L8- Permian Terrestrial Ecosystems

The Permian World:

• all continents have come together, fewer mid-ocean ridges, less coastline, less preserved shallow marine areas, less continental shelf (shallow sea where light penetrates <200m deep)

• Gondwana collided with Euramerica to create the central Pangean mountain range with deserts above and below this

  

• CO2 levels start to rise, O2 levels start to fall

• switch from an icehouse to a greenhouse world in the late Permian→ probably due to CO2 levels beginning to rise

  

• ice sheet disappears but sea levels are lower than today→ no mid-oceanic ridges that push up water

  

• tropical zone in mountains, cool temperate at poles, tropical Tethis sea→ diverse, marine life

  

Plants:

• new groups, cordites disappear

  

  • Bryophytes→ unchanged from Carboniferous

    

  • Lycopsids→ tree form gets wiped out at the end-Carboniferous as rainforests get uplifted, persist in China for a bit, reduced to small herbaceous forms

    

  • Ferns→ lots of forms from Carboniferous

    

  • Sphenopsids→ tree form disappears except in China, reduced to small herbaceous forms, similar to equisetums (horsetails today)

    

  • pteridosperms→ diversify, have characteristic leaves, Gigantopterids in China, Glossopterids in Pangea, found all over

    

  • Cordaites→ go extinct

    

  • Conifers→ primitive conifers diversify (relative of Cordaites)

    

  • Ginkgos→ new species, one species left today

    

  • Cycads→ new species, slow growing, male cones produce pollen, female cones produce seeds, appear in the Late Permian but possibly earlier in China

    

• clear shift in plant dominance at the end of the Permian

  

  • palaeophtic-mespohytic transition in vegetation→ change from tree lycopsids and sphenopsids to gymnosperms

  • seed plants are better adapted to dry environment

  • Permian-Triassic mass extinction shows a clear transition from west to east:

    

    • plants are only affected in the short term by the mass extinction

• not a strict latitudinal gradient of biomes, affected by the positioning of the Tethis ocean:

  

Invertebrates:

• jawed fish become the top predators instead of eurypterids

• not much change

• cycads were primary wind pollinated but there is some evidence that beetles pollinated some of them

  

Fish:

• End Devonian killed all basal groups

• still have chondrichthyes, ray-finned fish and lobe-finned fish

• starting to get the modern pattern of fish

Tetrapods:

• basal groups continue to diversify

• characteristic of tetrapod evolution→ appear, diversify, go extinct (high turnover)

• initially amphibians dominate but reptiles overtake them

• synapsids→

  • were previously split into pelycosaurs and therapsids (are actually paraphyletic)

  • pelycosaurs→ sails held up by single bones from vertebrate (possibly heat regulation), were very common then replaced by therapsids

    

  • therapsids→ have hairlike structures, possibly where mammals came from

    

  • late permian→ therapsids dominate

    

  • some tetrapods go back to the sea (**)

  • some tetrapods can glide (**Coelurosauravus)

Mass extinction:

• nearly all groups disappear, some survive and re-diversify

• animals affected, doesn’t really affect vegetation

• changes direction of tetrapod evolution

• synapsids, anapsids and neodiapsids make it through

• reason for mass extinction:

  • outpouring of siberian traps

  • overlaying siberia are volcanic deposits→ earth surface cracks open, basalt lava spills out, can work out how much co2 it releases, was a lot but not enough to make a huge climate change, the rocks it moved through are made of coal and evaporates, releases sulfur dioxide (dissolves into acid rain) and methane

  • initial deforestation due to acid rain, methane and co2 creates a greenhouse world→ super-heats planet

  • sea temperature rises→ some have metabolism that is more susceptible to heating than others- survive

Summary:

• coal measure forests start drying out due to equitorial uplift, from west to east (except from in North and South China)

  • vegetation changes from lycopsid dominant to tree fern dominant to cordaite/conifer dominant to mountain dominant

• switch from icehouse to greenhouse world in the late Permian

  • gradual change from lycopsid/sphenopsid dominant to seed plants