Premise of research. Five permineralized specimens of infructescences and dispersed fruits assignable to the Altingiaceae have been identified from the Late Cretaceous (Coniacian) Eden Main Quarry on Vancouver Island, British Columbia, Canada. Two infructescences and three isolated two-loculed fruits are preserved in calcium carbonate marine concretions.

Methodology. Concretions were sectioned using the cellulose acetate peel technique and were included in a phylogenetic analysis employing morphological characters using TNT.

Pivotal results. Infructescences are globose ca. 1 cm in diameter with at least 24 two-loculed fruits and a broad central axis. We have been unable to identify any perianth parts, but there are knob-like extrafloral processes similar to the phyllomes of other altingiaceous infructescences. The inner carpel lining consists of a single palisade layer of elongate rectangular cells. The endocarp also contains several layers of thick-walled, elongate sclerenchyma. The mesocarp is well differentiated, with fiber bundles interspersed with parenchyma and resin canals. There are at least 16 seeds (ovules) per carpel with axile placentation, but most of these are immature or aborted. Fruits have septicidal and ventricidal dehiscence. Specimens are assigned to Protoaltingia comoxense Scharfstein, Stockey & Rothwell gen. et. sp. nov.

Conclusions. These fossils represent the second-most ancient occurrence of Altingiaceae, and phylogenetic analysis of morphological characters confirms that P. comoxense is most similar to species of Altingia. Results of morphological analyses resolve Altingia and Liquidambar as sister clades, placing P. comoxense as the basal member of the Altingia clade and sister to Altingia spp., thus documenting that evolutionary diversification of the core eudicot family Altingiaceae (Saxifragales) was well underway by the mid–Upper Cretaceous.