by 19 Feb 2020

Kingdom: Animal
Phylum: arthropods
Class: Trilobita.
Era: Paleozoic
Period: Lower Cambrian- Permian
Environment: marine

The Trilobites owe their name to the characteristic tripartition of their body that the other Arthropods haven’t. In fact, if observed in longitudinal section it is possible to distinguish “three lobes”: cephalone (head), thorax (thorax) and pygidium (tail) and they also have bilateral symmetry.


But why are they so important?

Well, they are considered the first complex life appeared on Earth and they are Index Fossils, the symbol of the Paleozoic Era.
An index fossil found in a rock let us to know for sure at what time in the history of the Earth we are, in which Era and in which period, so we can determine the age of that rock.
The trilobites are excellent guide fossils since they have had a very rapid evolution rich in mutations and have spread on a large scale throughout the planet and in all marine and oceanic environments of the Paleozoic era. Their wide and abundant diffusion allows us to find many of their fossils in many places so we are able to correlate rocks form different and very distant geographical areas, and the fact that  trilobites have evolved and changed rapidly and extinct in relatively short times allows us to place them in a precise time space (Lower Cambrian – Permian, or between 521 and 250 million years ago) leaving no doubts about the age of the rock to which they belong and the type of environment in which it was formed.

We find these fossils in many places scattered around the globe, some famous examples are:
– Penn Dixie – New York state
– Wren’s Nest – Dudley – England
– Wheeler Shale – Utah
– Yoho National Park – Cananda

While, in Italy they can be found in
– southern Sardinia
– Sicily in the Sosio Valley
– Friuli Venezia-Giulia in the Carnic Alps where in some places, such as Passo Volaia, they are very abundant.


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