ephedroids from the Early Cretaceous Yixian Formation in Liaoning ...

240 C. Rydin et al.: Cretaceous ephedroids from China
1982) and from Australia (Krassilov et al.
1998). There are also many undescribed specimens
from China and Brazil (see e.g. Wu et al.
2000, Mohr et al. 2004). Early Cretaceous
mesofossils include coalified seeds with unique
Ephedra characters such as a sclerenchymatic
seed envelope with apical papillae, and in situ
polyplicate pollen (Rydin et al. 2004, Rydin et
al. 2006).
In addition to the ephedroid fossils there
are also a few Early Cretaceous megafossils
that may represent the Welwitschia-Gnetum
clade (Crane and Upchurch 1987, Rydin et al.
2003, Dilcher et al. 2005, Rydin et al unpubl.
data), as well as several gnetalean fossils that
are difficult to assign to any of the extant
lineages (e.g. Krassilov 1982, Krassilov and
Bugdaeva 1982, Krassilov 1986, Krassilov and
Bugdaeva 1988, Duan 1998, Sun et al. 2001).
Further, dispersed seeds and pollen assigned to
the extinct order Erdtmanithecales (Pedersen
et al. 1989, Friis and Pedersen 1996, Kvaček
and Pacltová 2001) are probably related to
Gnetales, but the vegetative morphology of
these plants is unknown.
Pre-Cretaceous evidence of the Gnetales
are mainly dispersed polyplicate ephedroid
pollen (e.g. Wilson 1962), but there are also
several records of megafossils that probably
belong to the Gnetales, for instance Ephedrites
sinensis Wu et al. and E. exhibens Wu et al.
from Early Jurassic deposits in Qinghai, China
(Wu et al. 1986). However, most pre-Cretaceous
gnetalean megafossils are difficult to
interpret. The Permian cone Palaeognetaleana
auspicia Wang with in situ polyplicate pollen
(Wang 2004), the Late Triassic plant Dechellyia
gormani Ash (Ash 1972), and the
Jurassic Ust-Balej fossils of East Siberia
(Krassilov and Bugdaeva 1988), are all examples
of fossils that have been discussed as
putative Gnetales, but for which a precise
systematic affinity remains to be established.
In this study we describe a number of
ephedroid fossils from the Liaoning province
of northeastern China collected in sediments of
the Yixian Formation. The Yixian Formation
and the overlaying Jiufotang Formation com-
prise the Jehol Group, famous for its exceptionally
rich biota, which include exquisitely
preserved invertebrates, osteichthyan fish,
amphibians, mammals and reptiles including
feathered dinosaurs and early birds (Chang
et al. 2003). Vigorous collisions of plates in the
western rim of the Pacific resulted in intensive
volcanic activity (Wang et al. 1983) during the
deposition of the Yixian Formation and ash
falls repeatedly entombed organisms present in
the area and effectively prevented scavenging
and bacterial decay. The immediate anoxic
conditions provided by the volcanic ash tuffs
permitted the preservation of original softtissue
features and stomach contents (Chen
et al. 1998, Zhou and Zhang 2002); even
questions on the physiology of Cretaceous
vertebrates and of plant-animal interactions
can be addressed (Zhou et al., 2003, and
papers in Chang et al. 2003).
In contrast to the anatomical preservation
of many animals of the Jehol Biota, plant
fossils rarely have cellular details intact. Similar
to the slightly younger Crato plants of
Brazil, the Jehol plants are compression or
impression fossils, often with various organs
such as stems, leaves and reproductive structures
still attached. In rare cases even whole
plants are preserved providing excellent information
on gross morphology. Anatomical
features, however, are rarely preserved (e.g.
Wu 1999, Sun et al. 2001, Chang et al. 2003,
Friis et al. 2003, Leng and Friis 2003) and
tissues are often replaced or filled in with pyrite
framboids and microcrystallines (Leng and
Yang 2003).
The Jehol flora comprises a diverse assemblage
of bryophytes, lycopods, sphenopsids,
ferns and various seed plants including many
conifers and rare angiosperms (Sun et al. 1998,
Wu 1999, Sun et al. 2001, Sun et al. 2002, Leng
and Friis 2003, Leng et al. 2003, Wu 2003).
Fossils assignable to the Gnetales (Wu 1999,
Sun et al. 2001, Wu 2003) also show some
diversity and include plants described as
Liaoxia chenii Cao et Wu and Eragrosites
changii Cao et Wu (Cao et al. 1998), Chaoyangia
liangii (Duan 1998, later synonym of