Yanoconodon
From Wikipedia, the free encyclopedia
| Yanoconodon Fossil range: Early Cretaceous |
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 Yanoconodon allini
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| Yanoconodon allini Chen, Chen, Li & Luo, 2007 |
Yanoconodon is a monotypic genus of extinct early mammal whose representative species Yanoconodon allini lived 125 million years ago during the Mesozoic in what is now China. It is considered to be a transitional fossil due to the formation of its middle ear, which is a cross between those of modern mammals and their nearest relatives, the mammaliaformes. Yanoconodon was a Eutriconodont, a group synonymous to the Triconodonts which lived during the time of the dinosaurs. Indeed, some such as Repenomamus grew so large that they were able to eat small dinosaurs in some cases.[1] In particular, Yanoconodon is considered to be closely related to Jeholodens.[2]
Yanoconodon's name is comprised of two elements: 'Yan' is taken from the Yan Mountains in the north of the Hebei Province near where the holotype of Yanoconodon was found in the Yixian Formation; 'Conodon' is an often used as a mammalian taxonomic suffix meaning 'cuspate tooth'. Its species name, "allini," is derived from mammalian researcher Edgar Allin, who was notable for his research on the mammalian middle ear.[2][3]
[edit] Description
Yanoconodon was a small mammal, barely 5 inches (13 centimetres) long, although at the time of its existence, it was significantly longer than most other animals due to a number of extra vertebrae the animal possessed. It was lightly-built and fed on insects, worms and other invertebrates. Like other Eutriconodonts, Yanoconodon probably hunted at night out of the danger posed by predatory dinosaurs during the day. Like most early mammals, Yanoconodon had short, sprawling legs and claws that were most likely used for burrowing underground or digging.[2][3]
Yanoconodon is the first Mesozoic mammal to be found in China to date. The holotype of Yanoconodon excavated from the fossil-rich Yixian Formation, about 300 kilometres from Beijing, was brilliantly preserved and allowed scientists to discover what the creature is most notable for, the transitional stage of its middle ear. This is said to be the "Rosetta Stone"[3] in regard to the development of the mammalian middle ear and the evolution of complex anatomic features over time. In addition to this discovery, scientists also discovered the presence of lumbar ribs, a particularly rare feature in mammals today. Due to these factors, Yanoconodon is thought to be one of the ancestors of modern Therians and Monotremes as well as other Eutriconodonts.[2][3]
The reason for these changes in Yanoconodon's anatomy has been attributed to the Hox gene, a gene related to changes in the physiology of modern mice. This gene may have also initiated the evolution of the mammals of that time.[2]
[edit] References
- ^ Hu, Y., Meng, J., Wang, Y. & Li, C. (2005). Large Mesozoic mammals fed on young dinosaurs. Nature. Vol 433, 12 January 2005, Number 7022, pp91-178, doi:10.1038/nature03102. See commentary on this article (Retrieved 25/6/2007).
- ^ a b c d e Luo, Z., Chen, P., Li, G., & Chen, M. (2007). A new eutriconodont mammal and evolutionary development in early mammals. Nature. Vol 446, 15 March 2007, doi:10.1038/nature05627.
- ^ a b c d Paleontologists Discover New Mammal from Mesozoic Era at www.physorg.com - Retrieved 25/6/2007.
