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What is a Fossil? | Invertebrate Fossils | Dinosaurs | Ice Age Animals | Victoria's Fossils |
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Insects
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Insects
Insects belong to the group of invertebrates called arthropods, which are characterised by a hard external skeleton and jointed limbs. Other arthropods include crustaceans (e.g. crabs), spiders, centipedes and the extinct trilobites. Insects were amongst the first animals to live on dry land, their oldest known fossilised remains occurring in rocks of Early Devonian age (about 400 million years old). These earliest insects were flightless, but by Middle Carboniferous time (about 325 million years ago) winged forms had evolved. At this time there were few predators on land to threaten them, so that in the Late Carboniferous and Permian some insects reached an enormous size, with wing spans of about 70 cm. The fossil record of insects in the Mesozoic is not as rich as that of the Palaeozoic, but the assemblage present in the Triassic resembled that of today. There was a marked increase in insect diversity in the Cretaceous, apparently associated with the appearance of the flowering plants. By the end of the Cretaceous (65 million years ago), most of the major modern groups of insects had appeared. In the Cainozoic, most of the insect fossil record comes from exquisitely preserved specimens in amber, which is fossilised tree gum in which the specimens became trapped. Many different types of insects are known from amber of Oligocene age from the Baltic region of northern Europe. At the present day insects are the most abundant and diverse group of all living creatures, with more species that all other animals and plants combined. The following two images are both of the same fossil insect. They are two halves of the same rock, that when split revealed the Prochoristella leongatha fossil. A fossil remnant was left on each half of the rock.
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