Hadrocodium Explained

Hadrocodium wui is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately in the Lufeng Formation in what is now the Yunnan province in south-western China(paleocoordinates).^[1] It is considered as the closest relative of the class Mammalia.The fossil of this mouse-like, paper-clip sized animal was discovered in 1985 but was then interpreted as a juvenile morganucodontid. Hadrocodium remained undescribed until 2001; since then its large brain and advanced ear structure have greatly influenced the interpretation of the earliest stages of mammalian evolution, as these mammalian characters could previously be traced only to some . Hadrocodium is known only from a skull long, and its body would have measured long in total and weighed up to, making it one of the smallest Mesozoic mammaliaforms.^{[2] [3]} The specimen is thought to have been that of a mature adult.^[4]

The name Hadrocodium alludes to its large cranial cavity,^[5] deriving from the Greek word ('large, heavy, fullness') and the Latin word Latin: codium, from Greek ('head [of a plant]'). The species name, wui, is the Latinized version of discoverer Xiao-Chun Wu's name.

While initially suggested to have possessed a fully mammalian ear akin to those of modern mammals, a 2022 restudy suggested that it actually had a primitive mandibular middle ear similar to those of other primitive mammaliaforms.

Phylogeny

See main article: Evolution of mammals.

Phylogeny ^[6]

See also

• Smallest organisms
• Evolution of mammalian auditory ossicles

References

Bibliography

• Web site: Hadrocodium wui . Carnegie Museum of Natural History . 2001 . 1 April 2013 . . dead . https://web.archive.org/web/20120617190702/http://www.carnegiemnh.org/vp/hadrocodium.html . 2012-06-17.
• Web site: Tiny creature may be ancestor of all mammals . CNN . May 24, 2001 . 1 April 2013 . . 18 September 2009 . https://web.archive.org/web/20090918213512/http://archives.cnn.com/2001/TECH/science/05/24/tiny.ancestor/index.html . dead .
• Web site: Liddell . Henry George . Henry Liddell . Scott . Robert . Robert Scott (philologist) . A Greek–English Lexicon: κώδεια . 1940 . Perseus Digital Library . 1 April 2013 .
• Luo . Zhe-Xi . Crompton . Alfred W. . Sun . Ai-Lin . A New Mammaliaform from the Early Jurassic and Evolution of Mammalian Characteristics . 2001 . Science . 292 . 5521 . 1535–1540 . 10.1126/science.1058476 . 11375489 . 2001Sci...292.1535L . 8738213 . dead . https://www.webcitation.org/6J0mLMZqR?url=http://www.bi.ku.dk/dna/course/papers/J1.luo.pdf . 2013-08-20 .
• News: Parsell . D.L. . Tiny Fossil From Early Jurassic Fills New Niche in Mammal Evolution . May 24, 2001 . National Geographic News . https://web.archive.org/web/20010813185423/http://news.nationalgeographic.com/news/2001/05/0524_paperclipmammal.html . dead . August 13, 2001 . 1 April 2013 .
• Rowe . Timothy . Macrini . Thomas E . Luo . Zhe-Xi . Fossil Evidence on Origin of the Mammalian Brain . May 2011 . Science . 332 . 955 . 10.1126/science.1203117 . 2011Sci...332..955R . 21596988 . 955–7. 940501 . (Supporting online material)

External links

• Web site: Rowe . Timothy . Macrini . Thomas E . Luo . Zhe-Xi . Hadrocodium wui (On-line) . Digital Morphology at the University of Texas . 2006 . 1 April 2013.  — 3D models from CT scans of the original fossil
• Palaeocritti - a guide to prehistoric animals

Notes and References

1. . Retrieved April 2013.
2. Book: 9780198507611. The Origin and Evolution of Mammals. Oxford University Press, USA. 2005. 22 September 2022. 183. T. S. Kemp. T. S. Kemp.
3. Book: The Princeton Field Guide to Prehistoric Mammals. Princeton University Press. November 15, 2016. 27. Donald R. Prothero. 9780691156828.
4. Luo . Zhexi . Bhullar . Bhart-Anjan . Crompton . Alfred . Neander . April . Rowe . Timothy . 2022 . Reexamination of the Mandibular and Dental Morphology of the Early Jurassic Mammaliaform Hadrocodium wui . Acta Palaeontologica Polonica . 67 . 10.4202/app.00949.2021 . 0567-7920. free .
5. Luo . Z.-X. . A New Mammaliaform from the Early Jurassic and Evolution of Mammalian Characteristics . Science . 292 . 5521 . 1535–40 . 2001 . 11375489 . 10.1126/science.1058476 . 2001Sci...292.1535L . 8738213 .
6. Close. Roger A.. Friedman. Matt. Lloyd. Graeme T.. Benson. Roger B.J.. 2015. Evidence for a mid-Jurassic adaptive radiation in mammals.. Current Biology. 25. 16. 2137–2142. 10.1016/j.cub.2015.06.047. 26190074. free.