【摘要】 本文描述了上寒武统凤山组头足类化石27种,分属于13属、3科、3目、3亚纲。其中2新目、2新科、10新属、26新种,并讨论了分布、起源及演化等问题。更多还原

【Abstract】 The present report is to describe the Cephalopods collected from the latestCambrian Fengshan Formation in northern Anhui,Zaozhuang and Jinan of Shantung,and Benqi of Liaoning.The Fengshanian cephalopods in North China have providedevidences for explicating the origin of the major Cephalopoda stocks,such as Acti-noceratoidea,Endoceratoidea and Nautiloidea.A fact has been proved from thepresent studies that the increase in complexity of siphuncle is shown in series from Plectroncerida,Yanhecerida to Endocerida.Hence,it seems probable that the Endo-ceratoidea was directly derived from Plectronoceras through its primitive stock i.e.Yanhecerida.Of particular interest is the occurrence of Protactinocerida,whichappears to represent the earliest form of Actinoceratoidea.Protactinocerida bears alarge,nummuroidal siphuncle and the endosiphuncular deposits.It is belived thatActinoceratoidea directly originated from Pleetronoceras through its ancestral stockof Protactinocerida.The Cephalopods here described consists of 13 genera and 27 species with 10 newgenera and 26 new species included.They all belong to 3 families,within 3 orders,of which 2 families and 2 orders are considered as new.The diagnoses of the newgenera,new families and new orders are given as follows:1.New genera:Paraplectronoceras Chen,Qi et T.E.Chen(gen.nov.)Type species:Papaptectronoceras pyriforme Chen,Qi et T.E.Chen(gen.et sp.nov.)Conch rather small,curved endogastrically,expanded moderately or rapidly,ovalin cross section,being compressed laterally and somewhat more narrowly roundeddorsally than ventrally.Siphuncle small,ventral in position,without calcareousdeposits.Segments slightly expanded,pearshaped in early stage.Septa necks short,curved,but straight in adult stage.Fengshan stage of Late Cambrian,northern Anhui.Jiagouceras T.E.Chen et Tsou(gen.nov.)Type species:J.cordatum T.E.Chen et Tsou(gen.et sp.nov.)Conch small,nearly straight,rapidly expanded,compressed in cross section.Si-phuncle empty,ventral in position.Segments expaneded,cardiac in shape.This genus bears a resemblance to Paraplectronoceras,but differs from the latterin its more strongly expanded siphuncular segments and its less concave septa.Fengshan stage of Late Cambrian,northern Anhui.Lunanoceras Chen et Qi(gen.nov.)Type species:L.precardium Chen et Qi(gen.et sp.nov.)Conch large,slightly curved endogastrically,oval in cross section,being slightlycompressed laterally and somewhat more narrowly rounded ventrally than dorsally.Siphuncle ventral in position;septal necks strongly recumbent;connecting ringsslightly expanded,with their tips curved around septal necks and thickened.Dia-phragms regularly concave;interval of diaphragms equal to that of septa,withoutcalcareous sediments.Fengshan stage of Late Cambrian,Shantung province.Eodiaphragmoceras Chen et Qi(gen.nov.)Type species:D.sinense Chen et Qi(gen.et sp.nov.)Conch large,nearly straight or slightly curved endogastrically,oval in crosssection,being compressed laterally and somewhat more narrowly rounded ventrallythan dorsally.Siphuncle ventral in position;septal necks subholochoanitic,nearlystraigt ventrally and dorsally,strongly bent outwardly in lateral sides.Connectingrings thick,nearly straight dorsally and expanded laterally.Diaphragms essentiallystraight,sloping orad from the venter,without calcareous sediments in their interval.Fengshan stage of Late Cambrian,North China.Rectseptoceras Tsou et T.E.Chen(gen.nov.)Type species:R.eccentricum Tsou et T.E.ChenConch small,rapidly expanded,straight or slightly curved endogastrically,ovalin cross section,being compressed laterally and somewhat more broadly rounded ven trally than dorsally.Siphuncle small,between center and venter in position.Septalnecks orthochoanitic in late stage,slightly bent outward in early stage.Septa ratherslightly concave.Fengshan stage of Late Cambrian,North Anhui.Protactinoceras Chen et Qi(gen.nov.)Type species:P.magnitubulum Chen et Qi(gen.et sp.nov.)Conch large,rapidly expanded,slightly curved endogastrically,oval in cross sec-tion,being compressed laterally.Siphuncle large,ventral and subventral in position,contracted orad in late stage.Siphuncular segments nummuroidal,about 5—9 timesbroad than long.Septal necks cyrtochoanitic in early stage,loxochoanitic in adult stage.Septa in broad contact with connecting rings.Diaphragms W-shaped;their intervalequal to the length of camera,occupied by calcareous deposits.Fengshan stage of Late Cambrian,North China.Physalactinoceras Chen et Qi(gen.nov.)Type species:P.bullatum Chen et Qi(gen.et sp.nov.)Conch large,rapidly expanded,slightly curved endogastrically.Living chambershort,slightly enlarged or contracted aperturally,oval in cross section being compres-sed laterally and more narrowly rounded dorsally than ventrally,or vice versa insome species.Siphuncle large,ventral in position.Septal necks recumbent in ven-ter and lateral sides,but nearly straight in dorsum.Connecting rings curved,ligulate-shaped in venter and lateral sides but circular-like in dorsum.Diaphragmscurved,rarely straight,with their interval occupied by calcareous deposits.Fengshan stage of Late Cambrian,Shantung province.Yanheceras Chen(gen.nov.)Type species:Y.endogastrura Chen(gen.et sp.nov.)Conch small,straight or slightly curved endogastrically,oval in cross section,being compressed laterally.Siphuncle ventral in position.Septal necks short,or-thochoanitic.Connecting rings thick in early stage,thin in adult stage.Diaphragmsconical in form,with their interval occupied by calcareous deposits.Fengshan stage of Late Cambrian,China.Archendoceras Chen et Qi(gen.nov.)Type species:A.conipartitum Chen et Qi (gen.et sp.nov.)Conch nearly straight,oval in cross section,being compressed laterally and morenarrowly rounded dorsally than ventrally.Siphuncle ventral in postilion.Septalnecks subholochoanitic and slightly curved in early stage,hemichoanitic and straightin adult stage.Diaphragms conical in form,without calcareous deposits in theirinterval.Fengshan stage of Late Cambrian,Shantung province.Aetheloxoceras Chen et Qi(gen.nov.)Type species:A.suxianense Chen et Qi(gen.nov.)Conch straight,oval in cross section,being compressed laterally and more nar-rowly rounded ventrally than dorsally.Siphuncle large,ventral in position.Septalnecks loxochoanitic,half the length of camera.Connecting rings thin,but thick inearly stage.Diaphragms strange in form,rather steep in their venter and dorsum,and slowly sloping in subdorsum.Fengshan stage of Late Cambrian,North Anhui.2.new families:Protactinoceratidae Chen et Qi(fam.nov.)Conch large,rapidly expanded,curved endogastrically,compressed in cross sec-tion.Siphnncle large,ventral and subventral in position.Segments expanded. Septal necks and connecting rings exhibiting widely morphologic variation.Septalnecks orthochoanitic,loxochoanitic,Cyrtochoanitic or recumbent in form.Connectingrings variable morphologically,curved slightly to strongly.Diaphragms straight,curv-ed or W-shaped;their interval equal to the length of camera,occupied by calcareousdeposits.Late Cambrian,North China.Yanheceratidae Chen et Qi(fam.nov.)Conch minute,straight,or curved endogastrically,compressed in cross section.Siphuncle small,ventral in position.Septal necks ranging from orthochoanitic tosubholochoanitic.Diaphragms conical;their interval with calcareous deposits or wi-thout calcareous deposits in some primitive.3.new orders:Protactinocerida Chen et Qi(ord.nov.)Diagnosis:Same as Protactinoceratidae.Yanhecerida Chen et Qi(ord.nov.)Diagnosis:Same as Yanheceratidae.更多还原