The taxonomy and biostratigraphy of the Ordovician and early Silurian articulate brachiopods of Tasmania

The Ordovician to earliest Silurian rocks of Tasmania belong to, or are correlates of, one of two subgroups ; the Denison Subgroup, a 3400 metre clastic sequence ranging in Franconian age from Franconian to Late Canadian, or the Gordon Subgroup, a 1200 - 1800 metre carbonate sequence ranging in age from Late Canadian or Whiterock to Early Llandovery. The rocks comprising the formations of these subgroups are, in the main, richly fossiliferous with articulate brachiopods and trilobites being the most ubiquitous elements of the fauna. Inarticulate brachiopods are very rare. Of the 60 species of brachiopod described herein, 42 are new. These 60 species belong to 42 genera of which 7 are new. Two new families and two new subfamilies are erected. A biostratigraphic scheme for the sequence of brachiopod faunas has been erected. This consists of 20 zones and an uppermost informal assemblage. The zones in ascending order are:- Apheoorthis humboldtensiszone which is characterised by the nominal species; Nanorthis, carinatazone which contains the nominal species and Apheoorthis humboldtensisLaurie 1980 ; Tritoechialewisi zone which contains T. lewisi Brown 1948 and Syntrophopsis karmbergi Brown 1948 ; Tritoechia florentinensis zone which contains T. florentinensis Laurie 1980 only ; Tritoechia careyi zone which contains T. careyi Brown 1948 only ; Leptella corbetti zone which contains L. corbetti sp. nov., Tritoechia karmbergensis Laurie 1980 and Archaeorthis subcarinata Laurie 1980 ; Hesperonomiella jurikae zone which contains H. jurikae sp. nov. only ; Railtonella scanloni zone which contains R. scanloni gen.et sp. nov. and Hesperonomiella jurikae sp. nov. ; Aporthophyla staiti zone which contains A. staiti sp. nov., an indeterminate orthide and an indeterminate porambonitacean; Leptellina sulcata zone which contains L. sulcata sp. nov. and an indeterminate strophomenacean; Lepidomena fortimuscula zone which contains L. fortimuscula gen.etsp. nov., Rhynchotrema bailliei sp. nov., Apatomorpha melrosensis sp. nov., ?Strophomena sp., Bellimurina cf. compressa Cooper 1956, Hesperorthis longirostroides sp. nov., Dactylogonia rara sp. nov., Chaganella sp., Teratelasmella plicata gen.etsp. nov., ? Ptychopleurella sp., oepikinid gen.et sp. indet. and an indeterminate orthide; Lepidomena pulchra zone which contains L. pulchra gen.et sp. nov., Oepikina banksi sp. nov., Hesperorthis longirostroides sp. nov., ? Rhynchotrema sp., Rhynchotrema bailliei sp. nov. Azamella sp. and Chaganella sp. ; Tasmanorthis calveri zone which contains T. calveri gen. et sp. nov., Azamella rotunda gen.etsp. nov. and Rhynchotrema ponderosa sp. nov. ; Tasmanorthis costata zone which contains T. costata gen.et sp. nov., Azamella sulcata gen. et . sp. nov. Macrocoelia stenomuscula sp. nov., Skenidioides alatus sp. nov., Ptychopleurella magna sp. nov., Rhynchotrema crossi sp. nov. and Murinella magna sp. nov.; Strophomena cf. oklahomensis zone which contains S. cf. oklahomensis Cooper 1956, Tasmanorthis costata gen.et sp. nov., Ptychopleurella cf. magna sp. nov., Azamella sulcata gen.et sp. nov. and an indeterminate atrypide ; Dinorthis westfieldensis zone which contains D. westfieldensis sp. nov, Strophomena burretti sp. nov., Rhynchotrema ?iowense Wang 1949, Protozyga aseptata sp. nov., Hallina inconspicua sp. nov., Macrocoelia brownae sp. nov., Tasmanella nova gen.etsp. nov., Ptychopleurella cf. magna sp. nov., Hesperorthis benjaminensis sp. nov., Sowerbyites vesciseptus Percival 1979, Holtedahlina sp., Sowerbyella (Sowerbyella) cf. anticipata Percival 1979 and Sowerbyella (Sawerbyella) ? lepta Percival 1979; ?Plectorthis dinorthoides zone which contains ?P. dinorthoides sp. nov. and Tasmanella nova gen.etsp. nov, ; Dinorthis holdenoides zone which contains D. holdenoides sp. nov., Rhynchotrema sp., Ptychopleurella sp., Hesperorthis sp. and two indeterminate atrypides ; Isorthis (Ovalella) arndellensis zone which contains I. (0) arndellensis sp. nov., Hirnantia enorme sp. nov. ; ?Onniella perplexa zone which contains (O). perplexa so. nov., Isorthis (Ovalella) arndellensis sp. nov., ?Eospirifer sp., Hirnantia sp. and an indeterminate leptaenid. At the top of the Gordon Subgroup in the Florentine Valley is a single horizon, designated herein the Kinnella ?kielanae assemblage which contains K. ?kielanae (Temple) and an indeterminate leptaenid. A brachiopod fauna associated with a small stromatoporoid mound in the Cashions Creek Limestone of the Florentine Valley was examined and found to be much more diverse than, and generically distinct from, that found in the surrounding sediments.