The Carboniferous Period - SYNAPSIDS RULE

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The Carboniferous Period - SYNAPSIDS RULE
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Continents are in collision course...
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• Marine Life of the Carboniferous
• See a recovery after the Late Devonian
  extinction of tabulate-stromatoporoid reefs,
  extinctions of many fish, floating and swimming
  animals, and many freshwater forms.
• Ammonoids rediversified quickly.
• Reefs remained poorly developed after the demise
  of the tabulate-stromatoporoid reefs near the end
  of the Devonian.
• Brachiopods continued to thrive.
• Bryozoans were prominent.
• Crinoids and blastoids were common in the sea.
• Large foraminifera (fusulinids) appeared. First
  occur in Upper Mississippian most abundant in
  Pennsylvanian and Permian.

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Ammonoids

• Ammonoids are relatives of the modern squid, as
  well as the octopus and chambered Nautilus, all
  of which belong to the group of animals called
  cephalopods.
• Ammonoids were important predators in the
  ancient oceans, eating fish, crabs, and other
  shellfish.
• Ammonoids appeared in the fossil record during
  the early part of the Devonian Period, about 400
  million years ago. They died out about 65 million
  years ago, during the mass extinction at the end
  of the Cretaceous Period that killed the
  dinosaurs and many other kinds of land and sea
  animals.

The top specimen belongs to the genus Goniatites.
The lower specimen is Schistoceras missouriense.
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Brachiopod
Fusulinid foraminifera
Bryozoans
Crinoid
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• A Golden Age of Sharks
• Sharks and ray-finned fishes persisted as a
  diverse group of predators.
• Heavily-armored fish were replaced by more
  mobile forms.
• Sharks have undergone two major adaptive
  radiations and survived at least five mass
  extinctions, with the first major shark radiation
  occurred during the Carboniferous Period
• Indeed, with the exception of acanthodians (a
  type of placoderm), few fishes swam in early
  Carboniferous seas.
• The fossil record indicates that more than 75
  of fish groups alive during the late Devonian
  died out before the beginning of the
  Carboniferous.
• The placoderms - a once dominant group of
  armored fishes - survived the devonian extinction
  event, but at greatly reduced diversity and
  abundance.

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• Stethacanthids
• The misfortune of the placoderms presented a
  splendid opportunity for sharks in general and
  one group in particular the stethacanthids.
• Perhaps in response to the ecological niches
  vacated by the placoderms, the stethacanthids
  exploded into a riot of bizarre forms and
  lifestyles.
• It was a kind of stethacanthid Mardi Gras -
  complete with outrageously unwieldy headgear and
  strange but fascinating rituals.

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Stethacanthus
Stethacanthus was an odd, dogfish-sized shark of
the Carboniferous Period, about 320 million years
ago. The brush-like dorsal fin with enlarged
denticles on its flattened top and corresponding
denticled patch on top of its head have generated
much speculation about their possible function.
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• Stethacanthus cont.
• It looked like a fish with a brush sticking out
  of its back. In addition, male Stethacanthus had
  similar enlarged scales on top of the head,
  making the whole contraption resemble a set of
  large, bristle-toothed jaws.
• It seems likely that the dorsal brush and
  cranial bristles of Stethacanthus played some
  role in their courtship rituals.
• Perhaps the brush and bristles were used during
  male-to-male pushing matches, enabling the
  combatants to grapple together as they tested
  each other's strength in competition for access
  to mating grounds or sexually receptive females.

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Falcatus

• Asmall stethacanthid inhabiting the warm,
  shallow seas that invaded the American mainland
  during the early Carboniferous
• A female Falcatus falcatus biting the shoulder
  spine of a male, possibly as a prelude to mating.
  Paleoichthyologist Richard Lund actually found a
  pair of Falcatus preserved together in this
  position.

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• Additional Comments on Sharks
• Shark diversity during the Carboniferous Period
  was nothing less than astonishing - Carboniferous
  boasted about 45 families of sharks (compared
  with about 40 families of modern sharks).
• But at the close of the Permian Period (250
  mya), there occurred what has been called the
  "Mother of All Mass Extinctions".
• In a geological instant, fully 99 of marine
  species were wiped out - including the
  extravagant stethacanthids.
• But some shark lineages squeaked through this
  catastrophe, one of which gave rise to modern
  sharks.
• Although modern sharks are remarkably diverse in
  form and lifestyle, no shark today matches those
  of the Carboniferous for sheer weirdness.

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• Freshwater Habitats
• Ray-finned Fishes
• The modern bony fishes (class Osteichthyes)
  appeared in the late Silurian or early Devonian
  (about 395 million years ago).
• The early forms were freshwater fishes, for no
  fossil remains of modern bony fishes have been
  found in marine deposits older than Triassic
  time, about 230 million years ago.
• Recall that the Osteichthyes may have arisen
  from the acanthodians.
• A subclass of the Osteichthyes, the ray-finned
  fishes (subclass Actinopterygii), became and have
  remained the dominant group of fishes throughout
  the world they were certainly common in the
  Carbonifierous

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• Freshwater Habitats cont.
• However, it was not the ray-finned fishes that
  led to the evolution of the land vertebrates.
• Ancestors of the land vertebrates are found
  among another group of bony fishes called the
  Choanichthyes or Sarcopterygii.
• Choanate fishes are characterized by internal
  nostrils, fleshy fins called lobe fins, and
  cosmoid scales.

• The choanate fishes appeared in the late Silurian
  or early Devonian, (390 mya) and possibly arose
  from the acanthodians.
• Choanate fishes include a group known as the
  Crossopterygii, which has one living
  representative, the coelacanth Latimeria.
• During the Devonian Period some crossopterygian
  fishes of the order Rhipidistia crawled out of
  the water to become the first amphibians.

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• Freshwater Habitats cont.
• Sharks
• Also in freshwater lakes swam lungfishes and
  xenacanth sharks (descendants of Antarctilamna
  that persisted in freshwater environments until
  the early Triassic Period, about 220 million
  years ago).
• Xenacanths were almost exclusively freshwater
  inhabitants, and had a long, rearward-pointing
  fin spine just behind the cranium (the name
  xenacanth means "strange spine"), diplodont
  teeth, a slender, eel-like body, an elongate
  dorsal fin extending along most of the back, and
  a symmetrical, tapering tail.

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Freshwater Xenacanth Sharks
Reconstruction of Xenacanthus, an eel-shaped
shark that haunted freshwater habitats in what is
now Europe during the early Permian (about 280
million years ago).
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Carboniferous Coal Forest
The Carboniferous is famed for extensive coal
beds, which were formed in swamps. That is, coal
deposits formed from plant remains in lowland
swamps. Coal represents an enormous biomass of
plants. Common coal swamp plants include
lycophytes, ferns, sphenopsids, cordaites
Large trees with straight trunks are lychophytes
tree to the left is a horestail
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Lycopod trees or club mosses
Lycopods are spore-bearing plants, and were
confined to swamps. Some grew to about 100 ft
tall and were 3 feet across at the base
Lepidodendron Note leaf scars on the trunk.
(Trees grew to 30 m tall 90 ft).
The club-moss tree Lepidodendron This tree, in
size up to 40 meters, grew in the coal-swamps of
the Carboniferous. 
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Spore-bearing ferns and seed ferns
Seed fern
Spore fern
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Sphenopsids
Calamites leaves
Sphenopsids (like Calamites) were spore-bearing
and similar to living horsetails or scouring
rushes. They are often interpreted as living in
moist areas, even perhaps standing water
Calamites trunk
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A Reconstruction of Calamites
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Cordaites
A common seed plant of drier areas was Cordaites,
a tall gymnosperms up to 100 ft in height
Note the horizontal ridges on this cast of the
pith cavity stem of Cordaites, together with a
leaf attached obliquely on the left side. The
small foliage on the right is likely a variety of
rhodea.
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Cordaites cont.
Reproductive structures of Cordaites. (A) Foliage
with fertile shoots. (B) Portion of the
ovule-bearing Cordaianthus including part of the
primary axis with ovulate secondary shoots
bearing pendant ovules. (C) Pollen-bearing
Cordaianthus
Tree growth-form of Cordaites.
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• Carboniferous Terrestrial Invertebrates
• Detritivores - land snail, millipedes, mites, and
  insects (roaches, earwigs)
• Wings appeared by the Late Carboniferous.
• Note Insects first appeared in Devonian as
  wingless.
• Types of wings
• Fixed wings (ex. dragonflies, damselflies,
  mayflies)
• Folding wings - many specializations develop
• Predators - scorpions, arachnids (spiders, mites,
  etc.), centipedes, insects
• Many kinds of spiders lived on the ground and
  from the late Carboniferous a millepede with a
  length of more than 1.8 metres is known.
• Gigantic dragonflies, with a wingspan of over 60
  centimetres, flew among the tree tops.
• Herbivores - insects with piercing, sucking,
  tearing - no clear leaf-eaters, however.

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Fossil Insects
Dragonfly reconstruction, Pennsylvanian coal swamp

• Paleodictyoptera Dunbaria fasciipennis Tillyard
  in Dunbar Tillyard 1924. 
• This insect, with its beautifully-patterned
  wings and long cerci (the "tails"), had a
  wingspan of about 37 mm. 
• It flew some 260 million years or so ago over
  what are today the prairies of central Kansas. 

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• Carboniferous Tetrapods
• During the Carboniferous and the Permian the
  basic groups of tetrapods (amphibian-like
  animals) evolved that would populate the
  post-paleozoic world.
• The early tetrapods were, like early land
  plants, tied to the water by their reproductive
  mechanisms.
• Like most "fish" they had external fertilization
  in water and laid eggs in water which developed
  into aquatic larvae.
• The larvae metamorphosed into land-living
  adults. Living "amphibians" have inherited this
  primitive mode of reproduction.

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Revisiting the Devonian Tetrapods
Neoceratodus
Lepidosiren
Protopterus
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Tetrapod Phylogeny
Amphibians-like tetrapods diversified
dramatically during the Carboniferous, and came
to dominate terrestrial and aquatic habitats
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Amphibian-like Tetrapods Temnospondyls - had a
rounded, crocodile-like snout.  They were diverse
fish eaters in both water and on land.  They
gave rise to the modern amphibians (frogs, toads,
etc.).
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Amphibian-like Tetrapods cont. Aistopods -
Legless, snake-like animals with large eyes and
light skulls.  They ate insects and fish. 
Probably aquatic.
An Aistopod or lepospondyls skull
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Amphibian-like Tetrapods cont. Nectridians -
Newt-like, aquatic, medium-sized animals.  Many
had bizarre horns on the back of their heads. 
They probably ate fish. Microsaurs -
Lizard-like bodies, short teeth perhaps for
puncturing arthropod cuticles.  Both aquatic and
terrestrial forms Reptile-like amphibians
Seymoriamorphs - Large (gt2m) reptile-like
animals with long snouts.  The Carboniferous
forms were aquatic, fish eaters.  In the Permian,
they became more fully terrestrial.
Diadectomorphs Large (gt2m) reptile-like
animals with short, deep skulls, massive limbs,
and peg-like teeth. Fully terrestrial. These
animals were the first tetrapod herbivores
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• The Amniotic Egg
• Sometime during the Carboniferous, one group of
  tetrapods developed the amniotic egg.
• Primitively, the amniotic egg has a shell
  hardened by calcium carbonate which is
  impermeable to water but allows gases to be
  transpired.
• The embryo lies floating in the amniotic fluid,
  which is formed by the embryo.
• The shell is formed by the mother.

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Amniotic Egg cont.

• The amniotic egg is a major shared derived
  character for the taxa in the Amniota, which
  includes us as well as the dinosaurs.
• Soon after the amniotes appeared, two distinct
  group are recognizable - these are the Synapsida
  (which includes us) and the Sauropsida (which
  includes the dinosaurs).

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• What is an amniotic egg, and why do we care?
• Amphibian females (like their fishy ancestors)
  lay a large number of eggs in water, which the
  male then fertilizes externally. 
• The larval amphibian emerges from the egg, and
  develops as a largely aquatic organism. 
• Some metamorphose into a more terrestrial form,
  and move onto land.  Others spend their entire
  life in water.
• Animals with an amniotic egg have similar
  stages, but they all take place inside a
  well-protected egg. 
• They emerge from the egg into air with an
  adult-like form.

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Key Innovations in the Amniotic Egg
Semipermable shell allowsO2 in and CO2 out, but
retains water.  Extra-embryonic membranes
Amnion encloses the embryo with a fluid very
similar to environmental water. Chorion coats
the inside of shell and the yolk (nutrient
source). Allantois encloses a cavity for solid
wastes.

• The amniotic egg allowed tetrapods to breed away
  from water.  It opened up a vast new landscape
  that they could invade.

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• The boundary between Amniotes and Amphibians is
  hard to define because
• Eggs don't fossilize well. 
• "Amphibians" aren't a clade (not a natural
  group).
• There are no novelties that are shared only by
  the animals we call Amphibians. This is because
  we have, rather arbitrarily, decided to call some
  descendents of amphibians something else.  As a
  consequence, the Amphibian-Amniote boudary is
  "fuzzy".
• Westlothiana lizziae - the first amniote, is
  known from the early Carboniferous.
• Despite this early appearance, Amniotes don't
  diversify until end Carboniferous.

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• What are the main groups of amniotes?
• The primary subdivisions of amniotes are based
  on "holes in the head".
• Early tetrapods had a braincase enclosed by
  bone, as well as outer skull armor that was
  separated from this braincase. 
• This interior space between the brain case and
  outer skull is filled with musculature to open
  and close the jaws. 
• Some amnniotes begin to open windows in this
  outer skull armor and begin to expand jaw muscles
  onto the outside of the head.
• It's thought that this expansion of jaw
  musculature allows greater diversity in chewing
  and food processing.  

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Main Groups of Amniotes

• Anapsids - no holes in head behind the eye. 
• This is the primitive state for tetrapods. 
• It occurs in the earliest tetrapods and is also
  seen in turtles, the most primitive reptiles.
• Synapsids - one hole in head behind the eye. 
• This is one of the evolutionary novelties in
  head holes. 
• It occurs in pelycosaurs, therapsids, and
  mammals.
• Diapsids - two holes in head behind the eye. 
• This is another evolutionary novelty in head
  holes. 
• It occurs in nearly all reptiles except turtles
  (i.e., lizards, snakes, crocodiles, pterosaurs,
  dinosaurs and birds).

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Main Groups of Amniotes
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Terrestrial Ecosystems of Permian Period
All the continents had crashed together to form
the supercontinent, Pangea.
The swamps of tropical Europe and America were
drying out. Evaporites (salt deposits) and red
beds (indicating dry soils) were more common.
Early Permian tetrapods are only known from the
equatorial zone.
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• Permian Plants
• Drying of the swamps took a long time spanning
  from Late Carboniferous through the late Permian.
  
• Seed plants came to dominate lowlands.
• Wet areas with spore-bearing plants persisted,
  but were increasingly rare.

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• Permian Tetrapods
• Amphibian diversity drops, but some groups
  persist and become better adapted for life in the
  air.
• The decline is tied to
• Drying of swamps. Amphibian reproduction is tied
  to water.
• Competition and/or Predation by amniotes.
• Amniotes were free to breed and feed away from
  water. Drying wasn't a problem.
• Synapsid amniotes (one hole) dominate landscapes
  in the Permian.
• There were two main synapsid groups in the
  Permian Pelycosaurs and Therapsids

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Permian Pelycosaurs

• Dominated in the late Permian.
• Pelycosaur communities of the early Permian only
  occur in the tropical zone.

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Carnivorous pelycosaurs up to 2 meters and 200
kg, big heads eyes, long snouts, strong jaws,
pointy teeth with some differentiation from
front-to-back. They ate fish amphibians. Some
had sails Sprawling front hind legs, but
vertebral spines prevented lateral undulation
during locomotion.
Dimetrodon (carnivorous)
Popularly known as the 'finback' because of the
large sail on its back supported by elongated
spines from the vertebrae . This sail may have
helped control temperature by acting as a
radiator, or may have been used for display. It
was a formidable predator , with huge canine teeth
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Herbivorous pelycosaurs medium to large (3 m,
300 kg), small heads, blunt undifferentiated
teeth, large gut cavity, some had sails.  The
same sprawling posture as in carnivorous
pelycosaurs.
Edaphosaurus (herbivorous)
This pelycosaur also featured a sail. Like
Dimetrodon, this may have been used for heat
exchange or display. Unlike Dimetrodon, its teeth
show it to have been a herbivore .
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Permian Therapsids
This is an artist's representation of the
possible appearance of a therapsid. Therapsids,
now extinct, were reptilians which were descended
from the stem reptiles. They are presumed to be
the ancestors of the mammals. "Non-reptilian"
characteristics of members of this group were
thoracic and pelvic skeletal features which
permitted the legs to be positioned directly
underneath the body.
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• Herbivory among the Tetrapods
• Plant eating arose many times in tetrapods.
• Plant feeding animals use two different
  strategies for dealing with this problem.
• Be small and picky - avoid cellulose-rich plant
  parts only eat nutrient-rich plant parts (fruits
  nuts). There is only enough high-nutrient food
  to support small animals with this strategy.
• Be big and indiscriminate - eat everything that
  you can. Pack your gut with microbes and let them
  ferment this low quality food. Eat the microbes
  and the waste products they exude. Must be large
  to fit the massive, fermenting-chamber gut.
• Herbivorous pelycosaurs took the big,
  indiscriminate route. 
• They were large, and probably evolved from large
  carnivorous ancestors. 
• They had small heads, so cellulose digestion
  must have come from microbes. 
• They did, in fact, have big guts.