A revision of the Devonian Malvinokaffric dalmanitid trilobite Dalmanitoides Delo, 1935, on the basis of new data from Argentina

Abstract

In light of new information on holotypes and additional material from the Lower Devonian type areas from Argentina, the dalmanitid trilobite Dalmanitoides Delo, 1935, is rediagnosed and considered a dalmanitine rather than a synphoriine. Comparisons suggest that Gamonedaspis Braniša and Vaněk, 1973, is a junior synonym of Dalmanitoides, so that this Early-Middle Devonian genus includes at least five species: four formally named from South America, D. drevermanni (Delo, 1935), D. boehmi (Knod, 1908), D. scutata (Braniša and Vaněk, 1973), and D. accola (Clarke, 1913), together with a species from South Africa herein treated in open nomenclature (D. sp. A). Although the number of Dalmanitoides species suggests a diversification of cosmopolitan dalmanitines already present in Malvinokaffric basins, a close relationship with the boreal and slightly older Roncellia Lespérance and Bourque, 1971, would suggest migration from the Eastern Americas Paleobiogeographical Realm during the Early Devonian as origin of the clade, which is in accordance with paleobiogeographic patterns recognized on the basis of evidence from synphoriine distributions. © Palaeontological Association March 2012.