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16.4: Marine Reptiles

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    Marine Reptiles

    Compared with the number of reptiles groups and species on Earth, relatively few are adapted to marine environments. The earliest marine reptiles appear in the Permian Period. Many groups emerged in the Mesozoic Era including more familiar varieties including ichthyosaurs, plesiosaurs, and mosasaurs. Many varieties of the Mesozoic Era vanish at the K/T Boundary extinction.



    ORDER Crocodiles
    ORDER Lizards
    ORDER Sea Turtles
    ORDER Sea Snakes


    There are 23 living crocodilian species in both terrestrial aquatic and coastal marine environments. Crocodilians are found in the tropical to subtropical regions on all continents (not Antarctica); they're found in over 90 countries and islands. They are unable to survive and reproduce successfully in cold climates.

    What's the difference between an alligator and a crocodile?

    American Alligator

    American Crocodile

    Habit: feisty Habit: more feisty, but shy and reclusive
    Habitat: freshwater to brackish water Habitat: brackish to salt water
    Color: gray to black Color: greenish gray
    Encounters with humans: common Encounters with humans: not so common
    Diet: most everything, fish, birds, pets Diet: mostly fish
    Maximum size: `12 feet Maximum size: ~13 feet
    Characteristics: Alligators snout is blunt and shovel like (used like a shovel too) Characteristics: Crocodile snout is pointed with more teeth sticking out (better for catching fish)
    Range in US: Gulf & Atlantic coasts (TX to SC) Range in US: South Florida only
    Example: Figure 16.25 Example: Figure 16.26
    Americal Alligator American crocodile
    Figure 16.24. Alligator Figure 16.25. Crocodile

    Marine Lizards

    The only marine lizard is the Galápagos marine iguana (Amblyrhynchus cristatus)—found only on the Galápagos Islands. This iguana lives along rocky island shorelines and can dive over 9 m (30 ft) into the water to forage for its main diet of red and green algae (Figure 16.27).

    Figure 16.26. Galápagos marine iguana

    Extinct Large Marine Reptiles

    Aquatic reptiles first noted from the Permian Period. There were many varieties of large marine reptiles during the Mesozoic Era. All vanished at the end of the Cretaceous Period (about 65 million years ago).

    Ichthyosaurs: Triassic to Late Cretaceous
    Plesiosaurs: Early Jurassic - Late Cretaceous
    Mosasaurs: Late Cretaceous

    The ancient marine reptiles illustrated convergent evolution - they had terrestrial ancestors like dolphins and whales.

    Figure 16.27. A fossil ichthyosaur from Berlin-Itchtyosaur State Park, Nevada

    Sea Turtles

    There are seven species of sea turtles worldwide. Sea turtles sea turtles can be found in all oceans except for the polar regions, along the continents shelves and islands. They are known to nest in more than 80 countries. Sea turtles first appear in the geologic record in early Cretaceous time (land proto-turtles appeared in Permian time).

    Unlike land turtles, sea turtles are unable to pull their heads or appendages into their shells. Sea turtle shells are lighter and more hydrodynamic than terrestrial turtle shells. There flippers enable them to swim long distances. Male sea turtles spend their entire lives at sea. Females return to the same beaches they were born on about every two years to lay eggs.

    All adult green sea turtles are herbivores, feeding on algae, sea grasses, and other vegetation. Juvenile are carnivorous, feeding on jellies and other invertebrates. Large adult green sea turtles can weigh upward of 400 pound and over 1 meter.

    Leatherback turtles are carnivorous, migrating thousands of miles each year to feed on jellyfish.
    Leatherback Turtles can weigh as much as 1500 pounds and reach lengths of over 2 meters.

    Sea Turtles

    Green sea turtle

    Leatherback sea turtle

    Loggerhead sea turtle
    Sea Turtle (Carribean) Leatherback sea turtle Loggerhead sea turtle
    Figure 16.28. Green sea turtle Figure 16.29. Leatherback sea turtle Figure 16.30. Loggerhead sea turtle.

    Sea Snakes

    There are about 50 species. They live in tropical waters of the west Pacific Ocean, around Australia, and in the Indian Ocean. Sea snakes inhabit marine environments for most or all their lives. Sea snakes are generally non aggressive, brightly colored, with small mouth and fangs. Sea snakes have very powerful venom. An average of about 20 deaths per year happen from fishermen trying to remove them from nets.

    Sea snake
    Figure 16.31. Sea snake.

    This page titled 16.4: Marine Reptiles is shared under a not declared license and was authored, remixed, and/or curated by Miracosta Oceanography 101 (Miracosta)) via source content that was edited to the style and standards of the LibreTexts platform.