Life of the Paleozoic

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Life of the Paleozoic

• CHAPTER 10

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Paleozoic Organism Innovations

• Shelly fauna
• Land plants
• Amniotes
• Vertebrates

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Precambrian Life

• Precambrian life begins as
• Prokaryotes (beginning at least 3.5 bya, possibly
  3.8 bya or more, in the Archean)
• Archaea (including thermophiles of deep sea
  hydrothermal springs)
• Bacteria (some of which were anaerobic)
• Photosynthetic cyanobacteria which constructed
  filamentous algal mats (stromatolites), sometimes
  called blue-green algae.

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Precambrian Life (continued)

• Eukaryotes (beginning about 1.4 -1.6 bya in the
  Mesoproterozoic)
• Microscopic unicellular organisms of various
  types (Protozoa)
• Acritarchs - probably phytoplankton
• Algae
• Metazoans or multicellular organisms (beginning
  in the Neoproterozoic)
• Soft-bodied Ediacaran fauna (beginning about 630
  mya or 0.63 bya)
• Small shelly fossils - tubes etc., few mm in
  size, possibly the remains of primitive molluscs,
  worms, sponges.

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Modes of Life in Marine Zone(pg. 130-132)

• Location nektonic, planktonic, benthic
• Bottom dwellers epifaunal, infaunal, mobile
• Feeding strategy filter-feeders, sediment-feeders

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Marine Ecosystem

• Where and how animals and plants live in the
  marine ecosystem

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Animals with shells

• Pre-Shells Proterozoic (Ediacaran) Fossils
• Tommotian Fauna Fossils from Siberia, Sweden, N.
  America, Antarctica, and England
• Shells and elements of tiny mollusks, sponges,
  and cap-shaped tubular shells (calcium carbonate
  or phosphate)
• Anabarites tubular fossils (three tubes joined
  together)
• Lapworthella cap-shaped and ornamented

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Late Precambrian and Early Cambrian shell-bearing
fossils from Siberia. (A) Anabarella, a
gastropod (B) Camenella, affinity uncertain
(C) Aldanella, a gastropod (D) sponge spicule
(E) Fomitchella, affinity uncertain and (F)
Lapworbella. (After Matthews, S. J., and
Missarzbevsky, V. V. J. 1975. Geol. Soc. London
131 289-304.)
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Lagerstätten!!

• Extraordinary Early Cambrian Soft-Body Fossil
  Sites
• Burgess Shale, British Columbia, Canada (525 m.y.
  old)
• viewed as one of the most important faunas in
  fossil record
• impressions and films on bedding planes
• limited exposure near Mt. Wapta, BC
• discovered by C.D. Walcott in 1909
• Chengjiang site, China (535 m.y. old)
• 10 m.y. older than Burgess Shale
• Early chordates

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Figure 10-2 (p. 332) Geologic time scale across
the Proterozooic-Cambrian boundary showing
position of the Ediacaran, Chengjiang, and
Burgess Shale faunas.
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Burgess Shale Fauna

• Several groups of arthropods, including
  trilobites and crustaceans
• Sponges
• Onycophorans
• Crinoids
• Molluscs
• Three phyla of worms
• Chordates (Pikaia)
• Many other species, some of which cannot be
  placed into known phyla

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Burgess Shale Fauna
Pikaia, one of the oldest known Chordates.
The giant predator of the Cambrian seas,
Anomalocaris, up to 60 cm long.
Hallucigenia-- Which way is up?
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Invertebrates of the Paleozoic

• Unicellular Groups (Protistans)
• Cup Animals archaeocyathids
• Pore-Bearers porifera (sponges)
• Corals and Other Cnidarians
• Bryozoans (Moss Animals)
• Brachiopods (most abundant diverse Paleozoic
  fossil)
• Mollusks
• Arthropods
• Echinoderms (Spiny-skinned)

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Protists of the Paleozoic

• While not members of Kingdom Animalia, they are
  animal-like (non-photosynthetic) single-celled
  organisms with shells or hard parts living during
  the Paleozoic.
• Both the Foraminifera and the Radiolaria belong
  to Phylum Sarcodina.

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Radiolaria
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Cup Animals archaeocyathids

• Conical or vase-shaped skeletons
• Extinct phylum by end of Cambrian
• Earliest reef builders
• N. America, Siberia, Antarctica, Australia
• Australian reefs 60 m x 200 km

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The archaeocyathan skeleton. (A) Longitudinally
fluted cup of an archaeocyathan, about 6
centimeters in height. (B) Transverse section of
a nonfluted archaeocyathan having closely spaced
parieties and a vesicular inner wall (maximum
diameter is 4 centimeters).
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Pore-Bearers porifera (sponges)

• Sessile, bottom dwellers
• Spicules--found commonly in sediment record
• Stromatoporoid

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Corals and Other Cnidarians

• Main groups
• sea anemones
• sea fans
• jellyfish
• Hydra
• reef-forming corals

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Corals

• Body form polyp or medusa
• Anthozoa (stony corals) polyp secrets Calcium
  carbonate cup and lives within it
• theca (cup) divided by vertical plates (septa)
• tabulae (horizontal growth plates in theca)

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Figure 10-22 (p. 341) Comparison of polyp and
medusa forms in cnidarians.
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Rugose versus tabulate corals

• Rugose have septa at four locations
• Tabulate corals have obscure septa, tabulae are
  dominant (e.g., honeycomb and chain corals)

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Rugose versus tabulate corals
Tabulate
Rugose
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Bryozoans (Moss Animals)

• Minute, symmetrical, colonial, twig-like
  macroscopic appearance
• Zooid individual fossil living site
• Zooecium capsule which contains zoids
• Range Lower Ordovician to present
• Paleozoic forms common in reefs
• Encrusting or arborescent
• Branching zooarium
• Star-shaped patterns
• Corkscrew fenestellid colony, Archimedes
• Fan-Shaped

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Bryozoans
Fenestrella, a lacy bryozoan from the Devonian
Specimen of the fossil bryozoan, Archimedes
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Brachiopods (most abundant, diverse, and useful
Paleozoic fossil group)

• Bivalves symmetrical across the valve (shell)
  valves are dorsal and ventral
• Calcium carbonate (most taxa), chitin, calcium
  phosphate
• Articulate brachipods valves hinged along
  posterior margin (teeth and sockets) commonly
  ribbed or ornamented
• first occurred during Cambrian
• flourished during Ordovician
• common during Late Paleozoic
• persist today
• Inarticulate brachiopods valves held by muscles
• commonly chitino-phosphatic
• simple spoon-shaped or circular valves
• major decline in diversity during Ordovician
  exist today

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Living positions of articulate and inarticulate
brachiopods. (A) The articulate (B) Interior of
brachial valve showing ciliated lophophore. (C)
The inarticulate brachiopod lives in a tube
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Articulate Brachiopods
Ordovician strophomenid articulate brachiopod,
Rafinesquina
Miscellaneous Paleozoic articulate brachiopods.
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Inarticulate Brachiopod
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Phylum Mollusca

• Clams, oysters, snails, slugs, Nautilus, squid,
  octopus, cuttlefish
• Mollusca means " soft bodied" .
• Chief characteristics Soft body enclosed within
  a calcium carbonate shell.  Muscular part of body
  of clams and snails and some other groups of
  molluscs is called the foot.
• Geologic range Cambrian to Recent.
• Mode of life Marine, freshwater, or terrestrial.
  Some swim, some float or drift, some burrow into
  mud or sand, some bore into wood or rock, some
  attach themselves to rocks, and some crawl.

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Figure 10-31 (p. 347) Some common members of
the phylum Mollusca. (From Levin, H. L., 1975.
Life Through Time. Dubuque, IA William C. Brown
Co.)
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Class Bivalvia (Pelecypoda)

• Includes Clams, oysters, scallops, mussels
• Name Bivalvia means " two" (bi) " shells"
  (valvia).
• Chief characteristics Skeleton consists of two
  calcareous valves connected by a hinge. Bilateral
  symmetry valves are same
• Geologic range Early Cambrian to Recent
• Mode of life Marine and freshwater. Many species
  are infaunal burrowers or borers, and others are
  epifaunal

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Class Gastropoda

• Includes Snails and slugs
• Name Gastropod means "stomach" (gastro) "foot"
  (pod).
• Chief characteristics Asymmetrical,
  spiral-coiled calcareous shell.
• Geologic range Early Cambrian to Recent.
• Mode of life Marine, freshwater or terestrial.

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Gastropods
Fossil gastropod
Modern gastropod
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Class Cephalopoda

• Includes Squid, octopus, Nautilus, cuttlefish
• Name Cephalopod means " head" (kephale) "
  foot" (pod).
• Chief characteristics Symmetrical cone-shaped
  shell with internal partitions called septae
  (singular septum). Shell may be straight or
  coiled in a spiral which lies in a plane. Smooth
  or contorted sutures visible on the outside of
  some fossils mark the place where septae join the
  outer shell.
• Geologic range Late Cambrian to Recent.
• Mode of life Marine only carnivorous
  (meat-eating) swimmers.

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Nautiloids and Ammonoids
Diagram of a nautiloid cephalopod illustrating
suture pattern.
Diagram illustrating ammonite sutures in an
ammonoid.
Nautilus.
Ammonite cephalopod.