''Maotherium'' is a genus extinct symmetrodont mammal that was discovered in

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

rocks in

Liaoning ) , image_skyline = , image_alt = , image_caption = Clockwise: Mukden Palace in Shenyang, Xinghai Square in Dalian, Dalian coast, Yalu River at Dandong , image_map = Liaoning in China (+all claims hatched).svg , ...

Province,

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, in 2003. Its scientific name directly translates to "fur beast", in reference to the impressions of fur around the fossil. ''Maotherium'' belongs to an extinct group of

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

mammal A mammal () is a vertebrate animal of the Class (biology), 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 ...

s called

symmetrodont Symmetrodonta is a group of Mesozoic mammals and mammal-like synapsids characterized by the triangular aspect of the molars when viewed from above, and the absence of a well-developed talonid. The traditional group of 'symmetrodonts' ranges in ...

s. Though little is known about this group, the symmetrodonts have several similarities - specifically their teeth. They have tall pointed, but simple molars in a triangular arrangement. Originally symmetrodonts were known since the 1920s. Now a vast majority have been restored, such as '' Zhangheotherium'' and ''

Akidolestes ''Akidolestes'' is an extinct genus of mammals of the family Spalacotheriidae, a group of mammals related to therians (the subclass containing marsupials and placentals). The genus name, ''Akidolestes'', is derived from ''akido'', Greek for p ...

'', during the early 21st century. One of the fossils of ''Maotherium'' preserved the imprints of fur, like the mammals '' Eomaia'' and ''

Sinodelphys ''Sinodelphys'' is an extinct mammal from the Early Cretaceous, estimated to be 125 million years old. It was discovered and described in 2003 in rocks of the Yixian Formation in Liaoning Province, China, by a team of scientists including Zhe-X ...

''. A species described in 2009, ''Maotherium asiaticus'', sheds light on the evolution of the mammalian middle ear. In modern mammals, the

Meckel's cartilage In humans, the cartilaginous bar of the mandibular arch is formed by what are known as Meckel's cartilages (right and left; also known as Meckelian cartilages), above which the incus and malleus are located. Meckel's cartilage arises from the fir ...

appears during

development Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped * Photographic development *Filmmaking, development phase, including finance and budgeting * Development hell, when a proje ...

but disappears before adulthood. In ''Maotherium asiaticus'', that cartilage not only remained, but turned into bone. This event in evolution may be an example of

heterochrony In evolutionary developmental biology, heterochrony is any genetically controlled difference in the timing, rate, or duration of a Developmental biology, developmental process in an organism compared to its ancestors or other organisms. This lea ...

, a change in the timing of development.

References

{{Taxonbar, from=Q2175998 Symmetrodonta Prehistoric animals of China Early Cretaceous mammals of Asia Prehistoric mammal genera Fossil taxa described in 2003