Ozakia, a new genus of winged fruit shared between the Miocene of Japan and western North America

Abstract

A new genus is recognized based on winged fruits with a single species shared between the Miocene of southwestern Honshu, Japan, and the Miocene of Oregon and Idaho, USA. Calyces of Ozakia emryi gen. et sp. n. were formerly attributed to Heptacodium (Caprifoliaceae) and Amelanchier (Rosaceae); however, newly recovered specimens reveal additional characters that contradict these assignments. The pedicellate fruits are obovate, tapering basally and truncate apically, with about 10 longitudinal ribs, a prominent epigynous synsepalous calyx of five lobes, each with a midvein and a pair of weaker, ascending intramarginal primary veins. The single style has a capitate stigma. Ozakia is considered to represent an extinct eudicot genus, the familial affinities of which remain uncertain. The eastern Asian–western North American disjunction of Ozakia occurrences suggests that this plant traversed the Beringia land bridge during or prior to the Middle Miocene. Relatively few extinct angiosperm genera are known as late as the Miocene.