Sauropodomorphs

THE SAUROPODOMORPHA ("lizard-feet forms.")

were herbivorous, usually quadrupedal (four-footed)

dinosaurs. A clade within Saurischia, they were 

characterized by small heads, bulky bodies, and

long necks and tails. Sauropodomorphs have

often been split into two groups: prosauropods

and sauropods. Prosauropods lived from Late

Triassic to Early Jurassic times (225-180 million years ago) and

included beats such as the small Anchisaurus and one of the first

very large dinosaurs, Plateosaurus. By Middle Jurassic times (about

165 million years ago), sauropods had replaced prosauropods and

spread worldwide. They included the heaviest and longest land animals

ever, such as Diplodocus and Brachiosaurus. 

Brachiosaurus

Sauropods persisted to the 

end of the Cretaceous period (65 million years ago). Many of these

huge bulk and powerful tails, which they could use to lash out at

attackers. Sauropodomorphs were the most common large

herbivores until Late Jurassic times (about 145 million years ago),

and appear to have survived in both southern and

northern continents until the end of the Cretaceous period.

Theropods

AN ENORMOUSLY SUCCESSFUL SUBGROUP of the Saurischia,

 the bipedal (two-footed) theropods (“beast feet”) emerged 

230 million years ago in Late Triassic times; the oldest known

Example comes from South America.

Fossil Skeleton of Archaeopteryx

Theropods spanned the age of

most dinosaurs (230-65 million years ago) and beyond, and included

most of the known predatory dinosaurs. The typical theropod had smallish

arms with sharp teeth; an S-shaped neck; long, muscular hind limbs;

and clawed, usually four-toed feet. Many theropods may have been

warm-blooded; most were exclusively carnivorous. Theropods ranged

from Tyrannosaurus and Baryonyx. The group also included 

ostrich-like omnivorous and herbivores with toothless breaks,

such as Struthiomimus and Gallimimus. Birds are dinosaurs and evolved

from within a group of tetanuran theropods called maniraptorans.

Archaeopteryx, small and feathered, was the first known bird and lived

Alongside other Dinosaurs.

The Dinosaurs (Important Facts) {Part-14}

THE DINOSAURS WERE A LARGE GROUP of reptiles that were the dominant land vertebrates (animals with backbones) for most of the Mesozoic era (245-65 million years ago).

Dinosaurs

They appeared some 230 million years ago and were distinguished from other scaly, egg-laying reptiles by an important feature dinosaurs had an erect limb stance. This enabled them to keep their bodies well above the ground, unlike the sprawling and semi-sprawling stance of other reptiles. The head of the dinosaurs' femur (thigh-bone) fitted into a socket in its pelvis (hip-bone), producing efficient and mobile locomotion. Dinosaurs are categorized into two groups according to the structure of their pelvis: Saurischian (Lizard-hipped) and Ornithischian (Bird-hipped) dinosaurs.

Types of Dinosaurs

In the case of most Saurischians, the pubis (part of pelvis) jutted forward, while in Ornithischians it slanted back, parallel to the ischium (another part of the pelvis). Dinosaurs ranged in size from smaller than a domestic cat to the biggest land animals ever known. The Dinosauria were the most successful land vertebrates ever, and survived for 165 million years, until most became extinct 65 million years ago.

Dinosauria

Amphibians and Reptiles (Important Facts) {Part-13}

THE EARLIEST KNOWS AMPHIBIANS, such as Acanthostega and Ichthyostega, lived about 363 million years ago at the end of the Devonian period (409-363 million years ago).

Fossil Skull of Acanthostega

Model of Ichthyostega

Their limbs may have evolved from the muscular fins of lungfish-like creatures. These fish can use their fins to push themselves along the bottom of lakes and some can breathe at the water's surface. While amphibiains exist on land, they are dependent on a wet environment because their skin does not retain moisture and most and most species must retain to the water to lay their eggs.

Skeleton of Eryops

 Evolving from amphibians, reptiles first appeared during the Carboniferous period (363-290 million years ago):  Westlothiana  a possible early reptile, lived on land 338 million years ago. The development of the amniotic egg, with an embryo enclosed in its own wet environment (the amnion) and protected by a waterproof shell, freed reptiles from the amphibian's dependence on a wet habitat. A scary skin protected the reptile from desiccation on land and enabled it to exploit ways of life closed to its amphibian ancestors. Reptiles include the dinosaurs, which came to dominate life on land during the Mesozoic era (245-65 million years ago).

Early signs of Life (Important Facts) {Part-12}

FOR ALMOST A THOUSAND MILLION YEARS after its formation, there was no known life on Earth. The first simple, sea-dwelling organic structures appeared about 3,500 million years ago; they may have formed when certain chemical molecules joined together.

Stromatolitic Limestone

Prokaryotes, single-celled micro-organisms such as blue-green algae, were able to photosynthesize , and thus produce oxygen had built up in the earth's atmosphere to allow multicellular organisms to proliferate in the Precambrian seas (before 570 million years ago).

Fossilized Jawless Fish

Soft-bodied jellyfish, corals and seaworms flourished about 700 million years ago. Trilobites, the first animals with hard body frames, developed during the Cambrian period (570-519 million years ago).

Fossilized Trilobite

However, it was not until the beginning of the Devonian period (409-363 million years ago) that early land plants, such as Asteroxylon, formed a water-retaining cuticle, which ended their dependence on an amphibians crawled onto the land, although they probably still returned to the water to lay their soft eggs.
By the time the first reptiles and synapsids appeared late in the Carboniferous, animals with backbones ad become fully independent of water.

Quaternary Period (Important Facts) {Part-11}

THE QUATERNARY PERIOD (1.6 million years ago- present) forms the second part of the Cenozoic era ( 65 million years ago- present), it has been characterized by alternating cold (glacial) and warm (interglacial) periods. During cold periods, ice sheets and glaciers have formed repeatedly on northern and southern continents.

Quaternary Period

The cold environments in North America and Eurasia, and to a lesser extent in southern South America and parts of Australia, have caused the migration of many life forms towards the Equator.

Examples of Tertiary Plant Groups:-

     Birch (Betula lenta)

Sweetgum (Liquidambar styraciflua)

Only the specialized ice age mammals such as Mammuthus & Caelodonia, with their thick wools and fat insulation, were suited to life in very cold climates.

Examples of Tertiary Animal groups:-

Procoptodon

Diprotodon

Deinotherium

Australopithecus

Humans developed throughout and Pleistocene period (1.6 million- 10,000 years ago) in Africa and migrated northward into Europe and Asia, Modern humans, Homo sapiens, lived on the cold European continent 30,000 years ago and hunted other mammals. 

The end of the last ice age and the climatic changes that occurred about 10,000 years ago brought extinction to many Pleistocene mammals, but enabled humans to flourish.

Tertiary Period (Important Facts) {Part-10}

FOLLOWING THE DEMISE OF THE DINOSAURS at the end of the Cretaceous period, the Tertiary period ( 65-1.6 million years ago), which formed the first part of the Cenozoic era (65 million years ago-present), was characterized by a huge expansion of mammal life.

Tertiary Period

Placental mammals nourish and maintain the young in the mother's uterus only a few groups of placental mammals existed during Cretaceous times, compared with several tens of groups during the Tertiary period. One of these tens included the early human Ardipithecus, which appeared in Africa.

Examples of Tertiary Plant Groups:-

A present-day oak
(Quercus palustris)

A present-day Birch
(Betula Grossa)

By the beginning of the Tertiary period, the continents had almost reached their present position. The Tethys Sea, which had separated the northern continents from Africa and India, began to close up, forming the Mediterranean Sea and allowing the migration of terrestrial animals between Africa and western Europe. 

Examples of Tertiary Animal groups:-

India's collision with Asia led to the formation of the Himalayas. During the middle part of the Tertiary period, the forest-dwelling and browsing mammals were replaced by mammals such as the horses, better suited to grazing the open savannahs that began to dominate. Repeated cool periods throughout the Tertiary period established the Antarctica as an icy island continent.

Hyaenodon

 

 

 

 

Mammut

Cretaceous Period (Important Facts) {Part-9}

THE MESOZOIC ERA ENDED WITH the Cretaceous period, which lasted from 146 to 65 million years ago. During this period, Gondwana and Laurasia were breaking up into smaller land-mass that more closely resembled the modern continents.

Cretaceous Period

The climate remained mild and moist but the seasons became more marked. Flowering plants including deciduous trees replaced many cycads, seed ferns and conifers.

Examples of Cretaceous Plant Groups:-

A present-day Conifer
(Pinus Muricata)

A present-day Deciduous tree
(Magnolia sp.)

Animal species became more varied, with the evolution of new mammals, insects, fish, crustaceans and turtles. Dinosaurs evolved into a wide variety of species during Cretaceous times; more than half of all known dinosaurs - including Iguanodon, Deinonychus, Tyrannosaurus and Hypsilophodon - lived during this period. At the end of the cretaceous period, however, most dinosaurs became extinct. The reason for this mass extinction is unknown but it is thought to have been caused by climatic changes due to either a catastrophic meteor impact with the Earth or extensive volcanic eruptions.

Saltasaurus
Length: 40 ft

Torosaurus
Length: 25 ft

Hypsilophodon
Length: 4 ft 6 in - 7 ft 6 in

Tyrannosaurus (T-Rex) - King of all Dinosaurs
Length: 40 ft

DeinonychusLength: 8-11 ft

Iguanodon
Length: 30 ft

Jurassic Period (Important Facts) {Part-8}

THE JURASSIC PERIOD, the middle part of the Mesozoic era, lasted from 199 to 145 million years ago. During Jurassic times, the land-mass of Pangaea broke up into the continents of Gondwana and Laurasia, and sea-levels rose, flooding areas of lower land.

Jurassic Period

The Jurassic Period climate was warm and moist. Plants such as ginkgos, horsetails and conifers thrived, and giant redwood trees appeared, as did the first flowering plants.
The abundance of plant food coincided with the proliferation of herbivorous (plant-eating) dinosaurs, such as the Large Sauropods (e.g., Diplodocus) and Stegosaurs (e.g., Stegosaurus).

Examples of Jurassic Plant Groups:-

A present-day Fern
(Dicksonia antarctica)

A present-day Horsetail
(Equisetum arvense)

A present-day Conifer
(Taxus baccata)

Carnivorous (flesh-eating) dinosaurs, such as Compsognathus and Allosaurus, also flourished by hunting the many animals that existed - among them other dinosaurs.

Further Jurassic animals included shrew-like mammals, and pterosaurs (flying reptiles), as well as plesiosaurs and ichthyosaurs (both marine reptiles).

Examples of Jurassic Dinosaurs:-

Diplodocus
Length: 88 ft

Camptosaurus
Length: 16-23 ft

Dryosaurus
Length: 10-13 ft

Allosaurus
Length: 36 ft

Scelidosaurus
Length: 13 ft

Stegosaurus
Length: 30 ft

Triassic Period (Important Facts) {Part-7}

THE TRIASSIC PERIOD (250-200 million years ago) marked the beginning of what is known as the Age of the Dinosaurs (the Mesozoic era).

Triassic Period

During this period, the present day continents were massed together, forming one huge continent known as Pangaea. This land-mass experienced extremes of climate, with lush green areas around the coast or by lakes and rivers, and arid deserts in the interior. The only forms of plant life were non-flowering plants, such as conifers, ferns, cycads and ginkgos; flowering plants had not yet evolved. The principal forms of animal life included diverse, often gigantic, amphibians, rhynchosaurs ("beaked lizards"), and primitive crocodilians.

Examples of Triassic Plant Groups:-

A present-day Cycad
(Cycas revoluta)

A present-day Ginkgo
(Ginkgo biloba)

A present-day Conifer
(Araucaria araucana)

Examples of Triassic Dinosaurs:-

Melanorosaurus
Length: 40 ft

Mussaurus
Length: 6 ft 6 in-10 ft

Herrerasaurus
Length: 10 ft

Pisanosaurus
Length: 3 ft

Plateosaurus
Length: 26 ft

Technosaurus
Length: 3 ft 3 in

Coelophysis
length: 10 ft

Staurikosaurus
Length: 6 ft 6 in

Dinosaurs first appeared about 230 million years ago, at the beginning of the late triassic period. Among the earliest dinosaurs were the carnivorous (flesh-eating) Herrerasaurids, such as Herrerasaurus and Staurikosaurus. Early herbivorous (plant-eating) dinosaurs first appeared in Late Triassic times and included Plateosaurus and Technosaurus. By the end of the Triassic Period, dinosaurs dominated Pangaea, possibly contributing to the extinction of many other reptiles.