CONODONT BIOSTRATIGRAPHY OF THE VISEAN SERIES IN EASTERN AUSTRALIA

Conodonts from Visean limestones of the Yarrol and Tamworth Belts of Q ueensland and New South Wales are, in general, sparsely preserved but widespread and about equally divided between endemic and cosmopolitan species. Patrognathus conjunctus sp. nov. is the commonest conodont in the early Visean and gave rise to Montognathus semicarinatus gen. et sp. nov. and to M. carinatus gen. et sp. nov., the trio being name-bea rers for three zones based on endemic elements. The fourth and highest Visean zone has the mondial Gnathodus texanus and Gnathodus bilineatu s as joint nominate species, the latter being included in the zonal na me to emphasise the restricted definition we adopt for G. texanus. Ade tognathus also probably evolved from Patrognathus to give a lineage of three new endemic species: - A. taphrognathoides, A. cannindahensis a nd A. subunicornis, all predating the earliest adetognathids of the no rthern continents. Cavusgnathus altifrons sp. nov. is intermediate in platform morphology and time-range between late Tournaisian Clydagnath us and late Mississippian species of Cavusgnathus; Synprioniodina? tho mpsoni sp. nov., likewise seems to be intermediate between S.? pulchra and Hindeodus cristula. Other new taxa are: Mestognathus convexus, Vo gelgnathus angustus, Gnathodus rugulatus and G. girtyi maxwelli. Descr ibed and illustrated but left in open nomenclature are Adetognathus ? sp. A, Cudotaxis sp. A, Gnathodus sp. A, and Rhachistognathus sp. J. C onodont zones and brachiopod zones give generally accordant divisions, apparent discrepancies being attributable to zonal boundaries locally lacking sufficient data control or being influenced by major facies c hanges. Approximate limits are indicated in the sequences of eastern A ustralia for the Lower (VI), Middle (V2) and Upper (V3) divisions of t he Visean, account being taken of ages suggested in the recent literat ure on ammonoids, algae and foraminifera. No evidence is found for any major hiatus in the Visean although regional disconformities mark its base in the Hunter Valley, N.S.W. and its top in parts of the Yarrol- Rockhampton area.