Much like modern oysters Liostrea lived as a stationary epifaunal suspension feeder, encrusting hard substrates, after an initially planktonic larval stage.
Much like modern oysters Liostrea lived as a stationary epifaunal suspension feeder, encrusting hard substrates, after an initially planktonic larval stage.
Phylum: Mollusca
Class: Bivalvia
Palial line/palial sinus
Adductor muscle scars
Growth lines
Dorsoventral symmetry (some exceptions, for example Gryphaea)
Two hinged valves
Umbo
Hinge
Gills (rarely preserved)
Cambrian to present
Bivalves have occupied many environmental niches, living in a variety of ways:
Epifaunal, infaunal, nektonic
Marine, freshwater, brackish
Filter feeders through gills
Majority of bivalves begin life in a planktonic larval stage
By looking at the shell shape and palial sinus of fossil bivalves it is possible to say something about its mode of life.
Apparent increase in bivalve diversity over time (or is this just a preservational bias?)
Bivalves makes their shells out of calite, aragonites, or both
The adductor muscles are used to keep the shell of the bivalve closed. This means that when they are relaxed, the ligament between the valves pulls them apart, so the 'relaxed state' for bivalves is 'open'.
The depth at which infaunal bivalves burrowed can be inferred from the palial sinus. The more prominent the palial sinus, the deeper the bivalve burrowed. This is because the size of the palial sinus is indicative of the size of siphon needed, which in turn depends on the depth of the burrow (deeper burrow, larger siphon).
youtube: scallops swimming
Cambridge University Museum of Zoology: Lifestyles of bivalves
Yale Peabody Museum of Natural History: differences between bivalves and brachiopods
Learn about types of preservation
Go to the front of the 1A Lab. A display on the right hand side (by the window) shows a number of bivalves in life position. Have a look at how they have adapted their shape and other features to their way of life.
]]>Phylum: Mollusca
Class: Bivalvia
Palial line/palial sinus
Adductor muscle scars
Growth lines
Dorsoventral symmetry (some exceptions, for example Gryphaea)
Two hinged valves
Umbo
Hinge
Gills (rarely preserved)
Cambrian to present
Bivalves have occupied many environmental niches, living in a variety of ways:
Epifaunal, infaunal, nektonic
Marine, freshwater, brackish
Filter feeders through gills
Majority of bivalves begin life in a planktonic larval stage
By looking at the shell shape and palial sinus of fossil bivalves it is possible to say something about its mode of life.
Apparent increase in bivalve diversity over time (or is this just a preservational bias?)
Bivalves makes their shells out of calite, aragonites, or both
The adductor muscles are used to keep the shell of the bivalve closed. This means that when they are relaxed, the ligament between the valves pulls them apart, so the 'relaxed state' for bivalves is 'open'.
The depth at which infaunal bivalves burrowed can be inferred from the palial sinus. The more prominent the palial sinus, the deeper the bivalve burrowed. This is because the size of the palial sinus is indicative of the size of siphon needed, which in turn depends on the depth of the burrow (deeper burrow, larger siphon).
youtube: scallops swimming
Cambridge University Museum of Zoology: Lifestyles of bivalves
Yale Peabody Museum of Natural History: differences between bivalves and brachiopods
Learn about types of preservation
Go to the front of the 1A Lab. A display on the right hand side (by the window) shows a number of bivalves in life position. Have a look at how they have adapted their shape and other features to their way of life.
Phylum: Mollusca
Class: Cephalopoda
Subclass: Coleoidea
Cohort: Belemnoidea
Diagram with labelled features of belemnites
'Bullet' shape
Phragmocone: chambers divided by aragonitic septa (often preserved as conical cavity)
Radial calcite crystals form the guard
Nektonic
Predatory
Marine
Exceptional preservation of belemnites showing soft parts has shown them to be very similar to squid in shape. The guard and phragmocone were held inside the soft parts of the animals, acting as a kind of backbone.
Because the phragmocone is made of aragonite it is often not preserved. In contrast the calcitic guard is very often preserved. This means that a common preservation of belemnites is of the guard with a conical hole where the phragmocone once was. This empty conical chamber is often crushed.
Phylum: Mollusca
Class: Cephalopoda
Subclass: Coleoidea
Cohort: Belemnoidea
Diagram with labelled features of belemnites
'Bullet' shape
Phragmocone: chambers divided by aragonitic septa (often preserved as conical cavity)
Radial calcite crystals form the guard
Nektonic
Predatory
Marine
Exceptional preservation of belemnites showing soft parts has shown them to be very similar to squid in shape. The guard and phragmocone were held inside the soft parts of the animals, acting as a kind of backbone.
Because the phragmocone is made of aragonite it is often not preserved. In contrast the calcitic guard is very often preserved. This means that a common preservation of belemnites is of the guard with a conical hole where the phragmocone once was. This empty conical chamber is often crushed.
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
[See labelled diagram above]
Aragonite shell
Septa
Suture (different for goniatites, ceratites and ammonites, see second diagram above)
Chambers
Siphuncle
Planispiral shape, involute or evolute (see third diagram on right hand side)
Devonian to Cretaceous
Nektonic (jet propelled)
Predatory
Marine
Internal mould
Learn about types of preservation
Ammonoids could passively remove or add water to chambers via the siphuncle. This allowed them to change their density, and maintain neutral buoyancy with the surrounding seawater. This meant that they were able to swim as efficiently as possible.
Ammonoids are extremely good index fossils on account of their diverse morphologies, good preservation potentials and widespread fossil locations.
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
[See labelled diagram above]
Aragonite shell
Septa
Suture (different for goniatites, ceratites and ammonites, see second diagram above)
Chambers
Siphuncle
Planispiral shape, involute or evolute (see third diagram on right hand side)
Devonian to Cretaceous
Nektonic (jet propelled)
Predatory
Marine
Internal mould
Learn about types of preservation
Ammonoids could passively remove or add water to chambers via the siphuncle. This allowed them to change their density, and maintain neutral buoyancy with the surrounding seawater. This meant that they were able to swim as efficiently as possible.
Ammonoids are extremely good index fossils on account of their diverse morphologies, good preservation potentials and widespread fossil locations.