Horsetails and ferns are pteridophytes, meaning that they reproduce and disperse via spores. Horsetails are in the genus Equisetum, the meaning of which can be deduced by breaking the word into the Latin roots equus (“horse”) and seta (“bristle”). Fossil horsetails are the genus Equisetites. Fern species were widespread in Cretaceous Denali and belonged to the genera Aspleninum, Gleichenia, and the extinct Cladophlebis.
Identification Level: Genus
Horsetail fossils are widespread in the Cantwell Formation of Denali. Fortunately, the tell-tale striations and segmentations allow for easy identification of the specimens to the genus level, and for some specimens to the species Equisetites arcticum. Three different fossil fern and fern foliage genera have been discovered in Denali: Aspleninum, Gleichenia, and Cladophlebis.
Where do I live?
Horsetails lived semi-aquatic lives in marshes and lakes, while ferns flourished in drier soils or sandier parts of the floodplain under the forest canopy.
How do we know I lived in Denali?
Fossil stems and rhizomes of Equisetites have been found near Sable Mountain, Double Mountain, and Polychrome Mountain in Denali. Amazingly, some stems are found relatively uncompressed and are preserved in three-dimensions. This is because the stems are hollow and filled with sediment during burial. Beautifully-preserved fern fronds have also been found in Cretaceous sediments in Denali.
Equisetum, which you can find throughout Denali today, is a “living fossil”. It is the only remaining modern genus of the entire class Equisetopsida, which has dominated forest understories for over 400 million years.
Last updated: August 16, 2016