Distribution of Miogypsinoides in the Zagros Basin,in southwest Iran

In the present study three species of Miogypsinoides are described from the Oligocene–Miocene Asmari Formation of the Zagros Basin in the southwest of Iran. This is the explanation of the morphological recognition and distribution of Miogypsinoides complanatus, Miogypsinoides formosensis (Upper Oligocene, Chattian) and Miogypsinoides dehaartii (Lower Miocene, Aquitanian). Nepionic acceleration is the most important factor for recognition of Miogypsinoides species. Also it is applied in stratigraphic correlation. Examination of samples indicates a decreasing number of nepionic chambers (Mx) as time passes so M. dehaartii with Mx < 10 belong to the Aquitanian age. The study of microfacies shows that these species lived in an open marine environment with normal salinity and medium hydraulic energy in a middle ramp position.