Trilobites / bugs with articulated legs
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TRILOBITES
BEARER OF ARTICULATED LEGS
First Period of Appearance
Trilobite emerged in the Cambrian period some 523 million years ago. It is an arthropod related to insects, spiders, and crustaceans such as lobsters.
Characteristics
It is protected by a exoskeleton made of chitin, same polymer that is found in our nails. Only the top of that shell is hardened by calcium, which explains that in time of danger, it protects its abdomen by rolling up. Its legs and antennas are not mineralized, and are thus rarely preserved.
The trilobite owe its name to the organization of its body into three vertical lobes. The eyes can be simple or complex like that of flies, while some other trilobites species were blind. Because it sheds its shell to grow, parts of its shell can often be found.
The Ordovician period (460 million years) is the golden age of trilobites, species followed one another rapidly. This invertebrate then becomes a precise time marker precious for dating the rock layers of that time.
With the glaciation that ends at the Ordovician, a great number of families disappear. The last ones went extinct at the end of the Permian period 250 million years ago at the same time that 90% of the marine fauna. It was a bigger extinction than the one that made dinosaurs become extinct.
In Témiscamingue
Témiscamingue is a region poor in trilobite with few species and specimen during the Ordovician period. The Silurian period was richer with 9 confirmed genus, however complete specimens are rare. Here are a few species of trilobite:
Ordovician
Bumastus trentonensis
Ceraurus dantatus
Isotelus gigas
Silurian
Encrinurus cf ornatus
Encrinurus sp.
Internet Resource
To know more about trilobites, we recommend you visit this very good web site of Dr Sam Won Ill Senior Scientist for The Nature Conservancy's Hawai'i Field Office in Honolulu:
Must see
