Stem Lagomorpha and the Antiquity of Glires.

LAGOMORPHA; PHYLOGENY; BIOLOGICAL evolution; CENOZOIC paleopedology; HYPOTHESIS; RODENTS

We describe several fossils referable to Gomphos elkema fromdeposits close to the Paleocene-Eocene boundary at Tsagan Khushu,Mongolia. Gomphos shares a suite of cranioskeletal characters withextant rabbits, hares, and pikas but retains a primitive dentition andjaw compared to its modern relatives. Phylogenetic analysis supports theposition of Gomphos as a stem lagomorph and excludes Cretaceous taxafrom the crown radiation of placental mammals. Our results support thehypothesis that rodents and lagomorphs radiated during the Cenozoic anddiverged from other placental mammals close to the Cretaceous-Tertiaryboundary. [ABSTRACT FROM AUTHOR]

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