摘要
一、前言安徽贵池一带的奥陶系发育良好,含丰富的头足类化石。1984年夏,笔者等在贵池百安的方村剖面采获不少头足类化石,其中以下奥陶统的紫台组、牯牛潭组及中奥陶统的大田坝组、宝塔组所产的头足类最为丰富。这批化石经研究共有33种(其中10新种),分属15属8科。另有2未定属种。这些化石的发现增加了我国奥陶纪头足类的新材料,并对这个地区奥陶纪地层的划分以及与国内外的对比提供了可靠的依据。笔者在研究过程中。
Ordovician strata are well-develope in Guichi, Anhui, containing abundant fossils such as cephalopods, conodonts, trilobites, etc. The cephalopods described in this paper were collected from the Lower Ordovician Zetan and Kuniutan Formations and the Middle Ordovican Datienba and Pagoda Formations, consisting of 33 species (including 10 new species), which are assigned to 15 genera and grouped under 8 families respectively. The horizons of each species described in this paper are shown in Table Ⅰ. The Zetan Formation yields the most abundant cephalopods, such as Protocycloceras Hyatt in Eittel, Vaginoceras Hyatt, Dideroceras Flower, Michelinoceras Foerste, Changyangoceras Wang Gangshanoceras Zou, Chisiloceras Gortani, Richardsonoceras Foerste, Clytoceras. Ulrich, Foerste, Miller et Furnish and Ancistroceras Boll. Among these genera; Pratocycloceras occurs in the lower and middle parts of this formation; while Chisiloceras in the upper part; Gangshanoceras is a pseudorthoceratid form newly discovered from Lunshan in Jurong, Jiangsu; and Clytpceras was found in China for the first time. Less cephalopods were obtained from the Kuniutan Formation, only with vaginoceras, Michelinoceras. and Bactroceras, Holm. The cephalopods of the Datienba Formation are dominated by Lituitidae, including Lituites Bertrand and Cyclolituites Remele, in addition to the occurrences of Michelinocerds and Rizosceras Hyatt. The cephalopods of the Pagoda Formation are characterized by Sinoceras Shimizu et Obata emend Yu, also with the occurrences of Michelinoceras and Bactroceras. Most of cian strata of the Yangtze Province, and are closely similar to those from West Hubei, West Hunan DESCRIPTION OF NEW SPECIES Protocycloceratidae Kobayashi, 1935 Protocycloceras Hyatt in Eittel, 1900 Protocycloceras angustisiphonatum Sp. Annulate orthoceracone, gently expanded,with circular cross section. Siphuncle small, oentral in position, approximately 1/10 of corresponding conch diameter. Sepal necks orthochoanitic. Connecting rings thick and straight. Siphoncular deposits of continuous lining. Concavity of septa as deep as 2/3 camera 3 camerae occupying a distance equal to conch diameter. Comparison: This new species is similar to Protocycloceras minosiphonatum Lai et Tsi, but differs from the latter in the central position of the siphuricle and the higher camerae. Horizon and Locality: Lower Ordovician Zetan Formation; Guichi, Anhui Baltoceratidaw Kobayashi, 1935 Bactroceras Holm, 1998 Bactroceras guichiense sp. nov. (P1. Ⅴ. figs. 7, 10; Text-fig. 1) Small orthoceracone, gently expanded, with cricular cross section small, ventral instead of marginal, approximately 1/15 of corresponding conch diameter, with a distance to ventral margin equal to siphuncle diameter. Septal necks long, orthochoanitic, extending apically for a distance as long as 1/4 camera. 2.5 camerae occupying a distance equal to conch diameter. Septa arcuate, with concavity as deep as 2/3 camera. Comparison: This species is similar to Bactroceras avus Holm, but differs from the latter in ventral instead of marginal siphuncle, which has a. distance ventral margin equal to siphucle diacrter Horizon and Locality: Lower Ordovican Kuoiutan Formation; Guichi, Anhui. Endoceratidae Hyatt, 1883 Vaginoceras Hyatt, 1883 Vaginoceras endogastrum sp. nov. (P1. Ⅰ, figs. 5,8,11) Conch endogastric gently expanded. Siphuncle marginal, 1/3 to 2/5 of conch diameter. Septal necks holochoanitic. Camerae high, with 2 of them occupying a distance equal to conch diameter. Comparison: This new species is similar to Vaginoceras belemnititforme Holm, but differs from the latter in the endogastric conch. Horizon and Locality: Lower Ordovician Zetan Formation; Gutichi, Anhui. Michelinoceratidae Flower, 1945 Michelinoceras Foerste, 1932 (p1. Ⅲ, fig.4) Orthoceracone, expanded gently, with circular cross section. Siphuncle small, central in position, approximately 1/15 of corresponding conch diameter. Septal. necks orthochoanitic. Camerae lower, with 4—4.5 of them occupying a distance equal to conch diameter. Comparison: This new species is similar to Michelinoceras chaoi Chang, but differs from the latter in the small siphuncle and dense septa. Horizon and Locality: Lower Ordovician zetan Formation; Guichi, Anhui. Michelinoceras guichiense sp. nov. (P1. Ⅲ, figs. 5,6) Orthoceracone, gently expanded, with circular cross section. Siphuncle small, subcentral by ventral in position, 1/12 of conch diameter. Septal necks very short, orthochoanidc. 2 camerae occupying a distance equal to conch diameter. Surface ornamented with sinuous growth lines, internal surface with faint annulations. Comparison: This new species is similar, to Michelinoceras paraelongatum Chang, but differs from the latter in the dense septa and the faintly annulated internal surface. Horizon and Locality: Middle Ordovician Datienba Formation; Ouichi, Anhui. Proteceratidae Flower, 1962 Gangshanoceras Zou, 1988 Gangshanoceas guichiense, sp. nov. (p1, Ⅰ 6; P1: Ⅱ figs. 13—16; Text-fig. 3) Conch faintly exogastric, expanded rapidlly in apical part and gently in middle part, contracted in base of living chamber Siphuncle ventrocentral in position 1/7 of conch diameter, Siphuncular segments subglobular in shape. Sepal necks faintly cyrtochoanitic, With free part of connecting rings conyex. Camerae. lower, with 6 of them occupying a distance equal to. conch diameter. Comparison: This new species is similar to Gangshannoceas jurongense Zou, but differs from the latter in the more ventral, position of siphuncle, the shape of conch and the continuous subglobular segments. Horizon and Locality: Lower Ordovician Zetan Formation; Guichi, Anhui. Gangshanoceras wannanense sp. nov. (P1. Ⅱ, fig. 10; P1. Ⅲ. figs. 8, 9; Text-fig. 4) Orthoceraeone, expanded rapidly. Siphuncle centro-ventral in position, 1/8 of conch diameter. Segments changing in shape on togenetically from early subcyrtochoanitic stage With inflated segments through suborthochoanitic stage with less inflated segments to orthochoanitic stage with tubular segments. Septa dense. 6 camerae occupying a distance equal to conch diameter. Comparison: This new species is similar to Gangshanoceras jurongense Zou and Gangshanoceras guichiense sp. nov., but, differs in the orthoceracone and ontogenetically changing of the siphuncular segments. Horizon and Locality: Lower Ordovician Zetan Formation; Guichi, Anhui. Oncoceratidae Hyatt, 1884 Richardsonoceras Foerste, 1933 Richardsonoceras beianense sp. nov. (P1. Ⅳ, figs. 8, 14; P1. v, fig. 9) Compressed exogastric brevicone, expanded rapidly. Siphuncle small, ventral. Septal necks orthochoanitic. Camerae dense. Surface ornamented with transverse ridges inclining dorsally in adapical part. Horizon and Locality: Lower Ordovician Zetan Formation; Guichi, Anhui. Rizoceras Hyatt, 1884 Rizoceras anhuiense sp. nov. (P1. Ⅳ. figs. 10, 11: Tet-fig. 5) Compressed exogastric brevicone, expanded rapidly, with tapering ratio about 1:3. Siphuncle small, ventral instead of marginal. Dorsal septal necks armenoceroid; ventral septal necks suborthochoanitic. Connecting rings inflated in the adapical part of segments. Siphuncular segments heartshaped. Camerae dense, with 8 of them in a distance equal to conch diameter. Concavity of septa as deep as 2 eamerae. Comparison: This new species is similar to Rizoceras, circulare Lai, but differs from the latter in the less expanded brevicone. It is also similar to Rizoceras oricntale Lai, but differs in the greater tapering ratio. Horizon and Locality: Middle Ordoviclan Datienba Formation; Guichi, Anhui. Estonioceratldae Hyatt in Zittel, 1900 Clytoceras Ulrich, Foerste, Miller et Furnish, 1942 Clytoceras yangtzeense sp. nov.(P1. Ⅳ, figs. 16,.'t7) Coiled conch; whorl rapidly expanded, and strongly compressed, with elliptical whorl section. Siphuncle large, subventral, about 1/10 of conch diameter. Septal necks orthochoanitic; septal foramina contracted; connecting rings thick, straight in dorsum and inflated in venter. Camerae lower, with 5 of them in a length equal to whorl height. Horizon and Locality: Lower Ordovician Zetan Formation; Guichi, Anhui.
出处
《古生物学报》
CAS
CSCD
北大核心
1989年第5期617-633,700-704,共17页
Acta Palaeontologica Sinica
