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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, (modern-day North America, Europe, and Asia). However, recent discoveries in China include some exceptionally well preserved, almost complete body fossils.Luo, Z., Meng, Q., Ji, Q., Liu, D., Zhang, Y., Neander, A. I. 2015 Evolutionary development in basal mammaliaformes as revealed by a docodontan. Science, 347, 6223, 760-764Meng, Q., Ji, Q., Zhang, Y., Liu, D., Grossnickle, D. M., and Luo, Z. 2015 An arboreal docodont from the Jurassic and mammaliaform ecological diversification. Science, 347, 6223, 760-764.

Description

Docodontans are an early branch of the mammaliaform tree, but unlike other early mammals they developed a more complex tooth shape, allowing them to pierce and crush food. This tooth shape includes a series of tall cusps in two rows, and a basin between them called a pseudotalonid.Luo Z-X, and Martin T. 2007 Analysis of molar structure and phylogeny of docodont genera. Bulletin of the Carnegie Museum of Natural History 39: 27-47 The 'pseudo-' refers to this structure's resemblance to the later true talonid basins on the tribosphenic teeth of crown Mammalia, which evolved convergently with those of the early docodontans. Docodonts and other Mesozoic mammals were traditionally thought to have been primarily ground dwelling and insectivorous, but recent more complete fossils from China have shown this is not the case. ''Castorocauda''Ji, Q., Luo, Z., Yuan, C. and Tabrum, A. R. 2006 A swimming Mammaliaform from the Middle Jurassic and ecomorphological diversification of early mammals. Science, 311, 1123-1127. from the Middle Jurassic of China, and possibly ''Haldanodon''Kühne W. G. and Krusat, G. 1972. Legalisierung des Taxon Haldanodon (Mammalia, Docodonta). Neues Jahrbuch für Geologie Monatshefte 1972:300-302Krusat, G. 1991 Functional morphology of Haldanodon exspectatus (Mammalia, Docodonta) from the Upper Jurassic of Portugal. Fifth Symposium on Mesozoic Terrestrial Ecosystems and Biota. from the Upper Jurassic of Portugal, were specialised for a semi-aquatic lifestyle. ''Castorocauda'' had a flattened tail and recurved molars, which suggests possible fish or aquatic invertebrate diet. It was thought possible that docodonts had tendencies towards semi-aquatic habits, given their presence in wetland environments, although this could also be explained by the ease with which these environments preserve fossils compared with more terrestrial ones. Recent discoveries of other complete docodontans such as the specialised digging species ''Docofossor'', and specialised tree-dweller ''Agilodocodon'' suggest Docodonta was more ecologically diverse than previously suspected. ''Docofossor'' shows many of the same physical traits as the modern day golden mole, such as wide, shortened digits in the hands for digging.

Taxonomy

Docodonts are not as closely related to the placentals and marsupials as the monotremes, and are not included in the crown-group mammals. The complexity of their molars and the fact that they possess the dentary-squamosal jaw joint, means that they were previously sometimes regarded as belonging to Mammalia. Modern authors usually limit the term "Mammalia" to the crown group, which excludes earlier mammaliaforms like the docodontans, but they are considered to be closer to Mammalia than many other early mammalian groups such as Morganucodonta, Kuehneotheriidae, Haramiyida and ''Sinoconodon''. One disputed docodont, ''Gondtherium'', has been described from India, which was previously part of the Southern Hemisphere continent of Gondwana.Prasad GVR, and Manhas BK. 2007. A new docodont mammal from the Jurassic Kota Formation of India. Palaeontologia electronica, 10.2: 1-11. However this identification is not certain, and some authors have chosen to exclude it from their analyses of Docodonta. In recent analyses, ''Gondtherium'' falls outside the docodont family tree. There has also been a suggestion of erecting two sub-families (Simpsonodontidae and Tegotheridae) within Docodonta, but these groups are not found in any other analyses, and therefore not accepted by all mammal palaeontologists. **Superfamily †Docodontoidea *** †''Dsungarodon zuoi'' Pfretzschner et al. 2005 '[[Acuodulodon''_Hu,_Meng_&_Clark_2007;_''[[Acuodulodon_sunae.html" style="text-decoration: none;"class="mw-redirect" title="Acuodulodon.html" style="text-decoration: none;"class="mw-redirect" title="'[[Acuodulodon">'[[Acuodulodon'' Hu, Meng & Clark 2007; ''[[Acuodulodon sunae">Acuodulodon.html" style="text-decoration: none;"class="mw-redirect" title="'[[Acuodulodon">'[[Acuodulodon'' Hu, Meng & Clark 2007; ''[[Acuodulodon sunae'' Hu, Meng & Clark 2007] *** †''[[Simpsonodon'' Kermack et al. 1987 **** †''[[Simpsonodon|S. splendens'' (Kühne 1969) **** †''[[Simpsonodon|S. sibiricus'' Averianov et al. 2010 ***Family †Docodontidae (Marsh 1887) Simpson 1929 **** †''Agilodocodon scansorius'' Meng et al. 2015 **** †''Borealestes'' Waldman & Savage 1972 ***** †''B. serendipitus'' Waldman & Savage 1972Waldman, M and Savage, R.J.G 1972 The first Jurassic mammal from Scotland. Journal of the Geological Society of London 128:119-125 ***** †''B. mussetti'' Sigogneau-Russell 2003 **** †''Castorocauda lutrasimilis'' Ji et al. 2006 **** †''Cyrtlatherium canei'' Freeman 1979 sensu Sigogneau-Russell 2001 isputed'[[Simpsonodon_oxfordensis''_Kermack_et_al._1987.html" style="text-decoration: none;"class="mw-redirect" title="Simpsonodon oxfordensis">'Simpsonodon_oxfordensis">'[[Simpsonodon_oxfordensis''_Kermack_et_al._1987****_†''[[Docodon.html" style="text-decoration: none;"class="mw-redirect" title="Simpsonodon oxfordensis'' Kermack et al. 1987">Simpsonodon oxfordensis">'[[Simpsonodon oxfordensis'' Kermack et al. 1987**** †''[[Docodon">Simpsonodon oxfordensis'' Kermack et al. 1987">Simpsonodon oxfordensis">'[[Simpsonodon oxfordensis'' Kermack et al. 1987**** †''[[Docodon'' Marsh 1881 [''Dicrocynodon'' Marsh in Osborn, 1888; ''Diplocynodon'' Marsh 1880 non Pomel 1847; ''Ennacodon'' Marsh 1890; ''Enneodon'' Marsh 1887 non Prangner 1845] ***** †''[[Docodon|D. apoxys'' Rougier et al. 2014 ***** †''[[Docodon|D. victor'' (Marsh 1880) [''Dicrocynodon victor'' (Marsh 1880); ''Diplocynodon victor'' Marsh 1880] ***** †''Docodon|D. striatus'' Marsh 1881 isputed***** †''D. affinis'' (Marsh 1887) 'Enneodon affinis'' Marsh 1887isputed***** †''D. crassus'' (Marsh 1887) 'Enneodon crassus'' Marsh 1887; ''Ennacodon crassus'' (Marsh 1887)isputed***** †''D. superus'' Simpson 1929 isputed**** †''Docofossor brachydactylus'' Luo et al. 2015 **** †''Gondtherium dattai'' Prasad & Manhas 2007 isputed**** †''Haldanodon exspectatus'' Kühne & Krusat 1972 sensu Sigoneau-Russell 2003 **** †''Krusatodon kirtlingtonensis'' Sigogneau-Russell 2003 **** †''Peraiocynodon'' Simpson 1928 ***** †''P. inexpectatus'' Simpson 1928 [possible synonym of ''Docodon'', Butler 1939Butler PM. 1939
The teeth of the Jurassic mammals
In Proceedings of the Zoological Society of London, 109:329-356). Oxford, UK: Blackwell Publishing Ltd.
***** †''[[Peraiocynodon|P. major'' Sigogneau-Russell 2003 [disputed] **** †''[[Tashkumyrodon|Tashkumyrodon desideratus'' Martin & Averianov 2004 ***Family †Tegotheriidae **** †''Hutegotherium yaomingi'' Averianov et al. 2010 **** †''Sibirotherium rossicus'' Maschenko, Lopatin & Voronkevich 2002 **** †''Tegotherium gubini'' Tatarinov 1994

See also

* Evolution of mammals

References



External links


Docodonta from Palaeos
{{Taxonbar|from=Q133270 Category:Fossil taxa described in 1946 Category:Middle Jurassic first appearances Category:Early Cretaceous extinctions Category:Taxa named by Miklós Kretzoi