Middle Ordovician (Darriwilian) brachiopods and trilobites from Thompson Creek, Northwest Nelson, New Zealand

A well preserved Middle Ordovician shelly fauna, represented by twelve species of lingulate brachiopods and one trilobite genus, was recovered from an allochthonous limestone lens exposed in Thompson Creek, northwest of Nelson, on the South Island of New Zealand. The stratigraphic setting is unclear as the limestone is situated in the Takaka Terrane adjacent to the Anatoki Fault, separating this terrane from the Buller Terrane. The original depositional environment of the limestone is interpreted as relatively deep water (outer shelf to upper slope). Lingulate brachiopods described include the new species Hyperobolus? thompsonensis sp. nov., Cyrtonotreta robusta sp. nov., Scaphelasma paturauensis sp. nov., Torynelasma takakaea sp. nov. and Nushbiella neozealandica sp. nov., together with representatives of Spinilingula, Schizotreta, Trematis, Cyrtonotreta, Physotreta? and Lurgiticoma? that remain in open nomenclature. Several additional acrotretoids and linguloids that cannot presently be confidently attributed to known genera are also documented. Undiferina nevadensis, previously described from Nevada and west Kazakhstan, is represented in the Thompson Creek fauna by the best preserved material of this genus yet known, revealing additional information about its morphology and life habit. The brachiopod fauna, the first of Middle Ordovician age to be described from New Zealand, shows strong affinities to Middle Ordovician faunas from Kazakhstan, Nevada, and to a slightly younger assemblage from the Pratt Ferry Formation of Alabama. The trilobite documented from Thompson Creek is tentatively assigned to Gogoella, a genus previously described from Western Australia and Argentina. Associated conodonts including Histiodella kristinae, Paroistodus horridus and Periodon macrodentatus indicate a mid-Darriwilian (late Da2 to early Da3) age for the limestone.

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