomyidae Dall and Simpson, 1901 Genus Archivesica Dall, 1908
Type species.—Callocardia gigas Dall, 1895 (by original designation); Recent, Gulf of California.
Remarks.—There is currently little consensus which species belong to the genus Archivesica.While the concept of Amano and Kiel (2007), which includes middle Eocene to Recent species is probably too broad (cf., Amano and Kiel, 2012), the view of Krylova and Sahling (2010) to include only two extant species in addition to the type,may be a little too narrow. In a recentmolecular phylogenetic analysis (Audzijonyte et al., 2012), a monophyletic
clade called the ‘gigas group’ emerged and included 14 named and five unnamed species, including the type species of Archivesica. Because the species described below are morphologically most similar to several members of this clade—Archivesica soyoae (Okutani, 1957) A. kilmeri (Bernard, 1974), A. okutanii
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