Early angiosperms from the Lower Cretaceous of Jixi, eastern ...

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92 G. Sun, D.L. Dilcher / Review of Palaeobotany and Palynology 121 (2002) 91^112 However, a few pollen records from the lower Lower Cretaceous (e.g. Valanginian) support the idea that the divergence of the angiosperms could be earlier (Hughes, 1994; Brenner, 1996).The recent discovery of early angiosperms (i.e. Archaefructus) from the western Liaoning, China could possibly even be traced to the Late Jurassic (Sun et al., 1998).Nevertheless, the middle Early Cretaceous appears to be a very important period in the evolution and development of angiosperms in the world.Therefore, the recent ¢ndings of angiosperm megafossils as well as some microfossils from the early^middle Early Cretaceous Chengzihe Formation of Jixi, eastern Heilongjiang, China reported here (Fig.1), are very signi¢cant for the study of early angiosperms in the world and particularly in eastern Asia. Sun et al.(1992a) ¢rst reported the early angiosperm megafossils from the Chengzihe Formation of Jixi and considered the age of the angiosperm fossils as Valanginian^ Hauterivian or early Barremian based mainly on the associated marine dino£agellates in the formation.Later, Sun and Dilcher (1996, 1997) studied these early angiosperm leaf remains and particularly the in£orescence and its pollen grains. He and Sun (2000) restudied the dino£agellates associated with the angiosperms of the Chengzihe Formation, and proposed their new determina- tions resulting in more precise dating as late Hauterivian in age. The early angiosperms from the Chengzihe Formation of Jixi, China described here all are dicotyledons with many leaf and reproductive characters new in the early history of the group and these are presented so they can be evaluated as primitive or derived angiosperm characters.At this locality, abundant fossil ferns and fern allies, cycadales, bennettitales, ginkgoales, conifers and caytoniales are associated with the angiosperms, including Equisetites burejensis, Coniopteris burejensis, Acanthopteris gothanii, Onychiopsis elongata, Acropteris sp., Cladophlebis sp., Nilssonia sinensis, Nilssonia angustissima, Pseudocycas sp., Ginkgo sp., Sphenobaiera sp., Elatocladus submanchurica, Sphenolepis kurriana, Schizolepis sp.and Sagenopteris sp.(Sun et al., 1992a; Sun, 1995). 2. Material and methods One important aspect of this investigation is the validity of the age determination for the fossil angiosperms described in this paper.The determination of the age involved a great deal of ¢eld mapping of the Chengzihe Formation and associated Muling Formation exposed along the Muling Fig.1.Geographic position of the locality of the early angiosperms from Jixi of Heilongjiang, China.
G. Sun, D.L. Dilcher / Review of Palaeobotany and Palynology 121 (2002) 91^112 93 Fig.2.Geological section of the Lower Cretaceous Chengzihe Formation from the Wanrengou to the Muling River Bridge near Chengzihe of Jixi, Heilongjiang, China. river of the Chengzihe district, Jixi City, Heilongjiang Province, China (Fig.2). Forty-seven beds have been recognized in the Chengzihe Formation.There is 822 m of sediment consisting of marine and non-marine alternating beds of sandstone, shale-siltstone and coals dipping towards the northwest.There are 34^36 coal seams that can be found and some of the coal is mined locally and the sandstone quarried for local construction material. Sun et al.(1992b) outlined the stratigraphy of the Jurassic^Cretaceous boundary sediments in eastern Heilongjiang Province, China.To the east there was more marine in£uence and species of the bivalve Buchia are used to establish the biostratigraphic zones of the Jurassic and Lower Cretaceous (Sun et al., 1989, 1992b; Sha, 1992; Sha and Fuersich, 1993).To the west, at Jixi there was less marine in£uence and dino£agellate fossils are preserved in several beds as represented by bed 12, which can be used to establish the age of that portion of the Chengzihe Formation (Figs.2 and 3).Prepa-
Page 1: Abstract Early angiosperms from the
Page 5 and 6: G. Sun, D.L. Dilcher / Review of Pa
Page 7 and 8: Angiospermae Dicotyledonae G. Sun,
Page 11 and 12: veins poorly preserved, arising fro
Page 13 and 14: Discussion: The present species is
Page 15 and 16: entire.Petiole about 4.5 mm long.Mi
Page 17 and 18: only from dispersed pollen grains.I
Page 19 and 20: pened to fall across one another.If

Early angiosperms from the Lower Cretaceous of Jixi, eastern ...

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