Araucariaceous fossil woods from the Upper Triassic Ischigualasto Formation (San Juan Province, Argentina): paleofloristic and paleoclimatic implications

A new species of fossil wood, Agathoxylon argentinum, has been identified from the Upper Triassic Ischigualasto Formation in Argentina. This discovery, preserved as silica permineralization, reveals unique anatomical features distinct from other Mesozoic Gondwanan species, linking it to the conifer family Araucariaceae. The study also documents fungal-mediated wood decay and spherical structures interpreted as holocarpic chytrid fungi, providing insights into paleoecological processes. Analysis of growth rings suggests that A. argentinum was an evergreen gymnosperm, thriving in humid conditions. Additionally, the research highlights a significant floristic change in the Ischigualasto Formation, marked by the decline of corystosperm genera and increased humidity, offering new paleoclimatic implications for this UNESCO-listed site.

Bodnar, J., Sagasti, A. J., Correa, G. A., Miranda, V., & Medina, F. (2022). Araucariaceous fossil woods from the Upper Triassic Ischigualasto Formation (San Juan Province, Argentina): paleofloristic and paleoclimatic implications. Journal of Paleontology, 96(6), 1354–1378. https://doi.org/10.1017/jpa.2022.45