Book review: Trilobites of the British Isles, by Dr Robert Kennedy and Sinclair Stammers

I’ve been waiting for a book like this for a very long time and am delighted that a publication of this quality has now arrived. New books covering British palaeontology are always welcomed by this magazine and we published an article a while ago by the founder of the publisher of this book – David Penney – explaining the need for such guides.

Giant trilobites and biotite nodules in Portugal

Peter Perkins (UK) The generally accepted reason for the fame of Arouca is Princess Mafalda, born 1195, who was responsible for the convent becoming Cistercian. Here is an interesting story – she was beatified in 1793. However, I won’t go into that now, but it is well worth investigating. For this article, there are other reasons for its fame, at least among geologists. Arouca is 38km to the south east of Oporto, in northern Portugal, and gives its name to one of two geoparks in Portugal. In Arouca Geopark (Fig. 1), which has an area of 330km2 (just a little smaller than the Isle of Wight), there are two quite remarkable geological features, one palaeontological and the other concerning igneous petrology. Fig. 1. Map of Arouca Geopark. A geopark is an area of significant size that has a particular geological heritage, with a certain number of sites of special importance – scientific quality, rarity, aesthetic appeal and educational value. It must also have a sustainable strategy for development to be accepted as a member of the worldwide network of geoparks. There are 42 in Europe, in 16 countries. The other Portuguese Geopark is Naturtejo, through which the River Tagus flows. There are nine geoparks in the British Isles, for example, NW Highlands (Scotland), Copper Coast (Ireland), Fforest Fawr (Wales) and the English Riviera. The website, http://www.europeangeoparks.org, gives website addresses for all. The geology of Portugal is very complex. There are no strata younger than Triassic, except for Holocene deposits in … Read More

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Trilobites: A short introduction

Dr Robert Sturm (Austria) Many people interested in palaeontology and collecting fossils have either found fragments of trilobites in the field or marvelled at fossil examples of these animals displayed in museums around the world. Although they are essential components of palaeontological collections, thereby acting as index fossils for the Palaeozoic epochs (from the Cambrian to the Permian), data regarding their systematic and taxonomic categorisation, biology, and ecology are largely unknown among amateur fossil collectors. In this short contribution, I will provide an overview of the main characteristics of trilobites, which are of great importance if you wish to gain an understanding of these fascinating organisms, which became extinct 220Ma. The systematics of trilobites Fig. 1. Crude systematics of the Trilobita (superclass). In general, ten main orders can be distinguished, from which six important orders can be identified (Agnostida, Redlichiida, Ptychopariida, Phacopida, Nectaspida and Lichida), while the remaining orders, referred to as Corynexochida, Asaphida, Harpida, and Proetida (not shown above), play only a minor role, due to their similarity to members of the Redlichiida and Ptychopariida. The heyday of the trilobites was during the Cambrian (570 to 505Ma). Due to increased competition for food resources (for example, graptolites and brachiopods), they were subject to a successive displacement from their original habitats. This process was also accelerated by the appearance of predators, such as large cephalopods, eurypterids (which looked like gigantic crayfishes) and fishes. The evolution of better predators and competition for food finally resulted in the extinction of the trilobites … Read More

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Looking through a crystal ball: Unravelling the wonders of trilobite eyes

Dr Clare Torney (UK) The weird and wonderful world of trilobite eyes has been subject to study since the late 1800s, but despite being scrutinised intensively over the decades, we are still left questioning how trilobite eyes actually worked due to the loss of their soft parts (that is, photosensitive cells) during the fossilisation process. The numerous strange forms that trilobite eyes come in no doubt plays a role in keeping researchers interested: from the bulging eyes of the Ordovician pelagic trilobite Carolinites to the eyes of Neoasaphus, which stand proud on stalks – trilobite eyes might seem better placed in a sci-fi movie than a palaeontology textbook. However, the study of their eyes can reveal an incredible degree of information, from details of how these extinct marine arthropods lived, to the change in chemistry and temperature of our oceans; and they can even help us understand how animals of today mineralise their (exo)skeletons. Unlike our own eyes, which are made of soft moving parts that allow most of us to focus on whatever we choose whether it be near or far, trilobite eyes in-vivo were actually composed of the hard mineral calcite (crystallised calcium carbonate), which they also used to construct the rest of their exoskeleton (Fig. 1). Fig. 1. An enrolled specimen of Acernaspis orestes from Anticosti Island. The calcitic eyes of trilobites are an extension of their exoskeleton. Although this may come with its advantages (essentially like wearing your safety specs all the time), using calcite to … Read More

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Geology and terrestrial life of the Carboniferous

Russell Garwood and Alan Spencer (UK) The Carboniferous Period is a fascinating time in earth history. It spanned 60Ma (359.2 to 299.0Ma), towards the end of the Palaeozoic era, falling between the Devonian and Permian. During the Carboniferous, the supercontinent Pangaea was assembling and the oceans were home to invertebrates such as corals, bryozoa, ammonoids, echinoderms, trilobites and crustaceans. Fish were also well represented (especially sharks), which were rapidly diversifying at the time. The continents were no barren wasteland either – they were host to some of the first widespread terrestrial forest and swamp ecosystems. In these lived both invertebrates, which had crawled onto land by the Silurian period (at least 423mya) and vertebrates, which were relative newcomers to this realm. This article provides us with an excuse to write about the Carboniferous. We will first introduce the geology and palaeogeography of the Carboniferous, including an overview of the most common mode of preservation we see in terrestrial fossils. Then, we will provide an overview of terrestrial life during the period, as land-based ecosystems of this age are among the best known from the Palaeozoic and an exciting time in the history of life. Fig. 1. Global paleogeographic reconstruction of the Earth in the late Carboniferous period 300mya. (C)opyright Dr Ron Blakey (Wikipedia Creative Commons). Carboniferous geology The Carboniferous is split into two epochs, the Mississippian (or Lower Carboniferous; 359.2 to 318.1mya) and the Pennsylvanian (or Upper Carboniferous; 318.1 to 299.0mya). As we shall see, the two are associated with … Read More

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Essential collectibles #1: Diacalymene trilobites

Dr Neale Monks (UK). In this series of articles we’re going to be looking at those fossils many people buy rather than collect. This doesn’t mean they’re less interesting of course, but because of the way they’re acquired hobbyists often don’t know much about them beyond what they are and very broadly where they’re from. Our first such fossil is the trilobites of the genus Diacalymene that are collected in vast quantities from Silurian sediments in the Draa Valley of Morocco and exported all around the world. They’re usually all described as Diacalymene ouzregui, but taxonomists would probably argue that name has been used a bit indiscriminately! In any case, apart from being abundant and therefore inexpensive, these particular trilobites are enduring popular because they’re such large fossils, anything between 8-10 cm is typical. That’s a lot bigger than the average trilobite, which means its a lot easier to see all their key features. Trilobites get their name, which means ‘three-lobes’, because if you look at one from the top, you can see it’s external skeleton, or exoskeleton, can be neatly divided into three parallel regions: the left and right hand sides which lay on top of the legs and gills, and the central region that went above the other organs including its digestive tract. Diacalymene ouzregui is a typical Diacalymene species and shows all three regions clearly. It can also be looked at in terms of body segments. Like all arthropods, trilobites had bodies consisting of a series of … Read More

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