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

G. Sun, D.L. Dilcher / Review of Palaeobotany and Palynology 121 (2002) 91^112 95
rations from bed 12 yielded species such as Canningia
pistica Helby, Kiokansium polypes (Cooks.
et Eis.) Below, Muderongia testudinaria Burger,
Muderongia tetracantha (Gocht.) Alberti, Oligosphaeridium
complex (White) Davey et Williams,
and Palaeoperidium cretaceum Pocock. Sun et al.
(1992b) suggest that the age of the dino£agellate
assemblage from bed 12 is Valanginian^Hauterivian.However,
He and Sun (2000) studied the
dino£agellates from the lower part of the Chengzihe
Formation of Jixi and reported the following
taxa: Odontochitina operculata (O.Wetzel) De£.
et Cooks., Muderongia tetracantha (Gocht.) Alberti,
Batioladinium? exiguum (Alberti) Brideaux,
Gardodinium trabeculosum (Gocht.) Alberti, Palaeoperidium
cretaceum Pocock, Kiokansium sp.,
Escharisphaeridia pocockii (Sarj.) Erkmen et Sarjeant,
Circulodinium asymmetricum (Burger) He et
Sun, Nyktericysta puyangensis Wang et Qiao and
Oligosphaeridium jixiense He et Sun.These two
authors considered the age of marine bed 12
yielding the dino£agellates to be late Hauterivian,
and the age of the lower part of the Chengzihe
Formation to be late Valanginian^late Hauterivian
(He and Sun, 2000).Therefore, we suggest
that the age of the early angiosperms collected
from beds 27^47 in the Chengzihe Formation is
late Hauterivian or late Hauterivian^early Barremian
(Fig.2).
The Chengzihe Formation is conformably overlain
by the coal-bearing Muling Formation.The
two formations correspond to the lower part of
Lipovich Formation and Ussuri Formation, dated
as Barremian^Aptian age.These correlations can
also be extended to the Ussuri Formation, which
is the equivalent of the Older Suchan Formation
from the neighboring Suchan Basin which overlies
the Berriasian^Valanginian marine beds (see Fig.
3 for details of this correlation).Therefore, the
Muling Formation is considered middle^late Barremian
to early Aptian, while the whole Chengzihe
Formation is considered Valanginian (or late
Berriasian) to late Hauterivian (or early Barremian)
in age (Sun et al., 1992a,b, 2000).
Only about 80 specimens of angiosperm megafossils
have been collected from the Chengzihe
Formation by the authors so far, including the
three angiosperm reproductive organs described
here, while specimens of the other plants associated
with the angiosperms number nearly 1000.
That means the early angiosperm megafossils are
rare (about 8%) in the assemblage.This is also the
case when the pollen from these sediments was
examined (Shang, 1997). Brenner and Bicko¡
(1992) and Brenner (1996) also found that early
angiosperm pollen is present at only very low percentages
in the Valanginian^Hauterivian of Israel.
Dilcher and Farley (1988) noted in Cenomanian
age sediments that 63^75% of the megafossils recovered
were angiosperms while only 21^23% of
the miospores recovered were angiosperms.This
demonstrates that angiosperm diversity and abundance
dominate as megafossils long before they
do so in the miospore record.
There are only a few specimens which are compressions
and with cuticle preserved.The preparations
for anatomical study of the reproductive
axis and the cuticles of the angiosperm leaves
were made with Schultze solution for the macerations,
and scanning electron microscopy (SEM)
observations were made with a JAL-3600 SEM.
The surface of the reproductive axis was examined
with Zeiss epi£uorescence and individual pollen
and clusters of pollen grains were studied.
Often extreme oblique light was used to discern
the nature of the leaf margins and the venation
while studying the specimens with a Wild M 500
dissecting microscope.The described specimens
are housed in Nanjing Institute of Geology and
Palaeontology, Academia Sinica, Nanjing, China.
3. Systematics
The following early angiosperm taxa from the
Early Cretaceous Chengzihe Formation of Jixi,
China are described in this paper: Asiatifolium
elegans Sun, Guo et Zheng emend.Sun et Dilcher,
Jixia pinnatipartita Guo et Sun emend.Sun et
Dilcher, Jixia chengzihensis Sun et Dilcher sp.
nov., Jixia sp., Shenkuoa caloneura Sun et Guo
emend.Sun et Dilcher, Zhengia chinensis Sun et
Dilcher gen.et sp.nov., Xingxueina heilongjiangensis
Sun et Dilcher, Xingxuephyllum jixiense
Sun et Dilcher gen.et sp.nov., Reproductive organ
A, Reproductive organ B.