文章基本信息

标题：New data on the Paleocene monotreme Monotrematum sudamericanum, and the convergent evolution of triangulate molars
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作者：ROSENDO PASCUAL ; FRANCISCO J. GOIN ; LUCÍA BALARINO 等
期刊名称：Acta Palaeontologica Polonica
印刷版ISSN：0567-7920
电子版ISSN：1732-2421
出版年度：2002
卷号：47
期号：3
页码：487-492
语种：English
出版社：Institute of Paleobiology PAS
摘要：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.
关键词：Monotremata;Monotrematum;pseudo-triangulate molars;molar structure;Gondwana;Patagonia;Paleocene