Burren and Cliffs of Moher UNESCO Global Geopark - Geology

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Fossil sponges: shining a light on some of our most overlooked fossils. Sponges are not the most glamorous things in the world, at best they might be delicious cakes or comforting bath scrubs, while in our kitchens they are man-made plastic porous blocks we use to help clean the dishes. The original sponges are living creatures however and most of us don’t stop to think about them, so here is a little background to the most overlooked creatures in the fossil record. These fascinating creatures are alive and well in all our seas today (a few live in fresh water), although many were in danger of extinction due to overfishing before the arrival of synthetic replacements. Sponges are simple multi-cellular organisms that don’t have a nervous or circulatory system or even a digestive tract. No limbs or eyes or teeth either. They have a porous jelly-like body that is supported by a network of microscopic skeletal elements known as ‘spicules’ that can be straight, cross or star-shaped. They draw water in through their porous bodies where microrganisms are filtered out and processed by the cells for food. It has been over 500 million years (half a billion years!) since the first sponges appeared and they are thought to be one of the earliest animal lineages to have evolved. Sponges can be found in all the geological ages from then to the present day and they have evolved a wide variety of lifestyles. Most are attached to rocks or the seafloor, but some can drift in currents; most filter microrganisms from the water, but some are predatory and capture prey with long sticky threads or hooked spikes; they can vary in sze from 1mm to several metres and can live in shallow water or down to the deepest ocean floor many kilometers below the sea surface. Sponges have an extraordinary ability to regenerate themselves from fragments. This is important in assuring their survival; even if a small part of a sponge survives a predator it can grow into a new animal. So, do we find fossil sponges in the rocks of the Burren and Cliffs of Moher UNESCO Global Geopark? Yes, we do, although they are not easy to spot because it is usually only the tiny (2mm) spicules that get preserved as fossils. This is why they are so overlooked. However, you might more easily find some evidence of the sponges that currently live along our coast, as some have the ability to dissolve limestone and make tiny complex burrows in the rock. Sponges are an important part of our modern ocean ecosystem and they were an equally important part of our geological ecosystems in the distant past. Finding fossil sponges adds one more piece of information to our understanding of our ancient biodiversity. Figure caption: A tiny spicule of a fossil sponge (left) recently collected in the Burren and Cliffs of Moher UNESCO Global Geopark and (right) modern sponge borings in a Burren limestone pebble.
Oh poop... We have quite a wide variety of the remains of once living creatures preserved as fossils in the rocks of the Burren area. Apart from their remains, recent finds tell us we also have their leavings! Yes, some of these creatures did what we all do and some of their leavings have been preserved, hidden for 320 million years until I split open a rock and found something new to here. Fossilized poops are known as coprolites. The name was given to them by William Buckland, a pioneering UK palaeontologist of the early 19th Century. He received his samples from Mary Anning, a collector and seller of fossils from Lyme Regis who had noticed that some unusual shaped stones found associated with the fossil ichthyosaurs (large marine reptiles) she collected had bits of fish and teeth inside them. She had also interpreted those stones as poop. Coprolites are classified as trace fossils as they are not the animal itself, just the result of the animal’s activity when it was alive. This is why the markings on the Moher flags are also classified as trace fossils, but they are the remains of burrowing activity not pooping activity. Coprolites are not commonly preserved; as poop,they would have been rich in food for scavenging creatures as well as bacteria, algae and fungi. Also, as most of our rocks were formed under the sea, the poops would have been very wet and disintegrated quickly on the seafloor. These leavings are extremely useful because they can preserve evidence that would otherwise have been lost. In the same way that a biologist can look into an owl or otter pellet to see what it was eating, we can see the remains of the food of creatures that died millions of years ago. Only the undigested remains are preserved, so Just like with fossils themselves, usually what is preserved are the hard bits. The most common remains found in coprolites are teeth and scales. In most cases the food has been so efficiently digested that nothing identifiable remains. Identifying who left the leaving is a different matter. Usually in any environment a number of predators eat more or less the same prey, so distinguishing the exact maker is difficult. There are some tell-tale signs however, for example sharks and some other fish such as the coelacanth have a spiral valve in their intestine, this gives a spiral, coiled appearance to their poop. The coprolites I found here recently are small (1-2cm) and some contain even smaller fish scales and bits of bone. As I found other remains of fish at the same place it is most likely the poops are the product of larger fish, which fed on smaller fish. This all adds to our understanding of the animals that lived here way before us. Good things come in small packages. Figure caption: Partially digested fish scale (2.5mm) inside one of the newly discovered coprolites.
Page 1 and 2: Managed By Supported By
Page 3 and 4: The patterns on Moher Flags are anc
Page 5 and 6: History in water flowing through th
Page 7 and 8: Our Fossil Roots In sandstone rocks
Page 9 and 10: Biokarst coastline, near Doolin. In
Page 11 and 12: Lough Garrig on top of Sleive Elva
Page 13 and 14: A clay layer between two layers of
Page 15 and 16: Big Brachiopods Large brachiopods a
Page 17 and 18: Our Geological Connection with Ukra
Page 19 and 20: The corals of the Burren National P
Page 21 and 22: Conodonts: bizarre fossils in the B
Page 23: Sedimentary layers: reading the pag

Burren and Cliffs of Moher UNESCO Global Geopark - Geology

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