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1999 Macmillan Magazines Ltd letters to nature

Summary: © 1999 Macmillan Magazines Ltd
letters to nature
60 NATURE |VOL 401 |2 SEPTEMBER 1999 |www.nature.com
reduces the already slim likelihood that the non-occurrence of therians
before ,110 Myr is due to a preservational/sampling artefact.
Finally, in offering the ®rst well-preserved holotherian dental
remains known from the Middle to Late Jurassic of Gondwana, A.
mahabo has important paleobiogeographic implications. Mesozoic
mammal faunas of Laurasia and Gondwana were long considered to
have remained isolated during much of the late Mesozoic; tribo-
sphenidans (regarded as Laurasian in origin) were thought to have
been excluded from the southern continents until latest Cretaceous or
early Paleocene time, because Mesozoic tribosphenidans remained
undiscovered in Gondwana4
. To the contrary, recent ®nds in Morocco25
and Australia17
indicate the occurrence of tribosphenidans on the
southern continents as early as the earliest Cretaceous (that is, as early
in Gondwana as in Laurasia). The discovery of A. mahabo inverts
this biogeographic scenario even further, showing tribosphenidans


Source: Abouheif, Ehab - Department of Biology, McGill University
Agrawal, Anurag - Department of Ecology and Evolutionary Biology & Entomollogy, Cornell University


Collections: Environmental Sciences and Ecology