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

Premise of the Study The fossil record of Agathis historically has been restricted to Australasia. Recently described fossils from the Eocene of Patagonian Argentina showed a broader distribution than found previously, which is reinforced here with a new early Paleocene Agathis species from Patagoni...

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Bibliographic Details
Published in:American journal of botany 2018-08, Vol.105 (8), p.1345-1368
Main Authors: Escapa, Ignacio H., Iglesias, Ari, Wilf, Peter, Catalano, Santiago A., Caraballo-Ortiz, Marcos A., Cúneo, N. Rubén
Format: Article
Language:English
Subjects:
Affinity
Agathis
Araucariaceae
Biological evolution
Cones
Cretaceous
Cretaceous‐Paleogene boundary
Dilwynites
Divergence
Eocene
Evolutionary biology
Fossils
Historical account
INVITED SPECIAL ARTICLE: For the Special Issue: The Tree of Death: The Role of Fossils in Resolving the Overall Pattern of Plant Phylogeny
Landscape
Landscape ecology
Leaves
Mesozoic
Molecular biology
New species
Organs
Paleocene
Paleogene
Patagonia
Phylogenetics
Phylogeny
Pollen
Reproductive organs
Seeds
Species extinction
systematics
Wollemia
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Summary:Premise of the Study The fossil record of Agathis historically has been restricted to Australasia. Recently described fossils from the Eocene of Patagonian Argentina showed a broader distribution than found previously, which is reinforced here with a new early Paleocene Agathis species from Patagonia. No previous phylogenetic analyses have included fossil Agathis species. Methods We describe macrofossils from Patagonia of Agathis vegetative and reproductive organs from the early Danian, as well as leaves with Agathis affinities from the latest Maastrichtian. A total evidence phylogenetic analysis is performed, including the new Danian species together with other fossil species having agathioid affinities. Key Results Early Danian Agathis immortalis sp. nov. is the oldest definite occurrence of Agathis and one of the most complete Agathis species in the fossil record. Leafy twigs, leaves, pollen cones, pollen, ovuliferous complexes, and seeds show features that are extremely similar to the living genus. Dilwynites pollen grains, associated today with both Wollemia and Agathis and known since the Turonian, were found in situ within the pollen cones. Conclusions Agathis was present in Patagonia ca. 2 million years after the K‐Pg boundary, and the putative latest Cretaceous fossils suggest that the genus survived the K–Pg extinction. Agathis immortalis sp nov. is recovered in a stem position for the genus, while A. zamunerae (Eocene, Patagonia) is recovered as part of the crown. A Mesozoic divergence for the Araucariaceae crown group, previously challenged by molecular divergence estimates, is supported by the combined phylogenetic analyses including the fossil taxa.
ISSN:0002-9122
1537-2197
DOI:10.1002/ajb2.1127