Rodent-like notoungulates (Typotheria) from Gran Barranca, Chubut Province, Argentina: phylogeny and systematics

MARCELO A. REGUERO AND FRANCISCO J. PREVOSTI

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia

Cambridge University Press

Año: 2009; p. 1 - 18

Rodent-like notoungulates, traditionally included insuborders Typotheria and Hegetotheria, experienced animportant evolutionary radiation in South America. Thisevolution is well documented in the fossil record at GranBarranca in Patagonia, Argentina, where 14 taxa occur.The phylogenetic position of Typotheria and Hegetotheriais poorly understood and has become controversial inrecent years. This study traces the origin and early evolutionof the rodent-like notoungulates (Typotheria andHegetotheria) through an analysis of phylogenetic relationshipsamong genera that are well known cranially anddentally. For this we use parsimony analysis on 51 taxausing 78 morphological characters. The results of thephylogenetic analysis suggest the abandonment of theconcept of Hegetotheria as a separate suborder of Notoungulata,and expand the concept of Typotheria to include themore advanced families of rodent-like notoungulates:Mesotheriidae, Archaeohyracidae, and Hegetotheriidae(the two latter originally allocated in Hegetotheria).Included within this clade is Campanorco inauguralisBond et al. 1984, the sister species of Archaeohyracidaeþ Hegetotheriidae þ Mesotheriidae. Oldfieldthomasiidaeand Archaeopithecidae, previously considered typotheres,are removed and form the sister clade to Typotheria. Byour definition Typotheria is a more inclusive monophyleticgroup containing the most recent common ancestor ofNotopithecus and Mesotherium and all of its descendants,including Campanorco inauguralis, archaeohyracids,and hegetotheriids. The implications of this phylogeneticanalysis for the early evolutionary history of rodent-liketypotherians are explored further in a separate chapterof this book.