LOWER CRETACEOUS BIVALVES FROM THE EASTERN HEILONGJIANG PROVINCE OF CHINA

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In this book 190 marine to brackish bivalvian species mainly from the LongzhaogouGroup and the lowermost Chengzihe Formation of Jixi Group together with 23 freshwaterspecies from the Chengzihe and Muleng Formations of Jixi Group in the eastern HeilongjiangProvince were described. These bivalves comprise 32 species and 1 new genus and species inthe Palaeotaxodonta ,1 species in the Cryptodonta , 95 species (7 species new) and 1 new genusin the Pteriomorphia,12 species in the Palacoheterodonta , 59 species in the Heterodonta ,and13 species in the Anomalodesmata. Based on Jupiteria (Ezonuculana) aff. mactraeformis (Na-gao) ,Portlandia aff. sanchuensis(Yabe et Nagao) and Thracia rotundata (Sow. ) in the uppermarine member of the Peide Formation and Aucellina aptiensis (D'Orb. ),A. caucasica (v.Buch), Exogyra? erecta Gu sp. nov.。Amphidonte subhaliotoidea (Nagao), Aetostreon aff.couloni (Defrance) ,Ostrea spp. ,Arctica cf. saussuri (Brongn. )and Thracia rotundata (J. de C.Sow. ) in the Yunshan Formation , the Longzhaogou Group is corrected to be of late Early Cre-taceous, probably Barremian to Aptian and principally Aptian. The Longzhaogou and JixiGroups could be correlated with each other. Aucellina and Arctica together with Pinna , Isog-nomon and Filosina indicate a temperate climate in the region of the Groups. The ingressedlate Early Cretaceous sea from the east in the ancient Wanda and Jixi areas as well as the LateJurassic sea in the Suibin area appeared not of great depths ,yet most probably of embaymentalpalaeoenvironment. The freshwater species of the Jixi Group belong to Jehol or Witim faunas，entirely of Asian or Holarctic nonmarine faunas ;they are of late Early Cretaceous instead ofLate Jurassic age as held for a long time.

LOWER CRETACEOUS BIVALVES FROM THE EASTERN HEILONGJIANG PROVINCE OF CHINA

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