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.
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: 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: Brachiopoda
Two valves (brachial and pedicle)
Bilateral symmetry
Growth lines
Adductor and ductor muscle scars
Pedicle
Commissure
Gape
Teeth and socket (articulates; no teeth or socket in inarticulates)
Cambrian to present
Marine
Attach to hard substrates using pedicle
Filter feeding
Sessile
Infaunal, epifaunal, reclining
Apparent decrease in diversity over time
Limited to marginal environments in the modern ocean
Adductor muscle used to close shell, ductor muscle used to open shell
Yale Peabody Museum of Natural History: differences between bivalves and brachiopods
Cortland Paleo, Brachiopoda: brachiopod morphology and ecology information
]]>Phylum: Brachiopoda
Two valves (brachial and pedicle)
Bilateral symmetry
Growth lines
Adductor and ductor muscle scars
Pedicle
Commissure
Gape
Teeth and socket (articulates; no teeth or socket in inarticulates)
Cambrian to present
Marine
Attach to hard substrates using pedicle
Filter feeding
Sessile
Infaunal, epifaunal, reclining
Apparent decrease in diversity over time
Limited to marginal environments in the modern ocean
Adductor muscle used to close shell, ductor muscle used to open shell
Yale Peabody Museum of Natural History: differences between bivalves and brachiopods
Cortland Paleo, Brachiopoda: brachiopod morphology and ecology information
Phylum: Cnidaria
Class: Anthozoa
Radial or biradial symmetry
External skeleton
Septa
Tabulae
Ordovician to present
Tabulate, rugose: Ordovician to Permian (extinct at P/T extinction)
Scleractinian: Triassic to present
Colonial or solitary
Filter feeding
Reef builders
Remember, although the most well-known modern corals enjoy a symbiotic relationship with photosynthesising algae (Zooxanthellea) many modern corals do not. When thinking about Palaeozoic corals do not assume that they lived as well known corals do now.
Corals built their skeletons out of aragonite (Ordovician to Permian) or calcite (Triassic to recent). They are often preserved as moulds, casts, intact or replaced.
Phylum: Cnidaria
Class: Anthozoa
Radial or biradial symmetry
External skeleton
Septa
Tabulae
Ordovician to present
Tabulate, rugose: Ordovician to Permian (extinct at P/T extinction)
Scleractinian: Triassic to present
Colonial or solitary
Filter feeding
Reef builders
Remember, although the most well-known modern corals enjoy a symbiotic relationship with photosynthesising algae (Zooxanthellea) many modern corals do not. When thinking about Palaeozoic corals do not assume that they lived as well known corals do now.
Corals built their skeletons out of aragonite (Ordovician to Permian) or calcite (Triassic to recent). They are often preserved as moulds, casts, intact or replaced.
Phylum: Mollusca
Class: Cephalopoda
Simple suture
Chambers
Central siphuncle
Straight, curved or coiled shell
Cambrian to recent
Straight forms: Cambrian to Permian
Coiled forms: Devonian to Present
Predatory
Buoyancy controlled by changing gas/liquid contents of chambers
Marine
Commonly preserved as internal moulds
Modern nautiloids preserved with original shell material
Learn about types of preservation
Nautiloids originated in the Cambrian period, and radiated during the Ordovician. These early nautiloids had conical shaped shells. In the Silurian some nautiloids used curved shells, and by the Devonian some were coiled. The evolution of the coiled shell from the straight is thought to be driven, at least in part, by increased mobility of a coiled shell compared to a long straight one.
Nautiloids could be confused with ammonoids. You can distinguish them by the location of the siphuncle and the complexity of the suture pattern. Nautiloids, unlike ammonoids, are not extinct, although only six species remain today (compared to thousands in the Palaeozoic). This means that if presented with modern shell material it is likely a nautiloid and not an ammonoid.
Phylum: Mollusca
Class: Cephalopoda
Simple suture
Chambers
Central siphuncle
Straight, curved or coiled shell
Cambrian to recent
Straight forms: Cambrian to Permian
Coiled forms: Devonian to Present
Predatory
Buoyancy controlled by changing gas/liquid contents of chambers
Marine
Commonly preserved as internal moulds
Modern nautiloids preserved with original shell material
Learn about types of preservation
Nautiloids originated in the Cambrian period, and radiated during the Ordovician. These early nautiloids had conical shaped shells. In the Silurian some nautiloids used curved shells, and by the Devonian some were coiled. The evolution of the coiled shell from the straight is thought to be driven, at least in part, by increased mobility of a coiled shell compared to a long straight one.
Nautiloids could be confused with ammonoids. You can distinguish them by the location of the siphuncle and the complexity of the suture pattern. Nautiloids, unlike ammonoids, are not extinct, although only six species remain today (compared to thousands in the Palaeozoic). This means that if presented with modern shell material it is likely a nautiloid and not an ammonoid.
Phylum: Hemichordata
Class: Graptolithina
Stick-shape (often branched)
One or both edges may appear serrated
Thecae
Rhabdosome
Stipes
Cambrian to Carboniferous (Dendroids)
Ordovician to Middle Devonian (Graptoloids)
Colonial
Planktonic (mostly, although some dendroids were sessile benthonic)
Suspension feeders
Flattened along bedding planes, normally in shales
Carbonization or pyritization of the animal
Learn about types of preservation
Graptolites, because of their abundance and variation in morphology are very good index fossils. At a very basic level the angle between the stipes and number of stipes can be used to give a rough age for the fossil, with Early Ordovician graptolites having two stipes with the 'sawtooth' facing each other (pendent), later Ordovician graptolites having a more open oblique or reflex angle between the 'sawtooth' faces, and Siluran graptolites having the 'sawtooth' faces back to back (scandent) or having lost one stipe altogether (for example monograptids).
Phylum: Hemichordata
Class: Graptolithina
Stick-shape (often branched)
One or both edges may appear serrated
Thecae
Rhabdosome
Stipes
Cambrian to Carboniferous (Dendroids)
Ordovician to Middle Devonian (Graptoloids)
Colonial
Planktonic (mostly, although some dendroids were sessile benthonic)
Suspension feeders
Flattened along bedding planes, normally in shales
Carbonization or pyritization of the animal
Learn about types of preservation
Graptolites, because of their abundance and variation in morphology are very good index fossils. At a very basic level the angle between the stipes and number of stipes can be used to give a rough age for the fossil, with Early Ordovician graptolites having two stipes with the 'sawtooth' facing each other (pendent), later Ordovician graptolites having a more open oblique or reflex angle between the 'sawtooth' faces, and Siluran graptolites having the 'sawtooth' faces back to back (scandent) or having lost one stipe altogether (for example monograptids).
Phylum: Arthropoda
Class: Trilobita
Pygidium (tail)
Thorax (body)
Cephalon (head)
Paired appendages (not often preserved)
Three lobed longitudinal division of body (2x pleural, 1x axial)
Calcitic exoskeleton
Segmented body
Glabella
Eyes (holochroal or schizochroal; only present in some groups)
Eye ridges
Occipital ring
Axial rings
Cambrian to Permian (most common Cambrian to Silurian)
Trilobites lived as planktonic, nektonic, epifaunal and infaunal organisms in deep and shallow marine environments. They lived as predators, filter feeders, deposit feeders, particle feeders, scavengers and even symbiotically.
By looking at the functional morphology of the trilobite in question you can be more specific about how it lived, by looking at body shape, size, legs, eyes and other characters.
Trilobites were very abundant during the Palaeozoic. Their preservation potential was increased further as they moulted their exoskeletons periodically as they grew. This means that one trilobite left numerous hard skeletons or partial skeletons as it grew, each of which has the potential to fossilise.
Phylum: Arthropoda
Class: Trilobita
Pygidium (tail)
Thorax (body)
Cephalon (head)
Paired appendages (not often preserved)
Three lobed longitudinal division of body (2x pleural, 1x axial)
Calcitic exoskeleton
Segmented body
Glabella
Eyes (holochroal or schizochroal; only present in some groups)
Eye ridges
Occipital ring
Axial rings
Cambrian to Permian (most common Cambrian to Silurian)
Trilobites lived as planktonic, nektonic, epifaunal and infaunal organisms in deep and shallow marine environments. They lived as predators, filter feeders, deposit feeders, particle feeders, scavengers and even symbiotically.
By looking at the functional morphology of the trilobite in question you can be more specific about how it lived, by looking at body shape, size, legs, eyes and other characters.
Trilobites were very abundant during the Palaeozoic. Their preservation potential was increased further as they moulted their exoskeletons periodically as they grew. This means that one trilobite left numerous hard skeletons or partial skeletons as it grew, each of which has the potential to fossilise.
Phylum: Mollusca
Class: Gastropoda
Coiled shell - planispiral or helical - consists of body whorl and spire
Mostly aragonitic shell
Shell consists of one large chamber (no septa)
Aperture
Siphonal notch
Marine, non-marine, land-dwelling
Carnivorous, scavenging, deposit feeding and more
Because of their conservative shell shape it is difficult to use gastropods as environmental or stratigraphic indicators.
Phylum: Mollusca
Class: Gastropoda
Coiled shell - planispiral or helical - consists of body whorl and spire
Mostly aragonitic shell
Shell consists of one large chamber (no septa)
Aperture
Siphonal notch
Marine, non-marine, land-dwelling
Carnivorous, scavenging, deposit feeding and more
Because of their conservative shell shape it is difficult to use gastropods as environmental or stratigraphic indicators.
Phylum: Echinodermata
Class: Crinoidea
Crown
Stalk
Pentaradial symmetry
Ossicles
Calyx
Pinnule
Holdfast
Benthic (some pseudoplanktonic)
Filter feeders
Ordovician to present
The heyday of the crinoids was the Palaeozoic, where they dominated shallow marine environments. Modern crinoids are exclusively deep marine, and the diversity of forms is far less than it was during the Paleozoic.
Were they victims of the increased grazing and predation pressure of the Mesozoic Marine Revolution?
youtube: modern crinoid behaving pseudoplanktonically. You can see the pinnules, crown and multiple stalks.
flickr: beautiful photographs of both living and fossil crinoids. Compare the levels of detail you can see, admire the colours, and spot the distinctive features that make these crinoids identifiable.
]]>Phylum: Echinodermata
Class: Crinoidea
Crown
Stalk
Pentaradial symmetry
Ossicles
Calyx
Pinnule
Holdfast
Benthic (some pseudoplanktonic)
Filter feeders
Ordovician to present
The heyday of the crinoids was the Palaeozoic, where they dominated shallow marine environments. Modern crinoids are exclusively deep marine, and the diversity of forms is far less than it was during the Paleozoic.
Were they victims of the increased grazing and predation pressure of the Mesozoic Marine Revolution?
youtube: modern crinoid behaving pseudoplanktonically. You can see the pinnules, crown and multiple stalks.
flickr: beautiful photographs of both living and fossil crinoids. Compare the levels of detail you can see, admire the colours, and spot the distinctive features that make these crinoids identifiable.