Agathis trees of Patagonia's Cretaceous-Paleogene death landscapes and their evolutionary significance

ESCAPA I.; ARI IGLESIAS; WILF PETER; CATALANO SANTIAGO; MARCOS A. CARABALLO-ORTIZ; CÚNEO, N. R.

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Lugar: St. Louis; Año: 2018 vol. 105 p. 1345 - 1368

0002-9122

Premise of the study. The fossil record of Agathis has been restricted to australasia. Recently describedfossils from the Eocene or Argentina showed a broader distribution in the past,which is reinforced here with a new Paleocene Agathis species from Patagonia. No previous phylogenetic analyseshave included under consideration fossil Agathisspecies. Methods. We describe macrofossils of Agathis vegetative and reproductiveorgans from early Danian and leaves with Agathisaffinities from the latest Maastrichtian, both from Patagonia, Argentina. Atotal evidence phylogenetic analysis is performed, including the Danian speciesdescribed here together with other fossil species agathioid affinities.Key results. Agathis immortalis sp. nov. is theoldest occurrence of fossils and one of the most complete species in the fossilrecord. Leafy twigs, leaves, pollen cones, pollen, ovuliferous complexes andseeds show features that are extremely similar to the living genus, with theexception two fully developed seed wings and the lack of basal scallops on theovuliferous complexes. Dilwynitespollen grains were found in situ within the pollen cones. Conclusions. Agathis is present 2million years after the K-Pg boundary, and putatively in the uppermostCretaceous of Patagonia. Agathisimmortalis sp nov. is recovered in a crown position for the genus, while Agathis zamunerae (Ecocene, Patagonia)is recovered as part of the stem. A Mesozoic divergence for Araucariaceae crowngroup, which has been previously challenged by molecular clock estimations, issupported by the combined phylogenetic analyses and the position of the fossiltaxa.