Fossil Insects

Fossil Insects in Rocks

admin — Wed, 06 Jun 2007 15:52:11 +0000

The fossil record of insects contrary to what we think, is abundant and very diverse. If outcrops with fossil insects are rare compared to those with other kinds of invertebrates, especially marine ones, then they compensate by yielding large number of specimens and taxa. The fossil insects are often well preserved and articulated, allowing morphological comparisons with Recent forms, adoption of the same systematic system, and inclusion in phylogenetic studies. Fossil insects also occur as disarticulated remains, especially wings, and various trace fossils recording ancient activity. In the fossil record we have feeding traces on leaves, colonial structures such as termite nests and combs, galls, burrows etc. In the same outcrops, insects can be found from different habitats, both aquatic and terrestrial. There is also evidence of palaeobiological associations such as symbiosis, parasitism, commensalism, phoretic associations, and examples of co-evolution. The earliest reference to fossil insects is by Gaius Plinius Secundus - Pliny the Elder (24-79 B.C.). In his work Naturalis Historia, he described amber and the insect inclusions in it. In this period another writer, Marcus Valerius Martalis (40-104 BC) poetically described the occurrence of fossil insect inclusions. (more…)

Fossil Insects

admin — Wed, 06 Jun 2007 15:51:44 +0000

Unlike the trilobite that has left a prodigious fossil record, the preservation of insects in sedimentary matrix is relatively rare. The reason for the reletive scarcity of insect fossil is the poor preservation potential of the insect’s exoskeleton. Like other Arthropods, insects have an external skeleton called an exoskeleton. Unlike the thick and calcified trilobite exoskeleton, the insect exoskeleton is made of a thin, plastic-like material called chitin, along with a tough protein. This thin, waterproof covering simple does not preserve well in most oxygenated environments, making insect fossils sparse despite the tremendous number that could have been preserved. The exception is in fossil resinite, formerly known as the amber, by street name, where it is possible for even the minutest details to be preserved. Despite their huge strength to weight ratio, insects were often to small to escape the sticky resin exuded by trees, and which later became a fossil itself, with physical properties akin to modern polymerized plastics. (more…)

Other Known Fossils

admin — Wed, 06 Jun 2007 15:50:58 +0000

Trace fossils. Trace fossils, also called ichnofossils, meaning a trace or track, are structures preserved in sedimentary rocks that record biological activity. While we are most familiar with relatively spectacular, fossilized hard-part remains such as shells and bones known as body fossils, trace fossils are often less dramatic, but nonetheless very important. Strictly defined, trace fossils must reflect both the anatomy of their maker in some way, and be the result of behaviour. Sedimentary structures made by empty shells rolling along the sea floor are thus excluded as death marks, as are structures such as stromatolites that, although the result of behaviour, do not reflect the anatomy of their maker. Spun coccoons and spiders webs are considered to be trace fossils, as they are manipulated by their makers after secretion; egg cases, on the other hand, are not. Trace fossils include burrows such as Chondrites, borings, ichnites or footprints and track marks, Zoophycus feeding marks, trails such as Cruziana scratched by trilobites, coprolites, fossilized droppings and other gut-derived objects, and rhizoliths or rhizocretions, the fossil remains of roots. The study of trace remains is called ichnology, which is divided into paleoichnology, or the study of trace fossils, and neoichnology, the study of modern trace remains. The science of ichnology is quite challenging, as most trace remains cannot be positively assigned to a specific organism or even to a specific class of organisms. Furthermore, trace remains such as burrows can make the work for paleontologists and paleobiologists more difficult as they rework sediments, causing older strata to be mixed with younger ones. This can cause some confusion in interpretation, unless viewed in geologic context. (more…)

Rarity of Fossils

admin — Wed, 06 Jun 2007 15:35:47 +0000

Fossilization is actually a rare occurrence because most components of formerly-living things tend to decompose relatively quickly following death. In order for an organism to be fossilized, the remains normally need to be covered by sediment as soon as possible. However there are exceptions to this, such as if an organism becomes frozen, desiccated, or comes to rest in an anoxic or oxygen-free environment such as at the bottom of a lake. There are several different types of fossils and fossilization processes. Due to the combined effect of taphonomic processes and simple mathematical chance, fossilization tends to favor organisms with hard body parts, those that were widespread, and those that lived for a long time. On the other hand, it is very unusual to find fossils of small, soft bodied, geographically restricted and geologically ephemeral organisms, because of their relative rarity and low likelihood of preservation. Larger specimens or macrofossils are more often observed, dug up and displayed, although microscopic remains also known as the microfossils are actually far more common in the fossil record. Some casual observers have been perplexed by the rarity of transitional species within the fossil record. The conventional explanation for this rarity was given by Darwin, who stated that “the extreme imperfection of the geological record,” combined with the short duration and narrow geographical range of transitional species, made it unlikely that many such fossils would be found. Simply put, the conditions under which fossilization takes place are quite rare; and it is highly unlikely that any given organism will leave behind a fossil. Eldredge and Gould developed their theory of punctuated equilibrium in part to explain the pattern of stasis and sudden appearance in the fossil record. (more…)

Introduction to Fossil

admin — Wed, 06 Jun 2007 15:33:39 +0000

Fossils, from Latin fossus, literally having been dug up are the mineralized or otherwise preserved remains or traces such as footprints of animals, plants, and other organisms. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous or fossil-containing rock formations and sedimentary layers or strata is known as the fossil record. The study of fossils across geological time, how they were formed, and the evolutionary relationships between taxa or phylogeny are some of the most important functions of the science of paleontology. Using radiometric dating techniques, geologists have determined most fossils to be several thousands to several billions of years old. Yet there is no minimum age for a fossil. Fossils vary in size from microscopic, such as single cells, to gigantic, such as dinosaurs. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous exoskeletons of invertebrates. Preservation of soft tissues is exquisitely rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or faeces of a reptile. These types of fossil are called trace fossils or ichnofossils as opposed to body fossils. Finally, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals; these are known as chemical fossils or biomarkers. (more…)