Fulletby brickyard: A classic locality in the Upper Jurassic Kimmeridge Clay of Lincolnshire

John P Green (UK) The Upper Jurassic Kimmeridge Clay Formation in Lincolnshire crops out along the western edge of the Lincolnshire Wolds scarp (Swinnerton and Kent, 1981) and many years ago was formerly exposed in many small workings that exploited the Lower and Upper Kimmeridge Clay Formation for brickmaking. The once famous brick pits at Market Rasen (TF120888) and at Stickney near Boston (TF342570), both richly fossiliferous and the source of many historic museum specimens (in particular, ammonites and marine reptiles) have long since closed and the sections are no longer accessible. Fig. 1. Saurian vertebra (crocodilian or possible plesiosaur), discovered on the reverse of a Pectinatites ammonite. Nevertheless, I have located another former, now largely overgrown brickyard, near the village of Fulletby (TF298734), situated just under five kilometres north of Horncastle. Whilst largely overgrown, small exposures remain of the Upper Jurassic Kimmeridge Clay Formation. The Palaeontographical Society lists the locality of Fulletby brickyard in its 1954 publication, Directory of British Fossiliferous Localities. It identifies the exposures present as belonging to the ammonite zone of Pectinatites wheatleyensis, and it was indeed thanks to this publication that I was able to discover this locality. The locality is also briefly discussed in Swinnerton and Kent (1981). The exposures that remain are intermittent and scattered, but shallow excavations made by me have revealed a sequence of richly fossiliferous mudrocks, which has allowed a rare opportunity to inspect and collect specimens from this rarely exposed horizon at this little known geological locality in Lincolnshire. … Read More

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Fossil folklore: Molluscs

Paul D Taylor (UK) The final article of this series on fossil folklore focuses on molluscs, excluding the ammonites, which were covered earlier (see Fossil folklore: ammonites in Deposits, Issue 46, pp. 20–23). Molluscs are second only to arthropods in the number of species living today and the resistant calcareous skeletons possessed by the majority of species accounts for their extremely rich fossil record. Most fossil molluscs belong to one of three major groups – bivalves (oysters, clams and so on), gastropods (snails and slugs) and cephalopods (ammonites, belemnites and so on). Added to these are a few minor groups, such as the monoplacophorans and scaphopods (tusk shells). Fossil molluscs are usually recognisable instantly as belonging to this phylum because of their close similarities with the shells of familiar species of modern molluscs. Some, however, are not quite so straightforward. These are more likely to have been the sources of fanciful stories about their origins and significance. Among the more obscure ancient molluscs are those dubbed ‘difficult fossils’ by Martin Rudwick in the context of the early history of palaeontology and doubts over the origin of fossils. They include the solid internal casts (steinkerns) formed by lithification of sediment enclosed by the shell and subsequent loss of the defining shell itself. In addition, there are some mollusc fossils – notably belemnite guards – that bear little resemblance to any living species, adding to their enigmatic nature. Belemnites: thunderbolts and Devil’s Fingers The first fossils I ever came across were belemnites … Read More

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Invertebrate fossils from the Lower Muschelkalk (Triassic, Anisian) of Winterswijk, The Netherlands

Henk Oosterink (The Netherlands) During the Muschelkalk part of the Ansian (240mya), the Central European area (Germany, Poland, Denmark, The Netherlands and north-eastern France) was covered by a shallow sea, referred to as the Muschelkalk Sea. While there were frequent regressions and transgressions (leading to both marine and terrestrial fossil being present in these regions), it is from this sea that the limestones from this quarry were deposited and in which most of the fossilised animals discussed in this article lived. The quarry in the Muschelkalk at Winterswijk, in the east of the Netherlands (Fig. 1), is especially well known for the skeletons, bones, footprints and tracks of Middle Triassic reptiles. I wrote about these in Issues 15 and 20 of Deposits. However, fossils of invertebrates, such as molluscs, brachiopods and arthropods can also be found. Included in the molluscs are bivalves, cephalopods and gastropods, and from the brachiopods, the Inarticulata are present. From the arthropods, there are Malacostraca, Merostomata and insects. Fig. 1. Lower Muschelkalk quarry near Winterswijk (Eastern Netherlands). Mollusca Bivalves Some strata contain a large number of moulds of bivalves. These are situated quite high in the profile and, if you find this level, it is important to split the rock along an irregular dark-grey line (Fig. 2). If you do this, you will find the moulds of the convex upper side of the separated shells on one slab, with the negative impression visible on the other. This makes clear that these are valves swept together by … Read More

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Hooks, paperclips and balls of string: Understanding heteromorph ammonites

Neale Monks (UK) Heteromorph ammonites were a group of externally shelled cephalopods that were particularly diverse during the Cretaceous period. Many species were abundant and geographically widespread and, for this reason, they have been used to date and correlate rocks. Unlike regularly coiled ammonites, which underwent a steady decline in diversity through the Cretaceous, the heteromorphs continually produced new and often bizarre species indicating a certain level of success at occupying new ecological niches. Only at the final mass extinction, at the Cretaceous-Tertiary boundary, did the heteromorphs finally fail. Fig. 1. Anisoceras armatus is a typical hamiticone heteromorph. In this reconstruction, it is shown as a benthic animal with the head oriented towards the substrate, though some recent work suggests that they were in fact planktonic animals that inhabited deep water. What makes a heteromorph? Broadly speaking, heteromorphs are ammonites with shells coiled in something other than the normal way. Whereas most ammonites had shells that can be described as flat, closed spirals where each whorl at least partially enclosed the one before it, heteromorphs had shells that coiled in a variety of ways. Some were simply open spirals, while others were helical like snails, or consisted of approximately parallel shafts connected by tight bends, so that the resulting shell looked a bit like a paperclip. At the most extreme, there was Nipponites. This is an ammonite with a shell formed from connected U-bends, each at an angle to the preceding one, resulting in something that looks more like a … Read More

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Tertiary cephalopods, or where did all the ammonites go?

Dr Neale Monks (UK) Most geologists will be familiar with Palaeozoic and Mesozoic cephalopods, but their Tertiary counterparts are much less well known. It isn’t that Tertiary cephalopods are rare as such – at some localities they can be quite common – but their diversity is extremely low. For example, the Gault Clay is a Lower Cretaceous formation that has yielded hundreds of cephalopods species, including ammonites, belemnites and nautiloids. Fast-forward to the London Clay, an Eocene formation, and that diversity falls to about five species, at most. At first glance, you would think this reflects the fatal decline of a group marching towards extinction. However, there are 700 cephalopod species alive today, so clearly that isn’t the case. In fact, what the lack of Tertiary cephalopod fossils shows is the switch within the group from forms with shells (such as ammonites and nautiluses) towards forms that don’t have shells (like squids and octopuses). Because they don’t have hard parts that fossilise easily, squids and octopuses have an extremely sparse fossil record. Nonetheless, the Tertiary isn’t entirely devoid of cephalopods if you know where to look. The London Clay exposure at Sheppey is a particularly good place to find nautiloid fossils. Occasional specimens from other cephalopod groups occasionally turn up as well and these give us some fascinating glimpses into the evolution of the post-Cretaceous cephalopods. Fig. 1. Warden Point, on the Isle of Sheppey, is one of the best places to collect Tertiary cephalopods (UKGE photo). Nautiloids Perhaps surprisingly, the … Read More

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Mollusc diversity for palaeontologists

Dr Neale Monks (UK) While arthropods and roundworms exceed the phylum Mollusca in terms of species, molluscs hold their own when it comes to anatomical diversity. There may be well over a million species of arthropod, but crabs, spiders and bees are all obviously related, sharing the same multi-limbed body plan organised around a jointed exoskeleton. Molluscs are very different. Clams, snails and squid are all molluscs, but their anatomy, ecology and behaviour couldn’t be more different. What molluscs have in common Although incredibly diverse, molluscs do have features in common. These include: A fleshy foot used for locomotion.A visceral mass containing the internal organs.A mantle that secretes the shell.A toothy tongue, known as a radula, for scraping food into smaller pieces.A shell made from calcium carbonate.Not all molluscs have all of these features, but they each have at least some of them. So, while an octopus doesn’t have a shell, it does have a mantle and a radula, as well as a foot divided up into the eight arms that give it its name. From the perspective of the palaeontologist, the key thing about molluscs is that most have (or had) shells. These fossilise more readily than soft tissues or even bones, and that means that molluscs have a remarkably rich fossil record. Origins The earliest fossil molluscs are known from the very base of the Cambrian, the Tommotian, about 530mya. This period of time was marked by the appearance of several major animal groups alongside molluscs, including arthropods, … Read More

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