Using the oldest, most complete fossil angiosperm
on record, Dr. David Dilcher, a palaeobotanist with the Florida Museum of
Natural History at the University of Florida, recently announced the
discovery of a new basal angiosperm family of aquatic plant, Archaefructaceae.
The announcement was published in the journal Science with coauthors Ge Sun
of the Research Center of Palaeontology at Jilin University, Qiang Ji of the
Geological Institute of the Chinese Academy of Geosciences at Beijing and
three others (full citation below).
The new family consists of a single genus, Archaefructus, with
two species, A. liaoningensis and A. sinensis sp. nov. from the Yixian Formation
in Liaoning, northeastern China. The fossils are believed to be at least 124.6
million years old and possibly as old as 145 million years (corresponding with
Lower Cretaceous to the uppermost Upper Jurassic periods). A specimen is
deposited with the Geological Institute of the Chinese Academy of Geosciences at Beijing.
Five nearly complete fossil plant specimens in various stages of reproductive maturity
were examined. When all characters of the two species were analyzed using a combined
matrix of morphology and molecular data, it was determined that a new
family of flowering plants was required, Archaefructaceae, which
should be considered a sister taxon to extant angiosperms.
The Archaefructaceae are believed to have been aquatic plants
because of the long, thin, herbaceous stems that would have required
water for support. The finely dissected compound leaves also suggest
an aquatic habitat. In addition, the leaves have a swollen petiole base,
especially the leaves closest to the reproductive organs and farthest
from the base of the plant. This feature would have provided buoyancy
to the plant and aided in supporting the reproductive organs above the
water during pollination and possibly seed dispersal. Numerous fish
(Lycoptera davidi Sauvage) are preserved with the fossil plants,
further supporting the conclusion that Archaefructus
was aquatic.
The researchers state that Archaefructus is part of a complex
basal group in angiosperm evolution and does not represent the original
angiosperm. They suggest that the original angiosperm may have been
a submerged aquatic plant such as some Nymphaeales.
For further information, contact Dr. Dilcher at the University
of Florida, Florida Museum of Natural History, POB 117800,
Gainesville, FL 32611; E-mail: dilcher@flmnh.ufl.edu
See Science Vol. 296 (3 May 2002):899-904,
Archaefructaceae, a New Basal Angiosperm Family by Ge Sun, Qiang Ji,
David L. Dilcher, Shaolin Zheng, Kevin C. Nixon, Xinfu Wang.