Gigantopterid
| Gigantopterid Temporal range: late Permian
| |
|---|---|
| Scientific classification | |
| Domain: | |
| Kingdom: | |
| Division: | |
| Genera | |
Gigantopterids (Gigantopteridales or Gigantonomiales) is the name given to fossils of a group of plants existing in the Late Permian, until some 250 million years ago.
They bore many of the traits of flowering plants, but are not known to have flowered themselves. Gigantopterid plants had simple, bilaterally symmetrical leaf structures, woody stems and spines. They grew new parts by producing shoots, like flowering plants. Judging from the fossil remains, they were probably robust plants with fronds that resembled fern fronds when young but were more like flowering plant leaves arranged in a frond when mature. They grew at least over 20 cm (around 10 in), probably over 50 cm (20 in) tall, depending on whether it grew as a scrambling vine (the initial assumption) or erect (nowadays considered more likely). Some were apparently amphibious, while others thrived in rather arid habitat.
Chemical analysis of fossil remains indicates that gigantopterids produced oleanane, a chemical otherwise only known to be used by flowering plants, for which it functions as a suppressant of insect pests [1]. The vascular tissue in at least some taxa resembles that of the Gnetophyta. They had a cuticula similar to that of other seed plants. Some male sporangia (Gigantotheca, Jiaochengia) and seeds (Gigantonomia, Cornucarpus) have been tentatively referred to this group. While the sporangia are certainly not flowers, they differ from other sporangia of Permian plants.
Gigantopterid fossils were documented as early as 1883, but was more thoroughly investigated in the early 20th century. Some of their most significant evidence has been initially found in Texas, but they may have been present worldwide: another key region for gigantopterid fossils is in China, and the consolidation of all major continents into Pangea would have allowed for easy global dispersal.
It is probable that the gigantopterids are a non-monophyletic form taxon. Plant life from their era is very difficult to document and organize. They have been variously allied with the "seed ferns" (another paraphyletic group of early seed plants) Peltaspermales and Callistophytales, Gnetum, and the Magnoliophyta. All that can be said at present is that they were spermatophytes.
Notable genera
- Cathaysiopteris
- Delnortea
- Emplectopteridium
- Emplectopteris
- Gigantonoclea
- Gigantopteris
- Vasovinea
- Zeilleropteris
References
- Zi-Qiang, Wang (1999): Gigantonoclea: an enigmatic Permian plant from North China. Palaeontology 42(2): 329–373. doi:10.1111/1475-4983.00076 (HTML abstract)