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TRILOBITES |
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NAUTILOIDS |
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AMMONOIDS |
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CRINOIDS |
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GRAPTOLITES |
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DINOSAURS |
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EURYPTERIDS |
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MAMMALS |
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VASCUALAR PLANTS |
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PLACODERM FISH |
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BIRDS |
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CORALS |
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GASTROPODS |
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BRACHIOPODS |
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KINGDOM |
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PHYLUM |
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CLASS |
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ORDER |
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FAMILY |
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GENUS |
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SPECIES |
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These are the most diverse group of extinct
animals in the fossil record. Trilobites are ARTHROPODS, related to the
Chelicerates (spiders!) and Crustaceans (lobsters and crabs). |
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The graptolites have a checkered history.
Graptolites are common fossils in Ordovician and Silurian rocks, but for a
long time no one was sure what kind of animals they were. Most fossil
graptolites look like nothing so much as tiny sawblades. However,
well-preserved graptolites can be seen to be tubular in cross-section, with
the "teeth of the saw" formed by short open branches from the
main tube. Careful study of the microscopic structure of the tubes of
graptolites showed that they are very similar to the tubes of pterobranchs. |
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Brachiopods are marine animals that, upon first
glance, look like clams. They are actually quite different from clams in
their anatomy, and they are not closely related to the molluscs. There are
about 300 living species of brachiopods. During the Paleozoic era, they
were extremely abundant. 250
million years ago, they were decimated in the worst mass extinction of all
time, the Permo-Triassic event. Their numbers have never been as great
since that time. |
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Crinoids are niether abundant or familiar
organisms today. However, they dominated the Paleozoic fossil record of
echinoderms and shallow marine habitats until the Permo-Triassic
extinction, when they suffered a near complete extinction: many Paleozoic limestones
are made up largely of crinoid skeletal fragments. Stalked crinoids, or
"sea lilies", lived attached to the bottom, and filtered food
particles from the currents flowing past them. |
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Nautiloids are the earliest and most primitive
of the Cephalopods. Appearing during the late Cambrian they evolved into a
great diversity of forms and lifestyles, as indicated by the amazing range
of shell types and structure. Remaining diverse throughout the early to mid
Paleozoic, they declined later in the era, and have remained relatively
unimportant ever since. There are only 3 or 4 living species, all
belonging to the single genus Nautilus (the pearly nautilus). |
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Also cephalopods, these among the most abundant
and well known fossils in the world.
Their rapid evolution and wide distribution make them a key index
fossil around the world. |
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3 key groups exist: |
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RUGOSE (or HORN) Corals- these existed from
Ordovician to Permian times, before going extinct They were solitary, and
look like ice cream cones. |
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TABULATES- also from Ordovician to Permian,
these corals were colonial. |
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SCLERACTINIAN- modern, reef-forming corals-
colorful! |
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Known as SNAILS, these critters are
single-shelled (unlike CLAMS). They have a soft foot, and many, many shell
shapes. |
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The oldest fossils come from the Lower Ordovician
of New York. Sea scorpions were most diverse in the Silurian and Lower
Devonian, after which they rapidly declined in diversity. They finally went
extinct in the Permian. |
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These are peculiar, heavily armored jawed
fish. Placoderms reached a peak of
development in the Middle Devonian but declined throughout the remainder of
the Paleozoic, going extinct in the Mississippian. |
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Vascular plants are the more common plants like
pines, ferns, corn, and oaks. |
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Stemmed, or vascular, plants appeared by 350
million years ago, with forests soon following (300 million years ago).
Seed plants next evolved, with flowering plants appearing around 140
million years ago. |
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Cooksonia, a NYS fossil plant |
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Dinosaurs were the dominant terrestrial (living
on land) vertebrates (having a back bone) from the Triassic to the
Cretaceaous. They ranged from small
to gigantic, eating plants, meat, other dinos, etc. The dinosaurs provide
some of the most spectacular fossil remains in the rock record. Some of the
mysteries of dinos include the question of whether they were warm or cold
blooded, how they grew to be so large, and why they went extinct, only to
be replaced by our ancestors- the mammals. |
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Some argue that dinosaurs are STILL alive, as
birds. Although the direct evidence of this evolutionary connection is
still missing, there are some key similarities. The key adaptations of
birds include feathers, and hollow bones! There is a direct connection
between bird feathers, and reptile scales, however… |
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Our ancestors, the earliest mammals were small,
rodent-like critters that evolved during the time of the dinosaurs. After
the extinction, mammals diversified into the dominant creatures on the
earth. Look at the book of human evolution to see some different
skeleltons… |
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Notes