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Equisetum columnareThe arborescent horsetails became extinct during the Permian. The horsetails from the Jurassic however could still attain a considerable size. The most common species in the Yorkshire area, Equisetum columnare, had a stem with a diameter of up to 5 cm at the base and 2 cm at the top. So this must have been a rather high plant.

The horsetails are not common in Yorkshire, in contrast with a lot of other Jurassic sites in the world. They are most abundant in Hasty Bank, which site we didn't visit. But in recently fallen blocks in Hayburn Wyke they were also present in abundance, but they were badly preserved. In Cayton Bay we came across some poor remains. Click on the photo.

Equisetum lateraleA second species we have found, Equisetum laterale, is much more slender. The stems have an average diameter of 1.5 cm and the internodes are about 3 cm. Typical for this plant are the diaphragms, which resemble a wheel with (on average) 32 spokes. We have found some specimens in Cayton Bay.

Annulariopsis simpsoniiA very rare find was Annulariopsis simpsonii, also in Cayton Bay. This plant had leaf whorls reminiscent to those of Annularia. Annularia however was the foliage of horsetail trees and those had been extinct for a long time. It is peculiar that only terminal leaf whorls have been found of Annulariopsis, while most probably more whorls were present on the stem. Perhaps the part above the whorl was breaking off very easily when the plant touched the ground. Click on the photo on the right.