The first mastixioid fossil from Italy and its palaeobiogeographic implications

An incomplete permineralized fruit was collected from Oligocene sediments of NW Italy (late Rupelian or early Chattian, roughly 30–27 Ma). Its three-dimensionally preserved seed cast shows a U-shaped cross-section, typical of the mastixioids, a group of plants of the Cornales. The particular shape of the dorsal valve infold and seed locule allowed assignment of the fruit to the genus Mastixia rather than Eomastixia, whose endocarps possess an identical external morphology. Such a thick wall and coarse sculpture of the endocarp was not previously known in the European fossil record of Mastixia, therefore the specimen is considered a new species Mastixia rattazzii Martinetto, whose complete endocarp appearance has been hypothetically reconstructed by comparison with similar fossils. This new fossil demonstrates that mastixioids were growing to the south of the Alps, at least in the Oligocene. Unlike other thermophilous plants of the Miocene forests, the mastixioids do not seem having found a refuge in Italy when the late Neogene cold pulses affected central Europe.

► Description of a mastixioid fruit from the Oligocene of north-western Italy.
► A combination of characters allowed to assign the fruit to the genus Mastixia.
► Moderately similar to North American species, but assigned to a new species.
► Part of an ancient “whole plant” which did not yield a fossil record up to now.
► Mastixioids are firstly recorded to the south of the Alps.