Ginkgoales

Ginkgoales or Ginkgophyte is a gymnosperm order containing only one extant species: Ginkgo biloba, the ginkgo tree.[1] It is monotypic, (the only taxon) within the class Ginkgoopsida, which itself is monotypic within the division Ginkgophyta. The order includes five families,[2] of which only Ginkgoaceae remains extant.[3]

Ginkgoales
Temporal range: 270–0 Ma
Permianpresent
Gingko fossile-jurassique 0
Jurassic Ginkgo leaves
Scientific classification
Kingdom: Plantae
Division: Ginkgophyta
Class: Ginkgoopsida
Order: Ginkgoales
Families

History

The first Ginkgo leaves were found from the Triassic period, but there were many species of Ginkgo during the Jurassic and Cretaceous periods as well. These periods, known collectively as the Mesozoic era, were when diversity and distribution for all plants were at their highest, including in Ginkophytes.[4] It was in the early Cenozoic period that Ginkgophytes nearly became extinct, specifically during the early Cretaceous and Tertiary periods.[2][4] The only remaining Ginkgophyte was Ginkgo adiantoides – a polymorphic species.[5] Modern Ginkgo trees are native to China.[2]

Reproduction

Ginkgo trees produce ovulate, pollen-bearing structures. These structures are dioecious, in that male and female structures come from different Ginkgo plants.[2] The pollen organs are very similar to angiospermous catkins. They come from the axils of the bud scales, and the leaves from the Ginkgo tree spur shoots. Pollen is contained in sacs of two to four at the tips of sporophylls on the strobiloid. Ovules of Ginkgo trees come from stalks from leaf axils on the short shoots, each containing two ovules. The ovule is fertilized by the flagellated male gametes, which can move about freely. This fertilization process begins on the tree itself in the spring. The swollen fruit-like ovules, about 2–3 cm in diameter, fall from the tree in the fall, and fertilization continues into the winter/spring.[4][5] This fruit contains a single large seed, similar to that of a cycad.[4]

Morphology

Ginkgophyte wood

Fossils that appear Ginkgo-like are filed under a morphogenus called Ginkgoxylon, Ginkgomyeloxylon, or Protoginkgoxylon. Fossilized ginkgophyte wood is not commonly found in the record, possibly because it degrades easily, and possibly because it is difficult to tell apart from the much more pervasive conifer samples.[4] Like conifer wood, it has secondary thin-walled xylem and a primary vascular system composed of eustele and bifacial vascular cambium. The tracheids in the secondary xylem rays have pitting that occurs only on the walls and is circularly bordered.[2]

Live reconstruction of Cretophasmomima melanogramma - journal.pone.0091290.g007
This recreation displays one example of early Gingkophyte foliage.

Ginkgophyte foliage

Ginkgophyte foliage has stayed largely consistent since the Mesozoic. Its historically wide territory makes it an important leaf morphology, and its unique stomata and isotopic profile give it a key role in recreations of the Mesozoic and Cenozoic. Leaf fossils that resemble the Ginkgophytes are known as Ginkgoites. There are similar, now extinct, morphogens, such as Sphenobaiera, which describes fan-shaped, deeply divided leaves without clear petioles.

The distinctive shape of the modern Ginkgo biloba gives the impression of a very narrow leaf morphology, but the group is varied and diverse. The genus Ginkgo by itself contains a range of morphologies. Ginkgo digitata, from the Jurassic, has long, wedge-shaped laminae with the intercostal regions covered in stomata and resin bodies, while G. pluripartita has at most 2 cm-long leaves and is intercostally hypostomatic.[4]

Fossil gallery

Ginkgo biloba leaf 01

A 6.7 cm tall Ginkgo biloba leaf, with insect herbivory. Klondike Mountain Formation, Republic, Ferry County, Washington, USA, Eocene, Ypresian, 49 million years old

Ginkgo biloba 01 SR 87-36-02 A

A 70 mm-wide Ginkgo biloba leaf. Klondike Mountain Formation, Republic, Ferry County, Washington, USA, Eocene, Ypresian, 49 million years old

Ginkgo biloba MacAbee BC

Ginkgo biloba Eocene fossil leaf from the Tranquille Shale of MacAbee, British Columbia, Canada

Ginkgo huttoni

Fossil of Ginkgo huttoni. Photo taken at Naturalis Museum in Leiden, The Netherlands.

Gingkoites huttoni 1

Fossil of Ginkgoites huttoni

References

  1. ^ Christenhusz, M. J. M., J. L. Reveal, A. Farjon, M. F. Gardner, R. R. Mill, and M. W. Chase (2011). A new classification and linear sequence of extant gymnosperms. Phytotaxa 19:55–70. http://www.mapress.com/phytotaxa/content/2011/f/pt00019p070.pdf
  2. ^ a b c d e Beck, Charles (2014). "Ginkgoales". Access Science. Retrieved April 13, 2017.
  3. ^ "Ginkgoaceae in Flora of China @ efloras.org". www.efloras.org. Retrieved 2017-04-12.
  4. ^ a b c d e f Taylor, Thomas N.; Taylor, Edith L.; Krings, Michael (2008-12-29). Paleobotany, Second Edition: The Biology and Evolution of Fossil Plants (2nd ed.). Academic Press. ISBN 9780123739728.
  5. ^ a b Jalalpour, Julie; Malkin, Matt; Poon, Peter; Rehrmann, Liz; Yu, Jerry (1997). "Introduction to the Ginkgoales". www.ucmp.berkeley.edu. Retrieved 2017-04-20.
Angwa Sandstone

The Angwa Sandstone is a geological formation of the mid-Triassic, consisting mainly of sandstone.

Baiera

Baiera is a genus of prehistoric gymnosperms in the order Ginkgoales. It is related to the genera Ginkgo and Ginkgoites. It is lobed into four segments and has no stalk. Fossils of Baiera have been known from the Permian to the Cretaceous.

Chiropteris

Chiropteris is an extinct genus of plants that existed from Permian to Triassic.

Ginkgo

Ginkgo is a genus of highly unusual non-flowering plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, possibly derived from "seed ferns" of the order Peltaspermales, and now only contains this single genus and species. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the Pliocene; the exception is the sole living species, Ginkgo biloba, which is only found in the wild in China, but is cultivated across the world. The relationships between ginkgos and other groups of plants are not fully resolved.

Ginkgo adiantoides

Ginkgo adiantoides is an extinct ginkgo species in the family Ginkgoaceae from the Late Cretaceous to the Miocene.

Ginkgo apodes

Ginkgo apodes is an extinct ginkgo species in the family Ginkgoaceae. It is known from the Yixian Formation

Ginkgo biloba

Ginkgo biloba, commonly known as ginkgo or gingko (both pronounced ), also known as the maidenhair tree, is the only living species in the division Ginkgophyta, all others being extinct. It is found in fossils dating back 270 million years. Native to China, the tree is widely cultivated, and was cultivated early in human history. It has various uses in traditional medicine and as a source of food.

Ginkgo digitata

Ginkgo digitata is an extinct ginkgo species in the family Ginkgoaceae. It lived in Great Britain from the Aalenian to the Bathonian, in Queensland in the Callovian and in British Columbia in the Cenomanian.

Ginkgo gardneri

Ginkgo gardneri is an extinct ginkgo species in the family Ginkgoaceae from the Paleocene of Scotland, described in 1936 by Rudolf Florin. This species is very closely related to G. biloba, the only living species of the genus Ginkgo.

Ginkgo yimaensis

Ginkgo yimaensis is an extinct ginkgo species in the family Ginkgoaceae.

Ginkgoaceae

The Ginkgoaceae is a family of gymnosperms which appeared during the Mesozoic Era, of which the only extant representative is Ginkgo biloba, which is for this reason sometimes regarded as a living fossil. Formerly, however, there were several other genera, and forests of ginkgo existed. Because leaves can take such diverse forms within a single species, these are a poor measure of diversity, although differing structures of wood point to the existence of diverse ginkgo forests in ancient times.

Ginkgoidae

Ginkgoidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass contains the single extant genus Ginkgo under order Ginkgoales, family Ginkgoaceae. Its only extant species is Ginkgo biloba, the Maidenhair Tree.

Ginkgoites

Ginkgoites is a genus that refers to extinct plants belonging to Ginkgoaceae. Fossils of these plants have been found around the globe during the Triassic, Jurassic and Cretaceous. The name was created as a form genus in 1919 by Albert Seward who stated: "I ... propose to employ the name Ginkgoites for leaves that it is believed belong either to plants generically identical with Ginkgo or to very closely allied types".

Karkeniaceae

Karkeniaceae is an extinct family in the order Ginkgoales.

Relict (biology)

In biogeography and paleontology a relict is a population or taxon of organisms that was more widespread or more diverse in the past. A relictual population is a population that presently occurs in a restricted area, but whose original range was far wider during a previous geologic epoch. Similarly, a relictual taxon is a taxon (e.g. species or other lineage) that is the sole surviving representative of a formerly diverse group.

Schmeissneria

Schmeissneria is a genus of possible early angiosperms recorded from the Lower Jurassic of Europe and the Middle Jurassic of China, traditionally included in the Ginkgophyta.

Sphenobaiera

Sphenobaiera is a form genus for plant leaves found in rocks from Triassic to Cretaceous periods. The genus Sphenobaiera is used for plants with wedge-shaped leaves that can be distinguished from Ginkgo, Ginkgoites and Baiera by the lack of a petiole. It became extinct about 72.6 million years ago. The family to which this genus belongs has not been conclusively established; an affinity with the Karkeniaceae has been suggested on morphological grounds.

Tiaojishan Formation

The Tiaojishan Formation is a geological formation in Hebei and Liaoning, People's Republic of China, dating to the middle-late Jurassic period (Bathonian-Oxfordian stages). It is known for its fossil plants, and is made up mainly of pyroclastic rock interspersed with basic volcanic and sedimentary rocks. Previously, the Tiaojishan Formation was grouped together with the underlying Haifanggou Formation (also known as the Jiulongshan Formation) as a single "Lanqui Formation."

Most researchers now agree that the Daohugou Bed, of formerly controversial dating, is a part of the Tiaojishan formation.

Yimaiaceae

Yimaiaceae is a family of extinct plants, in the order Ginkgoales. It closely related to the Ginkgo biloba, the only remaining species of Ginkgoales.

Rhodophyta
(red algae)
Glaucocystophyta
(glaucophytes)
Viridiplantae
(green algae,
& land plants)
Extant Life phyla/divisions by domain

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