Rhynie Chert: Zoological Significance

 

The Late Silurian saw the invasion of terrestrial environments by invertebrates, in particular groups of arthropods, including myriapods (such as millipedes, centipedes and the extinct arthropleurids) and arachnids. A rapid burst of evolution from this time to the end of the Devonian not only saw the expansion of these and other arthropod groups, most notably the development of winged insects, but also, significantly, the evolution of air-breathing vertebrates and their adaptation to terrestrial habitats.

The Early Devonian Rhynie chert was deposited early on in this period of evolution and diversification about 400 million years ago. The exceptional preservation of the Rhynie fauna allows zoologists and palaeontologists to examine these early terrestrial, and freshwater, invertebrates in terms of their anatomy, and to determine how the various arthropod groups evolved and adapted to live in these new habitats. For example how centipedes and arachnids separately developed the means to breath air: centipedes developed an internal network of tubes or trachea; whereas in arachnids (esp. trigonotarbids) the anterior abdominal appendages where developed into filliform book-lungs.

By studying the associated in situ biota in the individual chert beds, much information can also be gathered on the interactions between fauna, flora and the inorganic environment, thus helping to build a picture of early terrestrial and freshwater ecosystems.