Carboniferous period spans from 359.2 to 299 million years ago.
The Carboniferous period gets its name from the coal
measures found in deposits of this age. In the United States
this period is often divided into the Mississippian 359.2-318.1
mya (characterized by limestone deposits in the state of
Mississippi) and the Pennsylvanian 318.1-299 mya (characterized
by coal deposits in the state of Pennsylvania). Once again
life recovers from the crises; new evolutionary variations
and first appearances occur.
Producers & Reefs
dominant primary producers in the oceans continue to be cyanobacteria,
and red algae (Knoll, Summons, Waldbauer,
and Zumberge, 2007, p. 148). Fusulinids, a type of Foraminiferan,
make their appearance in the Carboniferous. Fusulinids are
single-celled amoeba-like organisms with shells made of calcium
carbonate (calcite). Like today’s Foraminiferans, these
fusulinids probably had a symbiotic relationship with algae
(Stanley, 1987, pp. 92-93). After the Devonian crises reef
building became almost non-existent. Calcarious algae formed
some small mound-like reefs in warm, shallow seas (Stanley,
1987, p. 92).
that flourish are not the reef-building varieties. Stony
while lacey forms evolve and diversify.
Brachiopods once again become abundant. Nautiloids with coiled
shells become more abundant than their straight-shelled relatives.
Other mollusks, such as ammonoids, bivalves, and gastropods
also recover and diversify. Trilobites become increasingly
rare. Echinoderms become very successful during the early Carboniferous,
especially the crinoids, which form vast “ocean meadows” on
the sea floor (Kazley, 2002, Carboniferous page). Delocrinus
missouriensis is a crinoid from the Pennsylvanian period,
which was chosen as Missouri's state fossil. The tabulate coral Lithostrotionella from
the Mississippian is West Virginia's state gem. Lithostotionella specimens
from West Virginia are permineralized with chalcedony. Impurities
in the chalcedony give these gem quality fossils blue, grey,
pink, and red hues.
Jawless fish become less numerous, with some groups becoming
extinct. While the class of spiny sharks (Acanthodii) would
survive, the armored Placoderms (Placodermi) would meet with
extinction. Many sarcopterygians (Lobe-finned fish and lungfishes)
would go extinct, making the subclass Sarcopterygii less diverse
and less common. Primitive ray-finned fish made a recovery
and diversified. Cartilaginous fish flourish during the Carboniferous
undergoing an adaptive radiation that included the appearance
of an entire new group, the holocephalians or chimaeras (subclass
holocephali) (Dixon, 1988, pp. 28-29).
the term amphibian has been used to refer to all tetrapods that
are not amniotes (reptiles, birds, and mammals). However, it
is now clear that this is a paraphyletic term. The class Amphibia
now refers to present-day amphibians and their extinct sister
underwent an adaptive radiation during the early Carboniferous.
The Carboniferous and Permian are often referred to as the age
of the amphibians. Two extinct groups of amphibians make
their first appearance during the Carobniferous.
Temnospondyls (Order Temnospondyli) are primitive amphibians that dominated the
terrestrial and freshwater habitats of the Carboniferous. Temnospondyli, Ichthyostegalia,
and Anthracosauria use to be grouped together as Labyrinthodonts. Labyrinthodtia
is now an obsolete term. In general, temnospondyls had long bodies, large flat
skulls, and short legs. Dendrerpeton from the Upper Carboniferous of Novia Scotia,
Canada is found associated with the hollows of lycopod trees.
Lepospondyls (Superorder Lepospondyli) are early amphibians that range from the
Carboniferous to the Permian. Microsaurs and nectrideans are the best-known lepospondyls.
Microsaurs (Order Microsauria) were the largest group of lepospondyls and had
a body form reminiscent of salamanders or lizards. Most microsaurs were terrestrial
feeding on arthropods although, some became secondarily adapted to aquatic environments.
The nectrideans (Order Nectridia) were aquatic organisms that had newt-like bodies
with long tails. Their heads were equipped with horn-like structures that grew
as the animal aged. Diplocaulus is a well-known nectridean with a “boomerang” shaped
skull. Biomechanical studies on models of a Diplocaulus head provide
evidence that it acted as a hydrofoil, providing lift. Diplocaulus swam
in streams and lakes feeding on fish (Benson, 2005, pp. 89-90).
amphibians are never free of the aquatic stage. Amphibians
lay their eggs in water. As
larvae, just like fish, they possess gills, a lateral line,
tail, and a single loop circulatory system with a two-chambered
heart. Limbs, lungs (for most), a tympanic membrane, and a
double loop circulatory system with a three-chambered heart
are developed through the process of metamorphosis. Many adult
amphibians supplement breathing with their skin and mouth.
Fossil amphibians are found with traces of gill structures
and canals for lateral lines. Fossils amphibians representing
different stages of metamorphosis have also been found (Dixon,
1988, p. 46).
superorder Reptiliomorpha includes reptile-like amphibians
that range from the Early Carboniferous to the Early
Triassic as well as the amniotes that evolved from
them. The classification of tetrapods that have both reptile
and amphibian-like characteristics continues to be
debated. The line between amphibians and amniotes is blurred
advanced reptiliomorphs. However, many paleontologists
regard some reptile-like amphibian groups as tetrapod
evolutionary lines that branched long after the amniotes
split off (Prothero, 2004, p. 378). Representatives of the
reptiliomorph order Anthracosauria make their first appearance
in the Early
Carboniferous. These reptile-like amphibians were fish eaters
adapted to both terrestrial and aquatic habitats. Proterogyrinus from
the Lower Carboniferous of West Virginia, USA and Scotland
was a 1 meter
long anthracosaur. Proterogyrinus had legs well
adapted for land and a flattened tail good for swimming.
became secondarily adapted for life in the water (Benton,
2005, p. 95). Sometime
in the Late Devonian or Early Carboniferous reptile-like
amphibians gave rise to amniotes that evolved a fully
terrestrial life cycle.
Reptiles were the first amniotes to conquer land. The evolution
of the egg would allow reptiles to free themselves from the aquatic
the amphibians. A watertight egg along with protective scales
and a rib cage that enhances breathing would help reptiles
better exploit dry terrestrial environments. This would give
them an advantage during the Permian period.
Reptiles & The
and the amniotic egg make their first appearance in the
The amniotic egg is a water tight,
independent life support unit that affords the developing embryo
protection, nutrients, and waste disposal. A protective leathery
shell and four membranes (amnion, yolk sac, allantois, and
chorion) help to define this evolutionary innovation. The embryo
is suspended in amniotic fluid contained within the amnion.
A yolk sac attached to the embryo’s gut acts as a source
of nutrients. Waste products are excreted through the allantois
and stored in the allantoic cavity. The chorion lines the inside
of the shell and allows oxygen to enter the egg. The amniotic
egg can be laid on land and frees amniotes from the aquatic
larval, tadpole stage, a great adaptation for dry conditions.
between amniotes and
can be studied
by examining four basic skull structures. The anapsid type
(subclass Anapsida) includes the earliest reptiles and modern
turtles; the diapsid type (subclass Diapsida), which includes
lizards, snakes, crocodiles, dinosaurs, sphenodonts and the
extinct marine reptiles (formerly grouped as the subclass Euryapsid);
and the synapsid type (class Synapsida and class Mammalia), which
encompasses protomammals (formerly referred to as mammal-like
reptiles) and mammals (Johnson and Stucky, 1995, pp 55-56 and
Dixon, 1988, p. 61). The subclass Anapsida and Diapsida are
in the reptilian class Sauropsida. Synapsids include all mammals
(class Mammalia) and protomammals (Class Synapsida). Sauropsids
(reptiles) and Synapsids (protomammals and mammals) make up
the two major groups of amniotes.
first reptiles (class Sauropsida) were small lizard-sized
tetrapods living in damp forests of the mid-Carboniferous
feeding on insects and worms. In Nova Scotia there are
sedimentary deposits that contain upright lycopod tree
stumps. Since 1852 thirty Sigillaria tree stumps
have produced abundant tetrapod remains. These tetrapods
were living in the rotted out Sigillaria trunks. Hylonomus and Paleothyris are
two tetrapods that were preserved in the hollow tree stumps
and represent the oldest known amniotes (Benton, 2005,
pp 110-111). Hylonomus had an anapsid type skull,
which is solid and box-like with no temporal openings.
These small insectivores could
not open their mouth very wide or close it with much force.
openings allow the jaw muscles to be longer and larger.
with diapsid skulls also appear in the late Carboniferous.
These reptiles have skulls with two pairs of openings on
either side of the skull behind the eyes. Initially, these
holes reduced the weight of the skull. Later muscles and ligaments
would stretch across these holes, resulting in a mouth that
could open wider and close with greater force (Dixon, 1988,
p. 84). The ealiest diapsid was the lizard-like Petrolacosaurus.
The jaws and sharp, pointed teeth of Petrolacosaurus are
similar to Hylonomus.
Mammal-like reptiles or protomammals (class Synapsida) with
the synapsid type skull also make their first appearance in
the late Carboniferous. The synapsid skull has a single large
opening behind each eye socket. This opening allows the jaw
muscles to be larger and longer, resulting in a wider, more
powerful bite. The pelycosaurs (order Pelycosauria) were the
first protomammals to evolve. Archaeothyris was a small lizard-like
pelycosuar. Archaeothyris was an insectivore with different
sizes of sharp, pointed teeth. Synapsids were the first to
evolve heterodont dentition (specialized tooth shapes).
Vertebrate herbivory gets its start in the late Carboniferous.
Edaphosaurus was a primitive herbivorous pelycosaur, which
had a sail similar to Dimetrodon. Edaphosaurus had teeth specialized
for chopping up plant material. Herbivory represents an important
evolutionary innovation in digestion, as it requires hosting
a community of bacteria within the gut that can help chemically
process the cellulose. Edaphosaurus would evolve into different
species during the Permian. Prior to organisms like Edaphosaurus all vertebrates were carnivores and detritivores.
Invertebrates on Land
and scorpions undergo an adaptive radiation during the Carboniferous
1996, p. 228). Millipedes become abundant
and also diversify. Insects with wings (Pterygota) make their
first appearance during the Carboniferous (Carpenter & Burnham,
1985, p 298). The fact that 99% of living insects belong to
the subclass Pterygota is a testament to the success of insect
flight. There is evidence to suggest that insects with fixed
wings (Paleoptera), like mayflies, came before those with folded
wings (Neoptera), like cockroaches. Folded wings allow insects
to hide and hunt in small spaces. Over geologic time the percentage
of insects with folded wings would increase. Today insects
with fixed-wings (Paleoptera) make up less than 1% of insect
species (Carpenter & Burnham, 1985, p. 299).
with wings (Neoptera) can be subdivided into two informal
undergo incomplete metamorphosis (egg,
nymph, and adult), while endopterygota undergo complete metamorphosis
(egg, larva, pupa, adult). Insects with complete metamorphosis
do not make their first appearance until the Permian, although
paleontologists speculate they evolved sometime during the
Carboniferous period. Many orders of winged insects (Pterygota)
make their first appearance during the Carboniferous. Over
half of these insect orders would go extinct. We will mention
just a few. Among fixed-winged insects the mayflies (Ephemeroptera)
and dragonfly-like insects (Protodonata) appear. Among insects
with folded wings and incomplete metamorphosis (exopterygota
Neoptera) cockroaches (Blattodea)
make their first appearance (Carpenter & Burnham, 1985,
for herbivory in insects appears in the Carboniferous. Like
the first insects were carnivores and detritivores.
Herbivory requires hosting cellulose-digesting bacteria through
a symbiotic relationship within the gut. The oldest examples
of marginal and surface feeding is on Carboniferous seed
fern leaves of Neuropteris and Glosspteris (Grimaldi
& Engel, 2005, p. 52). It is estimated that only 4% of
leaves in Carboniferous deposits
from feeding. Herbivores do not make a significant impact on
plant life until the Permian (Kenrick & Davis, 2004, pp.
are excessive growths on stems, leaves, cones, and flowers
caused by insect feeding or egg laying. The earliest
fossil galls are found on the petioles of Psaronius tree
ferns of the Late Carboniferous. Insect gall fossil diversity
abundance takes off with the advent of flowering plant evolution
in the Cretaceous. Insects produce tunnels in wood known
as borings or galleries. Some insects eat the cambial layer
others eat fungus that grows within the galleries, still
others eat the wood itself. The oldest borings and galleries
attributed to mites, are known
2005, pp. 53
We think of insects as small in size, but during the Carboniferous
insects and some other arthropods attained spectacular sizes.
Coal deposits in France have produced dragonfly-like insects
with wingspans of 2 feet. A 14-inch fossil spider was discovered
in Argentina. A 6 ft long, 1 ft wide millipede was found in
Nova Scotia (Johnson and Stucky, 1995, p. 58). Giant insects
probably indicate higher oxygen levels in the atmosphere and
first major coal deposits were formed during the Carboniferous.
Within the coal measures are found thin marine sediment layers,
which may represent interglacial periods (Kenrick and Davis,
2004, p. 81) or the periodic deposition and erosion of delta
lobes (Selden and Nudds, 2004, p. 59). The large coal deposits
in the eastern U.S. and Western Europe formed between 295 and
320 mya. These coal-forming forests grew in humid, tropical
environments. Lycopsids (clubmosses) and shenopsids (horsetails)
would reach their greatest diversity in these Carboniferous
forests, which have no analogues today (Kenrick and Davis,
2004, p. 35). Lycopods (Lycophyta) represented the dominant
tree form. Lepidodendron was a lycopsid that could
reach a height of 30 m and a width of 1m near its base. The
tapering and pole-like, studded with diamond-shaped leaf scars,
graced with a crown of bifurcating branches atop and a crown
of bifurcating roots at its base. Needle-like leaves were clustered
around spore-bearing cones at the end of branches (Janssen,
1979, p. 36). Sigillaria was similar to Lepidodendron,
but exhibits a different leaf scar pattern on its bark, did
tend to branch, and bore cones at the end of stems erupting
from the trunk (Janssen, 1979, p. 54). Both lycopsids were
fast growing, had trunks with soft inner tissues surrounded
protective layer of bark. These trees probably had photosynthetic
tissue in the bark, stems, and leaves. Calamites were
sphenopsids (Sphenophyta), represented today by horsetails
Calamites grew up to 10 m in height. This tree form
spread with rhizomes, grew a ribbed, segmented trunk adorned
needle-like whorled leaves. The whorled leaves are known as
Annularia. Spores grew in sacs organized into cones. Psaronius was
a tree-fern (Pterophyta), which grew to a height of 10 m. The
trunk of the tree was composed of vascular tissue surrounded
by a root mantle. Fronds adorned the top and reproduction was
accomplished with spores. The fronds of Psaronius are
known as Pecopteris. Medullosa was a seed
fern (Pteridospermales) that grew as a shrub-like plant reaching
heights of 3.5 m.
Fern-like foliage bore seeds on the midribs and margins. The
stems of these plants were made of many leaf bases. Neuropteris is
the frond of a seed fern. Pteridosperms are actually early
gymnosperms (Cleal & Thomas, 2009, p. 139). Another early gymnosperm,
the cordaites (Cordaitales), possessed the wood, cones, pollen,
of a conifer,
but had wide, strap-like leaves. Cordaites were shrub-like
plants (Kenrick and Davis, 2004, pp. 84-94). Primitive Walchian
conifers also appear in the Carboniferous.
special type of fossil, the coal ball, can be found in the
of the Pennsylvanian and Permian periods. Coal
balls are calcareous concretions that can disrupt the mining
of bituminous coal bearing strata. Coal balls contain swamp
vegetation, which has been permineralized with calcium carbonate,
preserving 3-D cellular structure. Although the formation
of the coal
balls is not totally understood there is evidence
for both marine incursions and ground water percolation as
sources for the carbonate (Kenrick & Davis, 2004, p. 115).
Coal balls are studied in serial section using the cellulose
acetate peel method to reveal microscopic structure. Serial
sections can be used to reconstruct organs and entire plants.
The five major groups of plants found in coal balls include:
Lycophytes, sphenopsids, ferns, seed ferns, and cordaiteans
(Rothwell, 2002, p. 40). The in situ preservation
of plant materials allows paleontologist to study plant associations
that tell us something about the palaeoecology of the coal
swamps. Coal balls reveal that the arborous fern Psaronius became
the dominant canopy tree after the extinction of Lepidondendrales
near the Middle Pennsylvanian. Certain species of small ferns
and horsetails have been found, which grew in association with
the roots of Psaronius (Rothwell, 2002,
p 42). One may argue that coal balls represent a kind of lagerstatten,
although they are found across multiple time periods.
In central Montana the upper Mississippian Bear Gulch beds
represent a Lagerstatten that preserves a Carboniferous bay
ecosystem. Platy limestone lenses contain a diverse fossil
assemblage representing paleocommunities in a shallow marine
basin. Periodic turbidite sedimentation smothered and buried
communities. Soft-tissues, phosphatic fossils, cartilaginous
fossils, and molds can be found. Preservation of circulatory
tissue, gut contents, skin and eye pigments, are just a few
examples of the important soft-tissue finds in Bear Gulch.
Algae, bacterial mats, and plankton represent the primary
producers of Bear Gulch. The most abundant invertebrates are
straight and coiled nautiloids, ammonoids, shrimp, and polychaete
worms. Horseshoe crabs, gastropods, trilobites, asteroids,
bryozoans, brachiopods, and branching sponges are also found.
Bear Gulch contains one of the most diverse assemblages of
fossil fish in the world. In 30 years, 108 fish species have
been documented. Sharks, skates, platysonids, paleoniscids,
dorypterids, tarrassiids, and coelacanths have been identified.
Coelacanths are the most common, but chondrichthyes are the
most diverse. Terrestrial plants such as lycopsid logs, leaves and other
plant material that drifted into the bay can also be found.
The diversity and exceptional preservation found at Bear Gulch
has allowed paleontologist to reconstruct life habits, feeding
strategies, sexual dimorphism, trophic structures, and evolutionary
history of some taxa (Hagadorn, 2002, p. 167)
examples of leaves, stems, cones, and seeds of Carboniferous
plants along with animal life can be found in the Lagerstatten
known as Mazon Creek, which is just 150 km southwest of Chicago,
Illinois. Mazon Creek provides the best window into late Carboniferous
shallow marine, freshwater, and terrestrial life (Selden and
Nudds, 2004, p.60). The soft and hard parts of plants and animals
are found in siderite (iron carbonate) concretions and can
reveal minute structural details. Subtle pH changes created
by the body of a buried organism caused available iron
carbonate to precipitate. Thus, the organism became its own
nucleation site for the formation of a siderite nodule. When
these nodules are split open, the fossil appears as a 3-D external
cast and mold. The concretions are small, never larger than
30 cm, thus for larger organisms only small parts are preserved.
The siderite nodules are found in the lower layers of the Francis
Creek Shale Member, which lies over the Colchester No 2 Coal
Member; both included in the Carbondale Formation. Access to
the fossils came from the tailings of coal pit mining.
The different habitats represented by Mazon Creek flora and
fauna were associated with a deltaic environment (Selden and
Nudds, 2004, p. 66). The Colchester No 2 Coal Member represents
a swamp forest composed of lycopsid and sphenopsid trees with
an understory of seed ferns. Nodules in the Francis Creek Shale
Member represent two biotas. Braidwood nodules represent freshwater
and terrestrial environments. Essex nodules represent a shallow
marine environment with material drifted in from a terrestrial
environment (Selden and Nudds, 2004, p. 63). The bark, leaves,
and reproductive structures of Lycopsids (clubmosses) and Sphenopsids
(horsetails) are found. Foliage and seeds of seed ferns, cordaites,
and gymnosperms are present. A list of some of the animal fauna
includes: Cnidaria (jellyfish), Mollusca (chitons, bivalves,
gastropods, and cephalopods), Crustacea (shrimp, banacles,
and ostracods), Chelicerata (horseshoe crabs, eurypterids,
scorpions, spiders, mites), Insecta (cockroaches, dragonfly-like,
and grasshopper-like winged insects), Diplopoda (millipedes),
Chilopoda (centipedes), Brachiopoda (Lingula), Echinodermata
(sea cucumbers), Fish (jawless, cartilaginous, lobe-finned,
and lungfish), Amphibia, and Reptilia.
Illinois state fossil, Tullimonstrum gregarium, is also found
Tully’s Monster has a segmented,
sausage-shaped body with a proboscis ending in a claw and teeth.
This organism may represent a type of shell-less gastropod
predator (Sheldon and Nudds, 2004, p. 67).
A Transition to Drying Conditions
Ecosystems of the Carboniferous did not experience extinction
on a massive scale. As the Permian period unfolded dryer climatic
conditions would become the norm. The drying trend would have
an impact on which groups of organisms would increase or decrease
It is interesting to note that the many forests that grew
in the U.S. and Western Europe during this time would eventually
transform energy from the Carboniferous sunshine into coal.
The stored sunshine in this coal would allow humans to power
the industrial revolution. Even today, over a third of our
electricity is powered by this fossil fuel.
M.J. (2005) Vertebrate Palaeontology [3rd
Edition]. Blackwell Publishing: Main, USA.
F.M., & Burnham, L. (1985). The Geologic Record of
Insects. Annual Review of Earth and Planetary Sciences 13: 297-314.
C.J. & Thomas, B.A. (2009). Introduction to Plant
Kingdom: Cambridge University Press.
D., Cox, B., Savage, R.J.G., & Gardiner, B. (1988).
The Macmillan Illustrated Encyclopedia of Dinosaurs
and Prehistoric Animals: A Visual Who’s Who of Prehistoric Life.
New York: Macmillan Publishing Company.
D. & Engel, M.S., (2005). Evolution of the Insects.
New York: Cambridge University Press.
J.W. (2002). Bear Gulch: An Exceptional Upper Carboniferous
In Bottjer, D.J., Etter, W., Hadadorn, J.W., & Tang,
C.M. [Eds.] Exceptional Fossil Preservation: A Unique View
on the Evolution of Marine Life (167-183). New York: Columbia
Janssen, R.E. (1979). Leaves
and Stems from Fossil Forests: A Handbook of the Paleobotanical
Collections in the Illinois
State Museum. Springfield, Illinois: Illinois State Museum.Johnson,
K.R. & Stucky
R.K. (1995). Prehistoric Journey: A History of Life on
Boulder, Colorado: Roberts Rinehart Publishers.
Kazlev, M.A. (2002). Palaeos
Website. see: http://www.palaeos.com/Timescale/default.htmKenrick,
P. & Davis,
P. (2004). Fossil Plants. Washington: Smithsonian Books.
Summons, Waldbauer, and Zumberge. (2007). The Geological
Succession of Primary Producers in the Oceans. In Falkowski,
P.G. Knoll, A.H. [Eds] Evolution of Primary Producers
in the Sea. (pp. 133-163). China: Elsevier Academic
P.V., Rich T. H., Fenton, M.A., & Fenton, C.L. (1996). TheFossil Book: A Record of Prehistoric Life.
Mineola, NY: Dover Publications, Inc.
G.W. (2002). Coal Balls: Remarkable Evidence of Palaeoxoic
the Communities in Which They Grew. .
In Dernbach, U. & Tidwell, W.D. Secrets of Petrified
Plants: Fascination from Millions of Years (pp. 39-47).
Germany: D’ORO Publishers.
Stanley, S.M., (1987). Extinction. New York: Scientific American
P. & Nudds,
J. (2004). Evolution of Fossil Ecosystems. Chicago: The University
of Chicago Press.