What is it about?

The discovery of large, nearly complete, fossil leaves of the fern Weichselia reticulata from the exceptional site of Las Hoyas site (129 million years old) has allowed for the formulation and application of a novel protocol based on measurements that provide new keys to address the growth and architecture of ferns. This study not only provides information about the shape of the plant, but also about the way it grew and where it lived.

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Why is it important?

Plants are essential elements of the ecosystem’s landscape, and therefore, knowing their form and habit is crucial to understand and reconstruct ecosystems from the past. However, fossil plants are generally found in a disarticulated state and the reconstruction of the whole plant proves to be impossible in many cases. The new reconstruction of the fossil fern Weichselia reticulata is unique in that it is based on small fragments of leaves (18 to 30 cm) that have been relocated to their original position in the leaf based on outstandingly well preserved, nearly complete, leaf remains. This is the first study dealing with growth in fossil plants from direct measurements, which capture the degree and direction of maturity. Additionally, inferences on the ecological adaptations of the plant or the type of environment it lived in can also be drawn from the architectural description.


This new protocol will aid in the reconstruction and understanding of other fossil ferns and plants with compound leaves. In the case of Weichselia, the results show two types of growth: from base to apex in the pinnae, and from apex to base in the complete leaf, formed by several pinnae. This discovery is the key that allows a correct reconstruction of the adult leaf, formerly reconstructed with pinnae of different sizes, and now as asymmetrical only in the younger stages. Moreover, in Weichselia reticulata the leaves were thick and grew horizontally and in zig zag, a suite of unique traits suggesting a high exposure to sunlight.

Candela Blanco-Moreno

Read the Original

This page is a summary of: A novel approach for the metric analysis of fern fronds: Growth and architecture of the Mesozoic fern Weichselia reticulata in the light of modern ferns, PLoS ONE, June 2019, PLOS,
DOI: 10.1371/journal.pone.0219192.
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