Morphology, affinities and phytogeographic history of Porosia Hickey in the Cretaceous and Paleocene of North America and Asia

Abstract

Morphology and anatomy of the extinct angiosperm fruit, Porosia verrucosa (Lesqueruex) Hickey, are documented in detail based on various modes of preservation including molds, casts, and permineralizations from more than seventy localities in the late Cretaceous and Paleocene. The fruits are schizocarpic with paired unilocular, single-seeded mericarps seated on a prominent gynophore with an hypogynous perianth borne on a long pedicel. The most distinctive feature of these fruits is the regularly spaced cylindrical intrusions over the surface of the endocarp. These are interpreted to represent oil cavities similar to those common in the fruits of extant Rutaceae. The oldest known occurrences of P. verrucosa are from the Late Cretaceous (Campanian to Maastrichtian) of western North America, but the genus traversed Beringia and became widespread in the Paleocene both in Asia (Kazakhstan, Amur Region, and Koryak Highlands), and North America (Montana, North Dakota, Wyoming, Colorado, Oregon, Washington, Alberta, Saskatchewan). It extended to the late Paleocene in the Rocky Mountain and Great Plains region, and appears to have become extinct near the Paleocene-Eocene boundary.

Keywords

• Fossil fruits
• Rutaceae
• Campanian
• Maastrichtian
• Paleocene