Post on 29-Dec-2015
• 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
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