Abstract
Marsupials, placentals and their close therian relatives possess complex (tribosphenic) molars that are capable of versatile occlusal functions. This functional complex is widely thought to be a key to the early diversification and evolutionary success of extant therians and their close relatives (tribosphenidans). Long thought to have arisen on northern continents, tribosphenic mammals have recently been reported from southern landmasses. The great age and advanced morphology of these new mammals has led to the alternative suggestion of a Gondwanan origin for the group. Implicit in both biogeographic hypotheses is the assumption that tribosphenic molars evolved only once in mammalian evolutionary history. Phylogenetic and morphometric analyses including these newly discovered taxa suggest a different interpretation: that mammals with tribosphenic molars are not monophyletic. Tribosphenic molars evolved independently in two ancient (holotherian) mammalian groups with different geographic distributions during the Jurassic/Early Cretaceous: an australosphenidan clade endemic to Gondwanan landmasses, survived by extant monotremes; and a boreosphenidan clade of Laurasian continents, including extant marsupials, placentals and their relatives.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
