A new Early Jurassic gastropod from Ellesmere Island, Canadian Arctic - an ancient example of holoplanktonic gastropods

Danish medical bulletin

Schneider S¹  Hülse P¹  Kelly SRA¹  Tilley L¹  Veit R¹  Nützel A¹ 

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关键词: Jurassic;    Canadian Arctic;    pelagic holoplanktonic gastropoda;    Pliensbachian;    anoxia;   

DOI  :  

学科分类：医学（综合）

来源: Den Almindelige Danske Laegeforening

【 摘 要 】

A new, most probably holoplanktonic gastropod genus and species, Freboldia fluitans Nützel & Schneider, is reported from the Early Jurassic (Pliensbachian) of Ellesmere Island, Canadian Arctic. Its shell is very thin, small, with a maximum diameter of 8 mm, inflated, planispiral and almost bilaterally symmetric, with deep umbilici. Hundreds of specimens of Freboldia occur in the matrix of transported siltstone concretions. In summary, these characteristics suggest a holoplanktonic lifestyle for Freboldia. Similar shells are present in the modern holoplanktonic gastropod family Limacinidae and in Cretaceous Bellerophinidae, and the new species is assigned to the latter family. The oldest records of holoplanktonic or pelagic gastropods are represented now by seven Early Jurassic genera: Coelodiscus, Tatediscus, Costasphaera, Pterotrachea, Simoniceras, Globorilusopsis and the new genus Freboldia. These are attributed to five different clades, which made their appearance at approximately the same time. We thus speculate that Early Jurassic anoxia triggered the rapid evolution of the holoplanktonic lifestyle in gastropods.

【 授权许可】

Unknown