The largest Menuites fresvillensis (Seunes, 1890) (Ammonidea, Pachydiscidae) from the Maastrichtian Quiriquina formation, Chile

Abstract

The pachydiscid ammonite Menuites fresvillensis, which is known from the Abathomphalus mayaroensis planktonic foraminifer zone, is considered an index taxon for the lower part of the Upper Maastrichtian (Upper Cretaceous), with records from Europe, Australia and South America. Two unusually large specimens are described here one of them being the largest individual ever recorded, with a diameter of 425 mm. Previously, the Quiriquina Formation has yielded specimens that reached diameters of 360 mm.

Based on the new material and specimens described previously in the literature, it is now possible to reconstruct the later growth stages of M. fresvillensis, in particular for specimens with diameters >117 and up to 425 mm. These data demonstrate that M. fresvillensis maintains its characteristic morphology, albeit slight variations, throughout ontogeny, including the largest specimens described here.