Paleozoic Life
description
Transcript of Paleozoic Life
Paleozoic Life
Invertebrates
• Major invertebrate phyla evolved in the Cambrian
• Trace fossils common• Echinoderms diverse• Trilobites, inarticulate
brachiopods, archaeocyathids –major skeletonized animals
Paleozoic Life – Introduction• Tectonics important role on evolution
– Opening and closing of ocean basins– Transgressions and regressions of epeiric seas– Change positions of continents
• Evolution– Skeletonized animals appear (PreЄ- Є boundary)– Marine invertebrates diversify – Vertebrates also evolved– Organisms move from water to land• Major Extinctions (end of Paleozoic)
– Marine invertebrate community– Many amphibians and reptiles on land
The First Shelled Fossils• Mineralized skeleton appeared abruptly – Why?
– Cambrian organisms complex Multi-celled organism must’ve had pre-Є history Lacked hard parts; did not leave a fossil record
– Ediacaran Fauna (570-670 Ma)
– Skeletons of chitin, silica, & CaCO3
1st multi-celled organism
Early Cambrian Emergence of Shelly Fauna
• Low diversity• Composed of CaCO3
& Ca3(PO4)2
• Fauna had fully developed features– Anatomies indicate
extended evolution– Extended from
Cambrian to Ordovician
Early CambrianShelly Fauna Abrupt Appearance
• Possible explanations– Changes in ocean
chemistry Deficient in Ca &
PO43- = no hard parts
Rejected; numerous carbonate rxs and phosphate deposits
– Invertebrates need to eliminate mineral matter
CambrianSkeleton Advantages
• Protect against UV radiation
– Move into shallower H2O• Prevent dry out • Protect against
predators • Skeleton for support;
increase size • Attachment site for
muscles Injured Trilobite
Middle CambrianShelly Fauna
• Many invertebrate groups evolved– Brachiopods (still around)– Archeocyathids– Trilobites
• Cambrian Marine Community
Middle CambrianMarine Community
• Brachiopod– Primitive type
Inarticulate (chitin phosphate)
– Present type Articulate
Hinged by muscles
• Archeocyathids
• Trilobites most common
– Benthonic, sessile, suspension feeder
– Made reef structure
– Benthonic, mobile, sed dep feeder, crawled or swam
• Echinoderms
Middle CambrianBurgess Shale
• Sauk Transgression– Black, anoxic seds
• Soft-bodied organisms preserved
– Fossils classified into existing phyla
– Most fossil in mid-Є, but fewer species
– Strange fossils– No living counterparts
– extinct?– Reassigned to known
phyla
Middle CambrianBurgess Shale
Cambrian Worm Cambrian WormCambrian Arthropod
Ordovician• Major transgression warm water
• Reef Builders
• More abundant
– Increased diversity Epifaunal, benthonic,
sessile, susp feeders Articulated brachs
Bryozoans Tabulate/Rugose
corals Stromatoporids
Conodont - tooth like CaPO43-
Graptolite - plankton Acritarchs
Graptolites
Graptolites
End of Ordovician
• Mass Extinction– 100’s of families did not make it to Silurian– 50% of brachiopods and bryozoans died– Maybe glaciation in Gondwana
Silurian & Devonian• Rediversification
• Major reef building
• Common guide fossils
– After Ordovician extinction
– Tabulate/rugose corals– Stromatoporids
– Euryterids– Ammonites
End of Devonian
• Mass Extinction (L. Frasnian – Famennian)– Lose most reefs– Decline of many organisms
Brachiopods, ammonites, acritarchs, gastropods, bryozoans
– Mostly tropical groups; not polar• Possible Causes
– Global cooling; Iapetus closing
Carboniferous & Permian• Rediversification
– After Devonian extinction
– Small, patchy reefs
– Brachiopods & ammonites
• Permian life restricted
Crinoids, blastoids, brachs, bryozoas
– Seas regressed– Fusilinids diverse Mississippian AmmonoidPermian Fusilinid
End of Permian• Mass Extinction
– 50% marine families 90% marine invertebrates
– Regression • Possible Causes
Less living area– Pangaea forms
Continental suturing– Decreased S ‰
Arid climate Evaporite formation
Other Permian Extinction Possibilites• Climate Change
– Warming at close of Permian– More CO2 in atmosphere
• More volcanism– Changes in ocean ciruculation
brings CO2 to surface/atmosphere• Meteorite Impact