in Jurassic and Cretaceous Stratigraphy

Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321
Palaeontology and Biostratigraphy of Jurassic Clam Shrimps of the
Sichuan Basin, China
34
G. Li 1* , H. Hirano 2 , T. Sakai 3 , T. Kozai 4 , H. Ishiguro 2
1. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of
Sciences, Nanjing 210008, China (E-mail: gangli@nigpas.ac.cn)
2. Waseda University, Tokyo, Japan
3. Kyushu University, Fukuoka, Japan
4. Naruto University of Education, Naruto, Japan
Clam shrimps are a common fossil group in the
non-marine Mesozoic sequences. They are normally
abundant and widely distributed in sediments that are
accumulated in quiet, freshwater environment. Their
rapid revolution makes them biostratigraphically useful
for subdividing and classifying non-marine sequences
(Chen et al., 2007). Abundant fossil clam shrimps have
been recovered in the Sichuan Basin (Fig.1). The earli-
est fossil clam shrimps, reported by Chi Rongshen in
1931, were collected by Zhao Yazeng and Huang Jiqing
from the Lower Shaximiao Formation. Since then,
during geological mapping, geological prospecting in
the Sichuan Basin, abundant clam shrimp fossils have
been recovered, and taxonomically described (Zhang et
al., 1976; Shen and Chen, 1982; Xu, 1982). Recently,
through the using of scanning electron microscope,
more detailed taxonomic research has been published
(Li, 2004; Li et al., 2009). Here the author would
introduce the five Jurassic characteristic clam shrimp
faunas of the Sichuan Basin.
1. Palaeolimnadia baitianbaensis-Bulbi-
limnadia fauna
The Early Jurassic clam shrimp fauna has been
first described from the Lower Jurassic Baitianba
Formation in the Guangyuan area of northern Sichuan.
The dominant taxon is Palaeolimnadia, with a few
species of Euestheria. Palaeolimnadia is characterized
by a big umbo, and has only several growth bands.
In south-eastern part of the Sichuan Basin, besides
the above mentioned tow genera, this fauna contains
another genus Bulbilimnadia, and has been recovered
in the Ziliujing Formantion. Bulbilimnadia differs from
Palaeolimnadia by bearing elongated nodulous pro-
tuberance on big umbo. It occurs in the lower and
middle part of the Ziliujing Formation of Wanxian,
Shizhu, Tieshan, and also in the Ma’anshan Member of
the Ziliujing Formation of Hechuan, Chongqing.
Although Palaeolimnadia ranges from Late
Permian through Middle Jurassic, but the fossil clam
shrimp fauna dominated by this genus is normally
occurred in Early Jurassic. This clam shrimp fauna
consists of P. baitianbaensis, P. sichuanensis, P.
longmenshanensis, P. chuan- beiensis, P. baoxingensis,
P. lingguanensis, P. rhombica, P. subtriangularis, P.
houjiensis, P pengxianensis, P. aff. dundugobica, P. cf.
parva, P. oblonga, P. guangyuanensis, Euestheria?
taniiformis, E.? elongate, Bulbilimnadia bullata, B.
wanxianensis, Pseudolimnadia? weixinensis.
2. Shizhuestheria fauna
The Shizhuestheria fauna occurs in the Middle
Jurassic Xintiangou Formation, and consists of S.
truncata, and Euestheria spp. Shizhuestheria has
relatively wider growth bands in the infancy stage, on
which there are medium-sized reticulation, and several
small reticulation (or puncta) occur within each lumina;
the growth bands become narrower since the adult stage,
and the reticulation become faint or disappeared, and
only small reticulation (or puncta) remains (Li et al.,
2009).
3. Euestheria ziliujingensis fauna
This Middle Jurassic fauna consists of Euestheria
ziliujingensis, E. haifanggouensis, E. yanjiawanensis, E.
complanata, E. rotunda, Pseudolimnadia? shaxiensis.
The carapace is normally small and rounded,
ornamented with small-sized reticulation. And it occurs
in the lowest member of the Guangyun Group in
Guangyuan, northern Sichuan, and in the Lower
Shaximiao Formation in southern part of the Sichuan
Basin. It also occurs in the Zhanghe and Hepingxiang
formations of Yunnan, the Haifanggou Formation of
western Liaoning, and in the contemporaneous deposits
in Gansu Province and Xinjiang Autonomous District
of north-western China.
4. Paleoleptestheria? chinensis fauna
This fauna occurs in the Middle Jurassic Upper
Shaximiao Formation in Nanchuan and Shizhu
Counties, south-eastern Sichuan Basin, and the Second
Member of Guangyuan Group in northern Sichuan
Basin. Paleoleptestheria? chinensis is small or medium
in size, with medium-sized cavernous reticulation,
which shows as isolated rounded or elliptical nodules
on external mould.
5. Eosestheriopsis dianzhongensis fauna
This fauna consists of Eosestheriopsis dian-
zhongensis, E. semiorbita, E. subovata, suiningestheria
minor, Qinghaiestheria Sichuanensis, Q. chuanzhon-
gensis, Huilongestheria rotunda. It is widely dis-
tributed in the Sichuan Basin, and occurs in the Upper
Jurassic Suining Formation of Leshan County, and in
the Penglaizhen Formation of Daying, Zhongjiang and
Shuangliu counties. This fauna has first been des-
cribed from the Upper Jurassic Tuodian Formation of