Abstract
We describe Early and Middle Ordovician brachiopod faunas from northeastern Spitsbergen and discuss their bio-stratigraphical and palaeoecological implications. We recognise 60 species and 41 genera representing both linguli-form and rhynchonelliformbrachiopods. These include one new genus, the obolid Lenticulella with the type species Lenticulella amphora (Krause & Rowell, 1975), and 23 new species: Ectenoglossal oviforma, Ellipto-glossa vulgaris, Rosobolusl elongatus, Broeggeria obscura, Mirilingulal svalbardensis, Schizotreta marginalis, Conotreta convexa, Cyrtonotreta profilbekkiensis, Cyrtonotreta spinosa, Eurytreta subtriangularis, Hisingerella maniformis, Semitreta basisslettaensis, Semitreta pustulosa, Semitreta spitsbergensis, Numericomalproclina, Eoconulus subquadratus, Dictyonites mugilis, Pelonomia sulcata, Leptella (Leptella) inequicostellata, Protosken-idioides promontorium, Anomalorthis rossi, Nothorthis subpyramidalis and Phragmorthis noda. The Ordovician succession contains bothintertidal and deep-sea deposits with brachiopod faunas from nearly the whole range of environments. The Tremadocian is represented by a succession of low-diversity, rhynchonelli-form-dominated assemblages occupying shallow-marine environments. With theabrupt and large-scale drowning during the Floian, these faunas were replaced by a sparse slope fauna of micromorphic linguliforms. The outer shelf environments established in the latest Floian were occupied by a highly diverse brachiopod fauna dominatedby micromorphic linguliform taxa. As the environment shifted toward the mid-shelf during the Darriwilian, however, the composition of the fauna changed to an Orthidiel la-dominatQd assemblage of mostly rhynchonelliform taxa. The very late occurrence ofthe Orthidiella assemblage suggests that the Dapingian Orthidiella Zone found in America is probably diachronic. Although it includes many endemic species, the Middle Ordovician fauna shows a strong resemblance to the brachiopod fauna of Nevada. This study is based on approximately 16 500 brachiopod specimens obtained from both crack-out samples and acetic-acid-treated bulk samples.
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