The lower part of the Late Ordovician Ardwell Farm Formation of the Girvan district in SW Scotland yields a low-diversity ostracod fauna comprising six species. Many of these ostracods are biostratigraphically short-ranging North American taxa limited to an interval equivalent to the gracilis and bicornis graptolite biozones. These species include ‘Ctenobolbinaventrospinosa and Baltonotella parsispinosa that permit inter-regional correlation with the Sandbian strata of the USA and Arctic Canada. This chain of correlation is also confirmed by chitinozoans, such as Belonechitina hirsuta, that occur with the ostracods in the Ardwell Farm Formation. Although allochthonous and transported by turbidity currents into a deep-water clastic-rich basin, the ostracod fauna of the Ardwell Farm Formation resembles other Ordovician deep-water ostracod biotopes, characterized by podocope ostracods and low species diversity. Alternatively the ostracods might simply have been transported from a carbonate ramp setting.

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