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Fossils
Ginkgo a living fossil |
| . | Classification:
Kingdom Plantae -- Plants Subkingdom Tracheobionta -- Vascular plants Superdivision Spermatophyta -- Seed plants Division/phylum Ginkgophyta -- Ginkgo Class Ginkgoopsida Order Ginkgoales Family Ginkgoaceae -- Ginkgo family Genus Ginkgo L. The only living representative of the order Ginkgoales is the Ginkgo biloba. Source: National PLANTS Database -USDA, NRCS. 2001. The PLANTS Database, Version 3.1 |
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| The genus Ginkgo is one
of the major groups in the phylum Ginkgophytes. Fossils of Ginkgo
are recognized by its leaves, reproductive organs and wood. Its leaf remains
are the most often found.
Its earliest leaf fossils date back to 270
million years ago in the Permian period of the
Paleozoic when seed ferns and ferns dominated and Ginkgo, cycads and conifers
came into prominence.
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 Ginkgoales is a group of gymnosperms composed of the family Ginkgoaceae traditionally described as consisting of six “families” and possibly 19 genera, for instance Baiera, Ginkgoites, Ginkgoidium, Ginkgo, Arctobaiera, Sphenobaiera, Windwardia, Trichopitys. However this classification is ill-defined, for instance variations in Baiera, Sphenobaiera and Ginkgoites are now considered to be Ginkgo as well. Its maximum diversity was achieved in the Jurassic
and Early Cretaceous periods of the Mesozoic.
The pteridosperms (‘‘seed ferns’’), and especially the Peltaspermales,
are at present thought to be the most plausible ancestral group.
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 Undoubted
oldest fossils of the genus Ginkgo (Ginkgo digitata) are
from
the Early Jurassic period in the Mesozoic from a single location (Fergana) in what is now the Asiatic part of the former USSR, and therefore it is considered to be the oldest extant genus among seed plants. During this time Ginkgo, Bennettitales, ferns, cycads and conifers dominated the vegetation of the world. Mesozoic climate: no polar ice, wet and warm climatic conditions followed after aridity in the early Mesozoic. During the Middle Jurassic there was an increase in species, Ginkgo digitata, Ginkgo huttoni, Ginkgo yimaensis, throughout the northern parts of the Laurasian supercontinent. |
click to enlarge Middle Jurassic of China, Shunosaurus under a Ginkgo yimaensis with chichi © Brian Engh |
Ginkgo
digitata
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Ginkgo sp. Upper Triassic, Stage: Rhaetian, Bed 2, Astartekloft, East Greenland photo courtesy The Field Museum, GEO86387d, Photographer John Weinstein |
Ginkgo yimaensis Middle Jurassic, Henan Province, China (redrawn from Zhou and Zhang, 1989a) |
Maximum diversity in species existed during the Cretaceous period in the Northern Hemisphere, areas now known as Asia, Europe and North America, for instance Ginkgo coriacea, Ginkgo adiantoides, Ginkgo tigrensis, Ginkgo apodes, Ginkgo digitata, Ginkgo yimaensis, Ginkgo gardneri. Ginkgo was also present in the Southern Hemisphere: Gondwana.
Ginkgo evolution (click to enlarge) From: Zhou Z, Zheng S , 2003
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Most species are mainly distinguishable
on the basis of leaf anatomy and geographical distribution. It is well
known that leaves on a living Ginkgo tree have a considerable variation
in form, therefore the fossil record is supposed to include many species
close to Ginkgo biloba (thus certain species names are adopted only as
a matter of convenience).
However fossils of Ginkgo yimaensis (170 mya) and Ginkgo apodes (121 mya) are found with Ginkgo-like reproductive organs and these discoveries leave no doubt about their belonging to the genus Ginkgo. |
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Ginkgo huttoni Middle Jurassic, Scalby, North Yorkshire, UK photo © David Scarboro |
Ginkgo sibirica Late Jurassic, Oregon National Museum of Natural History, Washington D.C. photo © Nico Bal |
Ginkgo dissecta Eocene, MacAbee Formation, Cache Creek, British Columbia, Canada photo © David Scarboro |
The World of Dinosaurs, Cretaceous landscape North America (left: Ginkgo tree) picture from The United States Postal Service
In structure and form (morphologically) indistinguishable
forms of Ginkgo biloba extend back to the Early
Cretaceous, therefore many researchers consider the fossil and modern
forms to belong to the same species. This fossil form is most commonly
identified as Ginkgo adiantoides,
however many other designations are considered essentially equal.
|
 picture Heinrich Harder |
At the end of the Cretaceous period all dinosaurs, marine reptiles, and about 75 percent of all other species on earth became extinct. |
Only three (or four) species were left in the
Tertiary
(65 million years ago): Ginkgo adiantoides (mainly Northern Hemisphere)
with leaves virtually indistinguishable from modern Ginkgo biloba,
andGinkgo gardneri (late Paleocene, only
found on the Isle of Mull, Scotland).
Ginkgo jiayinensis (Northeast China,
Wuyun Formation of Jiayin) differs from other Cenozoic ginkgos in having
amphistomatic leaves (stomata (pores) on both surfaces of the leaf)
due to environmental adaptation.
In the Southern Hemisphere a different, more
strongly digitate type of Ginkgo leaf persists into the
Eocene,
but so far it is not well documented (Ginkgo patagonica).
Ginkgo adiantoides, Paleocene, Scotland Naturalis, Leiden photo © Cor Kwant |
Video: Different shapes of leaves on Ginkgo biloba. More videos here. video © Cor Kwant |
The decline is possibly the result of the extensive
cooling that occurs throughout the Northern Hemisphere and rainfall gradually
shifting from one of the summer-wet to one of summer-dry. The rise of the
angiosperms might have played a role as well. The extinction of the dinosaurs
as potential seed dispersers of the large seeds may also have influenced
this decline, which is in line with the fossil records. Read more about
seed dispersers on my Propagation-page. Climate
of the
Cenozoic: very warm to glacial period.
About 7 million years ago Ginkgo disappeared
from the fossil record of North America.
In Eurasia only very limited numbers of fossils
are found from the Pliocene, and for the Pleistocene,
the only known occurences of Ginkgo are from southwestern Japan.
It was gone from Europe by about 2.5 million years ago.
Ginkgo biloba L. survived in some areas
of China where the impact of glaciation was minimal.
DNA analyses have demonstrated that isolated
Ginkgo
populations in southwestern China, especially around the southern slopes
of Jinfo Mountain (Jinfo Shan) of Nanchuan County at the boundary of Chongqing
Municipality and Guizhou Province (28°53'N; 107°27'E) possess a
significantly higher degree of genetic diversity than populations in other
parts of the country. Southwestern China was less affected by cold air
from Siberia during the glaciations. The area has a mesic, warm-temperate
climate with a mean annual temperature of 16.6°C and a mean annual
precipitation of 1185mm, with Ginkgo trees growing mainly between
elevations of 800 and 1300 m.
Evidence for the persistance of wild Ginkgo
biloba (Ginkgoaceae) populations in the valley and lower mountain slopes
of the Dalou mountains in southwestern China (27°43'44"- 28°56'14"N;
107°15'53"- 108°04'46"E; altitude 840-1200 m a.s.l.) was published
in 2012 (Tang et al.). More information and photos click
here.
Interesting is that nearly all fossil finds
of Ginkgo lie poleward of 40 oN
latitude, during the Tertiary more toward 40 o due to cooling
and increased seasonality. Its survival in China is deviating from the
long-term history of Ginkgo.
The Chinese Ginkgo biloba survived essentially unchanged. From the Jurassic till now there was a reduction of individual ovule-stalks and a decrease in the number of ovules. The size of the ovules increased. The ovulate organs may find their origin in the Middle Jurassic Ginkgo yimaensis (170 million years ago). The embryos of Ginkgo biloba seeds possess a temperature-dependent developmental-delay mechanism that allows seeds to survive winter by preventing premature germination in fall. This and other cold-climate adaptations appear to have evolved within the genus Ginkgo during the early Cretaceous, when the Northern Hemisphere was undergoing dramatic cooling after a long period of stable, warm conditions. Fossilized leaves and reproductive organs from the Lower Cretaceous period (Ginkgo apodes found in the 121 million years old Yixian Formation in N.E. China) show that their morphology has changed little until now.
Ginkgo adiantoides from the Tertiary
period (56 million years ago) is remarkably similar to the modern Ginkgo
biloba.
| Fossil
woods of
the Ginkgoales are rare. A well-known example is Ginkgo beckii named
after prof. George Beck, who discovered the petrified wood in the 1930s
near Columbia River Gorge, Vantage, central Washington, North America.
Dating from the Miocene period, 15 million-year-old petrified logs of Ginkgo beckii and many other tree species have been uncovered from flood sediments and lava flows near this region. Ginkgo logs were carried by raging flood waters to the vantage area, where they lay burried in lake bed sediments covered by lava flows for millions of years. 
petrified Ginkgo wood, 17 cm diam., Miocene Vantage, North America photo © Lewis Goodman |
larger image petrified Ginkgo wood, 6 x 7 cm, limb cross section, Triassic Arizona, north of Canyon de Chelly, Chinle formation photo © Cor Kwant Ginkgo beckii shows a striking similarity to Ginkgo biloba wood, with the possible exception of fewer pits per unit length on the radial walls of its tracheids. More fossil wood is known from the Lower Permian (Hueco Formation, New Mexico) and Late Triassic (Holbrook area, Chinle Formation, Petrified Forest National Park, Arizona). From the Eocene period a single specimen is known as Ginkgo bonesii, Clarno Formation, Oregon. Fossil ginkgoalean wood is probably scarce because of lack of chemical resistance of the wood to degradation of the cell walls after deposition in sediments. More photos and info about Ginkgo wood. |
| Life history traits of the genus Ginkgo
are for instance:
- highly conservative morphologically - slow space of evolution - slow reproduction rate (late sexual maturity) - large seeds - long life span - conservative in its ecological tolerance: well-drained disturbed habitats; now representing an ecological paradox because the living Ginkgo biloba L. has few of the life-history traits typical for plants that prosper in modern disturbed settings. But it now also thrives in for instance New York City Center, it does not suffer from air pollution and pests! video CreatureCast
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Special thanks to David Scarboro from Reading (UK), Open University tutor, for providing many pictures for this page.
© Cor Kwant 
Copyright information.
