Download The Triassic System

The Triassic System
The name Triassic derives from the
three parts into which the Triassic is
divided on the European platform:
3. Keuper (highest)
2. Muschelkalk
1. Bunter (lowest)
In North America
1. the Triassic is represented by the thick
Newark Group along the east coast,
2. by widespread red-bed and fluvial
sediments in the Great Plains,
3. and by marine sediments in scattered
basins in the western states.
Land Reptiles
• Reptiles first invaded the sea during the
Triassic System
• archosaur A reptile having a diapsid skull
type with teeth set in sockets. This group
includes the crocodiles, pterosaurs,
dinosaurs, and birds.
Ginkgophyta
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Gaining importance, but not
dominance
were the, dioecious plants of
which Ginkgo biloba is the only
extant genus and species.
The pollen is borne on
catkinlike structures [a catkin is
a type of inflorescence (cluster
of flowers on a common stalk)
in which the flowers are
attached directly to the
common stalk without an
individual stem].
•
The ovules, in pairs, are borne
on stalks and form seeds upon
pollination and fertilization.
These re-productive organs
are intermediate between
Marine Vertebrates
• plesiosaur: A Mesozoic marine reptile
with a euryapsid skull type, abroad body,
and large, and paddle like limbs.
• Ichthyosaur (literally "fish lizards"): A
Mesozoic marine reptile with a dolphin like
body.
The Plants
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The dominant Triassic land
plants were the Cycadales
CYCADALES: a class of
Cycadophyta that had evolved
from the Lycopodiophyta in
Late Permian time.
The Cycadales, in contrast to
the Lycopodiophyta, have
specialized pollen and seed
cones (strobili) that are borne
on different plants (they are,
therefore, dioecious).
•
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The ovules are borne on the
scales of female cones (as in
Coniferophyta).
In gross appearance the
cycads resemble palm trees,
with a bulbous or columnar
trunk and a crown offronds on
top. Heights range from 1 to 18
m.
The Triassic Plants
• The dominant Triassic
land plants were the
Cycadales, a class of
Cycadophyta that had
evolved from the
Lycopodiophyta in
Late Permian time.
The Cycadales, in contrast to
the Lycopodiophyta, have
specialized pollen and seed
cones (strobili) that are borne
on different plants (they are,
therefore, dioecious). The
ovules are borne on the scales
of female cones (as in
Coniferophyta). In gross
appearance the cycads
resemble palm trees, with a
bulbous or columnar trunk and
a crown of fronds on top.
Heights range from 1 to 18 m
The Triassic Plants: Ginkgo
• Gaining importance, but not dominance,
were the Ginkgophyta, dioecious plants of
which Ginkgo biloba is the only extant
genus and species. The pollen is borne on
catkin like structures [a catkin is a type of
inflorescence (cluster of flowers on a
common stalk) in which the flowers are
attached directly to the common stalk
without an individual stem].
Triassic Plants
• The Cycadeoidales (Bennettitales) are
an extinct (Triassic-Cretaceous) class of
plants that were common in the
Mesozoic forests. They closely
resembled the Cycad ales in the shapes
of their leaves and trunks. They had,
however, stalked fruiting structures
containing both pollen and seeds and
resembling primitive flowers.
• The Angiospermophyta (flowering
plants) may have evolved from this
group (Cretaceous).
The Reptiles
• In Early Triassic time a remarkable group
of reptiles, the thecodonts, evolved, of
which Euparkeria is a typical example.
• Euparkeria evidently was built for running.
The Reptiles
The Reptiles: Thecodonts
• During the Triassic, the thecodonts
evolved into the saurischian and
ornithischian dinosaurs. Both groups
appeared in Late Triassic time.
Classification and characteristics of dinosaurs
Order Saurischia
Suborder Sauropodomorpha: partly bipedal in Late Triassic, evolving
into large, quadrupedal, herbivorous types in the Jurassic and
Cretaceous [e.g., Aptosaurus and Diplodocus (Fig. 23.5A), Late
Jurassic]
Suborder Therapoda: fully bipedal, carnivorous
[e.g.. Tyrannosaurus (Fig. 23.58), Late Cretaceousl
Order Ornithischia
Suborder Ornithopod a: bipedal [e.g., Camptosaurus
(Fig. 23.6A). Late Jurassic to Early Cretaceous]
Suborder Stegosauria: bipedal/quadrupedal, with a double row of
plates along the back (vascularized heat-exchange devices?) and
horns on the tail [e.g.. Stegosaurus (Fig. 23.68), Late Jurassic]
Suborder Ankylosauria: quadrupedal, with bony
plates on back (e.g., Anky/osaurus. Late Cretaceous)
Suborder Ceratopsia: horned dinosaurs [e.g.,
Triceratops (Fig. 23.6C). Late Cretaceous)
Other important groups of reptiles that evolved
in the Triassic are:
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the lizards (Lacertilia, Early Triassic-Holocene),
the snakes (Serpentes, early Triassic-Holocene),
the crocodiles (Crocodylia, Late Triassic-Holocene),
the turtles (Chelonia, Late Triassic-Holocene)
and the marine reptiles (Ichthyosauria and
Plesiosauria, Early Triassic-Late Cretaceous).
• The turtles are a "primitive" group of reptiles (i.e.,
they have not evolved much since they first
appeared). Most species were and are freshwater
dwellers (rivers, lakes, marshes), but some have
become adapted to land (the tortoises,
Eocene-Holocene), and others became fully marine
(Chelonidae, Dermochelyidae: Late
Cretaceous-Holocene).
Early dinosaurs, including Rioarribasaurus,
were relatively small, sleek predators. This
skeleton is from Triassic rocks of New
Mexico.
Rioarribasaurus
Two types of synapsids are known
from Triassic strata
• Primitive synapsids (or
"mammal-like reptiles)
persisted from the
Late Paleozoic.
•Mammals,
represented first by a
group called the
multituberculates,
appeared in the Late
Triassic.