Collections Up Close
Fossil insects from the Sedgwick Museum feature in new international research
The Isle of Wight has many widely acknowledged claims to fame from its regattas and the annual rock festival to Osborne House and the spectacular chalk Needles but not perhaps for its fossil insects. However, in the international world of palaeoentomology (the study of fossil insects), the island’s 34 million year old Insect Limestone is world famous.
Fossil insects and plants were first discovered in the mid 19th century and collected from outcrops in the Bembridge Marls on the Isle of Wight over a period of some 20 by Joseph Edwin Smith (later known as Joseph Edwin Ely A’Court Smith, 1813-1900). Smith was a retired chief officer in the Merchant service and a very keen amateur geologist with a passion for collecting fossils, especially insects – over 4000 specimens in all. Most of these specimens were probably collected from Thorness Bay, which is part of the legally protected Gurnard Site of Special Scientific Interest (GCR 0796). Part of Smith’s collection, some 177 specimens, were acquired by the Sedgwick Museum in 1883 and were rediscovered in 2005 by palaeoentomologist Andrew Ross (National Museum of Scotland) and scientifically reunited with the rest of this historic collection held by the Natural History Museum in London.
This year the Royal Society of Edinburgh has published the first of two volumes of its Transactions (2014, volume 104, number 231, pp. 231-451) to be devoted to the wonderfully well preserved and diverse fauna and flora of these latest Eocene age deposits. The sediments and organic remains were originally laid down under a subtropical climate as limey muds in an hypersaline salt lake into which the insects were variously washed or trapped on the surface and drowned.
Smith only published short accounts of his ‘finding of a bed of insects - flies, gnats, and the larva and pupa of the latter, the larva in count-less thousands – also the wings, in great numbers, of a variety of flies, butterflies, and one or two grasshoppers; also a wing resembling that of a Mole Cricket..’. It was a wonderful find but it was not until 1889 that the first of Smith’s fossil insects, a butterfly, was namedas Lythopsyche antiqua and described by A.G. Butler in 1889. Since then an extraordinary diversity of well over 250 insect species belonging to some 14 orders have been described from this single deposit, which is only 10 cm or so thick, along with plants, molluscs, crustaceans and vertebrates. In recent decades it has been shown that the most abundant of the fossil insects from the Insect Limestone are species of ants and wasps followed by flies, beetles and bugs, which are all typical inhabitants of a subtropical forest with significant rainfall.
It is of particular interest that this British fossil biota is of closely similar age to the world famous fossil biotas of Florissant in the USA and Baltic amber deposits, both of which are rich in insects. Together, these three localities provide the vast majority of our information and understanding of the evolution of insects and flora at a critical time in the development of the biota of the modern world with changing climate and the increasing domination of the flora by flowering plants and the insects that coexisted with them.
The ten papers of the first published volume cover the geology and history of investigation of the Insect Limestone along with the results of current research on the fossil plants, molluscs, spiders, dragonflies, damselflies, bark-lice, thrips, caddis-flies, wasps, bees and ants. The second volume will include papers on other major components of the insect fauna, namely the beetles, flies and bugs along with the fossil mammals etc. The international interest in these Late Eocene age fossils is the result of a research project which began in 2004 and has involved 33 scientists, mostly Russian with a smattering of Poles, French, Germans, Spaniards and Brits.
The results include a review of the fossil plants whose importance has been acknowledged since the 1880s. Over the last decade or so the flora has been accepted as one of a series of global benchmarks for the study of Paleogene vegetation, which is important in understanding how vegetation changed during a period of global cooling with the buildup of the first major ice sheet on Antarctica.
The plant fossils reflect a dominance of wetland environments with an abundance of bulrush (Typha) along with fruits, seeds and leaves of non-wetland flowering plants, including trees and shrubs. The present review by Peta Hayes and Margaret Collinson corrects earlier records of plants such as palms from the assemblage. Surprisingly, despite the abundance of plant and insect remains there is little evidence of plant-insect interaction recorded by the plant fossils.
Updates on the fossil insects include a review of some 50 specimens of fossil spiders by Paul Selden, who has found representatives of a number of living families with different habits and different habitats, including a water spider (Vectaraneus), orb-web weavers, which live amongst aquatic vegetation, nocturnal segestriid hunters and salticid jumping spiders, which are diurnal hunters. The fossil dragonflies and damselflies (odonatans) are more diverse with nearly 20 species belonging to 11 different families and are of particular interest because of their strong similarities with Recent Afrotropical and Indo-Malayan odonatans,
The living bark lice (psocodeans) may not be familiar insects but there are some 10,000 known species and the presence of seven fossil species in the Isle of Wight fauna again reinforces the conclusion that 34 million years ago climates of the region were significantly warmer than today. Similarly the presence of some 32 species of thrips (thysanopterans), which require a temperature of 25 degrees C over a period of two to three weeks for their development, supports this.
Although fossil caddis-flies are a minor element of the fauna with just 71 specimens belonging to six species, they belong to a small and rare family, the Beraeidae. This group of caddis-flies is rarely found in fossil form and they represent one of the unusual elements of the Isle of Wight Insect Limestone biota. Some caddis-flies have larvae, which only occur in springs and cold streams and their presence indicates the existence of abundant cold freshwater and absence of slow, warm-running water as a source of the Insect Limestone deposits.
However, it is the fossil hymenopterans (wasps, bees and ants), which are the most remarkable element of the insect fauna. It is a wonderfully rich and diverse assemblage with some 1460 specimens known so far, which belong to 118 species. By comparison some 450 species of fossil hymenopterans have been described from Baltic amber, 290 species from the Florissant strata in the USA and 210 from Dominican amber. But, as with most biotas, living or fossil, just a few species are dominant and here it is two species of winged Oecophylla weaver ants, which comprise 84% of the known fossils. And, whilst studying the proctotrupomorph wasps as part this project one of the Russian scientists Mikhail A. Kozlov found a wasp specimen that is only 0.3mm long, which is unusually small for a fossil insect preserved in rock. There are however many living wasps that are even smaller – down to a 0.13 mm long Hawaiian species called Kikiki huna.
The Sedgwick Museum currently displays a range of fossils from the Bembridge Marls.
Photo: The fossilized wing of a 34 million year old termite, Mastotermes anglicus from the Isle of Wight Insect Limestone. Specimen number X.50140.103 (TN 158), the counterpart from the Sedgwick Museum of a specimen in the Natural History Museum, London. Photo taken by Phil Crabb.
Study of a unique rock collection – and its astonishingly beautiful microscopic crystal structures – could change our understanding of how the Earth works.
A new study funded by the Natural Environment Research Council in the University’s Department of Earth Sciences has turned to a unique rock collection, amassed since at least the early 1800s and held within the Sedgwick Museum, to provide fresh understanding of the composition of the mantle.
Dr John Maclennan, project leader, is working alongside Dr Arwen Deuss and Dr Tim Holland to look at the frozen remains of magma formed at depths of 100 km or more from the mantle and then 'spewed out of volcanoes'. More information and the film associated with the project can be found here.
Saharan dust on your bonnet - Dr Douglas Palmer
A powerful southerly airflow has been blasting fine dust all the way from the Sahara in north Africa to Cambridge over the past few days.
The dust is most noticeable on the bodywork of dark coloured cars.
If you have wondered what Saharan dust actually looks like, here is a view taken down a microscope by Jeannie Booth, research assistant in the Sedimentological Laboratory of the Department of Earth Sciences.
The dust grains are very small mineral particles, about a tenth of a millimeter in diameter and therefore light enough to be picked up by the wind and carried high up in the atmosphere over 3000km before being dropped over northern Europe.
The grains have a distinct pinkish colour from a coating of iron compounds, such as haematite, which is typical of the Saharan desert. They also have angular shapes, unlike larger desert sand grains, which are typically well rounded. The dust particles are too small and light to be ground into round shapes.
Naturalists are becoming an endangered species - Dr David Norman
The phrase “Natural History” is linked in most people’s minds today with places that use the phrase: the various Natural History Museums, or television programmes narrated so evocatively by renowned naturalist Sir David Attenborough.
As times have changed, used in its traditional sense the phrase now has an almost archaic ring to it, perhaps recalling the Victorian obsession with collecting butterflies or beetles, rocks or fossils, or stuffed birds and animals, or perhaps the 18th century best-seller, Gilbert White’s The Natural History of Selborne.
Full article available here
Dr Woodward's Fossils - Dr Kenneth McNamara
For three hundred years, 5 beautiful walnut veneer cabinets, like elegant Regency secretaires, have been the home to almost 10,000 “Fossils of all Kinds” in the University of Cambridge. These were originally the personal collection of Dr John Woodward (1665 (or 8) – 1728).
Full article available here