Gasteropods / sea snails
Mud filling show signs of transportation
New Liskeard (Ontario) - Collection Société d'histoire du
Internal cast, occurring in eastern United States and Canada
New Liskeard (Ontario) - Donated by Amélie Voynaud
Cast with marge of whorl turned inside
New Liskeard, Ontario
Donated by Andrée Nault
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.
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.
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.