The Triassic Period - 251-206 MY -

The Triassic Period
- 251 to 205 MY -
Tectonics and climate
Life in the Oceans
Jarðsaga 1
- Saga Lífs og Lands –
-Ólafur Ingólfsson
The Triassic Period
The first period of the Mesozoic Era is
the Triassic Period, which lasted from
251 to 205 million years ago. The name
Triassic comes from Germany where it
was originally named the Trias in 1834 by
Friedrich August Von Alberti (17951878) because it is represented by a
three-part division of rock types in
Germany.
Triassic tectonic development
In many ways, the Triassic was a time of transition.
Pangea was fully assembled and remained so through the
Triassic, affecting global climate and ocean circulation...
Early Triassic
climate
The Triassic was a greenhouse world, with no evidence of ice at the
poles. The interior of Pangea was hot and dry, and warm, temperate
climates extended to the Poles.
Pangea starts breaking up towards
the end of the Triassic
Towards the end of the Triassic, a rift develops between
Gondwana and Laurasia
The first chapter in the formation of
the Atlantic Ocean...
Late Triassic climate
Global climate was warm during the Late Triassic. There was no ice at
either North or South Poles. More pronounced climate zonation than
during the Early Triassic, less extension of arid areas. Warm temperate
conditions extended towards the poles.
Space for new life forms to develop
The Triassic followed the
largest extinction event
in the history of life,
when 75-90% of all
marine species vanished
at the end of the
Permian. This provided an
opportunity for new
lifeforms...
Triassic marine deposits
rather rare
Sea level was fairly constant
through the Triassic; lack of
transgressions makes marine
deposits rather rare in the
geological record.
Recovery from the Pemian extinction was slow
for many groups. It has been suggested that
increased salinity of shallow sea areas caused
problems for many marine organisms.
Slow start in the seas
The survivors of the Permian mass extinction:
- Geographically widespread
- From temperate areas (not tropical)
- Opportunistic ecologic generalists (meaning
they can live in many ways/settings)
- Tend to be mobile (not sessile)
These features suggest the survivors were
those who were suited to large changes in the
physical environment...not competitively
superior groups.
Pelagic life
Planktonic organisms are at the base of the food chain in
the Oceans, but most kinds leave little or no fossil record.
In Triassic times, dinoflagellates (skorusvipungar) were
one very important group of plankton.
Pherhaps the slow early Triassic recovery of marine life
was caused by a mass-extinction crisis of pelagic life?
Dinoflagellates are microscopic, unicellular, often
photosynthetic protists, commonly regarded as "algae"
(Division Dinoflagellata). They form a significant part
of primary planktonic production in oceans and lakes.
A gradual diversification of marine life
through the Triassic
Early Triassic: Bivalves (samlokur), ammonoids, a few
brachiopods (armfætlur) – other groups very rare.
Diversity is low. Stromatolites (strýtuþörungar) briefly
return – can live where grazing animals are excluded.
Middle Triassic:
Gastropods (sniglar) radiate. Echinoids (íguldýr) become
more common First appearance of scleractinians (steinkórallar) – modern reef-building corals. Marine conditions
are returning to normal from high salinity conditions.
Late Triassic:
Molluscs, echinoids, bony fish, and large marine reptiles
diversify. By the end of the Triassic, the modern marine
fauna is taking off.
Modern molluscs originate during Triassic
Bivalves and gastropods re-expanded
to become more diverse than in
Paleozoic. They filled many of the
niches previously occupied by the
brachiopods.
Molluscs are a
very diverse
groups of animals.
They first
evolved in the
Cambrian. There
are about 60,000
living species, and
at least 35,000
known fossil
species. Two of
the most important groups are
bivalves and
cephalopods
Triassic ammonides expanded
rapidly
The ammonides just barely escaped extinction in the Permian
mass-extinction. One genera,
the Ophiceras gave rise to an
enormous Triassic expansion.
Adaptive radiation of ammonoids from 2 to 100 genera.
Belemnides (álfasmokkar) also had a
great success
The belemnites had a straight, chambered
shell, similar to that of the nautiloids. The
strong, massive, projectile-like calcareous
shell, called the rostrum, is what usually is
found fossilised. The hard-parts were internal
in the living animal.
The belemnites are known from the late Carboniferous
until the latest Cretaceous. They were marine animals, who
developed strongly during the Triassic. They were very
abundant during the Jurassic and Cretaceous periods.
The modern
reef builders
stem from the
Triassic
Modern reef-building corals
appeared in mid-Triassic
times (Hexacorals or
scleractinian corals –
sexukóralar, steinkóralar).
They are probably not closely related to the extinct tabulate or rugose
corals (pípukóralar, hrukkukóralar) , but arose independently from a sea
anemone (sæfífill) ancestor.
Bony-fishes continue to develop
Paleozoic ray-finned fishes gave rise to forms that were
successful in early Mesozoic times, but were still primitive compared to most modern-day fishes. They had
partly cartillageous skeletons, primitive jaws and
assymmetrical tails.
Cleithrolepsis minor, a Triassic
bony-fish from South Africa
Lissodus africanus, another
Triassic fish from South Africa
The sharks
Sharks were numerous in
the early Mesozoic. Most
lived in near-shore or
freshwater habitats.
Helicoprion, 2-3 m. Carbon-Triassic shark, probably lived off shellfish.
Marine reptiles
Reptiles increasingly took to the sea during the Triassic.
The placodonts (broteðlur, 1-3
m) were blunt-toothed shell
crushers, with a broad,
armoured body that made
them look like large turtles.
Placodonts evolved during 35 MY. They were never fully adapted to the
open sea, but lived in the shallow coastal waters of the Tethys Sea.
Others tried to have the
best of both worlds...
The characteristic long neck of a Triassic protorosaur
(frumeðla) reached its extreme in Tanystropheus - its
neck was longer than body and tail combined, but with
only 10 neck vertebrae. The length of the neck suggested
that it may have lived in water, but there are no obvious
water adaptations. It may have lived on the seashore and
eaten shellfish or fish. Length: 6 m; weight: 300 kg
The Nothosaurs (slóðeðlur)
The Nothosaurs were 3-4 m long aquatic reptiles with a
long neck, a long low skull with sharp teeth and a long,
narrow tail. Its limbs were paddle-shaped. Nothosaurus
probably ate fish and shellfish.
The Plesiosaurs (svaneðlur)
The placodonts (broteðlur) and and the nothosaurs
(slóðeðlur), which were probably not completely aquatic, did
not survive the Triassic Period.
Their
descendants, the
Plesiosaurs,
developed to a
major group of
predatory marine
reptiles.
The plesiosaurs, which appeared in the
mid-Triassic, played an important role
through the Mesozoic
The Plesiosaurs - svaneðlur
Plesiosaurs were an important Mesozoic group of
marine reptiles.They were very well adapted for
life in the oceans. One group of plesiosaurs, the
elasmosaurs, had short tails and long necks.
The longest neck in the Ocean
The large Triassic elasmosaur (svaneðla -Thalassomedon
hanningtoni) was about 14 m long.
The “Head-on-tail” plesiosaur
It is well known in the history of paleontology that Edward
Cope of Philadelphia, who first described the E. Platyurus,
initially reconstructed the skeleton with the head on the
wrong end, that is, on the end of the tail.
His error was pointed out
by Othniel C. Marsh, thus
precipitating a life-long
feud, and a mortified Cope
attempted to buy up the
plates with the erroneous
reconstruction and replace
them with correct versions.
Ancestors of
Plesiosaurs (?)
Paleontologists are uncertain what the ancestors of the
first plesiosaurs looked like but it is probable that they
came from primitive aquatic reptiles found in China
(Keichousaurus hui). In these animals, the limbs were
probably used as paddles to some extent, but could also
still move the animal on land. The long neck and small
head are also early plesiosaur traits.
A complete Plesiosaur skeleton
The first nearly complete plesiosaur was discovered
in the Jurassic rocks of Lyme Regis, England in the
winter of 1820-21. The name Plesiosaurus means
"near-reptile", a reference to the view of the time
that plesiosaurs were closer to reptiles than were
the more fish-like ichthyosaurs.
How did they swim?
The plesiosaur limbs were very large and modified into
well developed, paddles which were the main means of
propulsion. Recent studies the limbs were 'flapped' up
and down much like the wings of a bird or the paddles of
a turtle. The plesiosaur, in effect, 'flew' through the
water like a modern penguin.
How did they reproduce?
There is still some controversy about if they laid eggs or
not, but the evidence seems to point toward plesiosaurs
giving live birth like ichthyosaurs. It is hard to imagine a
14 m plesiosaur struggling up on a beach to lay eggs like a
sea turtle. Besides having limbs that were unsuitable for
travel on land, there are several good reasons (such as
over-heating, and not being able to breathe) why egg
laying would not be possible for plesiosaurs...
What did they eat?
Plesiosaurs ate fish, ammonites and other invertebrates many specimens have been discovered with stomach stones
in their abdomens.
Gastrolites - magasteinar
For digestion and buyoancy
The Ichthyosaurs
The most fish-like reptiles of the Mesozoic seas
were the ichthyosaurs – fiskeðlur. Superficially
the ichthyosaurs bear a close resemblance to
modern dolphins (höfrungur = sjávarspendýr) .
Development of the Ichthyosaurs
Ichthyosaur =
fiskeðla
The most obvious
transformation
for aquatic life is
the one from feet
to flippers.
What were the ichthyosaurs like?
Ichthyosaurs were
stream-lined in
form, and ranged in
size from 4-23 m.
They had sharp teeth in long jaws, and big eyes. They
had four crescent-shaped fins, a stabilizing dorsal fin,
and a fish-like tail with two lobes. They breathed air
with lungs through nostrils which were close to the eyes
near the top of the snout.
They gave birth to life offsprings
A remarkable fossil from Posidonienschiefer, Germany
Numerous fossils
Fossil remains of ichthyosaurs have been widely found in North
and South America, China, Australia and Europe.
They had a
varied diet...
Ichthyosaurs probably
specialized on ammonites
amd belemnites, but
were probably pretty
opportunistic when it
came to food...
The preserved stomach contents of a 110 million- yearold fossilized ichthyosaur revealed that they ate
ammonites, belemnites, fish and turtles. Even the
remains of a small bird, whose corpse the beast
probably swallowed, have been found in their stomach.
...and could move long distances in
search of food
The ichthyosaurs were adapted to
swimming long distances, and deep
diving. Perhaps the best evidence for
the deep-diving habits of later
ichthyosaurs is their remarkably large
eyes, up to 23 centimeters across in
the case of Ophthalmosaurus. Relative
to body size, that fish-shaped
ichthyosaur had the biggest eyes of
any animal ever known.
Sometimes paleontologists work with
intresting materials...
British scientists discovered
the world's oldest fossilized
vomit, believed to have come
from a large marine reptile 160
million years ago. The vomit
contains the remains of dozens
of belemnites, eaten in great
numbers by ichthyosaurs.
National Geographic News, 12th of February 2002:
"We believe that this is the first time the existence of
fossil vomit on a grand scale has been proven beyond
reasonable doubt."
Enormous
Ichthyosaurs
The Late Triassic
produced some enormous
Ichthyosaurs, the
largest of which was the
Shonisurus (15-23 m). It
has been described from
Nevada, USA, and
British Columbia, Canada
The development of
terrestrial life during
the Triassic Period
250-205 MY
Jarðsaga 1
- Saga Lífs og Lands –
Ólafur Ingólfsson
Triassic critical for terrestrial life
The Triassic Period was critical for Terrestrial
life because all of the living dominant groups of
tetrapods evolved by its end. These include
• TURTLES
(boleðlur) and their descendants, the
DINOSAURS, PTEROSAURS (flugeðlur) and BIRDS
• THECODONTS
• MAMMALS
• CROCODILES
• LIZARDS (incl. snakes)
Development of plants
Unlike terrestrial animals, land plants
do not appear to have undergone a
dramatic mass extinction by the end
of the Permian Period.
Leptocycas was a cycad,
a primitive seed plant
from the late Triassic
period. It was a palmlike tree with a long,
woody trunk and tough
leaves. It lived in warm
climates. This tree was
about 1.5 m tall.
Early species of conifers dominated
the early Triassic terrain. Cycads
(köngulpálmar), with tough, palm-like
leaves and a woody trunk, were
abundant in the Triassic. Lycopods
(jafnar) and sphenopsids (elftingar),
mosses, ferns (burknar), tree ferns
and ginkgophytes (musteristré) were
also around...
Triassic development of plants...
• The great coal swamp lycopods, sphenopsids, and
tree-ferns, which reproduced by spores and hence
required moist habitats, didn't do too well in the dry
Triassic climate.
• Vegetation became increasingly dominated by
evergreen trees (conifers and other gymnosperms).
• In spite of the single global landmass, Triassic
terrestrial biotas were quite provincial, probably due
to climatic rather than geographical factors: monsoon
and extreme seasonality caused by symmetrical
placement of Pangea over the equator.
Biotas are divided into a northern, Pangean, and a
southern, Gondwanan, province,
Gondwana vegetation
The Permian Glossopteris flora
disappears, to be replaced by
the seed-fern Dicrodium.
Dicrodium occurs in all assemblages, from heath and broad-
leafed forest to dry woodlands. Often it is the only species
present. Other seed-ferns, conifers, cycads and ginkgos
also occur in Gondwanan floras.
Laurasia development of plants
The Laurasian Flora is made up of; a mixture of primitive
conifers, along with cycads, ginkgos ground and tree ferns,
and sphenopsids (elftingar). The conifers and ginkgos seem
to have been medium-sized to large trees that formed
diffuse canopies.
Development of plants...
Horsetails (elftingar) were an important source of
nutrition for plant-eating dinosaurs. These primitive
vascular plants were fast-growing and resilient. Their
underground stems meant that a hungry dinosaur could
eat the plant without killing it, since the plant would
regrow from the rhizome (jarðstöngull).
Triassic landscape
“Triassic Landscape” by Caren Carr; The Sam Noble Oklahoma
Museum of Natural History
Triassic insect development
Hymnoptera – bees, wasps,
ants
Pasmida – walking sticks
“True Flies”
The Permian extinction wiped out nine orders (ættbálkur) of insects.
However, surviving orders such as Neuroptera (netvængjur),
Mecoptera (sporðflugur), Diptera (tvívængjur), and Coleoptera
(bjöllur) underwent further adaptive radiation throughout the
Mesozoicum, establishing many families extant in modern times. Most
insect groups were well formed by the Cretaceous and remain largely
unchanged in appearance during modern times.
Góð vefsíða með upplýsingum um hvenær mismunandi ætbbálkar skordýra komu fram:
http://www.fossilmall.com/Science/Taxonomy/Insects/subphylum_insecta_fossils.htm
Spiders develop as predators
The spinning organs of spiders developed
significantly during the Mesozoic. Spinning of
silk and weaving of net became much more
advanced. Triassic spiders also developed a
range of prey catching strategies. Many were
ambush hunters, with good eyesight.
Triassic reptile development
The Mesozoic began with several major reptile groups
evolving. These groups were named from the number of
holes behind the eyes on each side of the skull - holes
that left room for jaw muscles to contract.
ANAPSIDS (no holes) include tortoises and turtles.
SYNAPSIDS (single hole) made up a group of mammallike reptiles (the Therapsids - þelskriðdýrin) that ruled
for 70 million years and gave rise to true mammals
before becoming extinct.
The largest group was the DIAPSIDS (2 openings) that
contained 2 subgroups (snakes and lizards, and
archosaurs - frumeðlur).
Turtles evolved during the Triassic
Turtles first appeared on
Earth by the end of the
Triassic Period. Proganochelys
quenstedi was the first known
turtle. It had a fully developed shell and a turtle-like
skull and beak. However,
Proganochelys had several
primitive features not found
in turtles today. These traits
included small teeth in its
mouth and a simple ear. This
early turtle also was unable to
withdraw its head or legs into
its shell.
The turtle shell is a remarkable evolutionary novelty, a
development of the vertebrate skeleton unique among
vertebrates. No other vertebrate has a casing made
almost exclusively of bone.
Triassic therapsid
(þelskriðdýr)
evolution
Diagram showing the
relationships between the
various mammal-like reptiles,
the Therapsids. They did not
survive beyond the end of
the Triassic period, but one
group, the Cynodontia
(“hundtennungar”), gave rise
to the first mammals at the
end of the Triassic, about
200 million years ago.
The Dicynodonts – “Tvær alvöru tennur”
There were numerous therapsids of the genus (ættkvísl)
Dicynodon in Triassic land environments. These bulky
animals made their way through coastal vegetation, feeding
on soft and juicy under-ground parts of large horstails.
With the exception of its prominent tusks, this animal was
toothless. Much like a turtle, it cropped vegetation with a
horny beak. Dicynodonts were one of the more successful
of the later therapsids, persisting until the very end of the
Triassic.
Lystrosaurus (“skóflueðla”) – a dicyodont
Lystrosaurus is known from
many parts of the ancient
megacontinent Gondwana. It is
known from India, Antarctica,
Africa, Russia, China and
Mongolia. The teeth of Lystrosaurus were reduced to a
pair of tusks. Probably it was
an amphibious feeder, in much
the same fashion as the living
hippopotamus. Lystrosaurus
dwelt in coastal environments,
and their wide paws permitted
them to walk in the most
boggy places.
Silphedosuchus orenburgensis
Early Triassic, 240 MY ago
Many Early Triassic therocephalians (“skrýmslishöfuð”)
were relatively small (<0.3 m), such as the insectivorous
Silphedosuchus (“Lítill Skógarkrókodíll”)
Sil (Silva=skógur);
Phedo (lítill; barn);
Suchus (krókodíll)
Ericolacerta was another small
(0.2 m) insect-eating Early
Triassic therocephalian
Cynodontia
(“hundstennungar” eða”alvörutennungar”)
The Cynodonts were the last and most advanced of the
therapsids, from which the true mammals developed.
Thrinaxodon – primitive cynodont -
Skeleton and body outline ofThrinaxodon, an early
Triassic cynodont with a number of advanced, mammallike features. Body length was ca. 0,5 m.
http://www.tmm.utexas.edu/research/ctlab/images/img4.mpg
Oligokyphus –
(“lítið ávalt dýr”)
Among the last cynodonts, this 0.5 m creature resembled
a weasel, and had a fully upright, four legged posture. It
had no canine teeth, and a pair of enlarged incisors like a
beaver. For a long time this animal was classified as a
mammal, but the jaw bones indicate that it was reptilian.
The cynodonts developed increasingly
towards small, mammal-like animals
As the Triassic Period wore on, the cynodonts
increasingly developed towards smaller animals. This was
probably an evolutionary answer to escaping the rapidly
developing reptiles and dinosaurs.
Dvinia prima – a step
towards mammals...
The cynodonts fed on anything
they could find, but most likely on
insects.This small, omnivorous
therapsid Dvinia, probably had
whiskers on its long snout and the
body might have been covered by
a tousled rigid fur, that made this
animal similar externally to some
mammals.
In contrast to mammals, the brain in cynodonts was
comparatively much less advanced. The jaws and eyes
constituted the main part of their skull, whereas the
brain case occupied a relatively small space
The
Procynosuchus
“First dog crocodile”
One small, seemingly insignificant, otter-like therapsid —
Procynosuchus — is thought to be the distant ancestor of
the hot-blooded mammals. Fossil occurrance in South
Africa and Germany
The first mammals
Reconstruction of the skeleton of Megazostrodon, one
of the earliest mammals known. Megazostrodon, with a
body length of about 13 cm, is from the Upper Triassic
Red Bed series of the Karoo, South Africa, and was
possibly a nocturnal, insect-eating animal.
The first mammals had to wait long
for their chance...
Megazostrodon evolved in a world where other groups of
animals, notably the dinosaurs, were developing towards
total dominance. Their survival strategy was to lay low,
move about during the night and try not to draw any
attention...
The evolution of dinosaurs and birds
The evolution of dinosaurs and birds...
Dinosaur evolution
Dinosaurs direct ancestors came from group of early
archosaurs, the thecodonts (“socket toothed”), which
were mostly big, heavy, 4-legged reptiles that ate flesh.
These competed so successfully with the therapsids
(mammal-like reptiles) that the latter died out during the
Triassic period. The early thecodonts were crocodile-like
beasts. Next in line were the pseudosuchians (sham
crocodiles) with long back legs and much shorter front
legs. Although they walked on all fours, the short front
legs made running difficult so they ran on their rear legs
for short sprints, balanced by their long tail. By 215 MY,
these pseudosuchians had given rise to the first flesh
eating dinosaurs, most likely from the erythrosuchians of
the ornithosuchian sub-group.
The dinosaurs developed from the
reptilian thecodonts (Archosaurs)
The archosaurs ('ruling
reptiles') were the
direct ancestors of the
dinosaurs. They evolved
from more primitive
reptiles in the Triassic,
following the Permian
mass extinction.
The evolution of the archosaurs is a very significant event
in the history of life on land, since they not only led to the
evolution of dinosaurs and birds, but also to the pterosaurs
and crocodiles.
The Archosaurs
The primitive archosaur
Euparkeria, from the
lower Triassic. This
reptile, about 50 cm long,
was related to the
ancestors of dinosaurs,
crocodiles and birds.
Euparkeria probably
raised itself on to its
hind-legs when running.
The first archosaurs appear in the
fossil record in the Early Triassic;
about 245 million years ago, just
after the great end-Permian
extinction. They include weird
hippo-size beaked herbivores
(called rhynchosaurs), long-necked
reptiles called (prolacertiforms),
evil-looking terrestrial predators
(like the erythrosuchians and
proterosuchians), and close
relatives of the Euparkeria. Many
of these early groups are limited
to the Triassic period.
The Rhynchosaurs
Hyperodaspedon. Fossils found in India and Scotland. Size: 1.3 m.
These were the most abundant reptiles of the mid to late
Triassic period, particularly in South America and Africa.
They were heavy, barrel-shaped plant-eaters with a
double row of upper teeth into which the row of bottom
teeth fitted, giving them a very efficient chopping action
ideal for the seed ferns found everywhere at this time.
These ferns were replaced in the early Jurassic by
conifers, and the rhynchosaurs also died out.
The proterosuchians
The Early Triassic (240 MY) proterosuchian Garjainia
triplicostata, the size of a lion. Garjainia was a carnivore, which probably hunted therapsids like the
dycinodonts. By Early Triassic some dicynodonts got
as large as modern rhinoceroses. But the increase in
size in hervivorous animals is always accompanied by a
parallel increase in size of the predators hunting for
them...
The Saurosuchus (“lizzard crocodile”)
A Late Triassic carnivorous thecodont reptile, with a lot
of smile. This animal was a huge predator, reaching
length of up to 7 meters. It was not in the evolutionary
line of crocodiles. It was a Rauisuchian. They were largeskulled archosaurs from the mid to late Triassic period.
These meat-eating reptiles
had powerful jaws and were
the top predators of their
time, but went extinct at the
end of the Triassic.
Simplified phylogeny of the dinosaurs
The Saurischia (“reptilehipped”- eðlungar) dinosaurs
and the Ornithishia (“birdhipped” - fleglar) dinosaurs
Evolution of dinosaurs
From thecodonts to dinosaurs. A. Euparkeria, Early Triassic, length 50 cm. B.
Lagosuchus, Middle Triassic, length 30 cm. C. Staurikosaurus, very primitive
dinosaur, Middle-Late Triassic, length 2.1 m. D. Coelophysis, Late Triassic,
length 2.5 m. E. Dilophohosaurus, Early Jurassic, length 6 m. The figures below
the diagonal line are drawn to scale.
Euparkeria
Euparkeria is known only from a single locality in the Lower Triassic of
southern Africa. Most grew to about half a meter in length. Euparkeria
is unusual in that the relative length of its hind limbs to its forelimbs
exceeds that of other comparable reptiles of its time. Some have
suggested that Euparkeria may have been able to run on two legs for
short distances as pictured above.
Lagosuchus
The Lagosuchus (“rabbit crocodile” – hérakrókódíll) were
archosaurs, or “pre-dinosurs”, which have been found in
Argentina. They were small animals (40 cm, weighed 80100 gr),
Plateocaurus
Plateocaurus
(“flateðla”) was a
herbivorous
dinosaur, living in
Late Triassic
times. It reached
a length of 7 m,
and was one of the
biggest early
dinosaurs. It has
been found in
France, Germany
and Switzerland
Coelophysis, a Late Triassic dinosaur
This small dinosaur was built for speed and agility. While
Coelophysis (“hollow form”) stood about 2.5 m tall, its
powerful rear legs and slender body made it a fast and
deadly predator. It had a long narrow head and a mouth
filled with numerous razor-edged teeth. Unlike other
dinosaurs, the leg bones of Coelophysis were hollow,
which helped reduce body weight and increase its speed.
Coelophysis...
Coelophysis was one of the earliest-known dinosaurs. It
lived in what was then a seasonally dry, desert-like
environment, a savanna-type climate (perhaps like
modern-day Kenya). Coelophysis was a carnivore, and a
scavenger. Coelophysis' fossilized stomach remains have
been found containing small reptiles, fish, and other
Coelophysis bones of different sizes, indicating that it
was a cannibal.
Coelophysis probably lived and
hunted in packs; this is
suggested by the existence of
fossil bonebeds of hundreds
of Coelophysis at one location,
found at the Ghost Ranch in
New Mexico, USA.
Eoraptor
Eoraptor (“early plunderer”) was
another Late Triassic (228 MY)
carnivorous dinosaur. It was small,
only about 1 m long. It has been found
in Argentina
Herrerosaurus
Herrerosaurus
(“Herreras lizzard”)
was yet another
carnivorous Late
Triassic dinosaur. It
was up to 3 m long.
Found in Argentina.
Enter the
crocodiles...
Early and extinct forms of
crocodiles descended from
archosaurs who walked on
their hind legs, and lived
during the late Triassic period.
The skull of the crocodile still
resembles in many ways those
of the primitive archosaurs.
Though modern crocodiles walk
on 4 legs, their two legged
ancestry is revealed by their
hind legs which are longer than
the front legs, making them
slant forward when they stand.
The crocodilian skull still has a
basically archosaurean shape..
Crocodile evolution
A. Hesperosuchus, Late
Triassic, length 1.3 m. B.
Ornithosuchus, Late
Triassic, length 4 m. C.
Saltoposuchus, Late
Triassic, length 1 m. D.
Tanystropheus, Middle
Triassic, length 3 m. E.
Gracilisuchus, Late
Triassic, length 30 cm. F.
Terristrisuchus, length
50 cm. Figures not drawn
to scale.
Gracilisuchus
This tiny carnivore (30 cm) is very unlike a modern
crocodile. However, the structure of Gracilisuchus' skull,
neck vertebrae and ankle joints place it firmly among the
crocodiles. Gracilisuchus was a well-adapted land animal,
protected by a double row of bony plates that interlocked down the length of its backbone, to the tip of the
tail. It probably chased after small lizards on its long
hindlegs, snatching them up in its powerful jaws, with
sharp, recurved teeth.
Proterosuchus
Proterosuchus was a Late Triassic archosaur,
that is closely linked to the developing line of
crocodiles. It was 1.5 m long, and probably lived
in a similar habitat to modern crocodiles.
Erythrosuchus
During the later part of the Early Triassic, the
Protorosuchus gave rise to the gigantic Erythrorsuchus
africanus. It was five metres in overall length, with a
stocky body and an enormous head a metre in length. This
creature is known from South Africa, Russia and in China.
It was the largest creature of its day, being the size of a
large crocodile, and must have been a fearsome predator
on contemporary large herbivores, such as the
Kanneymerya dicynodonts.
Orthosuchus
The Late Triassic fossil
crocodile Orthosuchus
and the reconstructed
animal. Although the 70
cm long Orthosuchus
lived about 200 MY ago,
it already had many of
the characteristics of
todays living crocodiles.
Its fossils have been
found in South Africa
Snakes and lizzards
The ancestors of our modern snakes and lizards
appeared during the late Triassic period, although fossil
records of these reptiles are sparse. The modern lizards
(suborder Lacertilia) are likely to have branched off
from the primitive order Eosuchia during the Triassic
period, but the oldest definite fossil links between
modern lizards and their ancestors originated in the
Upper Jurassic period, about 140 million years ago.
It is generally accepted that modern snakes (suborder
Serpentes) arose from the lizards in the early
Cretaceous period, about 130 million years ago, but there
is no hard and fast fossil evidence to link the two
suborders.
Frogs: Triadobatrachus massinoti
Triadobatrachus massinoti, a small Triassic amphibian. It
is not a true frog - it lacks the characteristic skull and
strong hind legs – but is regarded the ancestor of modern
frogs. It probably could not jump, but rather waddled
about the marshes of the Triassic, relying on camouflage
to protect it from predators. Fossil finds in Madagaskar.
Creatures that took to the air...
Late in the Triassic Period, vertebrate animals first
took to the air as the pterosaurs (flugeðlur) came into
beeing.
Pterosaurs
Pterosaurs were an order of flying reptiles, ranging in
size from a few cm to >13 m, and weighin few grams to
almost 100 kg. They had hollow bones, were lightly built,
and had small bodies. They had large brains and good
eyesight. Some pterosaurs had fur on their bodies, while
others had leathery skin.
Triassic Mass Extinction
The Triassic Period ended with a large mass
extinction. This crisis struck both on land and in the
sea:
• About 20% of all marine families went extinct.
• Conodonts, and placodont reptiles went extinct.
• So did most species of marine bivalves, ammonoids,
plesiosaurs and ichthyosaurs (these groups recovered
in Jurassic times).
• The terrestrial victims included most genera of
therapsids and large amphibians, as well as the large
sauropods.
Stanley´s
presentation
of the
Triassic mass
extinction
What caused the Triassic mass
extinction?
The main beneficiaries of the mass extinction were
the dinosaurs, which came out of it as the rulers of
the world. Terrestrial plants were also unaffected by
the mass extinction.
The cause of the Triassic extinction remains
unknown. Climate changes, sea-level changes,
changes in the chemistry of the atmosphere or
the oceans, asteoride impact, volcanism...
We just do not know!
References, web resources
• Stanley, Earth System History, kafli 16
• Skemmtileg heimasíða frá BBC, Walking With Dinosaurs
http://dsc.discovery.com/stories/dinos/bbc/chronology/220/index.html
• http://www.ucmp.berkeley.edu/mesozoic/triassic/triassic.html
• http://www.palaeos.com/Mesozoic/Triassic/Triassic.htm
• http://leute.server.de/frankmuster/S/Shonisaurus.htm
• http://leute.server.de/frankmuster/I/Ichthyosaurus.htm
• www.fossilmall.com/Science/Taxonomy/Insects/subphylum_insecta_fossils.htm
• http://www.sunshine.net/www/2100/sn2192/therapsid-index.htm
• http://www.mathematical.com/dinosilphed.html
• www.oceansofkansas.com/placodnt.html
• http://palaeo.gly.bris.ac.uk/communication/Mcgowan/MAMS
• http://www.scotese.com/earth.htm
• http://palaeo.gly.bris.ac.uk/Palaeofiles/Triassic/titlepage.htm
• http://www.mathematical.com/dinoindex.html