Asfaltomylos

• South America ( Cañadón Asphalt Formation)

Asfaltomylos is a genus of fossil mammals from the late Middle Jurassic of South America. It is an almost complete lower jaw ( mandible ) with teeth known and was the first mammal from the Jurassic of South America, which was described in terms of fossil remains. The tiny jaw was found in late 2000 in Patagonia of Argentina's Pablo Puerta taxidermist in the Cañadón Asphalt Formation in the Argentine province of Chubut and described by a German - Argentine research team led by Oliver Rauhut as a new genus and species, Asfaltomylos patagonicus, 2002.

The molars ( molars ) of Asfaltomylos already have a more modern, tribosphenische structure with hochkompexen cutting edge and grating surfaces on a talonid (tooth pool), which is formed by three cusps. Such a structure reminiscent of the modern mammals ( Theria, or more generally Tribosphenida ). Mammals with such complex molars, which are considered the ancestors of modern mammals were, up to the findings of Ambondro and Asfaltomylos earliest from the upper Cretaceous of the northern hemisphere ( Laurasia ) known. The discovery of Ambondro in the Middle Jurassic of Madagascar in 1999 was therefore a surprise, which led to the theory that modern mammals much earlier than previously thought and in Gondwana (ie in the southern hemisphere ) emerged. Asfaltomylos showed, however, that the complex molars are combined with a primitive jaw, indicative of a convergent development of these teeth. The notion that tribosphenische teeth therefore born twice in the evolutionary history of mammals, was also confirmed by the detailed study of the find, which indicates that the Kaumechanismus is significantly different from that of modern mammals.

Thus Asfaltomylos supports the theory that today's monotremes ( Monotremata, egg-laying mammals) and the Theria very early in the evolution of mammals separated from each other and independently developed molars in the course of their development, the one just before the discovery of had been set up American- Polish research team led by Luo Zhexi (see Australosphenida ).