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New data on the Paleocene monotreme Monotrematum sudamericanum, and the convergent evolution of triangulate molars

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Pascual R., Goin F. J., Balarino L., Udrizar Sauthier D. E.

Acta Palaeontologica Polonica

2002

tom 47

nr 3

We describe an additional fragmentary upper molar and the first lower molar known of Monotrematum sudamericanum, the oldest Cenozoic (Paleocene) monotreme. Comparisons suggest that the monotreme evolution passed through a stage in which their molars were “pseudo−triangulate”, without a true trigonid, and that the monotreme pseudo−triangulate pattern did not arise through rotation of the primary molar cusps. Monotreme lower molars lack a talonid, and consequently there is no basin with facets produced by the wearing action of a “protocone”; a cristid obliqua connecting the “talonid“ to the “trigonid” is also absent. We hypothesize that acquisition of the molar pattern seen in Steropodon galmani (Early Cretaceous, Albian) followed a process similar to that already postulated for docodonts (Docodon in Laurasia, Reigitherium in the South American sector of Gondwana) and, probably, in the gondwanathere Ferugliotherium.

Ograniczanie wyników

1 Acta Palaeontologica Polonica

1 Balarino L.

1 Goin F. J.

1 Pascual R.

1 Udrizar Sauthier D. E.

1 2002

Wyniki wyszukiwania

New data on the Paleocene monotreme Monotrematum sudamericanum, and the convergent evolution of triangulate molars