Which of the following is a fossil plant ?

Question

Accepted Answer

The correct option is 1: Rhynia

The genus *Rhynia* is a prime example of a fossil plant, belonging to the extinct group of early vascular plants known as Rhyniophytes. It is known exclusively from the extraordinarily well-preserved fossils found in the Rhynie Chert in Scotland, which dates back to the Early Devonian period, approximately 400 million years ago. *Rhynia gwynne-vaughanii* was a simple, leafless, and rootless plant, characterized by dichotomously branching aerial stems bearing terminal sporangia. Its discovery was a landmark event in paleobotany, confirming the existence of primitive vascular plants that align with theoretical models of the earliest land flora. Since the entire genus became extinct by the Upper Devonian period, it is classified purely as a fossil plant, existing only as preserved remains in the geological record.

The incorrect option is 2: Ginkgo

*Ginkgo* is an incorrect option because, while it possesses an extensive fossil record and is often described as a "living fossil," the species *Ginkgo biloba* is still alive today. The term "living fossil" refers to a species that has survived for a vast geological time, retaining a morphology virtually unchanged from its ancient ancestors, whose relatives are mostly extinct. Although its lineage dates back over 200 million years, the existence of a single, extant species means it cannot be exclusively categorized as a fossil plant. It is widely cultivated globally and is the sole surviving member of the division Ginkgophyta.

The incorrect option is 3: Psilotum

*Psilotum*, commonly known as the whisk fern, is a genus of living, extant pteridophytes (seedless vascular plants). This plant, despite its highly simple and primitive appearance (lacking true roots and leaves, similar to early fossil plants), is very much a part of the modern flora and is found in tropical and subtropical regions worldwide. Its simple anatomy leads many to believe it is a modern-day representative of the earliest vascular plants, but the species themselves are not extinct and therefore are not fossil plants. It is placed in the class Psilopsida, and its simple structure is generally considered a result of evolutionary reduction rather than being an unchanged relic of the Devonian period.

The incorrect option is 4: Equisetum

*Equisetum*, or horsetail, is the only extant genus of the class Equisetopsida (or Sphenopsida). Like *Ginkgo*, this plant group has a tremendously long geological history, with large, tree-like relatives being dominant components of the swamp forests during the Carboniferous period (e.g., *Calamites*). The modern horsetails are, therefore, also considered "living fossils." However, the genus *Equisetum* is widespread and consists of about 15 living species today. Because it is a thriving, extant genus with living representatives, it cannot be defined solely as a fossil plant, despite its ancient lineage.