Papuacedrus(Cupressaceae) in Eocene Patagonia: A new fossil link to Australasian rainforests

Abstract

The 51.9 Ma Laguna del Hunco (LH) and 47.5 Ma Río Pichileufú (RP) floras from Patagonia, Argentina are unusually rich, angiosperm-dominated assemblages with living relatives in the low-latitude West Pacific, neotropics, and temperate southern latitudes. The diverse gymnosperms in these floras are important for Gondwanan biogeographic history and paleoclimatic interpretations. "Libocedrus" prechilensis Berry 1938 (Cupressaceae), previously known only from the holotype (RP), a vegetative branch, is revised here based on new material from both localities, including a seed cone attached to a shoot with cuticle (LH). Characters of these fossils are diagnostic of monotypic Papuacedrus (highlands of New Guinea and Moluccas). Living P. papuana is most abundant in cloud forests receiving up to 4 m rainfall annually, whereas Austrocedrus (Libocedrus) chilensis, the basis of comparison when the fossil species was named, inhabits dry, cold steppe margins to mediterranean climates in southern South America. We establish Papuacedrus prechilensis comb. nov., which simultaneously invalidates a southern South American connection for the fossil floras and reveals a link to West Pacific montane rainforests. Combined evidence indicates a biome similar to extant subtropical, or tropical montane, rainforests that persisted for at least 4.4 Myr, linking elevated floral richness to abundant rainfall.

G-fibers and Florin ring-like structures in Dioon (Zamiaceae)

“…Florin rings are associated with the subsidiary cells observed in both living and fossil gymnosperms such as Pinus strobus by Deckert et al (2001), Papuacedrus (Wilf et al, 2009) and in Falcatifolium (Podocarpaceae) by Stockey et al (1992). In Dioon these structures can also seen under epifluorescence microscopy of the abaxial cuticular surface using 400-440 nm exciter filters ( Figure 1E) comparable to the Florin rings reported by Wilf et al (2009) on fossil Papuacedrus and Paull and Hill (2010) on fossil Cupressaceae. Dilcher (1969) describes Florin rings as "conspicuous thickened rings of cutin overlying the accessory cells and surrounding the stomata.…”

The last Patagonian cycad,Austrozamiastockeyigen. et sp. nov., early Eocene of Laguna del Hunco, Chubut, Argentina

“…This inference is similar to recent interpretations of numerous other genera now known as Paleogene fossils from Patagonia, southern Australia, and occasionally Antarctica (Hill and Brodribb 1999;Wilf et al 2009Wilf et al , 2013Carpenter et al 2014;Kooyman et al 2014). For the Encephalarteae, as for so many other examples (R.S.…”

“…Hill 1998;Heibloem 1999) that broadly fit recent paleoenvironmental interpretations of ancient Laguna del Hunco (Wilf et al 2009;Carvalho et al 2013). Both Lepidozamia species and several Macrozamia species inhabit Australian rainforest areas that Merkhofer et al (2015) identified as particularly rich in Laguna del Hunco "survivor" taxa.…”

“…6000 recently collected specimens, dominated by angiosperms but also including ferns and gymnosperms (Wilf et al 2005;Carvalho et al 2013;Merkhofer et al 2015). The gymnosperm flora, which we contribute to here, primarily represents living Old World rainforest taxa that are also known as fossils elsewhere in Gondwana, especially southeastern Australia (e.g., Hill and Brodribb 1999 (Wilf et al 2005(Wilf et al , 2009Wilf 2012). All of these conifer taxa are also found at reduced relative abundance in the early middle Eocene Río Pichileufú flora.…”

Anatomía comparada de la madera de Cupressaceae y su correspondencia con los estudios de filogenia

“…Por último, dentro del clado callitroid, los géneros Austrocedrus y Papuacedrus no se encuentran dentro de ningún clado establecido por filogenie molecular, aunque estudios fósiles han descubierto la presencia de un ancestro de Papuacedrus en la Patagonia (Wilf et al 2009), pudiendo explicar una posible relación con Austrocedrus. Muchos autores han estudiado la diversidad y variación genética que aparece en las masas naturales de Austrocedrus (Pastorino y Gallo 2001;Pastorino et al 2004;Arana et al 2010;Pomponio et al 2013), debido a su amplia distribución.…”