Abathomphalus is a
genus of
fossil foraminifera present in the
Maastrichtian (77.2 to 66 million years ago), the geological age preceding the
Cretaceous–Paleogene extinction event. Due to its geological range and
cosmopolitan distribution, The test of
Abathomphalus forms a low to flat umbilicate trochospiral, with four to five petaloid chambers per whorl. Its sutures are curved and oblique, depressed to thickened and nodose on the spiral side, but depressed and radial on the umbilical side. The umbilicus is small. The periphery is angular to truncate, with two variously spaced keels (i.e., bicarinate); the keel on the umbilical side may be reduced to a row of short transversal costellae. The wall is calcareous, its surface perforated, commonly ornamented with fine pustules and short aligned costellae. The primary aperture is interiomarginal, extraumbilical-umbilical, with a porticus. The portici of successive chambers coalesce in the early stage, become larger in the adult stage and join only at a few points. This genus differs from
Globotruncana in the radial sutures on the umbilical side, the extraumbilical position of its primary aperture, and the closed umbilical area. It differs from
Globorotalia and
Rotalipora by the presence of the tegillum and accessory infralaminal apertures. It differs further from
Rotalipora by lacking secondary sutural apertures on the umbilical side.
Globotruncanella is considered the ancestor of
Abathomphalus. == Taxonomy ==