Multiple terminal apertures in the foraminiferal genus Arthrodendron Ulrich, 1904

Arthrodendron is a large primitive agglutinated foraminifera known from deep-water settings. It builds large chambers in a uniserial or occasionally branching arrangement, with apertures situated on the terminal chambers. In Arthrodendron specimens from the Upper Cretaceous and lower Paleocene deposits of the Outer Carpathians and Umbria Marche Basin, variability in the development of the last chamber is observed. Terminal chambers of Arthrodendron grandis (Grzybowski) commonly have one aperture situated on a short neck, but we also observe specimens that possess multiple apertures, having up to seven elevated openings that are circular in outline, forming a circular or sub-circular ring in the central part of the chamber. The apertural field occupies from 1/3 up to 1/5 of the chamber diameter. The species description of Arthrodendron grandis (Grzybowski) is here emended.