The entotympanic is a bone found in the ear region of many

placental Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished ...

mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...

. When present it forms the medioventral part of the

auditory bulla The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal. It originates as a separate bone (tympanic b ...

; it is a neomorphic element derived from the tubal cartilage and the sheath of the tympanohyal. It is found in a wide variety of placental mammals, including

Xenarthra Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a superorder and major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and ...

, Afroinsectophilia,

Hyracoidea Hyraxes (), also called dassies, are small, stout, thickset, herbivorous mammals in the family (biology), family Procaviidae within the Order (biology), order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Modern hyraxes ...

Pholidota Pangolins, sometimes known as scaly anteaters, are mammals of the order Pholidota (). The one Neontology, extant family, the Manidae, has three genera: ''Manis'', ''Phataginus'', and ''Smutsia''. ''Manis'' comprises four species found in Asia, ...

Carnivora Carnivora ( ) is an order of placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 279 species. Carnivor ...

Perissodactyla Perissodactyla (, ), or odd-toed ungulates, is an order of ungulates. The order includes about 17 living species divided into three families: Equidae (horses, asses, and zebras), Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They t ...

Chiroptera Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

Dermoptera Colugos (), flying lemurs, or cobegos (), are arboreal gliding euarchontogliran mammals that are native to Southeast Asia. Their closest evolutionary relatives are primates. There are just two living species of colugos: the Sunda flying lemur ...

, and Scandentia; it is (apparently secondarily) reduced or absent in

Glires Glires (, Latin ''glīrēs'' 'dormice') is a clade (sometimes ranked as a grandorder) consisting of rodents and lagomorphs ( rabbits, hares, and pikas). The hypothesis that these form a monophyletic group has been long debated based on morph ...

Primates Primates is an order of mammals, which is further divided into the strepsirrhines, which include lemurs, galagos, and lorisids; and the haplorhines, which include tarsiers and simians ( monkeys and apes). Primates arose 74–63 ...

Eulipotyphla Eulipotyphla (, from '' eu-'' + '' Lipotyphla'', meaning truly lacking blind gut; sometimes called true insectivores) is an order of mammals comprising the Erinaceidae ( hedgehogs and gymnures); Solenodontidae (solenodons); Talpidae ( mole ...

, and

Artiodactyla Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...

(including

Cetacea Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

). It is the only common neomorphic element of the mammalian

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

. The entotympanic contacts the

ectotympanic The ectotympanic, or tympanicum, is a bony structure found in all mammals, located on the tympanic part of the temporal bone, which holds the tympanic membrane (eardrum) in place. In catarrhine primates (including humans), it takes a tube-shape. ...

, with which it makes up the auditory bulla.

References

Skull Mammal anatomy Musculoskeletal system stubs Vertebrate anatomy stubs {{Vertebrate-anatomy-stub