March 2011 – Trilobite

cliff.rigg — Wed, 02 Mar 2011 22:13:04 +0000

These are an extinct order of arthropod (animals having a jointed and segmented body plan) which make their first appearance in the fossil record during the Cambrian Period, commencing about 520 million years ago. Trilobites, meaning ‘three-lobes’, are some of the earliest known arthropods and lived on the sea floor at a variety of depths. During their most successful episode trilobites cover nine evolutionary orders which are further subdivided into literally thousands of genera.

Trilobite of the species Paradoxides.

They are one of the earliest creatures to have evolved hard-parts, presumably to protect against predators and, as such, are well-represented in the fossil record. The oldest rocks in the Tees Valley, the Carboniferous and Permian strata, may hold fossilised examples of these remarkable creatures. Trilobites have three parts to their bodies: the head or cephalon, body or thorax and tail or pygidium. They were marine animals which lived on the sea floor at a variety of depths.

Trilobites are so named for the three longitudinal lobes: 1 – left pleural lobe; 2 – axial lobe; 3 – right pleural lobe. The trilobite body can also be divided into three major sections (tagmata): 4 – cephalon; 5 – thorax; 6 – pygidium.

Trilobites survived until the end of the Palaeozoic Era, marked by the Permo-Triassic Mass Extinction which occurred around 250 million years ago.

This trilobite is Walliserops trifrucatus from Djebrl Oufaten in Morocco.

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February – Woolly Mammoth Tooth.

admin — Tue, 03 Feb 2009 11:38:07 +0000

Mammoth lived on most of the continents in the Northern Hemisphere during the last big ice age 70-10,000 years ago. Woolly Mammoths were about the same size as Indian elephants are today and covered in a layer of coarse hair. They are a good indicator of a cold climate and tundra or Steppe conditions. They are well known about and understood as whole frozen carcasses have been found in several places in Siberia. Mammoths are the symbols of the last ice age and many stories have evolved about them. The Siberian tribes believed that they lived in the centre of the earth and died when they came into contact with air. This explained to them why they never found one alive before the theory of extinction had been developed. Mammoths became extinct due to rapid climate change and large-scale human predation.

Mammoths have six sets of teeth throughout their lifetime. (Much like modern day elephants). They moved forward from the back of the jaw and replaced older worn out teeth as they fell out. This means that there are lots of teeth that can be preserved. Thin enamel plates cemented together. This makes a tall strong, wear resistant tooth.

They are often dredged up from the North Sea. Here they are from a land bridge between England and the Netherlands, which was cut off as sea levels rose 6 – 8,000 years ago. The teeth have then been reworked by the sea bringing them to the surface to be collected by trawlers.

The remains of a species of Dwarf Woolly Mammoths have been found on an island between Russia and North America. These have been dated back to 7,000 – 3,500 at the same time that the pyramids and Stonehenge were being built.

tvrigs.org.uk » Fossil

March 2011 – Trilobite

February – Woolly Mammoth Tooth.