Propeamussium fuganjiensis Omori & Inoue in Yamana, 1997
YAMANA, I. 1997. Fossil Records from Tottori Prefecture. 303 p. Fuji-Shorten, Tottori (in Japanese). [p. 88, pl. 21, figs. 1a- 3; pl. 22, figs. 1- 6]
1997 Propeamussium fuganjiensis Omori & Inoue in Yamana, 1997
«Remarks. — A single deformed internal mold of right valve ( GMNH - PI2039, 27.0 mm long, 35.4 mm high ) partly possessing the shell material was obtained. The shell is higher than long with nine n arrowly- elevated internal ribs. The shell material preserved near the ventral margin shows that the external surface is covered with fine commarginal lamellae. Judging from these characters, the present specimen is referable to Propeamussium fuganjiensis Yamana from the lower Middle Miocene Tottori Group, Tottori Prefecture. As shown in the above synonym list, the species name fuganjiensis has become available according to the International Code of Zoological Nomenclature since Yamana ( 1997) gave a diagnosis for the species. P. fuganjiensis is characterized by the relatively large size (commonly larger than 20 mm high and often attaining more than 55 mm high), higher shell outline (ratio of length/ height ranging 0.78-0.92), right external surface covered with commarginal lamellae, left external surface with a cancellate pattern of commarginal lamellae and radial striations, and nine narrow internal ribs that are shorter in left valve than in right valve (Yamana, 1972, 1997).
This species often occurs in association with Propeamussium tateiwai Kanehara, but the latter is easily distinguishable from the former in its smaller shell size (commonly less than 12 mm in height) and nearly circular outline. P. takasensis Ômori (1955, p. 12-13, pl. 2, fig. 1) from the Miocene of Yamagata Prefecture resembles this species in having a higher shell outline with nine internal ribs. However, P. takasensis is based on a small poorly-preserved specimen, thus its detailed comparison with this species is now difficult. The species most similar to the present one is Propeamussium watsoni (Smith), a Recent Indo-Pacific species. These two species resemble in shell size, outline and external sculpture, but differ in degree of the development of the internal ribs between right and left valves. Length of the internal ribs of P. watsoni is nearly same between right and left valves, whereas that of P. fuganjiensis is considerably different as illustrated by Yamana (1972). Occurrence. — Loc. HN02. Distribution. -- Upper Lower Miocene: Shidara and Morozaki Grs., Aichi Pref. Lower Middle Miocene: Tottori Gr., Tottori Pref.; Bihoku Gr., Hiroshima Pref.» KURIHARA, Y. 2000. Middle Miocene deep-water mollusks of the Haratajino formation in the Isobe district, the Annaka-Tomioka area, Gunma prefecture, central Japan. Bulletin of Gunma Museum of Natural History, 4: 1-22, pls. 1-4. [p. 11, 12]
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Propeamussium fuganjiensis Yamana; T. Kurihara, 2000, Middle Miocene deep-water mollusks of the Haratajino formation in the Isobe district, the Annaka-Tomioka area, Gunma prefecture, central Japan, plate 4, figure 22.
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