Archaefructus
| Archaefructus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Archaefructus liaoningensis |
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| Temporal occurrence | ||||||||||||
| Lower chalk , Barremium / Aptium border area | ||||||||||||
| approx. 125 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Archaefructaceae | ||||||||||||
| Sun , Ji , Dilcher , Zheng , Nixon & Wang | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Archaefructus | ||||||||||||
| Sun , Dilcher , Zheng & Zhou |
Archaefructus is an extinct genus and was present at their discovery in 1998, the earliest known flowering of angiosperm . It forms the family Archaefructaceae , which is placed at the base of the Bedecktsamer (Magnoliopsida).
features
Archaefructus were herbaceous, aquatic plants. They had a main root or a rhizome . At least Archaefructus eoflora was persistent . The find of Archaefructus liaoningensis consisted of two axes, each 8.5 centimeters long, with two leaves and around 60 carpels . Archaefructus eoflora was 27 centimeters high and had a seven centimeter long rhizome with roots. Several long fertile and shorter sterile shoot axes rose from the rhizome in a helical arrangement.
The upper leaves had a thin cuticle , but the lower ones did not.
The reproductive axes formed a laterally branched system or zymous inflorescences with a main axis. They were branched or unbranched. In the proximal part of these axes had petioles with pinnate leaves. Their pinnate lobes were in turn divided three to six times into linear to spatula-shaped lobes. In the distal part they carried protogynous hermaphroditic reproductive organs.
Male flower organs
The lower part carried groups of stamens arranged in a spiral . These consisted of one to three stamens, the cone-shaped stems stood. Each stamen consisted of a short stamen and a bithek tetrasporangiate anther. The identity as a hermaphrodite flower could only be clarified with the discovery of Archaefructus eoflora , since the earlier finds were only fruits and the leaf stigmas in the lower part of the flower could not be assigned to petals or stamens.
Female flower organs
The carpels took up the upper two-thirds of the axis and were also arranged helically. The carpels were folded. They stood individually, sometimes in pairs, on a short handle. In rare cases there were also one or two carpels and a stamen on a stalk. Ji et al. define these parts of Archaefructus eoflora as a hermaphrodite. These would be the oldest known hermaphrodite flowers. Sun et al. defined the entire fruit axis as a flower in Archaefructus liaoningensis in 1998 .
The orthotropic ovules stood in a row and were attached to the abaxial side inside the carpel. In Archaefructus liaoningensis three (two to four) were ovules in each carpel. In Archaefructus eoflora a lack scar , as described for the other two species.
The follicles were on short stalks. The fruits ripened distally, i.e. from the base to the tip.
blossoms
In the original publications by Sun et al. (1998, 2002) all axes were interpreted as flowers. Recent studies suggest that only the mostly two stamens or one or two carpels standing on the short stems are to be regarded as flowers. Thus the flowers would be unisexual. Only the flowers in the transition area between male and female flowers, which had both stamens and carpels, would be true hermaphroditic flowers.
Flower ecology
Sun et al. (1998) speculated about the pollination mechanisms of Archaefructus and considered pollination by Diptera as well as possible wind pollination ( anemophilia ). The leaves at the base of the flower axes could have served to attract, but no coloration has been proven. The scar tissue could also have secreted nectar.
Location
Archaefructus eoflora grew on the edge of rivers . The lower parts of the shoot grew under the water, while the longer flower sprouts rose above the water.
Systematics
The first species, Archaefructus liaoningensis , was discovered in 1998 by Sun et al. described. The holotype has been deposited in the Nanjing Institute of Geology and Palaeontology of the Academia Sinica as number SZ0916. After a second species ( Archaefructus sinensis ) was found in 2002, the Archaefructaceae family was established.
The Archaefructaceae were considered by the first descriptors to be the sister group of all other angiosperms. According to other studies, Archaefructus was not a basal angiosperm, but belonged to the magnoliids or the basal eudicotyledons .
Three types have been described:
- Archaefructus liaoningensis
- Archaefructus sinensis
- Archaefructus eoflora
The age of the genus was initially given by the first descriptors as the latest Jurassic (at least 145.5 million years). However, the age of Archaefructus was later set to the Early Cretaceous ( Barremium / Aptium border area) due to a new dating of the find history (124.6 ± 0.1) .
Sources and further information
- Ge Sun, David L. Dilcher, Shaoling Zheng, and Zhekun Zhou: In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China. In: Science . Vol. 282, 1998, pp. 1692-1695, doi : 10.1126 / science.282.5394.1692 ( free ).
- Ge Sun, Qiang Ji, David L. Dilcher, Shaolin Zheng, Kevin C. Nixon, Xinfu Wang: Archaefructaceae, a New Basal Angiosperm Family. In: Science. Vol. 296, 2002, pp. 899-904, doi : 10.1126 / science.1069439 .
- Qiang Ji, Hongqi Li, L. Michelle Bowe, Yusheng Liu, David Winship Taylor: Early Cretaceous Archaefructus eoflora sp. nov. with Bisexual Flowers from Beipiao, Western Liaoning, China. In: Acta Geologica Sinica. Vol. 78, 2004, ISSN 1000-9515 , pp. 883-892, doi : 10.1111 / j.1755-6724.2004.tb00210.x , ( online (3.2 MB; PDF) ).
Individual evidence
- ↑ The genus description follows Ji et al .: Early Cretaceous Archaefructus eoflora sp. nov. with Bisexual Flowers from Beipiao, Western Liaoning, China , 2004.
- ^ A b c d e Sun et al .: In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China. 1998
- ↑ a b c Richard M. Bateman, Jason Hilton, Paula J. Rudall: Morphological and molecular phylogenetic context of the angiosperms: contrasting the 'top-down' and 'bottom-up' approaches used to infer the likely characteristics of the first flowers . In: Journal of Experimental Botany. Vol. 57, 2006, ISSN 0022-0957 , pp. 3471-3503, doi : 10.1093 / jxb / erl128 .
- ↑ Ji et al .: Early Cretaceous Archaefructus eoflora sp. nov. with Bisexual Flowers from Beipiao, Western Liaoning, China , 2004.
- ^ Sun et al .: Archaefructaceae, a New Basal Angiosperm Family , 2002.