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Rhynie flint is a fossil deposit in Scotland containing well-preserved fossils of early terrestrial life, including plants and arthropods. The fossils date back to the early Devonian period, and the preservation is due to hot spring silica water. The land plant fossils are diverse and contain vascular tissues, and the arthropods are small and include springtails, harvestmen, and mites. No winged insects have been found, but some exhibit characteristics associated with them.
Rhynie flint is a fossil deposit located near the village of Rhynie in Scotland. It is famous for containing exceptionally preserved fossils of some of the earliest known forms of terrestrial life, including plants and animals (arthropods). The Rhynie flint is dated to the early Devonian, about 396 million years ago. The preservation is so remarkable that the outlines of individual cells can be observed when the flint is polished.
Chert is a sedimentary rock composed of an agglomeration of different varieties of quartz. At Rhynie, the fossiliferous strata formed when a hot spring released silica water that rose and preserved the plants and animals in situ. The ecosystem was mineralized in excellent condition, to be discovered 396 million years later. A modern example of this phenomenon could be at the Yellowstone Park hot springs in the United States.
The land plant fossils preserved in Rhynie flint are the best and most diverse of their era, making flint a cornerstone of paleobotany. Although land plants, such as algae and mosses, have existed since the Late Cambrian, about 500 million years ago, they did not diversify until the Silurian, about 420 million years ago. Around the Rhynie flint period, the first plants with vascular tissues appeared. Vascular tissues are used to transport water and nutrients within plants. Without them, plants are basically mosses and close relatives and can’t grow more than a few inches tall.
Some of the plant varieties found in Rhynie flint include Aglaophyton, Asteroxylon, Horneophyton, Nothia, Rhynia, Trichopherophyton, and Ventarura. Five of the seven Rhynie flint land plant genera contain vascular tissue. These plants were 15 to 40 cm (6 to 16 inches) tall, small for today, but large for their time. The plants had extensive underground branching networks of rhizomes, bulbs covered with root hairs to absorb nutrients. There is evidence of symbiosis with fungi in roots, a symbiosis which continues in most land plants to this day. Plants use the greater surface area of the tiny fungal hyphae to absorb nutrients, while fungi take part of the nutrients for their survival.
Arthropods found with Rhynie flint are all relatively small and include springtails (Collembola), harvestmen (also known as daddy long-legs), pseudoscorpions (small scorpion-like predators), mites (Acari), myriapods (ancestors of millipedes) , small crustaceans (in the freshwater portion), strange aquatic organisms called euthycarcinoids, and trigonotarbids (extinct relatives of spiders). No winged insects have been found, but some exhibit derived characteristics often associated with winged insects, so it is possible that insect flight evolved millions of years earlier.
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