What is the medium sized marine animal that is part of the order of placental mammals?
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Evolution of sirenians Sirenia is the order of placental mammals which comprises modern "sea cows" (manatees and the Dugong) and their extinct relatives. They are the only extant herbivorous marine mammals and the only group of herbivorous mammals to have become completely aquatic. Sirenians are thought to have a 50-million-year-old fossil record (early Eocene-recent). They attained modest diversity during the Oligocene and Miocene, but have since declined as a result of climatic cooling, oceanographic changes, and human interference. Two genera and four species are extant: "Trichechus", which includes the three species of manatee that live along the Atlantic coasts and in rivers and coastlines of the Americas and western Africa, and "Dugong", which is found in the Indian and Pacific oceans.
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Dugong The dugong ( , ; "Dugong dugon") is a medium-sized marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow ("Hydrodamalis gigas"), was hunted to extinction in the 18th century. The dugong is the only strictly marine herbivorous mammal.
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Tethytheria Tethytheria is a clade of mammals that includes the sirenians and proboscideans, as well as the extinct order Embrithopoda.
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Microcosmodontidae Microcosmodontidae is a poorly preserved family of fossil mammals within the extinct order Multituberculata. Representatives are known from the Lower Paleocene of North America. The family is part of the suborder Cimolodonta. Other than that, their systematic relationships are hard to define.
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List of placental mammals introduced to Australia A variety of placental mammals have been introduced to Australia since the arrival of Captain Cook in 1770. They have ranged in size from rodents to deer. One other species, the Dingo, was introduced much earlier, but is nevertheless included in this list.
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Macropodiformes The Macropodiformes are one of the three suborders of the large marsupial order Diprotodontia. Kangaroos, wallabies and allies, bettongs, potoroos, and rat kangaroos are all members of this suborder.
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Pinniped Pinnipeds ( ) (from Latin "pinna" "fin" and "pes, pedis" "foot"), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals). There are 33 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their closest living relatives are bears and musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago.
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Nuculanoida Nuculanoida is an order of very small saltwater clams, marine bivalve molluscs in the subclass Protobranchia.
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Meridiolestida Meridiolestida is a clade of non-therian mammals from South America and Africa, and potentially also Australia. It is generally classified within Dryolestida, barring one study recovering them as the sister taxa to spalacotheriid symmetrodonts. However, more recent studies have stuck to the dryolestoid interpretation. They differ from northern dryolestoids in the absence of a parastylar hook on the molariform teeth and the lack of a Meckelian groove.
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Amphipoda Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from 1 to and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far described. They are mostly marine animals, but are found in almost all aquatic environments. Some 1,900 species live in fresh water, and the order also includes terrestrial animals and sandhoppers such as "Talitrus saltator".
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Mytiloida Mytiloida is an order of marine bivalve mollusks, commonly known as true mussels. There is one extant superfamily, the Mytiloidea, with a single family, the Mytilidae.
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Placenta The placenta (also known as afterbirth) is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother's blood supply; to fight against internal infection; and to produce hormones which support pregnancy. The placenta provides oxygen and nutrients to growing fetuses and removes waste products from the fetus's blood. The placenta attaches to the wall of the uterus, and the fetus's umbilical cord develops from the placenta. These organs connect the mother and the fetus. Placentas are a defining characteristic of placental mammals, but are also found in marsupials and some non-mammals with varying levels of development. The homology of such structures in various viviparous organisms is debatable, and in invertebrates such as Arthropoda, is analogous at best.
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Pentamerida Pentamerida is an order of biconvex, impunctate shelled, articulate brachiopods that are found in marine sedimentary rocks that range from the Middle Cambrian through the Devonian.
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Verticordiidae Verticordiidae is a taxonomic family of very small saltwater clams, marine bivalve molluscs in the order Pholadomyoida.
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Holothuria Holothuria is a genus of marine animals of the family Holothuriidae. Members of the genus are found in coastal waters in tropical and temperate regions. They are soft bodied, limbless invertebrates that dwell on the ocean floor. They resemble a cucumber in form.
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Desmostylia The Desmostylia (from Greek δεσμά "desma", "bundle", and στῦλος "stylos", "pillar") are an extinct order of aquatic mammals that existed from the late Oligocene (Arikareean) to the late Miocene (Tortonian) ().
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Pacific loon The Pacific loon or Pacific diver ("Gavia pacifica"), is a medium-sized member of the loon, or diver, family.
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Phormosoma placenta Phormosoma placenta is a species of sea urchin in the order Echinothurioida. It is a deepwater species, seldom being found at depths less than 500 m , and occurs on either side of the Atlantic Ocean on the continental slope.
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Cachalot (disambiguation) The sperm whale, or common cachalot, is a large toothed whale belonging to the order Cetacea.
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Cambaytherium Cambaytherium is an extinct placental mammal genus of the family Cambaytheriidae. Known from the Eocene whose fossils were found in an open pit coal mine located in Gujarat, India.
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Theria Theria ( ; Greek: "θηρίον", wild beast) is a subclass of mammals amongst the Theriiformes (the sister taxa to Yinotheria). Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials).
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Oceanic dolphin Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Thirty extant species are described. They include several big species whose common names contain "whale" rather than "dolphin", such as the killer whale and the pilot whales. Delphinidae is a family within the superfamily Delphinoidea, which also includes the porpoises (Phocoenidae) and the Monodontidae (beluga whale and narwhal). River dolphins are relatives of the Delphinoidea.