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Mesozoic mammals of Madagascar
Several mammals are known from the Mesozoic of Madagascar. The Bathonian (middle Jurassic) ''Ambondro'', known from a piece of jaw with three teeth, is the earliest known mammal with molars showing the modern, tribosphenic pattern that is characteristic of marsupial and placental mammals. Interpretations of its affinities have differed; one proposal places it in a group known as Australosphenida with other Mesozoic tribosphenic mammals from the southern continents (Gondwana) as well as the monotremes, while others favor closer affinities with northern (Laurasian) tribosphenic mammals or specifically with placentals. At least five species are known from the Maastrichtian (late Cretaceous), including a yet undescribed species known from a nearly complete skeleton that may represent a completely new group of mammals. The gondwanathere ''Lavanify'', known from two teeth, is most closely related to other gondwanatheres found in India and Argentina. Two other teeth may represent another gondwanathere or a different kind of mammal. One molar fragment is one of the few known remains of a multituberculate mammal from Gondwana and another (UA 8699) has been interpreted as either a marsupial or a placental.
==Jurassic==
(詳細はAmbondro mahabo'' was described from the middle Jurassic (Bathonian, about 167 million years ago) of northwestern Madagascar in 1999. It is known from a single lower jaw fragment with three teeth, probably the last premolar and first two molars. The molars have been interpreted as showing the tribosphenic pattern that is characteristic of modern mammals; ''Ambondro'' is the oldest known mammal with such a pattern. This led its discoverers to propose that the ancestors of tribosphenic mammals arose in the south (Gondwana), not, as generally assumed, in the north (Laurasia). In 2001, however, paleontologist Zhe-Xi Luo and colleagues alternatively proposed that ''Ambondro'' was part of a clade with ''Ausktribosphenos'' from the Cretaceous of Australia and the monotremes that developed tribosphenicity independently from other mammals (Boreosphenida). This clade, Australosphenida, has since been expanded with more recently discovered species from Argentina (''Asfaltomylos'' and ''Henosferus'') and Australia (''Bishops''). Other paleontologists have disagreed with this interpretation and proposed different models; for example, in 2001 Denise Sigogneau-Russell and colleagues proposed that although ''Ausktribosphenos'' and monotremes were related, ''Ambondro'' was not and was in fact more similar to boreosphenidans, and in 2003 Michael Woodburne and colleagues excluded monotremes from Australosphenida and placed the remaining australosphenidans close to placentals. The deposits that produced ''Ambondro'' have yielded some reptiles, but no other mammals.〔Flynn et al., 1999; Luo et al., 2001, 2002; Sigogneau-Russell et al., 2001; Woodburne, 2003; Woodburne et al., 2003; Rougier et al., 2007〕
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