FIRST MESOZOIC MAMMAL FROM CHILE: THE SOUTHERNMOST RECORD OF A LATE CRETACEOUS GONDWANATHERIAN

FRANCISCO GOIN; CAROLINA VIEYTES; PINO JUAN PABLO; MARCELO REGUERO; RUBILAR-ROGERS DAVID; SOTO-ACUÑA SERGIO; FERNANDEZ ROY; JONATAN KALUZA; ORTIZ HECTOR; MARTINELLI AGUSTÍN; MANRIQUEZ LESLIE; TREVISAN CRISTINE; LEPPE MARCELO; ALEXANDER VARGAS

Boletín del Museo Nacional de Historia Natural, Chile

Museo Nacional de Historia Natural

Lugar: Santiago; Año: 2020 vol. 69 p. 5 - 31

0719-935X

We describe Magallanodon baikashkenke gen. et. sp. nov., a new gondwanatherian mammal fromthe Late Cretaceous of the Magallanes Region in southern Chile (Río de Las Chinas Valley, EstanciaCerro Guido, north of Puerto Natales city, Última Esperanza Province). The mammal-bearing layer isplaced within the Late Campanian-Early Maastrichtian levels of the Dorotea Formation (Magallanes/Austral Basin). The new remains constitute the southernmost record of a Mesozoic gondwanatherianmammal, as well as the first Mesozoic mammal from Chile. This taxon is comparable in size to thehypsodont-toothed Gondwanatherium (Late Cretaceous) and Sudamerica (Early Paleocene) but withnoticeably brachyodont molariforms supported by four to five roots. As in other gondwanatherians, ithas at least one hypertrophied, rodent-like incisor in the upper jaw. The new taxon is here diagnosedand described, and is regarded as a possible ferugliotheriid (?Ferugliotheriidae). If confirmed, it wouldrepresent the largest known taxon for this family. Its molariform occlusal crown pattern, after wear,resembles that of other gondwanatherians, particularly ferugliotheriids and that of the sudamericidGondwanatherium. This adds new evidence on the phylogenetic proximity of ferugliotheriid andsudamericid gondwanatherians. An analysis of the enamel microstructure of the upper incisor ofMagallanodon was performed demonstrating several crucial similarities with the pattern shown byGondwanatherium (Sudamericidae). We discuss the significance of Magallanodon for understandingthe acquisition, within gondwanatherians, of a lophed molariform pattern. Finally, we discuss thesignificance of the new finding in the context of southern biotas, including those of Patagonia andAntarctica.