Caytoniales
| Caytoniales Temporal range: Mesozoic |
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| Fig.1 A whole-plant reconstruction of Caytonia nathorstii | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Spermatophyta |
| Division: | Pteridospermophyta |
| Order: |
Caytoniales Gothan 1932 |
| Family: | Caytoniaceae |
| Form genera | |
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The Caytoniales (Figs. 1-2) are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, specifically in the late Triassic to Maastrichtian period, around 250 to 70 million years ago. They are regarded as seed ferns because they are seed-bearing plants with fern-like leaves. Although at one time considered angiosperms because of their berry-like cupules, that hypothesis was later disproven. Nevertheless, some authorities consider them likely ancestors of angiosperms, whereas others consider angiosperms more likely derived from Glossopteridales. The origin of angiosperms remains an intriguing puzzle (see Evolutionary history of plants).
The first fossils identified in this order were discovered in the Middle Jurassic Gristhorpe bed of the Cloughton formation in Cayton Bay, Yorkshire – hence the name CAYTONiales. They have since been found in Mesozoic rocks all over world. It is likely that Caytoniales flourished in wetland areas, because they are often found with other moisture-loving plants such as horsetails in waterlogged paleosols. The first fossil Caytoniales were preserved as compressions in shale with excellent preservation of cuticles allowing study of cellular histology.
The woody nature of associated stalks and preserved short shoots are evidence that Caytoniales were seasonally deciduous, shrubs and trees. Caytoniales had fertile branches with seed-bearing cupules . The ovules were located inside fleshy cupules with tough outer cuticle. Individual ovules had an apical tube called a micropylar canal, that allowed pollen to pass into the pollen chamber. The outer layers of the cupules were fleshy and fruit-like; it is possible this was to aid in animal dispersal. The cupules are 4-5mm in diameter and about 3 mm long (Fig 1-2), and resemble a blueberry. The extra protection of the reproductive organs gave rise to the idea that Caytoniales were predecessors to angiosperms, which have completely enclosed seeds.
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