Ginkgoales

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Ginkgoales
Ginkgoites huttoni, fossil leaf print, Middle Jurassic

Ginkgoites huttoni , fossil leaf print, Middle Jurassic

Systematics
without rank: Streptophyta
Empire : Plants (Plantae)
Department : Vascular plants (tracheophyta)
Subdivision : Seed plants (Spermatophytina)
Class : Ginkgo plants
Order : Ginkgoales
Scientific name of the  class
Ginkgoopsida
Engl.
Scientific name of the  order
Ginkgoales
Gorozh.

The Ginkgoales are the only order in the class Ginkgoopsida within the seed plants (Spermatophytina). It includes several fossil groups, but only one recent species, the ginkgo ( Ginkgo biloba ).

features

The representatives of the Ginkgoales are trees with long and short shoots, the latter, however, are missing from the oldest representatives. The wood is pycnoxyl (has narrow medullary rays ). Leaves and veins are forked. The leaf blade is leathery, striped or fan-shaped and often deeply divided. On the fertile sprouts, which are branched or almost unbranched, there are two to ten ovules . The seeds are large and have a fleshy outer layer and a stony middle layer. The male organs are formed on axillary, unbranched kitten-like axes. They carry micro Sporangiophores , each two to twelve hanging microsporangia carries. The sperm have a lash line, so they are spermatozoids .

Systematics

External system

The origins and the phylogenetic relationship of the ginkgoales are still unclear. There is no fossil evidence for the origin of the ginkgoales. Nor is there any generally accepted theory for their origins. They saw older classifications near the Cordaitales and Coniferales . Some cladistic analyzes based on morphological features show them as a group with the Cordaitales, Coniferales and Cycadales . They saw several works with the Cordaitales, Coniferales and Anthophytes . The close relationship with the Cycadales, which was previously widely assumed, is now largely attributed to common primeval features ( plesiomorphies ).

According to V. Meyen (1982, 1984, 1987) the class Ginkgoopsida includes not only the Ginkgoales but also the Peltaspermales , Umkomasiaceae and Dicranophyllum . In 2003 Anderson and Anderson added two new orders to the Ginkgoales, the Matatiellales and Hamshawviales , both of which are only known from the Upper Triassic of the Molteno Formation in South Africa. In 2007 Naugolnykh added two families to the Ginkgoopsida, the Cheirocladaceae and the Psygmophyllaceae .

Internal system

The following classification of ginkgoales in the narrower sense follows Zhou (2009).

In addition to the ginkgoales, the following Morphotaxa are counted:

Several other genera that have been described are so poorly known that they cannot be classified in more detail, cannot be clearly delimited from other genera or for which it is questionable whether they can even be counted among the ginkgoales.

distribution

The early history of the ginkgoales is poorly known. Their distribution in the Paleozoic can only be roughly outlined. Ginkgo-like leaves are known from the Permian or even from the Upper Carboniferous of continents in the northern and southern hemispheres. Reproductive organs from this period are only known from Laurasia : Trichopitys from the Lower Permian of France is generally considered to be one of the oldest representatives of the Ginkgoales. Karkenia comes from the upper lower Permian of the Cis-Urals . The ginkgoales should therefore have their origin in Laurasia.

From the middle Triassic onwards there was a clear radiation of the ginkgoales, which reached its peak in the late Triassic. At that time, all five Mesozoic families were represented at the same time. The order also flourished during the Jurassic and early Cretaceous . Major morphological innovations occurred in the Upper Triassic with the widespread occurrence of short sprouts and the differentiation of the leaves into blade and stem .

In Anisian and the Lower Triassic few Morphotaxa occur. From Ladinium to Carnium , they occur almost simultaneously in many parts of Laurasia. From Gondwana except Antarctica, there are numerous fossils from this period. In the middle to late Triassic, the geographic distribution increased in parallel with the biodiversity. In Eurasia the ginkgoales are one of the most important floral elements in the Jurassic and early Cretaceous flora. In Gondwana after the Jura, with the exception of Karkenia, no reproductive organs are known anymore, in particular no seed organs of Ginkgo are known.

From the Middle Cretaceous on, the biodiversity as well as the geographical distribution of the Ginkgoales decreased significantly. All families with the exception of the Ginkgoaceae were probably already extinct by this time. During the Late Cretaceous and Paleogene , the ginkgoales largely retreated to Northeast Asia and Northwest America. They were extinct in North America in the late Miocene and in Europe in the Pliocene . Eighteen species of ginkgo have been described from the Palaeogene and Neogene , but only two from the southern hemisphere. Today there is only the species Ginkgo biloba , whether its last locations in China are actually natural locations is controversial.

Paleoecology

Little detailed information about its natural ecological conditions is available for the recent species, Ginkgo biloba . The best locations for growth have an annual average temperature of 10 to 18 ° C and annual precipitation of 600 to 1000 mm. The late Cretaceous and Cenozoic species Ginkgo adiantoides was largely dependent on disturbed locations on river banks and embankments. Detailed studies are lacking for pre-Cretaceous ginkgos. Given their wide distribution, they are likely to have grown in different climates and environmental conditions.

Late Paleozoic ginkgos are likely to have grown in warm to hot, uniform climates with long periods of growth. The radiation of the ginkgos in the Middle and Late Triassic may be related to a change and greater variety of climates and growing conditions that occurred after the mass extinction at the end of the Permian. It is unclear whether the Paleozoic ginkgos were deciduous like the ginkgo that lives today, but this is assumed for most Mesozoic and Cenozoic species.

The representatives in the Late Triassic to Early Cretaceous were found in a variety of climates and locations. However, the greatest number and diversity is found in Mesian, warm to temperate climates.

Mesozoic ginkgos are likely to have been residents of stable and ecologically saturated locations, such as today's ginkgo. The latest Cretaceous and Cenozoic representatives are largely limited to disturbed locations.

Very little is known about the seed dispersal of the Ginkgoales, especially about the animal spreaders. Mesozoic ginkgos may have been spread by primitive birds, dinosaurs, or other larger reptiles. The extinction of these vectors at the end of the Cretaceous Period could be one of the reasons for the extinction of many ginkgoales. Primitive Carnivora , especially from the families Viverravidae and Miacidae , are discussed as vectors for the paleogene . From China and Japan, three omnivores among the Carnivora are known, which eat the seeds of the recent ginkgo. 

supporting documents

  1. ^ KR Sporne: The Morphology of Gymnosperms . Hutchinson University Library, London 1965. (without ISBN) p. 164.
  2. a b c d e f g h i j k l Zhi-Yan Zhou: An overview of fossil Ginkgoales . Palaeoworld, Volume 18, 2009, pp. 1–22, doi : 10.1016 / j.palwor.2009.01.001

Web links

Wiktionary: Ginkgoales  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Ginkgoopsida  - explanations of meanings, word origins, synonyms, translations