Fungal cortices in kauri resin from New Zealand as taphonomic and ecological analogues of Cretaceous amber cortices: an actualistic approach

Several papers have been published in the last two decades about the peculiar cortices that commonly are present in Cretaceous amber pieces from diverse terrestrial western Tethyan localities. These cortices are constituted by networks of filamentous structures, and have been identified as mycelia composed of hyphae of resinicolous fungi according to a multidisciplinary research of Albian Spanish samples using diverse techniques. Main evidence indicating its fungal nature was the taphonomic scenario inferred and the detection of preserved chitin polysaccharides in the filamentous structures, using specific chitin markers visualized under confocal laser microscopy. Herein is present a similar fungal colonization pattern forming thin cortices observed in extant kauri pine resin (Agathis australis: Araucariaceae) from New Zealand. It has been compared with the typical pattern previously observed in the Spanish Cretaceous amber cortices. The similar fungal cortices in Agathis resins are considered as taphonomic and ecological analogues, but no phylogenetic relationship is suggested. The palaeoecological implications, with regard to Spanish Cretaceous forest environmental conditions that this extant correlate suggests, are discussed; also a new unusual growth of resinicolous fungus with the same microscopic hyphae features in Cretaceous amber are presented. Conclusions can be extended to Cretaceous amber cortices from other Laurasian localities.