摘要
本文记述的材料系作者和我队陆相盆地研究组储澄、黄宗和等于1982-1983年在广东南雄盆地实测坪岭一古城剖面(以下简称坪岭剖面)黄坑组和白垩-第三系界线时采集的。共生的主要化石有恐龙蛋、轮藻和介形类。文中描述的腹足类口盖化石有3属3新种,它们为确定上白垩统的地质时代,划分与对比地层提供了新依据,同时也为腹足类口盖化石的分布积累了素材。对文中图版摄影者吴为敏、李松柏和标本的辛勤采集者储澄等,在此深表感谢。
The Upper Cretaceous Gastropod opercula described here were discovered for the first time and collected from the Upper Cretaceous Nanxiong Formation and Huangkeng Formation of the Nanxiong Basin in Guangdong, containing 3 new species in 3 genera, namely, Reesidella nanxiongensis sp. nov., Bithynia gigantea sp. nov., and Mirolaminatus (Monolaminatus) comextus sp. nov.
According to a recent study of plentiful fossils such as dinosaurian eggs, ostracods, charophytes, etc. collected from the same formation, which are regarded as Late Cretaceous in age, these fossil gastropod opercula can also be assigned to the same age.
Reesidella nanxiongensis sp. nov. (Pl. Ⅰ, figs. 7, 8; Pl. Ⅱ, figs. 3—13)
Operculum large and thick, cuticular-calcareous in composition, belonging to the concentric type. Posterior end bluntly pointed, while anterior end broadly round. Peristome of inner and outer lips nearly arcuate; while that of parietal lip slightly concave. Periphery of operculum gradually becoming strongly depressed and bowl-like in appearance toward the center. Concentric lines on operculum clear. Ventral with 7—10 concentric layers, which gradually become narrower from periphery toward the core. Opercular core situated anteriorly and close to the peristome of columellar edge, not identical with the depressed center of the operculum. An obliquely depressed facet present beside the peristome of inner and outer lips, with a wilth of 0.561—0.612mm.
Bithynia gigantea sp. nov. (Pl. Ⅰ, figs. 1—6)
Operculum in the shape of melon seed, larg and thick, with calcarcous cutin, belonging to spiral type. Peristome of outer lip edge more convex than of inner lip; peristome of parietal edge straight or slightly concave. Operculum strongly depressed in central part, with two protruding facets. First protruding facet larger, with a narrow outer ring and concentric lines. Second protruding facet relatively small, located in central depression and inclined to peristome of the inner lip, with spiral lines; outer ring broad, with concentric lines. First intergroove between operculum and the first protruding facet broad and deep, especially at the peristome of outer lip, second intergroove between first and second protruding facets narrow and shallow. Opercular core located anteriorly and close to peristome of columellar edge. Ventral with periphery of outer lip wider than that of inner lip, and possessed of broad concentric layers.
Mirolaminatus (Monolaminatus) contextus sp. nov. (Pl. Ⅰ, figs. 9—14; Pl. Ⅱ, figs. 1, 2)
Operculum not so large, cuticular—calcareous in composition. Anterior end broadly round, while posterior end sharply round. A protruding facet present, with posterior end inclining toward, and connexted with peristome of outer lip. Spiral lines on the exposed side of operculum fascicular ridge-like; spiral lines on protruding facet gradually broadening and thickening from the location of the core's spiral ridges toward the peristome of outer lip. Curls regular, protruding like ridges, differentiated from operculum to form the protruding facets. Opercular core circular, strongly depressed, located amid the spiral ridges and close to peristome of columellar lip. Ventral with no lines and ornaments, but with a subeircular and slightly concave plane at the location correspongding to the opercular core. Peristome of outer lip wider than that of inner lip.
出处
《古生物学报》
CAS
CSCD
北大核心
1991年第3期406-412,439-440,共7页
Acta Palaeontologica Sinica
