Fossils of the Fagaceae and their implications in systematics and biogeography

ZHOU Zhe-Kun

Received:1900-01-01 Revised:1900-01-01 Online:1999-07-10 Published:1999-07-10
Contact: ZHOU Zhe-Kun

Abstract:

The fossil history of the Fagaceae from China and its systematic and biogeographic

implications are discussed based on revisionary studies of the fossil records. No creditable

macrofossil record of the Fagaceae exists in the Cretaceous deposits and all the Cretaceous mi-

crofossil reports remain equivocal and require further study. The Paleocene fossils show the

appearance and diversification of the two groups corresponding to the subfamilies Fagoideae

and Castaneoideae sensu Nixon. By the Eocene, all modern genera had been present. The

oldest fagaceous fossils represent subfamily Fagoideae with affinities to the extant genus

Trigonobalanus. The leaf fossil genus Berryophyllum, with affinities to Quercus subg. Cy-

clobalanopsis, has been documented by the early Eocene and might have occurred earlier than

other fossils assignable to Quercus. The appearance of evergreen sclerophyllous Ouercus

with entire leaves might have occurred earlier than those with toothed leaves. Deciduous, ur-

ticoid-leaved oak fossils (Quercus subg. Quercus sect. Quercus) had not appeared until the

Miocene. Fossil equivalents of Trigonobalanus, Castanopsis and Lithocarpus had occurred

in Europe and North America by the early Tertiary, suggesting that continuous distributions

were achieved via the northern hemisphere land bridges. Three groups of evergreen sclero-

phyllous oaks of apparent close phylogenetic relationships occurred in the Hengduan moun-

tains, the Mediterranean area and northwestern North America. Their fossil forms have be-

come dominant elements of those vegetation zones since the Miocene. A shared fossil history

indicates a possible biogeographic boundary formed by the ancient Mediterranean. The evi-

dence suggests that the oaks might arrive in North America during two distinct geologic peri-

ods: evergreen sclerophyllous entire-leaved oaks appeared by the Early Tertiary, whereas the

deciduous oaks with urticoid leaves appeared in the Late Tertiary.

Key words: Fossi history, Biogeography, Fagaceae, Systematis

ZHOU Zhe-Kun. Fossils of the Fagaceae and their implications in systematics and biogeography[J]. .

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