title: Stem Lagomorpha and the antiquity of Glires.
abstract: We describe several fossils referable to Gomphos elkema from deposits close to the Paleocene-Eocene boundary at Tsagan Khushu, Mongolia. Gomphos shares a suite of cranioskeletal characters with extant rabbits, hares, and pikas but retains a primitive dentition and jaw compared to its modern relatives. Phylogenetic analysis supports the position of Gomphos as a stem lagomorph and excludes Cretaceous taxa from the crown radiation of placental mammals. Our results support the hypothesis that rodents and lagomorphs radiated during the Cenozoic and diverged from other placental mammals close to the Cretaceous-Tertiary boundary.
authors.affiliation: Museum für Naturkunde, Humboldt Universität, Invalidenstrasse 43, 10115 Berlin, Germany. robert.asher@museum.hu-berlin.de
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Asher
authors.forename: Jin
authors.initials: J
authors.lastname: Meng
authors.forename: John R
authors.initials: JR
authors.lastname: Wible
authors.forename: Malcolm C
authors.initials: MC
authors.lastname: McKenna
authors.forename: Guillermo W
authors.initials: GW
authors.lastname: Rougier
authors.forename: Demberlyn
authors.initials: D
authors.lastname: Dashzeveg
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Novacek
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005529:Foot Bones / Q000033:anatomy & histology; D005580:Fossils; D007568:Jaw / Q000033:anatomy & histology; D007793:Lagomorpha / Q000033:anatomy & histology / Q000145:classification; D007867:Leg Bones / Q000033:anatomy & histology; D008322:Mammals / Q000033:anatomy & histology / Q000145:classification; D008986:Mongolia; D010161:Paleodontology; D010802:Phylogeny; D012377:Rodentia / Q000033:anatomy & histology / Q000145:classification; D012886:Skull / Q000033:anatomy & histology; D013131:Spine / Q000033:anatomy & histology