Fossils are the remains or traces of past life. The most common ‘body’ fossils are formed from the hard parts of an organism e.g. tooth, bones, shells or wood. In exceptional circumstances the soft parts, such as muscle tissue, may be preserved. Trace fossils record the behavior of an organism, for example in the form of footprints, trackways or burrows. Finally, molecular fossils are organic molecules derived from a living organism, which are stable on a geological timescale. They are particularly important for investigating the origins of life on earth, but due to their microscopic nature and the challenges of extraction they are unlikely to feature in a museum collection.

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Simplified geological timescale. (Ma = million years)

In Ireland we have fossils which range in age from the Cambrian to the Quaternary.  The Giant Irish deer will be familiar to many, and two specimens stand in the hallway of the Trinity Museum Building. They date from around 11,000 years ago, during the last ice age. In the Carboniferous Ireland was covered by a shallow sea, and limestones of that age yield a diversity of fossils including corals, brachiopods, crinoids, cephalopods and bryozoans. Key evidence of the transition of vertebrate life to land can be seen in the tetrapod trackways on Valencia Island, Co. Kerry, from the Devonian. Ireland is also known for some exceptional plant fossils, including examples of one of the earliest vascular plants, Cooksoniafrom the Silurian.

The fossil collections of the Trinity Geological Museum include representatives of all the major groups – plants, invertebrates and vertebrates, as well as trace fossils. Specimens range in size from the giant Irish deer, which stands around 6ft tall, to microfossils less than 2mm in size, which can only be seen with the aid of a microscope.