Hadrocodium
Hadrocodium wui (hadro from Greek ἁδρός/hadros, "large, heavy, fullness";[1] Latin: codium, from Greek κώδεια/kodeia, "head [of a plant]" [2] (alluding to its enlarged cranial cavity);[3] and wui, the Latinized version of discoverer Xiao-Chun Wu's name[4]) is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately 195 million years ago[5] in the Lufeng basin in what is now the Yunnan province in south-western China[4]
(25°12′N 102°06′E / 25.2°N 102.1°E / 25.2; 102.1, paleocoordinates 34°18′N 104°54′E / 34.3°N 104.9°E / 34.3; 104.9).[6]
The fossil of this mouse-like, paper-clip sized animal was discovered in 1985 but was then interpreted as a juvenile morganucodontid.[1] Hadrocodium remained undescribed until 2001; since then its large brain and advanced ear structure[7] have greatly influenced the interpretation of the earliest stages of mammalian evolution, as these mammalian characters could previously be traced only to some 150 million years ago.[8] Hadrocodium is known only from a skull, but the body is estimated to have been a mere 3.2 cm (1.3 in) in length and about 2 g (0.071 oz) in mass, making it one of the smallest mammals ever.
Features
Hadrocodium might have been the first animal to have a nearly fully mammalian middle ear. It is the earliest known example of several features possessed only by mammals,[9] including the middle-ear structure characteristic of modern mammals and a relatively large brain cavity.[7] These features had been considered limited to the crown group mammals, who emerged in the Middle Jurassic; the discovery of Hadrocodium suggests that these attributes appeared earlier (45 million years earlier) than previously thought.
Whether Hadrocodium was warm-blooded or cold-blooded has not been settled, although its apparent nocturnal features would seem to place it in the endotherm group.
Family Tree
- Phylogeny [10]
See also
References
- 1 2 Luo, Crompton & Sun 2001, Note 1
- ↑ Liddell & Scott 1940
- ↑ Luo, Z.-X. (2001). "A New Mammaliaform from the Early Jurassic and Evolution of Mammalian Characteristics". Science. 292 (5521): 1535–40. PMID 11375489. doi:10.1126/science.1058476.
- 1 2 Parsell 2001
- ↑ Luo, Crompton & Sun 2001, Abstract
- ↑ Hei Koa Peng, Lufeng (CUP, IVPP) (Jurassic of China) in the Paleobiology Database. Retrieved April 2013.
- 1 2 CNN 2001
- ↑ CMNH 2001
- ↑ Symmetrodonta - Palaeos
- ↑ Close, Roger A.; Friedman, Matt; Lloyd, Graeme T.; Benson, Roger BJ (2015). "Evidence for a mid-Jurassic adaptive radiation in mammals.". Current Biology. 25 (16): 2137–2142. PMID 26190074. doi:10.1016/j.cub.2015.06.047.
Bibliography
- "Hadrocodium wui". Carnegie Museum of Natural History. 2001. Retrieved April 2013.
- "Tiny creature may be ancestor of all mammals". CNN. May 24, 2001. Retrieved April 2013.
- Liddell, Henry George; Scott, Robert (1940). "A Greek–English Lexicon: κώδεια". Perseus Digital Library. Retrieved April 2013.
- Luo, Zhe-Xi; Crompton, Alfred W.; Sun, Ai-Lin (2001). "A New Mammaliaform from the Early Jurassic and Evolution of Mammalian Characteristics" (PDF). Science. 292 (5521): 1535–1540. Bibcode:2001Sci...292.1535L. PMID 11375489. doi:10.1126/science.1058476.
- Parsell, D.L. (May 24, 2001). "Tiny Fossil From Early Jurassic Fills New Niche in Mammal Evolution". National Geographic News. Retrieved April 2013.
- Rowe, Timothy; Macrini, Thomas E; Luo, Zhe-Xi (May 2011). "Fossil Evidence on Origin of the Mammalian Brain". Science. 332 (955): 955–7. Bibcode:2011Sci...332..955R. PMID 21596988. doi:10.1126/science.1203117. (Supporting online material)
External links
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Related categories |
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- Mammaliaformes
- Docodonts
- Morganucodonts
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