3D model of a sand cast of a fossil horsetail stem (NHMW-GEO-2024/0188/11189)

<p>This is the fossil stem of a giant horsetail plant: <i>Calamites</i>. This fossil is Late Triassic in age (237 - 201 million years ago) and is from Zeil in Bavaria, Germany. Horsetails&nbsp;are closely related to ferns, so they produce spores rather than seeds. Today, there are only 18 species of horsetails, all of which are small (typically less than 1 m tall) and belong to a single genus: <i>Equisetum</i>. But their small stature and low diversity is only a recent phenomenon; there have been thousands of species of horsetails over the last several hundred million years, and many of them were enormous! <i>Calamites </i>could grow to more than 30 m tall!</p><p>This object is part of the historical ‘Ettingshausen collection’, which is on permanent loan from the Institute of Biology, University of Graz.</p>