The 'Metacryphaeus tuberculatus Group' (Trilobita, Calmoniidae) from the Devonian of the Parnaíba Basin, Brazil

Calmoniid trilobites of the “Metacryphaeus tuberculatus group” occur in many Devonian localities within the Malvinokaffric Realm. In the Parnaiba Basin, in northeastern Brazil, the group is represented by Metacryphaeus tuberculatus Kozlowski, 1923, and M. meloi Carvalho, Edgecombe and Lieberman, 1997, from the late Eifelian—early Givetian Pimenteira Formation in the environs of the city of Picos and the early Givetian Passagem Member (Pimenteira Formation) from the vicinities of Picos and Pimenteiras in Piaui State. Based on specimens found in the region of Joao Costa, southeastern Piaui State, the present study reinforces data on the occurrence of M. tuberculatus in the Pimenteira Formation and reports the presence of genal spines in some individuals of M. meloi, indicating a feature previously unknown for this species.