Name: Brachiopods in limestone
Classification: Chemical sedimentary rock, bioclastic packstone
Mineral composition: Calcite, other
Fossils:Brachiopods, echinoderms (not visible)
Location:Giau Pass, Mount Cernera (46°28'22.0"N 12°04'30.1"E)
Formation: San Cassiano formation
Era: Lower Carnian (approximately 235 million years ago)
Depositional environment:Carbonate substructure

brachiopode

This image shows a fossil as seen under the microscope; in particular it shows the shell of a brachiopod. Brachiopods are very similar in appearance to the bivalves which the mussel, clam and scallop enthusiasts among us will be familiar with, because their shell is composed of two parts, the valves, which enclose the organism. Brachiopods are however not even closely related  

to bivalves. Yes, they have a shell made up of two valves, but it is made from calcite and not from aragonite; and they live at the top of a horny peduncle. Today they are very rare, but in the past they outnumbered the bivalves. They can’t have been very easy to eat though, because many had two calcite spirals in the muscle between the valves.

 

 

References:

http://en.wikipedia.org/wiki/Brachiopod