Parvamussium donaiense (Mansuy, 1914)
MANSUY, H. 1914. Gisément liasique des schistes de Trian (Cochinchine). Mémoires du Service Géologique de l'Indochine, 4: 37-39 (3, 2). [p. 37, pl. 4, fig. 3]
1914 Pecten (Amussium) [sic] donaiensis Mansuy, 1914
«Diagnosis
Small- to medium-size species of Parvamussium, characterized by subequilateral outline, faint concentric plicae on right valve, weak radial riblets on left valve, and six to seven sharp straight internal ribs which extend nearly to valve margin. Material: A total of 11 specimens encompassing six complete, five incomplete internal and external moulds and casts of the left and right valves from locality BH1, from the Khlong Min Formation; locality BH1 (Fig. 6A), grid reference 0476676E 0942352 N, Ban Mak quadrangle (47251), along Highway no. 44 (km 10+300), Ao Luk District, Krabi Province. Description
Small- to medium-sized, rarely exceeding 14 mm in height, subcircular in outline, inequivalve, nearly equilateral, slightly convex, slightly higher than long. Test thin, apical angle exclusive of auricle about 115°, beak not projecting above straight hinge line; auricles unequal, anterior usually larger than posterior; byssal notch undeveloped; surfaces of right valves generally smooth but with faint concentric threads; left valves with weak spaced radial riblets approximately corresponding to internal ribs; interspaces of external ribs with numerous faint radial threads in some specimens but lacking any concentric ornament on left valves; 6–7 internal ribs very sharp and straight, extending from umbo nearly to valve margin, gradually strengthening ventrally. Dimensions
(Table 1, in mm): The average size is 7.7 mm length, 9.1 mm height, and range of L/H ratio 0.85, but individual specimens may reach 12 mm in length, 14 mm in height, with a L/H ratio of 0.85. Occurrence
Common in dark grey mudstones, and rare in fossiliferous limestone of the Khlong Min Formation at the Ban Khao Ngam, western flank of road-cut outcrop on the Highway no. 44 (km 10+ 300), Ao Luk District, Krabi Province. Age
Toarcian–Early Bajocian (late Lower–early Middle Jurassic). Distribution
Parvamussium donaiense (Mansuy) occurs in the Pa Lan, Mae Sot, and Umphang areas of the westernmost part of Thailand (Fontaine and Suteethorn, 1988; Kozai et al., 2006), Vietnam (Vu et al., 1991) and outside Sundaland, the species was also identified in Tibet (Yin and Grant-Mackie, 2005).» SAENGSRICHAN, W., T. CHAROENTITIRAT, A. MEESOOK, K. HISADA & P. CHARUSIRI. 2001. Paleo-environments and tectonic setting of the Mesozoic Thung Yai Group in Peninsular Thailand, with a new record of Parvamussium donaiense Mansuy, 1914. Gondwana Research, 19: 47-60, figs. 1-10. [p. 59]
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Parvamussium donaiense (Mansuy, 1914); W. Saengsrichan et al., 2011, Paleo-environments and tectonic setting of the Mesozoic Thung Yai Group in Peninsular Thailand, with a new record of Parvamussium donaiense Mansuy, 1914, figures 8A-8F.
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