paleontology, one of the important topic. mass extinction

1. Presentation on,
By,
Haritha A

2. MASS EXTINCTION
 An extinction event (also known as a mass
extinction or biotic crisis) is a widespread and rapid
decrease in the amount of life on Earth
 Extinction occurs at an uneven rate
 Marine fossils are mostly used to measure extinction
rates because of their superior fossil record and
stratigraphic range compared to land organisms.
 Since the Cambrian explosion five further major mass
extinctions have significantly exceeded the background
extinction rate.

3.  The extinction rate that is normal in the fossil record is
known as background extinction.
 Background extinction rates are constant within clades but
vary greatly between clades.
 Extinction events are relatively short (in terms of
geological time) periods with greatly increased extinction
rates.
 A mass extinction event must eliminate >60% of species in
a relatively short period of geological time with
widespread geographical and taxonomical impacts.

4.  Mass extinction events are important because of the
disruptive effect they have on the way biodiversity
develops.
 The principle subdivisions of geologic time are
identified by distinctive fossils and major faunal
breaks (extinction events) were used as the
boundaries.
 Mass extinction events may occur periodically.

5.  Ordovician-Silurian - 435 mya
 Late Devonian - 370 mya
 Permian-Triassic - 240mya
 End Triassic - 205 mya
 Cretaceous-Tertiary - 65 mya

7. Ordovician -
Silurian
Late Devonian Permian -
Triassic
End Triassic Cretaceous -
Tertiary
25% Families
50% Genera
85% Species
22% Families
57% Genera
82% Species
53%
Families
84% Genera
96% Species
22% Families
52% Genera
76% Species
16% Families
47% Genera
76% Species
including the
dinosaurs

8. ORDOVICIAN – SILURIAN EXTINCTION
• Also known as the Ordovician extinction
• Second-largest of the five major extinction events in
Earth's history in terms of percentage of genera
• Between about 447 Ma to 443 Ma
•Started at a major extinction, called Cambrian –
Ordovician extinction (488.3 +/- 1.7mya)lasted about
44.6 million years
•Ended with the Ordovician – Silurian event , about 443.7
+/- 1.5mya , it wiped 60% of marine genera

9. CAUSES:
• The immediate cause of extinction appears to
have been the movement of Gondwana into the
south polar region. This led to global cooling,
glaciation and consequent sea level fall.
• The falling sea level disrupted or eliminated
habitats along the continental shelves . Evidence for
the glaciations was found through deposits in
the Sahara Desert.
• A combination of lowering of sea level and
glacially driven cooling are likely driving agents for
the Ordovician mass extinction.

10. VICTIMS
• most complex multicellular organisms lived in the sea,
and around 100 marine families became extinct,
covering about 49% of faunal genera
•More than 60% of marine invertebrates died including
two-thirds of all brachiopod and bryozoans families.
•Brachiopods, bivalves, echinoderms, bryozoans
,cconodonts graptolites ,trilobites and corals were
particularly affected

11. •The end of the event occurred when melting glaciers
caused the sea level to rise and stabilize once more.
• The rebound of life's diversity with the sustained re-
flooding of continental shelves at the onset of
the Silurian saw increased biodiversity within the
surviving orders.
END OF THE EVENT

12. Fossil of a “tuning fork”
graptolite,Didymograptus

13. LATE DEVONIAN EXTINCTION
• 419.2 to 359 million years ago
• Extinction include certain events
I. Lower zilchov
II. Taghanic event
III.Kellwassar event
IV. Hangenberg event
• All event together eliminate 70 to 80% of animal species
LOWER ZILCHOV
•Occurred at the beginning of Ensian stage
407.6mya
•Extinction off graptolites and appearance of
goniatites

14. I. TAGHANIC EVENT
•Boundary between middle and upper Devonian
•Extinction of goniatites , coral , brachiopod
I. KELLWASSAR EVENT
• extinction of beloceratides and manticoceratids ,
goniatite group & many conodont species
•Most colonial corals , several group of trilobite , some
brachiopods also got extinct
I. HANGENBERG EVENT
•Extinction of phacopid trilobites, several group of
goniatites , coiled cephalopods etc

15. Affected the organisms such as ;
 Trilobites
 Brachiopods
 Corals
 Cephalopods
 Fishes
10 m long predator Dunkleosteus was one of the
biggest ever placoderm , group of armoured fish .
The entire group met its end in the Late Devonian
Extinction.
Corals(rugose and tabulate corals) suffered badly in
the Late Devonian mass extinction. Extensive reef
ecosystem collapsed.

16. Dunkleosteus Brachiopod from the Devonian of Ohio, USA

17. CAUSE OF EXTINCTION…..

18. CAUSES
• The sedimentological record shows that the late Devonian
was a time of environmental change
• Evidence exists of widespread anoxia in oceanic bottom
waters, the rate of carbon burial shot up
and benthic organisms were decimated, especially in the
tropics, and especially reef communities.
Bolide impact
•Bolide impacts can be dramatic triggers of mass extinctions.
•

19. •Impact craters, such as the Kellwasser-
aged Alamo and the Hangenberg-aged Woodleigh,
cannot generally be dated with sufficient precision to
link them to the event
•Although some minor features of meteoric impact
have been observed in places (iridium anomalies and
microspherules), these were probably caused by other
factors
•An asteroid impact was posited as the prime cause of
this faunal turnover,but no secure evidence of a
specific extraterrestrial impact has been identified in
this case.

20. PERMIAN – TRIASSIC EXTINCTION
•About 250 million years ago.
•Informally called the “Great Dying”.
•It was the most severe extinction.
•96% of all marine species were killed .
•70% of terrestrial vertebrate were killed .

21. CAUSES OF THE EXTINCTION EVENT
 Impact event
 Volcanism
 Methane hydrate gasification
 Anoxia
 Hydrogen sulfide emissions
 The supercontinent Pangaea
 Microbes
 Combination of causes

23.  Trilobites
 Brachiopods
 Corals
 Cephalopods
 Fusulinid Foraminifera
 Echinoderms
 Crinoids
 Blastoids
 Clams
 Ammonoid Cephalopods
 Terrestrial Reptiles
 Sea Scorpions, the
Eurypterids were probably
the largest Arthropods ever
to have lived . They
disappeared in the world’s
most devastating mass
extinction.
 The last remaining
Trilobites died out in the
mass extinction event.

24. SEA SCORPIONS, EURYPTERIDS Fusilinids - foraminifera - reef lagoon
area of the west texas permian sea.
Sessile filter feeders like crinoid

25. •The Triassic–Jurassic extinction event marks the boundary
between the Triassic and Jurassic periods
•201.3 million years ago
•In the seas, a whole class (conodonts) and 34% of marine genera
disappeared.
• On land, all pseudosuchians (non-dinosaurian archosaurs) other
than crocodylomorphs (Sphenosuchia and Crocodyliformes), some
remaining therapsids, and many of the large amphibians became
extinct.
• At least half of the species now known to have been living on
Earth at that time went extinct, allowing the dinosaurs to assume
the dominant roles in the Jurassic period.
• event happened in less than 10,000 years and occurred just
before Pangaea started to break apart
TRIASSIC–JURASSIC EXTINCTION

26. CAUSES OF THE EXTINCTION EVENT
•Gradual climate change, sea-level fluctuations or a pulse of oceanic
acidification] during the late Triassic reached a tipping point.
However, this does not explain the suddenness of the extinctions in
the marine realm
•Asteroid impact, but so far no impact crater of sufficient size has
been dated to coincide with the Triassic–Jurassic boundary.
•Massive volcanic eruptions, specifically the flood basalts of
the Central Atlantic Magmatic Province (CAMP), would
release carbon dioxide or sulfur dioxide and aerosols, which would
cause either intense global warming (from the former) or cooling
(from the latter).
• a critical CO2 greenhouse and a marine biocalcification crisis.

27. Affected by animals like;
 Mammal like Reptiles
 Amphibians
 Reef building creatures
 Cephalopods
Mammal like reptiles such as Thrinaxodon , which lived about 200
million years ago , thrived in the Early Triassic. But the next mass
extinction at the end of the Triassic resulted in the group’s demise.

29. CRETACEOUS–TERTIARY (K–T) EXTINCTION
•also known as the Cretaceous–Paleogene (K–Pg) extinction event
•a mass extinction of some three-quarters of plant and
animal species on Earth—including all non-avian dinosaurs
• 66 million years ago
•In the geologic record, the K–Pg event is marked by a thin layer
of sediment called the K–Pg boundary
•The boundary clay shows high levels of the metal iridium, which is
rare in the Earth's crust but abundant in asteroids.[5]

30. CAUSES OF THE EXTINCTION EVENT
K–Pg extinction was triggered by a massive comet or asteroid impact 66
million years ago
It was possibly accelerated by the creation of the Deccan Traps

31. VICTIMS
A wide range of species perished in the K–Pg extinction
The most well-known victims are the non-avian dinosaurs
the extinction also destroyed a plethora of other terrestrial
organisms, including but not limited to
certain mammals, pterosaurs, birds,[11] lizards,[12]insects,[13][14] and
plants
In the oceans, the K–Pg extinction killed off plesiosaurs and the
giant marine lizards (Mosasauridae) and devastated fish,[16] sharks,
mollusks (especially ammonites, which went extinct) and many
species of plankton

32. In the wake of the extinction, many groups underwent remarkable adaptive
radiations—a sudden and prolific divergence into new forms and species within
the disrupted and emptied ecological niches resulting from the event.
Mammals in particular diversified in the Paleogene,[18]producing new forms
such as horses, whales, bats, and primates. Birds,[19] fish[20] and perhaps
lizards[12] also radiated.
Species that depended on photosynthesis declined or became extinct as
atmospheric particles blocked sunlight and reduced the solar energy reaching
the Earth's surface. This plant extinction caused a major reshuffling of the
dominant plant groups
Omnivores, insectivores and carrion-eaters survived the extinction event,
perhaps because of the increased availability of their food sources.

35.  50% of all species on the planet will be either
endangered or extinct
 Habitat destruction
 Global Warming
 25% mammalian species
 15% bird species

37. Five major extinctions :
 The Ordovician- Silurian Extinction(440 my)
Reason – Glaciation . Affected the marine organisms
 Late Devonian Extinction (360 my)
Reason – Glaciation . Fish were extinct.
 Permian-Triassic Extinction(250my)
Reason –asteroid impact / volcanic eruption . Trilobites were
completely died off
 Triassic-Jurassic Extinction(200 my)
Reason – Lava eruption . Mammal like reptiles were extinct
 Cretaceous-Tertiary Extinction(66my)
Reason –Asteroid impact / volcanic eruption . Dinosaurs were
extinct

38.  Charles fletcher ; Physical geology ;The
science of Earth,2011
 www.nhmm.ac.uk/nature-
online/life/dinosaurs-other-extinct-
creatures/mass-extinctions/index.html