EOSC 116 Final Exam 2 Questions &
Answers 2025/2026
Permian-Triassic Extinction - ANSWERSgreatest catastrophe the biosphere faced
96% of species went extinct
~250 Ma
Early Triassic - ANSWERSdominated by Pangea
harsh hot deserts
- evaporites and red desert sandstones
- rocks: ventifacts and calcretes
oxygen isotopes from conodonts show hot ocean temperature (36°C)
remains of life in Early Triassic - ANSWERSLystrosaurus (member of reptiles)
Plants
- Pleuromeia and Dicroidium
- few conifers
Ocean faunas
- no corals ("coral gap")
,equator was a dead zone
Lilliput Effect
- smaller adult size and increased juvenile mortality rate, is seen to occur as a response to rising
temperatures.
Disaster taxa - ANSWERSthe creatures that struggle to survive in the now impoverished world
- especially in Early Triassic
High in abundance but of low diversity
ex. Lystrosaurus
Lystrosaurus - ANSWERS- most abundant in Early Triassic (90% of vertebrates)
- a member of a group of reptiles called the dicynodonts named for their paired tusks meaning
"dog-like tooth"
- no teeth -herbivores
- an able burrower (digging)
- walk like crocodiles
- important for evolution of mammals
Plants (Early Triassic) - ANSWERSno forests
land dominated by smaller herbaceous forms like Pleuromeia and Dicroidium (types of seed
ferns) and few species of conifers
,chaotic braided streams
Ocean (Early Triassic) - ANSWERSOcean faunas were dominated by high abundance, low
diversity faunas of 'disaster taxa'
ex. Brachiopod Lingula and bivalve Claraia
no corals
- "coral gap"
Only reef like structures are stromatolites (in salty water)
Geography of the impoverished biota (early triassic) - ANSWERSequator is a dead zone for
fossils
life forms not present at low latitudes
in the oceans, fish, marine reptiles and corals are absent around the equator
Lilliput effect - ANSWERSduring Early Triassic
reduction in body size of surviving taxa
smaller adult size and increased juvenile mortality rate
- due to rise in temp
Drivers of the impoverishment (Early Triassic) - ANSWERSincreasing temp (pushing organisms
beyond their tolerance)
- hottest at equator
, reduced oxygen conditions (dyslexic or anoxic) in oceans
- more CO2 in ocean (acidic)
Recovery (early triassic) - ANSWERSEarth started to recover during the Middle and Late Triassic,
the numbers and diversities of lineages increased
development of:
- corals and reefs
- bivalves and gastropods
- vertebrates
- flying vertebrates
- first mammals
corals and reefs (Middle Triassic) - ANSWERSlong term reef development ending the "reef gap"
that existed from the end-Permian and into the Early Triassic
in Middle Triassic scleractinian corals appear
- the main reef forming metazoans today
Bivalves and Gastropods (Middle Triassic) - ANSWERSby Mid Triassic mollusks like bivalves
(clams) and gastropods (snails) that really recover and diversify
Brachiopods = the shells washed up on the beach
- resemble clams
- feed using a lophophore
Answers 2025/2026
Permian-Triassic Extinction - ANSWERSgreatest catastrophe the biosphere faced
96% of species went extinct
~250 Ma
Early Triassic - ANSWERSdominated by Pangea
harsh hot deserts
- evaporites and red desert sandstones
- rocks: ventifacts and calcretes
oxygen isotopes from conodonts show hot ocean temperature (36°C)
remains of life in Early Triassic - ANSWERSLystrosaurus (member of reptiles)
Plants
- Pleuromeia and Dicroidium
- few conifers
Ocean faunas
- no corals ("coral gap")
,equator was a dead zone
Lilliput Effect
- smaller adult size and increased juvenile mortality rate, is seen to occur as a response to rising
temperatures.
Disaster taxa - ANSWERSthe creatures that struggle to survive in the now impoverished world
- especially in Early Triassic
High in abundance but of low diversity
ex. Lystrosaurus
Lystrosaurus - ANSWERS- most abundant in Early Triassic (90% of vertebrates)
- a member of a group of reptiles called the dicynodonts named for their paired tusks meaning
"dog-like tooth"
- no teeth -herbivores
- an able burrower (digging)
- walk like crocodiles
- important for evolution of mammals
Plants (Early Triassic) - ANSWERSno forests
land dominated by smaller herbaceous forms like Pleuromeia and Dicroidium (types of seed
ferns) and few species of conifers
,chaotic braided streams
Ocean (Early Triassic) - ANSWERSOcean faunas were dominated by high abundance, low
diversity faunas of 'disaster taxa'
ex. Brachiopod Lingula and bivalve Claraia
no corals
- "coral gap"
Only reef like structures are stromatolites (in salty water)
Geography of the impoverished biota (early triassic) - ANSWERSequator is a dead zone for
fossils
life forms not present at low latitudes
in the oceans, fish, marine reptiles and corals are absent around the equator
Lilliput effect - ANSWERSduring Early Triassic
reduction in body size of surviving taxa
smaller adult size and increased juvenile mortality rate
- due to rise in temp
Drivers of the impoverishment (Early Triassic) - ANSWERSincreasing temp (pushing organisms
beyond their tolerance)
- hottest at equator
, reduced oxygen conditions (dyslexic or anoxic) in oceans
- more CO2 in ocean (acidic)
Recovery (early triassic) - ANSWERSEarth started to recover during the Middle and Late Triassic,
the numbers and diversities of lineages increased
development of:
- corals and reefs
- bivalves and gastropods
- vertebrates
- flying vertebrates
- first mammals
corals and reefs (Middle Triassic) - ANSWERSlong term reef development ending the "reef gap"
that existed from the end-Permian and into the Early Triassic
in Middle Triassic scleractinian corals appear
- the main reef forming metazoans today
Bivalves and Gastropods (Middle Triassic) - ANSWERSby Mid Triassic mollusks like bivalves
(clams) and gastropods (snails) that really recover and diversify
Brachiopods = the shells washed up on the beach
- resemble clams
- feed using a lophophore
