A distinctive type of pentamerous calyx has long been known from fossil leaf deposits in the Eocene of western North America and Miocene of eastern Asia. In North America, the fruits were first placed in Porana (Convolvulaceae) by Lesquereux in 1883 and later transferred to Astronium truncatum by MacGinitie in 1953. In Asia, similar fruits from the Miocene of Korea were placed in Porana kokangensis by Endo in1939, in Antholithes malvoides by Hu and Chaney in 1940 and more recently in the North American-based species, Astronium trucatum, by the Chinese Paleobotanical Working Group in1978. We have compared fruits from Eocene Princeton, Clarno, Green River, Grant and Florissant floras in western North America with those from the Middle Miocene Shanwang flora of China and conclude that they represent the same genus. The fruits typically have a globose fruit body and a persistent hypogynous calyx of five obovate sepals. The sepals have five subparallel primary veins interconnected by arched secondary veins. Investigation of specimens in different stages of maturation indicates that the flower bore a cycle of five apocarpous ovaries, three or four of which usually abort and remain small in mature fruits. Mature fruits show one or two globose fruit bodies. Preparations of calyx cuticle from the Shanwang specimens reveals longitudinally aligned stomata--an unusual feature among dicotyledons. The suite of characters now known for these disseminules indicates that they cannot belong to Porana or Astronium. We conclude that these fossils belong to an extinct genus, the familial affinities of which remain to be determined. The former widespread distribution of this plant, which also seems to have included the Miocene of Europe (Porana oehningensis Heer) indicates an interesting phytogeographic history. Although it disappeared from North America following the Eocene, it survived well into the Neogene in Europe and Asia.

Key words: Camptotheca, Cornaceae, Cornus, Davidia, Nyssa, Paleocene