New Carboniferous Dimorphoceratid Ammonoids from Algeria and Arkansas

Discovery of new dimorphoceratid ammonoids provides clarification of earlier taxonomic assignments within the family and expands the record of Trizonoceras Girty, 1909 to include T. horreitense n. sp. from Algeria and T. peregrinsum n. sp. from Arkansas. Sulcodimorphoceras sedraense n. gen. and n. sp. is proposed for unusual dimorphoceratids with ventrolateral sulci and bifid sutural elements. These new taxa are of early Namurian age and occur in strata equivalent to the Lower Pendleian Stage (E1) of the standard British succession.