An Extinct Genus with Affinities to ExtantDavidiaandCamptotheca(Cornales) from the Paleocene of North America and Eastern Asia

Abstract

A new genus of Cornales is recognized based on infructescences and foliage from the Paleocene of Wyoming, Montana, and North Dakota in the United States; southern Alberta, Canada; Heilongjiang, northeastern China; and Kamchatka and the Koryak Upland, northeastern Russia. Amersinia obtrullata gen. et sp. nov. has globose to ellipsoid infructescences with four or five basal deciduous bracts and numerous obtrullate, trilocular fruits with epigynous calyces. Each locule bears one seed and has a dorsal germination valve near the apex. The infructescences and fruits show many similarities to those of extant Camptotheca, but the extant genus is distinguished by only one or two locules and the absence of infructescence bracts. Fossil leaves previously assigned to “Viburnum” cupanioides (Newberry) Brown, Viburnum kingiensis Chelebaeva, and Viburnum pseudoantiquum Golovneva are transferred to the extinct foliage genus Beringiaphyllum gen. nov. They are distinguished from Viburnum by their long petioles and compare favorably to the leaves of extant Davidia. The fossil leaves are elliptical to ovate with pinnate secondary veins, percurrent tertiary veins, and obtuse teeth. Beringiaphyllum leaves and Amersinia fruits are considered likely to represent a single extinct genus because of their shared cornalean affinity and co‐occurrence at numerous sites both in North America and Asia. Although the leaves share more characters with Davidia, the Amersinia fruits share more characters with Camptotheca. The existence of Amersinia and Beringiaphyllum both in Asia and North America, together with their absence or rarity in the Paleogene of Europe, indicates that this plant probably dispersed across Beringia in the late Cretaceous or early Tertiary.