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Crocodiles: Crocodiles have existed since the
middle Triassic (230 million years ago-mya), though modern crocodiles
did not appear until the Upper Cretaceous (100-65 mya). |
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Dinosaurs: We found evidence of serveral types
of dinosaurs, both herbivores and carnivores. This drawing is of a small
theropod, a diverse group of bipedal ("two-footed") carnivorous dinosaurs.
This group of dinosaurs varied in size. Evidence now shows that birds
are the descendants of small nonflying theropods. |
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Fish: We found fossils of several kinds of
bony fish (Osteichythyes). Bony fish have a long evolutionary history
beginning as far back as the Early Devonian (400 mya). |
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Gar: This is a predatory fish which includes
several freshwater species of the genus Lepisosteus. Its body is
covered with very hard diamond-shaped scales and it has a beak armed with
large teeth. Gars appear in the fossil record beginning in the Late Cretaceous
(100-65 mya). |
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Multi-tuberculates: Multi-tuberculates are
the only major branch of mammals now completely extinct. They first appeared
in the Late Jurassic (163-144 mya) and went extinct in the early Oligocene
(36-30 mya). Over 200 species are known, some as small as the tiniest
of mice, the largest the size of beavers. |
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Sharks: Sharks, skates, and rays make up the
Chondrichthyes, or "cartilaginous fish." They first appeared on Earth
almost 450 mya (Ordovician). What we identify as sharks probably appeared
in the Triassic (245-208 mya), but modern-looking sharks did not appear
until the Cretaceous (144-65 mya). |