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The earliest marine reptiles arose in the Permian. During the Mesozoic many groups of reptiles became adapted to life in the seas, including ichthyosaurs, plesiosaurs, mosasaurs, nothosaurs, placodonts, sea turtles, thalattosaurs and thalattosuchians. Marine reptiles were less numerous after mass extinction at the end of the Cretaceous.
The blue whale is the largest animal known ever to have existed. [42] [43] [44] Some studies have estimated that certain shastasaurid ichthyosaurs and the ancient whale Perucetus could have rivalled the blue whale in size, with Perucetus also being heavier than the blue whale with a mean weight of 180 t (180 long tons; 200 short tons).
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. Only about 100 of the 12,000 extant reptile species and subspecies are classed as marine reptiles, including marine iguanas , sea snakes , sea turtles and saltwater crocodiles .
Marine invertebrates have a large variety of body plans, which are currently categorised into over 30 phyla. Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum.
For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; a group of amphibians, the labyrinthodonts, have given rise to the reptiles (traditionally including the mammal-like synapsids), which in ...
The pygmy blue whale is the only one of the three identifiable subspecies to be found regularly in tropical waters. It occurs from the sub-Antarctic zone to the southern Indian Ocean and southwestern Pacific Ocean, breeding in the Indian and South Atlantic oceans, and travelling south to above the Antarctic to feed, [4] [7] although they very rarely cross the Antarctic Convergence.
Aside from humans, just five toothed whale species are known to go through this natural biological process. Menopause ‘may explain why some female whales live decades longer than others’ Skip ...
The oldest known animal that may have been an amniote, a reptile rather than an amphibian, is Casineria [3] [4] (though it has also been argued to be a temnospondyl amphibian). [5] A series of footprints from the fossil strata of Nova Scotia, dated to 315 million years, show typical reptilian toes and imprints of scales. [6]