Marine reptile
Marine reptiles are
The earliest marine reptile was
Some marine reptiles, such as ichthyosaurs, plesiosaurs, metriorhynchid thalattosuchians, and mosasaurs became so well adapted to a marine lifestyle that they were incapable of venturing onto land and gave birth in the water. Others, such as sea turtles and saltwater crocodiles, return to shore to lay their eggs. Some marine reptiles also occasionally rest and bask on land.
Extant (living) varieties
- Sea turtles: there are seven extant species of sea turtles, which live mostly along the tropical and subtropical coastlines, though some do migrate long distances and have been known to travel as far north as Scandinavia. Sea turtles are largely solitary animals, though some do form large, though often loosely connected groups during nesting season. Although only seven turtle species are truly marine, many more dwell in brackish waters.[1][6]
- Sea snakes: the most abundant of the marine reptiles, there are over 60 different species of sea snakes. They inhabit the tropical and subtropical waters of the Indian and Pacific oceans, though very limited reports of sightings suggest they may be extending into the Atlantic Ocean. Sea snakes are venomous and their bites have been known to be fatal, though generally they only bite when provoked and often inject only a very small, non-fatal quantity of venom. Sea snakes are distinguished from terrestrial snakes by a vertically flattened tail.[1][7]
Extinct groups
- Ichthyosaurswere marine reptiles with a dolphin-like body shape that flourished during the Mesozoic era.
- placodonts.
- squamates(relatives of modern-day lizards and snakes) which became the dominant marine predators towards the end of the Cretaceous period.
- thalattosauroids, are known for their unusual downturned snouts and crushing dentition.
- Synapsid.
- crocodylomorphsthat flourished during the Jurassic era.
Adaptation to the marine environment
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Conservation
Most species of marine reptiles are considered endangered to some degree. All but one species of sea turtles are endangered due to destruction of nesting habitats on coastal lands, exploitation, and marine fishing;[6] many species of sea snakes are threatened or endangered due to commercial exploitation (sale of skins) and pollution especially in Asia; marine iguanas are threatened due to their very limited habitation range.[1] Saltwater crocodiles are at low risk for extinction.[9]
See also
References
- ^ PMID 22087300.
- .
- ISBN 1-4021-4677-9
- PMID 27395602.
- ISBN 978-1-56098-418-4.
- ^ a b Zug, George R. "Sea Turtle". Encyclopædia Britannica Online. Retrieved December 8, 2015.
- ^ "Sea Snake". Encyclopædia Britannica Online. Retrieved December 8, 2015.
- ^ "Marine Iguanas". National Geographic. Archived from the original on May 21, 2011. Retrieved December 8, 2015.
- ^ a b "Saltwater crocodile". National Geographic. Archived from the original on February 4, 2010. Retrieved December 8, 2015.
- JSTOR 1563379.