16.4: Marine Reptiles

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.

CLASS	Reptilians
	ORDER	Crocodiles
	ORDER	Lizards
	ORDER	Sea Turtles
	ORDER	Sea Snakes

Crocodiles

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

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
	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.

Figure 16.31. Sea snake.