EOSC 116 modD

• Paleogeography


  The study of the ancient geography of the Earth
• Early Triassic Pangea


  • One giant landmass dominating one side of the planet
  • Surrounded by the giant ocean Panthalassa
• Climate


  The weather conditions prevailing in an area in general or over a long period

  • The early Triassic climate was harsh
  • Hot arid deserts covered most of Pangea interior
  • evidence found in rocks, evaporites, common & red desert sandstones
  • other evidence : ventifacts & calcretes
  • There was likely no ice at the poles, poles were relatively temperate
  • more diverse fauna of animals & forests could survive
• Ventifacts


  Wind-made rocks eroded by rocks
• Calcretes


  Terrestrial materials cemented/replaced by calcium carbonate
• Ocean Temperature


  Fluctuations in temperature measured by oxygen isotopes

  • equitorial deposits in South China cover extinction at end of Permian and early Triassic
  • shows rapid warming to 36°C a round 252.1 MA
  • rapid cooling following main extinction & second rise in temp around 250.7MA
  • temperature in water column rose to about 38°C, maybe exceeding 40°C at surface
• Stable isotopes


  Have same number of protons but different number of neutrons that DO NOT decay like radioactive isotopes
• Oxygen isotopes


  • 16O
  • 18O
  • 99.763% of oxygen is 16O, 0.191% of oxygen is 18O
  • molecules w/isotope are heavier, differences influence behaviour during natural physical properties
  • Oceans contain H2O16 and H2O18
  • H2O16 evaporates more, becomes rain, had rapid return to ocean. Water remains balanced, not much change in animals at the time
  • during glacial period: H2O16 evaporates, becomes snow and locks up in ice sheet, ocean is H2O18 enriched, animals are affected
• Lystrosaurus

  • Strange shovel-fed animal, group of dicynodonts named for paired tusks and dog-like teeth, wider group of therapsids ("mammal-like reptiles")
  • One of the most abundant animals on the planet, evolved during Permian, more abundant early Triassic, 251-247Ma
  • Made up over 90% of terrestrial vertebrates on Earth
  • Very short shovel-like face with eyes set high on skull and forward, no evidence of teeth, thought to have beak
  • Likely herbivore, shear off plant material with beak, had tusks on either side to grub up roots & tubers
  • Jaw analysis indicates it doesn't move up & down or side-side, moved back and forth, plant ground down by palate
  • Walk had sprawling gait, didn't have legs under body, sticks out on sides, similar to geckos and crocodiles
  • Skeleton suggests they supported powerful musculature, indicates was a burrower, aid to search for roots & tubers
  • Ability to crop vegetation on surface or dig up material when it got tough
• Disaster Taxa

  life forms that would limp through Permo-Triassic that would struggle through Triassic period
• • forests not common becaus was a desert planet
  • Plants were often dominated by smaller herbaceous Pleuromen and Dicroidium (seed ferns)
• Transition from meandering river systems with banks stabilized by plantsTo chaotic braided systems signals plant communities retreated with their inability to stabilize, reduction in flora links with increased delivery of sediment to ocean basin 

• Lack of peat in the Early Triassic is the suggested cause of the "coal gap"
• First coals didn't appear in equatorial regions until 5Myr after the end-Permian mass extinction
• Early Triassic ocean fauna

  • Dominated by low diversity fauna of "disaster taxa"
  • There were no corals, coral gap in oceans, coral reefs not returning until 10Myr after Triassic beginning
• Stromatolites only reeflike structures at the time

  • common before predators evolved in Cambrian
  • limited to periods following mass extinction, few isolated community managed to survive unusual environments
  • made of cemented sediment created by mats & microbes
• Geography of Impoverished Biota

  Modern biodiversity peaks at equator, lessens at poles
• Geographical pattern to impoverishment of taxa in both marine & Terrestrial environments
• Disturbing gap in fossils occurs at equator during early Triassic
• Equator was dead zone
• Majority of life forms not present at low altitudes
• Noticeable at peak temperature rise at end of Smithian
• Oceans fish, marine reptiles & corals were absent
• Life found in area tend to be invertebrates
• Majority of land fauna retreated to poles
• Life during early triassic was impoverish & pattern of life flipped to equator almost inhabitable, life mostly in higher latitudes
• Lilliput Effect

  • Many taxa found were very small, includes smaller adult size & increased juvenile mortality
  • occurs as response to rising temperatures
  • result in fossil record composed of smaller individuals
  • Explains why trace fossils only record presence of small organisms not really burrowing deeply at the time
• Drivers of impoverishment

  • Temperature increase during Early Triassic pushed organisms beyond thermal intolerance
  • many plants survive up to 35°C, few survive over 40°C, absence/rarity of active creatures at equator due to temperature
  • more active you are, more active metabolism, greater oxygen needed
• • earth recovering from largest mass extinction
  • took longer to cool down & recover biosphere
  • rising Temperature causes cascade of problems
  • reduce oxygen levels in oceans
  • rise in H2S due to sulphur-loving bacteria
  • increase CO2 leading to acidic seawater, affect calcium carbonate, shell creatures
  • Siberian traps active & releasing C0₂
  • responsible for increased warming at end of Smithian Stage
  • helped destabilize more methane hydrates, further warming
  • no evidence found yet
• Recovery

  Numbers & diversities of lineages increased significantly in continental & marine realms

  • general increase in numbers continued into Early Jurassic
• Corals and Reefs

  • Long term reef development began Middle Triassic
  • ended reef gap
  • main Paleozoic reef bulders rugose and tabulate corals
  • went extinct during end-Permian extinction
  • some minor reef formation 1.5 mil years after PT boundary
  • Around 10Mill years, after extinction, Stony Corals made comeback
  • extinction of corals led to many invertebrates & vertebrates extinction
• Bivalves and Gastropods


  • Common shells found washed up on beaches, likely brachiopods
  • brachiopods belong to group of animals lophophorates
  • Feed using lophophore, ring of ciliate tentacles, used to capture material suspended in water column
  • Mollusks like bivalves gastropods recover and diversify
  • Brachiopods survive extinction
  • never dominate ocean floor like in Paleozoic
  • sea shells of Mesozoic & Cenozoic dominated by mollusks
• Land Based Vertebrates


  • Lystrosaurs replaced by rise of archosaurs
  • rauisuchia become apex predators of terrestrial environment
  • resembled crocodile but on long legs tucked below body, ranged in size, 4-6m, dinosaurs didnt dominate Triassic
  • rapidly diversifying vertebrate, Coelophysis-slender bipedal carnivore
  • 3m long, common in SW United States
  • agile runner, forward eyes give stereoscopic vision
  • good view of road ahead, good depth perception
  • thousands found in Ghost Ranch, New Mexico
  • may have roamed Triassic in flocks, possible only gathered to location to drink before flash flood
• Flying Vertebrates


  Archosaurs move vertebrates to hew level in Triassic, allow them to get off ground & soar into atmosphere
• First Mammals


  Earliest mammals evolved from mammal-like reptiles, difficult to distinguish last therapsids & true mammals, Late Triassic Megazostrodon Started to look like mammalian, Permian extinction and barren hot Earth started mammal story
• DII Triassic Mass extinction

  Triassic-Jurassic Interval, explosion of life in later Triassic followed by setback, end of triassic, Triassic-Jurassic Mass extinction, one of the Big 5 extinctions, impact on oceans, extinction or conodonts, important in Paleozoic fauna, reef systems affected, ammonites, brachiopods, bivalves suffered, estimated 22% all marine families, 53% all genera, 76-84% of all species driven to extinction
• Causes of Triassic-Jurassic Extinction

  Falling Sea Levels, reduction in shallow, warm seas, restriction of reef spread and increased competition, possible extreme temperatures and seasons on bind, return of deep water low in oxygen as sea level rose

  fragmentation of Pangea, rift Formation lead to break up of Pangea, major igneous activity in rift zones, CAMP Eruptions coincided w/extinction event, release large volumes of magma, effects similar to end-Permian mass extinction, including global cooling & warming, possible spread of anoxic conditions in oceans
• End-Triassic event see how ecosystem dawn in Jurassic
• Transition to Mesozoic oceans, Palezoic marine faunas characterized by predominance of certain types of creatures, Brachiopods, echinoderms, corals dominated Paleozoic oceans, After Permian extinction, large marine reptiles emerged as top predators, bivalves & gastropods replaced brachiopods, cephalopods became more abundant in Mesozoic, rugose & tabulate corals became extinct, other organisms took over reef building roles, shift from Stalked crinoids to more mobile echinoderm, only 6 species survived, underwent radiation throughout Mesozoic Cenozoic eras, lead to diversity of echinoids
• Cephalopods

  Belong to group of Mollusks, meaning "head foot", relatives of squid & octopus

  Early Cephalopods, Present in Paleozoic, diversified and evolved by Mesozoic, internal shells usually the only part preserved as fossils, sometimes evidence of outlines of soft parts, ink sacks preserved, Belem nites thought to be produced by thunderbolts, greek for dart or arrow, had 10 arms, double row of hooks, no suckers