460
Journal of Paleontology 91(3):444–466
Remarks.—Extant species with similar hinge dentition and pallial line include Archivesica gigas, A. kawamurai, A. kilmeri,and A. okutanii (Dall, 1895; Kuroda, 1943; Bernard, 1974;Kojima and Ohta, 1997). Among the characters used to distinguish Phreagena from Archivesica was the anterior pedal retractor scar, which is deeply impressed in Phreagena, but shallow in Archivesica (Krylova and Janssen, 2006); in A. strigarum it is deeply impressed. Archivesica strigrarum n. sp. is more elongate than Archivesica aharoni n. sp. and has a more oval (rather than round) anterior adductor muscle scar. It lacks the arched posterodorsal margin and posterodorsal ridge of A. apenninica n. sp. and its anterior adductor muscle scar is oval in contrast to the more quadrate scar of A. apenninica n. sp. Compared to the elongate specimens of A. apenninica n. sp., it has a longer anterior portion. It is also more elongate than most other species of Archivesica, except the early Miocene A. sakoi Amanoetal.,2014from southern Japan.
Archivesica apenninica new species Figure 14
Type specimens.—Holotype: MGGC 23001. Paratypes: MSF 2121, 2123, 2125, 2126; all types from Castelvecchio.
Diagnosis.—Large for the genus; dorsal margin broadly arched, ridge running from umbo to posterior margin; anterior adductor muscle scar oval with groove running toward umbo; no pallial sinus; three radiating and almost equally strong cardinal teeth in each valve.
Occurrence.—Only known from the middle Miocene (early Serravallian) seep carbonate at Castelvecchio in northern Italy.
Description.—Elongate-veneriform shell, up to 125mm long, umbo broad, elevated, slightly prosogyrate, anterior at ~28–33% total shell length. Anterior shell margin strongly convex; ventral margin gently and evenly curved; posterodorsal margin broadly arched, transition to posterior margin indistinct, angulate only in very elongate specimens; posterior margin strongly convex and somewhat pointed. External sculpture of rough growth lines; distinct ridge or angulation from umbo to posterior margin; no
Figure 14. Archivesica apenninica new species, from the middle Miocene seep deposit at Castelvecchio in northern Italy: (1, 2, 10) holotype MGGC 23001, right valve with damaged posterior margin; view of outer shell surface, dorsal view, and close-up of hinge dentition, respectively; (3, 4, 9) paratype MSF 2125, left valve; view of outer shell surface, dorsal view, and close-up of hinge dentition, respectively; (5) paratype MSF 2123, right valve of very elongate specimen; (6) paratype MSF 2121, right valve with damaged posterodorsal margin; (7, 8) paratype MSF 2126, internal mold showing muscle attachment scars and pallial line; view of left valve and dorsal view, respectively.
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