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

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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.