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Gasteropods / sea snails

gastéropode escargot marin

Mud filling show signs of transportation

Macrulites manitobensis
Ordovicien
New Liskeard (Ontario) - Collection Société d'histoire du 
Témiscamingue

gastéropode escargot marin

Internal cast, occurring in eastern United States and Canada

Hormotoma Trentonensis
Ordovician
New Liskeard (Ontario) - Donated by Amélie Voynaud

 

 

 

Cast with marge of whorl turned inside

Homotama major
Ordovician 
New Liskeard, Ontario
Donated by Andrée Nault

 

GASTEROPOD
SUCCESSFUL MOLLUSCS

 

 

 

First Period of Appearance

 

They appeared some 570 million years ago during the Cambrian period.

460 to 420 million years ago, gasteropods fossilized in rocks in Témiscamingue, in the eastern coast of America, and in England lived. At that time, gasteropods were exclusively marine animals living near the shores. Today, they are primarily herbivore, sometimes sponge eaters. Others were eating corpses as well.

Gasteropods make up the biggest class of animals after the insects. There are about 40,000 species alive, most of which are in the seas, while a few have conquered land like snails.

 

Characteristics

Gasteropods, such as slugs, are molluscs which means they are cousin to mussels and octopus (from the cephalopods). They have a shell protecting their internal organs.

  • The most ancient form, which is planispiral in two dimensions, goes back about 530 million years.
  • The conic form spiralling on 3 dimensions first appears at the beginning of the Ordovician, 488 million years ago.

This spiral makes the shell stronger. The body follows that spiral and was most likely already twisting itself in the shell during the Ordovician and Silurian period as they are today.

Gasteropods have numerous organs : eyes, gills, a locomotor foot, and a heart with two chambers among other things.

 

In Témiscamingue

 

The area is particularly rich in gasteropods in the Ordovician period about 460 million years ago. We distinguish at least 6 different species.

Hormotoma major is a good stratigraphic indicator, i.e. it gives a very good marker of the period and also of the age of the rock in which it was found. It is known to have only existed 460 million years ago.   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



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