【摘要】 海神石类新种Cymaclymenia acuminata产于桂林南边村Ⅰ剖面,属于Wocklumeria 带上部Parawocklumeria paradoxa亚带的分子,是中国南方上泥盆统顶部三个已知的菊石种之一。更多还原

【Abstract】 A specimen of Cymaclymenia acuminata sp. nov. has been collected by one of the writers from the top of the bioclastic limestone 0.5m below the Devonian-Carboniferous boundary in Nanbiancun Section Ⅰ, 6.6 km northwest of the Guilin city cener, northeastern Guangxi, coexisting with crowded brachiopods and some representatives of the middle Siphonodella praesulcata Zone. Here the stratigraphic sequence is generally in accordance with that in Nanbiancun Section Ⅱ, Which has been introduced by Yu Chang-rain et al. (1987). The top of the bioclastic limestone (NbⅡ-ld) in Nanbiancun Section Ⅱ is equivalent to the aforesaid clymeniid-bearing bioclastic limestone in Section Ⅰ, yielding Cymaclymenia warsteinensis Korn and Wocklumeria sphaeroides (Richter) belonging to the Parawocklumeria paradoxa Subzone of the upper Wocklumeria Zone, and therefore C. acuminate, sp. nov. is believed to be a member of the Parawocklumeria paradoxa Subzone.The representatives of the upper Wocklumeria Zone in South China have been known from three areas, namely, the Daihua-Muhua area of southern Guizhou; the Liuzhai area of northern Guangxi and the Nanbiancun Section area, containing Cym clymenia warsteinensis Korn, Wocklumeria sphaeroides (Richter), Sporadoceras longilobatum Petter, Prionoceras sulcatum (Muster) and Kosmoclymenia (Lissoclymenia) cf. wocklumeri (Wedekind). The discovery of C. acuminata sp. nov. would help understand the upper Famennian ammonoids in the Nanbiancun Section to some extent. Genus Cymaclymenia Hyatt, 1884 Cymaclymenia acuminata sp. nov. (Text-figs. 1—3)Diagnosis Shell discoidal, with relatively wide umbilicus about 2/7 of diameter. Whorls rather high, with a bud-shaped cross-section. Venter carinate. Ventral saddle broad, subdivided into three secondary saddles by two secondary lobes.Description: Shell considerably complete, less than 45 mm in diameter, discoidal and semi-evolute, with an umbilicus about 2/7 of diameter (textfigs. 1, 2). Whorls compressed with a bud-shaped cross-section. Flanks arched, with inner half gently inclined towards the veneer and outer half markedly convergent to a carinate venter. Umbilical edge narrowly rounded; umbilical wall low and inclined (text-fig. 3).External sutures (text-fig. 4) with a rather broad ventral saddle, subdivided into three secondary saddles, and two shallow secondary lobes between them. Lateral lobe quite asymmetric and hatchet-shaped with S-form sides. Tip of the umbilical lobe situated at the umbilical seam.Dimensions and proportions of the new species as shown in the Chinese text.Comparison The present new species can be easily distinguished from other known species of Cymaclymenia by its carinate venter. Moreover, in the configuration of its flanks, it also differs from those species without any ribs but with a similar umbilicus, such as C. striata (Munster), C. warsteinensis Korn and C. nephroides Korn.更多还原