摘要
本文描述了河北秦皇岛和东北南部下奥陶统马家沟组鹦鹅螺化石10个新种,分属于5个新属、1个新科,并讨论了其分布、起源及演化等问题。
The present paper is to describe the Nautiloids collected from the basal part of Majiagou Formation of lower Ordovician in Qinhuangdao of Hebei, Betixi of Liaoning and Tonghua of Jilin.They were not found and studied formerly. Almost each of these Nautiloids has a small,straight brevicone or cyrto-cone.The exterior surface of the shell is little known. Siphuncle is relatively large, subcentral, occupied by annulosiphonate deposits and endocones are ntar endosiphoncone.Kndosiphuneular canal system is developed.Septal necks are holo-choanitic, connecting rings are weak. From the broad siphuncle aspect,the endocones and the holochoanitic septal necks, they are similar to Endoceroids, However,Judging by annulosiphonate deposits,endosiphuneular canal system and cameral deposits, they resemble Polydesmiids or Actinoceroids.Therefore.it is believed that the Polydesmiidae and Actinocerotidae were directly originated from Endocerida through their ancestral stock, the Deformoceratidae.The Deformocercs-Peripatoceras zone is established under the Polydesmia zone.This zone is situated in the basal part of Majiagou Formation and overlying the Manchucoceras-Coreanoceras zone of Liangjiashan Formation.The nautiloids here described consist of 5 new genera with 10 new species included.They all belong to one new family,of Order Endocerida.The five new genera are Deformoceras,Kionodeformoceras,Eurydeformoceras, Peripatoceras and Cyrtodeformoceras,in which Deformoceras is the type genus of the new family,and Deformoceras zhaoi is the type specis of the new genus Deformoceras.The diagnoses of the new family are given as follows; Deformoceratidae Li et L.F.Li (fam.nov.)Conch small,straight,endogastrally curved cyrtocone,circular or subcircular in cross section.Siphuncle large,eccentric or submarginale, concavosiphocate. Septa! necks holochoanitic, connecting rings weak, rarely preserved.Siphuncle occupied by annulosiphonate deposits and endocones near endosiphoncone, endosiphuncular canal system developed.Cameral deposits developed or weakly developed. Early Ordovician, Northern Hebei, China.
出处
《吉林大学学报（地球科学版）》
EI
CAS
1985年第4期11-20,119-122,共14页
Journal of Jilin University：Earth Science Edition
