Mesozoic Marine Revolution
Geologic Time
• The Mesozoic is from about 243 million years
ago up until 65million years ago
• Contains
-Cretaceous
-Jurassic
-Triassic
Climate
• The Triassic was generally dry, a trend that
began in the late Carboniferous, and highly
seasonal, especially in the interior of Pangaea.
Low sea levels may have also raised
temperature extremes.
• Sea levels began to rise during the Jurassic,
Temperatures continued to increase and
began to stabilize. Humidity also increased
with the proximity of water, and deserts
retreated.
Con’t
• In the Cretaceous the sea levels also
continued to rise and so did the temperature
Focus
• The Focus on the next following slides will be
that of the invertebrates that were mainly
dominant in the Mesozoic era.
• Mulluscs
• Echinodemata
Invertebrates
• Molluscs
– pelecypods (or bivalves)
– gastropods (snails)
– cephalopods (ammonoids, belemnoids, squids,
etc.)
Mulluscs Characteristics
• unsegmented soft body
• most have internal or external shell
• have a mantle - a fold in the body wall that
secretes the hard protective shell
• muscular foot and/or tentacles
• have a radula - a toothed structure used to
grate food
• two pairs of gills except in polmonate snails
Anatomy
• almost all molluscs divided into two functional regions:
head-foot and the visceral lump
• head-foot is most visible part, easily seen in snails and slugs
• also is mostly muscular and covered in cilia to help the
molluscs move around
• visceral mass is the rest of the body, which is entirely nonmuscular and contains the species organ (digestive,
reproductive, etc)
• most molluscs have a shell, a thick layer made of calcium
carbonate
• the mantle, the fold of tissue covers the visceral mass and
shell (if present)
• the mantle cavity is where the lungs and gills are housed
Echinodermata
• Ophiuroides (brittle stars)
• Asteroidea (starfish)
• Echinoidea (sea urchins)
• Holothuroidea (sea cucumbers)
• Crinoidea (sea lilies).
Echinoderms
• Are part of the phylum Echinodermata
• Two main subdivisions of Echinoderms are
traditionally recognized: the more familiar,
motile eleutherozoa, which encompasses the
Asteroidea (starfish), Ophiuroidea (brittle
stars), Echinoidea (sea urchin and sand dollar)
and Holothuroidea (sea cucumbers and the
sessile pelmatazoa, which consist of the
crinoids.
Characteristics
• The characteristics that distinguish Phylum Echinodermata
are: radial symmetry, internal skeleton, and water-vascular
system. Echinoderms appear to be quite different than other
‘advanced’ animal phyla, having radial (spokes of a wheel)
symmetry as adults, rather than bilateral (worm-like)
symmetry as in other triploblastic (three cell-layer) animals.
Viewers of this program will observe that echinoderm radial
symmetry is secondary; echinoderms begin as bilateral freeswimming larvae and become radial at the time of
metamorphosis
• Examples: Starfish and Crinoid
Starfish Anatomy
• Starfish are composed of a central disc from
which arms sprout in pentaradial symmetry.
Most starfish have 5 arms, but some have
more or fewer. Some starfish have shown
differing numbers of limbs within a single
species. The mouth is located underneath the
starfish, or ventral surface, is located on the
top of the animal..
Con’t
• The spiny upper surface is called the aboral or
dorsal surface. On the aboral surface there is a
structure called the madreporite ,a small
white spot located slightly off-center on the
central disc which acts as a water filter and
supplies the starfish's water vascular system
with water to move
Crinoids
• Crinoids are also typically characterized by
their pentameral radial symmetry.
• Crinoids are spilt into three parts
• Basic Structure of a Crinoid
The Calyx: contains the vital organs of the
animal. It is small when compared to the total
mass, most of which is devoted to food collection.
The mouth and anus are located on the upper
surface of the body, and are connected by a simple
gut.
The Arms: composed of an articulated series of
ossicles that are used in suspension feeding and
respiration. The gonads are also located in the
arms; fertilisation takes place in open sea water
during mass spawnings.
The Stem: this supports the animal and together
with the roots and cirri served as a means of
attachment to the sea bed or other useful substrate
such as logs
Works Cited
http://ebiomedia.com/prod/BOechin
oderms.html
http://en.wikipedia.org/wiki/Mollusk
http://www.amonline.net.au/inverte
brates/mal/index.htm
http://images.google.com/imgres?im
gurl=http://www.reefs.org/
http://www.cyhaus.com/marine/Echi
noderm.htm