Sinoconodon

Taxobox
name = "Sinoconodon"
fossil_range = fossil range|208 Late Triassic
regnum = Animalia
phylum = Chordata
subphylum = Vertebrata
unranked_classis = Amniota
classis = Synapsida
unranked_ordo = Mammaliaformes
ordo = Sinocodonta
familia = Sinoconodontidae
genus = "Sinoconodon"
genus_authority = Patterson & Olson, 1961

"Sinoconodon rigneyi" is an ancient proto-mammal that appears in the fossil record in the late Triassic period, about 208 million years ago. Although the animal seems more related to "Morganucodon" than anything else, it differed substantially from other Mammaliaformes in its dental and growth habits. Similar to reptiles, it replaced many of its teeth (its incisors, canines, and postcanines) throughout its lifetime, and it seems to have grown slowly but continuously until its death.

Therefore, "Sinoconodon" is generally considered more primitive (less mammalian) than related Mammaliaformes, including docodonts and morganucodonts, which appear a few million years later. Some label it the most primitive mammal taxon, while others do not label it a mammal at all.

References

*Luo, Z.-X., Z. Kielan-Jaworowska, and R.L. Cifelli (2001). In quest for a phylogeny of Mesozoic mammals. "Acta Palaeleon." Pol. 47:1-78

External links

* [http://www.pitt.edu/~biohome/Dept/Frame/Faculty/luoabstract.htm Abstracts from Publications by Dr. Luo]
* [http://www.palaeos.com/Vertebrates/Units/Unit420/420.000.html Mammaliformes from Palaeos]
* [http://www.geocities.com/trevor_dykes/mammalsbasal.htm Mammals of the Mesozoic: The least mammal-like mammals]