instance_of ginkgo-toothed beaked whale
The narwhal , or narwhale (" Monodon monoceros "), is a medium - sized toothed ___MASK17___ that possesses a large " tusk " from a protruding canine tooth . It lives ___MASK98___ - round in the Arctic waters around Greenland , Canada , and Russia . It is one of two living species of ___MASK17___ in the Monodontidae ___MASK1___ , along with the ___MASK42___ . The narwhal males are distinguished by a long , straight , helical tusk , which is an elongated upper left canine . The narwhal was one of many species described by Carl Linnaeus in his publication " Systema Naturae " in 1758 . The cetacean ___MASK1___ Monodontidae comprises two unusual whale species , the narwhal , in which the male has a long tusk , and the dorsal fin - lacking , pure white ___MASK42___ . They are native to coastal regions and pack ice around the Arctic ___MASK56___ . Belugas can be found in the far north of the Atlantic and Pacific Oceans ; the distribution of narwhals is restricted to the Arctic and Atlantic Oceans . The toothed whales ( systematic ___MASK69___ Odontoceti ) are a parvorder of cetaceans that includes all the dolphins and porpoises , as well as the whales that have teeth , such as the beaked whales and sperm whales . Seventy - ___MASK20___ species of toothed whales ( also called odontocetes ) are described . They are one of two living groups of cetaceans , the other being the baleen whales ( Mysticeti ), which have baleen instead of teeth . The two groups are thought to have diverged around 34 million years ago ( mya ). The Pliocene ( also Pleiocene ) Epoch is the epoch in the geologic timescale that extends from 5 . 333 million to 2 . 58 million years BP . It is the second and youngest epoch of the Neogene ___MASK2___ in the Cenozoic Era . The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch . Prior to the 2009 revision of the geologic ___MASK99___ scale , which placed the four most recent major glaciations entirely within the Pleistocene , the Pliocene also included the Gelasian ___MASK39___ , which lasted from 2 . 588 to 1 . 806 million years ago , and is now included in the Pleistocene . Marine mammals are aquatic mammals that rely on the ___MASK59___ and other marine ecosystems for their existence . They include animals such as seals , whales , manatees , ___MASK56___ otters and polar bears . They do not represent a distinct ___MASK7___ or systematic grouping , but rather have a paraphyletic relation . They are also unified by their reliance on the marine environment for feeding . Baleen is a ___MASK37___ - feeder ___MASK94___ inside the mouths of baleen whales . The baleen ___MASK94___ works by whale opening its mouth underwater and taking in ___MASK44___ . The whale then pushes the ___MASK44___ out , and animals such as krill are filtered by the baleen and remain as food source for the whale . Baleen is similar to bristles and is made of keratin , the same substance found in human fingernails and hair . Baleen is a skin derivative . Some whales , such as the bowhead whale , have longer baleen than others . Other whales , such as the gray whale , only use one side of their baleen . These baleen bristles are arranged in plates across the upper jaw of the whale . Baleen is often called whalebone , but that name also can refer to the normal bones of whales , which have often been used as a material , especially as a cheaper substitute for ivory in carving . Baleen whales ( systematic ___MASK69___ Mysticeti ), known earlier as whalebone whales , form a parvorder of the infraorder ___MASK34___ ( whales , dolphins and porpoises ). They are a widely distributed and diverse parvorder of carnivorous marine mammals . Mysticeti comprise the families Balaenidae ( right whales ), Balaenopteridae ( rorquals ), Cetotheriidae ( the pygmy right whale ), and Eschrichtiidae ( the gray whale ). There are currently 15 species of baleen whale . While cetaceans were historically thought to have descended from mesonychids , molecular evidence supports them as relatives of even - toed ungulates ( Artiodactyla ). Baleen whales split from toothed whales ( Odontoceti ) around 34 million years ago . Ginkgo biloba , known as ginkgo or gingko ( both pronounced ), also known as the ginkgo ___MASK63___ or the maidenhair ___MASK63___ , is the only living species in the division Ginkgophyta , all others being extinct . It is found in fossils dating back 270 million years . Native to China , the ___MASK63___ is widely cultivated and was introduced early to human ___MASK66___ . It has various uses in traditional ___MASK86___ and as a source of food . The genus name " Ginkgo " is regarded as a misspelling of the Japanese " gin kyo ", " silver apricot ". Beaked whales are the members of the ___MASK1___ Ziphiidae , which consists of 22 species . These toothed whales are notable for their elongated beaks . Among air - breathing animals , beaked whales are some of the most extreme divers : Cuvier ' s beaked whales regularly dive for an hour at a depth over , and the longest and deepest foraging dive recorded is 137 . 5 minutes at . This is the greatest dive - depth known for a mammal . Dolphins are a widely distributed and diverse ___MASK62___ of aquatic mammals . They are an informal grouping within the ___MASK80___ ___MASK34___ , excluding whales and porpoises , so to zoologists the grouping is paraphyletic . The dolphins comprise the extant families Delphinidae ( the oceanic dolphins ), Platanistidae ( the Indian river dolphins ), Iniidae ( the new world river dolphins ), and Pontoporiidae ( the brackish dolphins ), and the extinct Lipotidae ( baiji or Chinese river dolphin ). There are 40 extant species of dolphins . Dolphins , alongside other cetaceans , belong to the clade Cetartiodactyla with even - toed ungulates . Their closest living relatives are the hippopotamuses , having diverged about 40 million years ago . The gray ___MASK17___ (" Eschrichtius robustus "), also known as the grey ___MASK17___ , gray back ___MASK17___ , Pacific gray ___MASK17___ , or California gray ___MASK17___ is a baleen ___MASK17___ that migrates between feeding and breeding grounds yearly . It reaches a length of , a weight of , and lives between 55 and 70 years . The ___MASK14___ of the ___MASK17___ comes from the gray patches and white mottling on its dark ___MASK27___ . Gray whales were once called devil fish because of their fighting ___MASK41___ when hunted . The gray ___MASK17___ is the sole living species in the genus Eschrichtius , which in turn is the sole living genus in the family Eschrichtiidae . This mammal descended from filter - feeding whales that appeared at the beginning of the Oligocene , over 30 million years ago . Rorquals ( Balaenopteridae ) are the largest ___MASK62___ of baleen whales , a ___MASK1___ with nine extant species in two genera . They include what is believed to be the largest animal that has ever lived , the blue whale , which can reach , and the fin whale , which reaches ; even the smallest of the ___MASK62___ , the northern minke whale , reaches . In ___MASK97___ , a ___MASK51___ ( abbreviated sp ., with the plural form ___MASK51___ abbreviated spp .) is the basic unit of ___MASK21___ and a taxonomic rank . A ___MASK51___ is often defined as the largest group of organisms in which two individuals can produce fertile ___MASK24___ , typically by sexual reproduction . While this definition is often adequate , looked at more closely it is often problematic . For example , in a ___MASK51___ complex , the boundaries between closely related ___MASK51___ become unclear or disappear altogether . Other ways of defining ___MASK51___ include similarity of DNA , morphology , or ecological niche . The presence of locally adaptive traits may further subdivide ___MASK51___ into infraspecific taxa such as subspecies . Porpoises are a ___MASK62___ of fully aquatic marine mammals that are sometimes referred to as mereswine , all of which are classified under the ___MASK1___ Phocoenidae , parvorder Odontoceti ( toothed whales ). There are six extant species of porpoise . They are small toothed whales that are very closely related to oceanic dolphins . The most obvious visible difference between the two groups is that porpoises have shorter beaks and flattened , spade - shaped teeth distinct from the conical teeth of dolphins . Porpoises , and other cetaceans , belong to the clade Cetartiodactyla with even - toed ungulates , and their closest living relatives are the hippopotamuses , having diverged from them about 40 million years ago . The ginkgo - toothed beaked ___MASK17___ ( Mesoplodon ginkgodens ) is a poorly known ___MASK51___ of ___MASK17___ even for a beaked ___MASK17___ , and was named for the unusual shape of its dual teeth . It is a fairly typical - looking ___MASK51___ , but is notable for the males not having any scarring . A fern is a ___MASK48___ of a group of about 10 , 560 known extant species of vascular plants that reproduce via spores and have neither seeds nor flowers . They differ from mosses by being vascular , i . e ., having certain tissue that conducts ___MASK44___ and nutrients . They have branched stems and leaves like other vascular plants . These are " megaphylls ", which are more complex than the simple " microphylls " of clubmosses . Most ferns are Leptosporangiate ferns , sometimes denominated the " true ferns ": they produce what are called " fiddleheads " that uncoil and expand into fronds . Ginkgo is a ___MASK76___ of highly unusual non - flowering plants . The scientific name is also used as the ___MASK6___ . The order to which it belongs , Ginkgoales , first appeared in the Permian , 270 million years ago , possibly derived from " seed ferns " of the order Peltaspermales . The rate of evolution within the ___MASK76___ has been slow , and almost all its species had become extinct by the end of the Pliocene ; the exception is the sole living species , " Ginkgo biloba ", which is only found in the wild in China , but is cultivated across the world . The relationships between ginkgos and other groups of plants are not fully resolved . Ginkgoales is a ___MASK32___ ___MASK80___ containing only one extant species : " Ginkgo biloba ", the ginkgo ___MASK63___ . It is monotypic , ( the only ___MASK7___ ) within the class Ginkgoopsida , which itself is monotypic within the division Ginkgophyta . The ___MASK80___ includes five families , of which only Ginkgoaceae remains extant . The Permian is a geologic ___MASK2___ and ___MASK94___ which spans 46 . 7 million years from the end of the Carboniferous Period million years ago ( Mya ), to the beginning of the Triassic Period 252 . 2 Mya . It is the last ___MASK2___ of the Paleozoic Era ; the following Triassic Period belongs to the Mesozoic Era . The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison , who named it after the city of Perm . The even - toed ungulates ( ___MASK80___ Artiodactyla ) are ungulates ( hoofed animals ) whose weight is borne equally by the third and fourth toes . By contrast , odd - toed ungulates , such as horses , ___MASK58___ their weight primarily on their third toe . The aquatic Cetaceans ( whales , dolphins , and porpoises ) evolved from even - toed ungulate ancestors , and therefore modern taxonomic classification combines Artiodactyla and ___MASK34___ into Cetartiodactyla . Balaenidae is a ___MASK1___ of whales of the parvorder Mysticeti that contains two living genera . Historically , it is known as the right whale ___MASK1___ , as it was thought to contain only species of right whales . Through most of the 20th Century , however , that became a much - debated ( and unresolved ) topic amongst the scientific community . Finally , in the early 2000s , science reached a definitive conclusion : the bowhead whale , once commonly known as the Greenland right whale , was not in fact a right whale . The ___MASK1___ of Balaenids , therefore , comprises the right whales ( ___MASK76___ " Eubalaena "), and in a ___MASK76___ all to its own , the very closely related bowhead whale ( ___MASK76___ " Balaena "). The common ___MASK57___ (" ___MASK57___ amphibius "), or hippo , is a large , mostly herbivorous mammal in sub - Saharan Africa , and one of only ___MASK71___ extant ___MASK51___ in the ___MASK1___ Hippopotamidae , the other being the pygmy ___MASK57___ (" Choeropsis liberiensis " or " Hexaprotodon liberiensis "). The name comes from the ancient Greek for " river horse ". After the ___MASK64___ and rhinoceros , the common ___MASK57___ is the third - largest type of land mammal and the heaviest extant artiodactyl . Despite their physical resemblance to pigs and other terrestrial even - toed ungulates , the closest living relatives of the Hippopotamidae are cetaceans ( whales , porpoises , etc .) from which they diverged about . The common ancestor of whales and hippos split from other even - toed ungulates around . The earliest known ___MASK57___ fossils , belonging to the genus " Kenyapotamus " in Africa , date to around . A ___MASK76___ ( genera ) is a taxonomic rank used in the ___MASK21___ of living and fossil organisms in biology . In the ___MASK81___ of ___MASK21___ , ___MASK76___ comes above species and below family . In binomial nomenclature , the ___MASK76___ name forms the first part of the binomial species name for each species within the ___MASK76___ . The sperm ___MASK17___ (" ___MASK100___ "), or cachalot , is the largest of the toothed whales and the largest toothed predator . It is the only living ___MASK48___ of ___MASK76___ Physeter , and one of three extant species in the sperm ___MASK17___ family , along with the pygmy sperm ___MASK17___ and dwarf sperm ___MASK17___ of the ___MASK76___ " Kogia ". The Kogiidae are a ___MASK1___ comprising two extant species of ___MASK34___ . A number of genera are extinct . Whales are a widely distributed and diverse ___MASK62___ of fully aquatic placental marine mammals . They are an informal grouping within the infraorder ___MASK34___ , usually excluding dolphins and porpoises . Whales , dolphins and porpoises belong to the order Cetartiodactyla with even - toed ungulates and their closest living relatives are the hippopotamuses , having diverged about 40 million years ago . The two parvorders of whales , baleen whales ( Mysticeti ) and toothed whales ( Odontoceti ), are thought to have split apart around 34 million years ago . The whales comprise eight extant families : Balaenopteridae ( the rorquals ), Balaenidae ( right whales ), Cetotheriidae ( the pygmy right whale ), Eschrichtiidae ( the gray whale ), Monodontidae ( belugas and narwhals ), Physeteridae ( the sperm whale ), Kogiidae ( the dwarf and pygmy sperm whale ), and Ziphiidae ( the beaked whales ). Eschrichtiidae or the gray whales is a ___MASK1___ of baleen whale ( suborder Mysticeti ) with a ___MASK15___ extant species , the gray whale (" Eschrichtius robustus "). The ___MASK1___ , however , also includes three described fossil genera : " Archaeschrichtius " and " Eschrichtioides " from the Miocene and Pliocene of Italy respectively , and " Gricetoides " from the Pliocene of North Carolina . The names of the extant genus and the ___MASK1___ honours Danish zoologist Daniel Eschricht . ___MASK34___ are a widely distributed and diverse clade of aquatic mammals that today consists of the whales , dolphins , and porpoises . Cetaceans are carnivorous and finned . Most species live in the ___MASK56___ , some in rivers . The name is derived from the Latin " cetus " " whale " and Greek " ketos " " huge fish ". Cuvier ' s beaked ___MASK17___ or the goose - beaked ___MASK17___ (" Ziphius cavirostris "), the only ___MASK48___ of the ___MASK76___ Ziphius , is the most widely distributed of all the beaked whales . Though it is pelagic , prefers ___MASK44___ deeper than , and avoids ships , it is still one of the most frequently spotted beaked whales . Mammals are any vertebrates within the ___MASK75___ Mammalia ( from Latin " mamma " " breast "), a ___MASK77___ of endothermic amniotes distinguished from reptiles and birds by the possession of a neocortex ( a region of the ___MASK92___ ), hair , three middle ear bones and mammary glands . The sister group of mammals may be the extinct " Haldanodon ." The mammals represent the only living Synapsida , which together with the Sauropsida form the Amniota ___MASK77___ . The mammals consist of the Yinotheria including monotrema and the Theriiformes including the theria .