Hadrocodium
| Hadrocodium Temporal range: Early Jurassic | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vertebrata |
| (unranked): | Amniota |
| Class: | Synapsida |
| (unranked): | Mammaliaformes |
| Genus: | Hadrocodium Luo, Crompton & Sun 2001 |
| Species | |
| |
Hadrocodium wui (hadro from Greek ἁδρός/hadros, "fullness";[1] Latin: codium, from Greek κώδεια/kodeia, "head [of a plant]";[2] and wui, the Latinized version of discoverer Xiao-Chun Wu's name[3]) is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately 195 million years ago[4] in the Lufeng basin in what is now the Yunnan province in south-western China[3] (25°12′N 102°06′E / 25.2°N 102.1°E, paleocoordinates 34°18′N 104°54′E / 34.3°N 104.9°E).[5]
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[6] 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.[7] 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.
Hadrocodium is the earliest known example of several features possessed only by mammals,[8] including the middle-ear structure characteristic of modern mammals and a relatively large brain cavity.[6] 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.
References
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". Science 292 (5521): 1535–1540. Bibcode:2001Sci...292.1535L. doi:10.1126/science.1058476. PMID 11375489.
- 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). Bibcode:2011Sci...332..955R. doi:10.1126/science.1203117. PMID 21596988. (Supporting online material)
External links
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Wikispecies has information related to: Hadrocodium |
- Rowe, Timothy; Macrini, Thomas E; Luo, Zhe-Xi (2006). "Hadrocodium wui (On-line)". Digital Morphology at the University of Texas. Retrieved April 2013. — 3D models from CT scans of the original fossil