The document summarizes the Mesozoic Era from 251 to 65 million years ago, known as the Age of Reptiles. It describes the rise and fall of dinosaurs and other marine reptiles that dominated during this time period. Key events included the breakup of Pangaea, the emergence of dinosaurs and flying reptiles, and the dominance of various marine reptiles like ichthyosaurs, mosasaurs, and plesiosaurs. The document also discusses prominent dinosaur genera that lived during the Triassic, Jurassic, and Cretaceous periods, such as Plateosaurus, Allosaurus, Tyrannosaurus Rex, and Velociraptor. It concludes by outlining the asteroid

1. Rise and fall of dinosaurs
including Mesozoic Marine Reptiles
AKASH.A
22MAB04
1st M.Sc., Marine Biology

2. Mesozoic Era
 The time period is 251 million to 65 million years ago.
 Mesozoic literally means “middle life” deriving from the Greek.
 It is also known as the age of reptiles or the age of dinosaurs.
 Its subdivided into 3 periods:
i. Triassic period
ii. Jurassic period
iii. Cretaceous period 2

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4. Mesozoic Reptiles
 Turtles
 Crocodiles / Alligators
 Lizards
 Ichthyosaurs
 Pterosaurs
 Dinosaurs
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5. The Triassic Period
 The first period of the Mesozoic Era is known as the Triassic
Period.
 This period is 251 million to 199.6 million years ago.
 At the beginning of the Triassic, virtually all the major
landmasses of the world were collected into the
supercontinent of Pangea.
 Climate is warm and dry.
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6. Marine Reptiles
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Ichthyosaurus
Nothosaurus
Placodonts

7. Ichthyosaurs
 Ichthyosaurs had a very wide geographic distribution, and their fossil remains span
almost the entire Mesozoic Era.
 It is most highly specialized aquatic reptiles, but ichthyosaurs were not dinosaurs.
 3 meters (10 feet) long and was probably able to move through the water at high
speeds.
 The body was streamlined; no distinct neck was present, and the head blended
smoothly into the body.
 The limbs were modified into paddle like appendages used to steer the animal.
 It propelled itself by using a well-developed fishlike tail and by undulating the body.
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8. Nothosaurs
 251 million to 200 million years ago
 Nothosaurus was characterized by a slender body, long neck and tail, and
long limbs. Although the animal was aquatic, the limbs were less
specialized for swimming.
 The skull was long and flat with large openings.
 Numerous pointed teeth were present along the margins of the jaws.
 Nothosaurus moved through the water by undulating its body and by
swimming with its limbs.
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9. Terrestial Reptiles
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Lizards
Turtles
Rhynchocephalians crocodilians

10. Plateosaurs
 Lived during the Late Triassic period, around 214 to
204 million years ago.
 Plateosaurus was a bipedal herbivore with a small skull on
a long flexible neck, sharp but plump plant-crushing teeth,
powerful hind limbs, short but muscular arms and grasping
hands with large claws on three fingers, possibly used for
defence and feeding.
 Fully grown individuals were between 4.8 and 10 meters
(16 and 33 ft) long and weighed between 600 and 4,000
kilograms (1,300 and 8,800 lb).
 Commonly, the animals lived for at least 12 to 20 years 10
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11. Flying Reptiles
Icarosaurs
 Some of the earliest lizards may have been the
first vertebrates to take to the air.
 Gliding lizards, such as the small Late
Triassic Icarosaurus, are thought to have
developed an airfoil from skin stretched between
extended ribs, which would have allowed short
glides similar to those made by present-day
flying squirrels.
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12. Sharovipteryx
 Sharovipteryx ("Sharov's wing", "foot wing"), is
a genus of early gliding reptiles containing the
single species Sharovipteryx mirabilis.
 It is known from a single fossil and is the only
glider with a membrane surrounding the pelvis
instead of the pectoral girdle.
 the middle-late Triassic period (about 225
million years ago).
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13. The Jurassic Period
 The Jurassic period is 199.6 to 145.5 million years ago.
 During this period the supercontinent Pangea split apart,
allowing for the eventual development of what are now the
central Atlantic Ocean and the Gulf of Mexico.
 During the Early Jurassic, animals and plants living both on
land and in the seas recovered from one of the largest mass
extinctions in Earth history.
 On land, dinosaurs and flying pterosaurs dominated the
ecosystems.
 Plants were dominated by the gymnosperms. 13
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14. Allosaurus
 Large carnivorous dinosaurs that lived from 150 million to 144 million years ago during
the Late Jurassic Period.
 Allosaurus weighed two tons and grew to 10.5 m(35 feet) in length, although fossils
indicate that some individuals could have reached 12 m.
 Half the body length consisted of a well-developed tail.
 The skull was large and had sizable laterally compressed teeth, which were sharp and
recurved.
 Speed: 30 – 55 km/h.
 age 15 and lived up to 28 years old.
 Allosaurus likely preyed upon ornithischian dinosaurs, small sauropod dinosaurs.
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16. Cretosaurus
 Ceratosaurus, large carnivorous dinosaurs whose fossils date from the
Late Jurassic Period (161 million to 146 million years ago) in North
America and Africa.
 Ceratosaurus lived at about the same time as Allosaurus and was similar in
many general respects to that dinosaur, but the two were not closely related.
 It weighed up to two tons, this dinosaur was slightly smaller
than Allosaurus and bore a distinctive “horn” on its snout and a row of bony
plates down the middle of its back.
 Ceratosaurus also differed from allosaurs in that it retained remnants of a
fourth clawed finger, unlike the three typical of most theropods. 16

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18. Tyrannosaurus
 Tyrannosaurus rex is the 'one true king of the dinosaurs' .
 The species Tyrannosaurus rex , often called T. rex or colloquially T-Rex, is one of
the best represented theropods.
 It was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative
to its large and powerful hind limbs, the forelimbs of Tyrannosaurus were short but
unusually powerful for their size.
 Which were 15 or more meters (50 feet) long, more than 5 meters (16 to 18 feet) tall,
and weighed 6 tons or more.
 T-Rex is smarter and built to kill.
 The Tyrannosaurus rex had about 60 teeth. The largest T. rex tooth found was 12
inches long. Its jaw had to be about 4 feet long to fit all 60 teeth. 18

19. Cont..
 T. rex would have
weighed between 5,000 and
7,000 kilograms (11,000 to
15,500 pounds) with skin and
flesh on its huge bones. That's
about as much as the largest
African elephant.
 Life span: 30 years, Speed:
27Km/h
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20. Archaeopteryx
 Time period is 163.5 million to 145 million years ago.
 Archaeopteryx is known to have evolved from small carnivorous dinosaurs,
as it retains many features such as teeth and a long tail.
 It had well-developed wings, and the structure and arrangement of its wing
feathers-similar to that of most living birds-indicate that it could fly.
 The three fingers bore claws and moved independently, unlike the fused
fingers of living birds.
 evidence suggests that the animal’s powered flight differed from that of most
modern birds.
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22. The Cretaceous Period
 The Cretaceous began 145.5 million to ended 65.5 million years ago.
 The name Cretaceous is derived from creta, Latin for “chalk”, and was first proposed
by J.B.J. Omalius d’Halloy in 1822.
 That Period began with Earth’s land assembled essentially into two continents, Laurasia in
the north and Gondwana in the south.
 Dinosaurs were the dominant group of land animals, especially “duck-billed” dinosaurs
(hadrosaurs), such as Shantungosaurus, and horned forms, such as Triceratops.
 Giant marine reptiles such as ichthyosaurs, mosasaurs, and plesiosaurs were common in
the seas, and flying reptiles (pterosaurs) dominated the sky.
 Flowering plants (angiosperms) arose close to the beginning of the Cretaceous and became
more abundant as the period progressed. 22

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24. Mosasaurs
 mosasaur, extinct group of aquatic lizards that attained a high degree of adaptation to
the marine environment and were distributed worldwide during the Cretaceous
Period (145.5 million to 66 million years ago).
 The longest mosasaurs are estimated to have been 17 meters (about 56 feet) in length.
 Mosasaurs had a snake like body with a large skull and a long snout.
 Their limbs were modified into paddles having shorter limb bones and more numerous
finger and toe bones than those of their ancestors.
 The tail region of the body was long, and its end was slightly downcurved in a manner
similar to that of the early ichthyosaurs.
 Weight : 14000 Kg
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26. Plesiosaur
 Plesiosaur, any of a group of long-necked marine reptiles found as fossils from the
late Triassic Period into the late Cretaceous Period (215 million to 66 million years
ago).
 Early plesiosaur, was about 4.5 meters (15 feet) long, with a broad, flat body and a
relatively short tail.
 It swam by flapping its fins in the water, much as sea lions do today, in a modified
style of underwater “flight.”
 The nostrils were located far back on the head near the eyes.
 The neck was long and flexible, and the animal may have fed by swinging its head
from side to side through schools of fish, capturing prey by using the long sharp
teeth present in the jaws.
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28. Velociraptor
 During the Late Cretaceous Period 99 million to 65 million years ago.
 length of only 1.8 meters (6 feet) and perhaps weighing no more than 45 kg
(100 pounds).
 Large claw on each foot, as well as ossified tendon reinforcements in the tail
that enabled them to maintain balance while striking and slashing
at prey with one foot upraised.
 Velociraptor appears to have been a swift, agile predator of small herbivores.
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30. The Fall of Dinosaurs
 What happened on that day, when the Cretaceous ended with a bang and the
dinosaurs’ death warrant was signed.
 The asteroid theory of the dinosaurs’ demise was first suggested in 1980. the
identification of the Chicxulub Crater in the Gulf of Mexico.
 A comet of asteroid – we aren’t sure which – collided with the Earth, hitting what is
now the Yucatan Peninsula of Mexico.
 It was about 6 miles (10 Km) wide, probably moving at a speed of around 64,000
miles per hour.
 It hit with the force of over 100 trillion tons of TNT.
 It plowed some 25 miles (40Km) through the crust and into the mantle, leaving a
crater that was over 100 miles (160 Km) wide.
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31. Cont…
 Creating a crater more than 115 miles across and instantly vaporizing thousands of cubic miles
of rock.
 Coastal regions, the impact triggered tsunamis as high at 1,000 feet (305 metres) as well as
earthquakes more severe than anything experienced by modern humans.
 Red-hot debris began raining down, covering the ground with deadly ash and dirt.
 Then ash, smoke, and debris in the atmosphere spread around the planet, turning daylight into a
constant twilight that lasted for months and possibly years. Temperatures dropped, and food
became increasingly scarce.
 It is assumed by many that the dinosaurs went extinct very quickly following the asteroid strike.
 Times were tough for the dinosaurs: their world was starting to cool, and they faced significant
competition for dwindling food supplies.
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References
The Mesozoic era: age of dinosaurs/edited by John P. Rafferty, p.cm.- (The geologic
history of Earth) “In association with Britannica Educational Publishing, Rosen
Educational Services.” ISBN 978-1-61530193-5
Steve Brusatte, (A New History of a Lost World) The RISE and FALL of the
DINOSAURS, “William Morrow An Imprint of Harper Collins Publishers”.
HECTOR E. RIVERA-SYLVA, et.al., Dinosaurs and other Reptiles from the Mesozoic
of Mexico,“Indianan University Press”, ISBN 978-0-253-01183-1.
https://www.britannica.com/science/Mesozoic-Era
https://www.livescience.com/38596-mesozoic-era.html
Video links:
3. https://youtu.be/kpLY0YwMACE
2. https://youtu.be/q4nSXEgYQiM
1. https://youtu.be/UQQeSnrVSMw

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