Fossil spiders in Baltic amber

Anthonie Hellemond (Belgium) Spiders represent the most diverse group of obligate predators (that is, predators that feed solely on other animals) in terrestrial ecosystems today, with almost 48,000 extant species in 118 families described to date. The number increases annually by approximately 500 species as a result of new discoveries and it has been estimated that the true diversity may number around 160,000 extant species. This great diversity is no doubt at least in part due to their geological longevity, with the oldest known fossil spider dating back to the Carboniferous. In addition, spiders appear to have co-radiated along with their insect prey over geological time and they also appear to have been relatively resistant to extinction during the major events that eliminated many other terrestrial animal groups, such as the dinosaurs (Penney and Selden, 2011). Most people seem to presume that spiders do not have a very good fossil record on account of their very small size and their lack of a mineralised, bony skeleton. However, spiders actually have a very good fossil record, with 1,347 fossil species currently recognised. Fossil spiders occur in rocks of various different types, but the vast majority and best-preserved spiders are found as inclusions in amber from various localities dating back to the Cretaceous, although preservation tends to be better in the younger (for example, Miocene and Eocene) ambers. The best known of these deposits is Baltic amber, with more than 650 fossil spider species recognised (Penney et al., 2012), representing close to … Read More

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Sub-fossils in copal: An under-valued resource

Dr David Penney and Dr David I Green (UK) Copal (derived from the Spanish copalli meaning incense), the precursor of amber, is subfossilised tree resin not old or polymerised enough to be classed as amber. Given that the transformation of resin into copal and then into amber is dependent on factors such as temperature and pressure, there is no set age at which one turns into the other and the nomenclature (with respect to age) of these different transitional stages is still being debated. Some authors have proposed an arbitrary age of 2Ma to demarcate the transition from copal to amber, whereas others have suggested classifying anything that can be carbon dated as copal and anything too old for radiocarbon dating as amber. The debate continues and it seems that the age at which copal becomes amber will remain controversial for the foreseeable future. Furthermore, reaching a consensus terminology has been hampered by both amber researchers and dealers complicating the issue with terms such as sub-fossil resin, young amber, copal amber and so on. Fig. 1. Orb-web spider (Araneae: Araneidae) in Colombian copal. (From the collection of S Shawcross.) Nonetheless, copal preserves insects and other arthropods in the same way as amber and, given the younger age, the inclusions are often preserved with stunning, life-like fidelity. Remarkably, and in contrast to amber, very little research has focused on inclusions in copal because of its young age relative to amber. Such specimens are not deemed old enough to be of any … Read More

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Fossil insects from the Lower Cretaceous of southern England

Dr James E Jepson (UK) It was over 150 years ago that the first major work began on the fossil insects of the Lower Cretaceous of England. The pioneers were Victorian naturalists, including the Rev Osmond Fisher, John O Westwood and, in particular, the Rev Peter Bellinger Brodie. 1845 saw the publication of Brodie’s A History of the Fossil Insects in the Secondary Rocks of England, the earliest English language book on fossil insects and the first major study of the fossil insects of England. The Victorians collected and described many species from Wiltshire, Dorset and the Weald, and started the ball rolling for British palaeoentomology. The twentieth century saw little activity in British Cretaceous palaeoentomology. At this time, there was a shift towards the Palaeozoic insects from the Carboniferous, with Herbert Bolton leading the way – Bolton’s major work was published in a monograph on British Carboniferous insects in 1921–1922. A few descriptions were made on British Cretaceous insects in the early twentieth century, most notably Anton Handlirsch’s monograph of fossil insects (1906–1908) included some British Cretaceous insects; but there was no major studies completed. However, in the late twentieth century, interest in the Cretaceous insects of Britain was reawakened by Edmund A Jarzembowski, with his studies on Wealden insects and later the Purbeck insects with Robert A Coram. Into the twenty-first century, Jarzembowski and Coram have remained a driving force for the study of Lower Cretaceous insects of southern England and, through their work and their collaborations with … Read More

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