Maotherium

Last updated

Maotherium
Temporal range: Early Cretaceous, 124.6  Ma
O
S
D
C
P
T
J
K
Pg
N
Maotherium.jpg
Maotherium skeleton
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Symmetrodonta
Family: Zhangheotheriidae
Genus: Maotherium
Rougier et al., 2003
Type species
Maotherium sinensis
Rougier et al., 2003
Species
  • M. sinensis
  • M. asiaticus

Maotherium is a genus extinct symmetrodont mammal that was discovered in Early Cretaceous rocks in Liaoning Province, China, in 2003. [1] Its scientific name directly translates to "fur beast", in reference to the impressions of fur around the fossil. [1] Maotherium belongs to an extinct group of Mesozoic mammals called symmetrodonts. 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 , during the early 21st century. One of the fossils of Maotherium preserved the imprints of fur, like the mammals Eomaia and Sinodelphys .

A species described in 2009, Maotherium asiaticus, sheds light on the evolution of the mammalian middle ear. In modern mammals, the Meckel's cartilage appears during development but disappears before adulthood. In Maotherium asiaticus, that cartilage not only remained, but turned into bone. [2] This event in evolution may be an example of heterochrony, a change in the timing of development. [3]

Related Research Articles

<i>Eomaia</i> Extinct genus of mammals

Eomaia is a genus of extinct fossil mammals containing the single species Eomaia scansoria, discovered in rocks that were found in the Yixian Formation, Liaoning Province, China, and dated to the Barremian Age of the Lower Cretaceous about 125 million years ago. The single fossil specimen of this species is 10 centimetres (3.9 in) in length and virtually complete. An estimate of the body weight is between 20–25 grams (0.71–0.88 oz). It is exceptionally well-preserved for a 125-million-year-old specimen. Although the fossil's skull is squashed flat, its teeth, tiny foot bones, cartilages and even its fur are visible.

<span class="mw-page-title-main">Synapsid</span> Clade of tetrapods

Synapsids are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptiles and birds. The group includes mammals and every animal more closely related to mammals than to sauropsids. Unlike other amniotes, synapsids have a single temporal fenestra, an opening low in the skull roof behind each eye orbit, leaving a bony arch beneath each; this accounts for their name. The distinctive temporal fenestra developed about 318 million years ago during the Late Carboniferous period, when synapsids and sauropsids diverged, but was subsequently merged with the orbit in early mammals.

<i>Hadrocodium</i> Extinct genus of mammaliaforms

Hadrocodium wui is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately 195 million years ago in the Lufeng Formation of the Lufeng Basin in what is now the Yunnan province in south-western China (25.2°N 102.1°E, paleocoordinates 34.3°N 104.9°E). It is considered as the closest relative of the class Mammalia.

<i>Sinodelphys</i> Extinct genus of marsupialiform mammals

Sinodelphys is an extinct eutherian 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-Xi Luo and John Wible.

<span class="mw-page-title-main">Symmetrodonta</span> Extinct order of mammals

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 age from the latest Triassic to the Late Cretaceous, but most research in the last 20-30 years has concluded that they are not a true taxonomic group, but include several unrelated branches of the mammal tree. Despite this, the name is still used informally by some researchers for convenience, usually restricted to the spalacotheriids and zhangheotheriids.

<i>Akidolestes</i> Extinct genus of mammals

Akidolestes is an extinct genus of mammals from the family spalacotheriid.

<span class="mw-page-title-main">Docodonta</span> Extinct order of mammaliaforms

Docodonta is an order of extinct mammaliaforms that lived during the Mesozoic, from the Middle Jurassic to Early Cretaceous. They are distinguished from other early mammaliaforms by their relatively complex molar teeth, from which the order gets its name. Until recently, Docodonta were represented primarily by teeth and jaws found across former Laurasia,. However, recent discoveries in China include some exceptionally well preserved, almost complete body fossils.

<span class="mw-page-title-main">Mammaliaformes</span> Clade of mammals and extinct relatives

Mammaliaformes is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia, and Placentalia. Besides Morganucodonta and the crown group mammals, Mammaliaformes includes Docodonta and Hadrocodium as well as the Triassic Tikitherium, the earliest known member of the group.

<i>Volaticotherium</i> Extinct family of mammals

Volaticotherium antiquum is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus Volaticotherium.

<span class="mw-page-title-main">Volaticotherini</span> Extinct clade of mammals

Volaticotherini is a clade of eutriconodont mammals from the Mesozoic. In addition to the type genus Volaticotherium, it includes the genera Argentoconodon, Ichthyoconodon, and potentially Triconolestes.

<span class="mw-page-title-main">Evolution of mammals</span> Derivation of mammals from a synapsid precursor, and the adaptive radiation of mammal species

The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synapsid species that looked like mammals. The lineage leading to today's mammals split up in the Jurassic; synapsids from this period include Dryolestes, more closely related to extant placentals and marsupials than to monotremes, as well as Ambondro, more closely related to monotremes. Later on, the eutherian and metatherian lineages separated; the metatherians are the animals more closely related to the marsupials, while the eutherians are those more closely related to the placentals. Since Juramaia, the earliest known eutherian, lived 160 million years ago in the Jurassic, this divergence must have occurred in the same period.

<span class="mw-page-title-main">Eutriconodonta</span> Extinct order of mammals

Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack et al. in 1973 as a replacement name for the paraphyletic Triconodonta.

<i>Yanoconodon</i> Extinct family of mammals

Yanoconodon is a monotypic genus of extinct early mammal whose representative species Yanoconodon allini lived during the Mesozoic in what is now China. The holotype fossil of Yanoconodon was excavated in the Yan Mountains about 300 kilometres from Beijing in the Qiaotou member of the Huajiying Formation of Hebei Province, China, and is therefore of uncertain age. The Qiaotou Member may correlate with the more well-known Early Cretaceous Yixian Formation, and so probably dates to around 122 Ma ago.

<span class="mw-page-title-main">Evolution of mammalian auditory ossicles</span> Middle ear bones evolved from jaw bones

The evolution of mammalian auditory ossicles was an evolutionary event that resulted in the formation of the bones of the mammalian middle ear. These bones, or ossicles, are a defining characteristic of all mammals. The event is well-documented and important as a demonstration of transitional forms and exaptation, the re-purposing of existing structures during evolution.

<span class="mw-page-title-main">Dryolestida</span> Extinct order of mammals

Dryolestida is an extinct order of mammals, known from the Jurassic and Cretaceous. They are considered members of the clade Cladotheria, close to the ancestry of therian mammals. It is also believed that they developed a fully mammalian jaw and also had the three middle ear bones. Most members of the group, as with most Mesozoic mammals, are only known from fragmentary tooth and jaw remains.

<span class="mw-page-title-main">Cladotheria</span> Clade of mammals

Cladotheria is a clade of mammals. It contains modern therian mammals and several extinct groups, such as the dryolestoids, amphitheriids and peramurids. The clade was named in 1975 by Malcolm McKenna. In 2002, it was defined as a node-based taxon containing "the common ancestor of dryolestids and living therians, plus all its descendants". A different, stem-based definition was given in 2013, in which Cladotheria contains all taxa that are closer to Mus musculus than to the "symmetrodont" Spalacotherium tricuspidens.

<span class="mw-page-title-main">Gobiconodonta</span> Extinct order of mammals

Gobiconodonta is an order of extinct mammals known from the Early Jurassic to early Late Cretaceous. They are generally held to be part of Eutriconodonta.

Spinolestes is an extinct mammal genus from the Early Cretaceous of Spain. A gobiconodontid eutriconodont, it is notable for the remarkable degree of preservation, offering profound insights to the biology of non-therian mammals.

Vilevolodon is an extinct, monotypic genus of volant, arboreal euharamiyids from the Oxfordian age of the Late Jurassic of China. The type species is Vilevolodon diplomylos. The genus name Vilevolodon references its gliding capabilities, Vilevol, while don is a common suffix for mammalian taxon titles. The species name diplomylos refers to the dual mortar-and-pestle occlusion of upper and lower molars observed in the holotype; diplo, mylos.

<i>Maiopatagium</i> Extinct genus of mammaliaforms

Maiopatagium is an extinct genus of gliding euharamiyids which existed in Asia during the Jurassic period. It possessed a patagium between its limbs and presumably had similar lifestyle to living flying squirrels and colugos. The type species is Maiopatagium furculiferum, which was described from the Tiaojishan Formation by Zhe-Xi Luo in 2017; it lived in what is now the Liaoning region of China during the late Jurassic .Maiopatagium and Vilevolodon, described concurrently, offer clues to the ways various synapsids have taken to the skies over evolutionary time scales. A second species, M. sibiricum, was described from the Bathonian aged Itat Formation in western Siberia, Russia in 2019

References

  1. 1 2 Rougier, Guillermo W.; Qiang, JI; Novacek, Michael J. (2003). "A New Symmetrodont Mammal with Fur Impressions from the Mesozoic of China". Acta Geologica Sinica. 77 (1): 7–14. doi:10.1111/j.1755-6724.2003.tb00104.x. S2CID   129655279.
  2. Ji Qiang; Luo Zhe-Xi; Zhang Xingliao; Yuan Chong-Xi; Xu Li (2009). "Evolutionary development of the middle ear in Mesozoic therian mammals". Science. 326 (5950): 278–281. doi:10.1126/science.1178501. PMID   19815774. S2CID   206522236.
  3. Martin, Thomas & Ruf, Irina (2009). "On the mammalian ear". Science. 326 (5950): 243–244. doi:10.1126/science.1181131. PMID   19815765. S2CID   26545052.