Araucaria mirabilis
- 演化之聲
- Mar 19
- 3 min read
Age
Jurassic（Late Jurassic）
160 Ma
Taxonomy
Kingdom: Plantae
Phylum: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Araucariaceae
Genus: Araucaria
Species: Araucaria mirabilis
Morphological description
Araucaria mirabilis was an exceptionally tall conifer. Fossilized trunks indicate diameters reaching up to 3.5 meters, with estimated living heights exceeding 100 meters. The plant also possessed enlarged woody basal structures.
Its cones ranged from spherical to elliptical, typically measuring 2.5 to 8 cm in length, with the largest specimens reaching up to 10 cm in diameter. The cone center consisted of a parenchymatous pith, surrounded by fused vascular tissues. The ovuliferous scales bore broad, thick woody wings that tapered toward the base, measuring approximately 13 to 16 mm in length and about 10 mm in width. Each scale carried a single seed on its upper surface, arranged in a spiral pattern. Cone size did not necessarily indicate maturity, as fully developed embryos have been found even in cones as small as 5 cm in diameter.
The mature seeds measured approximately 0.8 to 1.3 cm in length and 0.2 to 0.6 cm in width. The integument consisted of three layers: a fleshy outer layer, a thickened hard layer, and an inner layer. The hard layer contained sclereids arranged in a serrated pattern. The integument was attached to the nucellus only at the base.
Etymology
The genus name Araucaria is derived from the Spanish term Araucanos, referring to the Mapuche people of Chile and Argentina.
The species name mirabilis is Latin for "remarkable" or "extraordinary".
Biological description
Araucaria mirabilis was discovered in Middle Jurassic deposits in Patagonia, Argentina, where an entire fossil forest has been preserved. This forest was likely buried by volcanic activity, leading to exceptional fossil preservation.
Local inhabitants had long collected fossilized cones, and in 1919 the German-Argentine botanist Anselmo Windhausen recognized their significance. His subsequent investigations led to the discovery of the fossil forest in 1923.
The leaves of Araucaria are energy-rich but require prolonged digestion, and Araucaria mirabilis likely shared this trait. During the Jurassic, members of the genus Araucaria were globally widespread and may have served as a major food source for sauropod dinosaurs.
Damage found on fossil specimens indicates feeding traces from beetle larvae, interpreted as early relatives of the tribe Tomicini. These insects, which remain significant pests of conifers today, may have already been associated with Araucaria during the Mesozoic, suggesting a long-term ecological relationship between host and herbivore.
(Author: Bai Leng)
References
1.Mary Gordon Calder (1953). A coniferous petrified forest in Patagonia. Bulletin of the British Museum (Natural History), Geology.
2.Linda Klise., Leo J. Hickey (2003). Petrified wood: rainbows in stone. Yale Environmental News.
3.Thomas N. Taylor., Edith L. Taylor., Michael Krings (2009). Paleobotany: the biology and evolution of fossil plants. Academic Press.
4.Genaro R. Hernandez-Castillo., Ruth A. Stockey (2002). Palaeobotany of the Bunya Pine. Queensland Review.
5.Christopher J. Earle (2010). Araucaria Jussieu 1789. The Gymnosperm Database. Retrieved November.
6.IUCN Commission on National Parks and Protected Areas (1982). IUCN directory of neotropical protected areas. IUCN.
7.Hiroaki Setoguchi., Takeshi Asakawa Osawa., Jean-Cristophe Pintaud., Tanguy Jaffré., Jean-Marie Veillon (1998). Phylogenetic relationships within Araucariaceae based on rbcL gene sequences. American Journal of Botany.
8.Jürgen Hummel., Carole T. Gee., Karl-Heinz Südekum., P. Martin Sander., Gunther Nogge., Marcus Clauss (2008). In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection. Proceedings of the Royal Society B: Biological Sciences.
9.Andrea S. Sequeira., Benjamin B. Normark., Brian D. Farrell (2000). Evolutionary assembly of the conifer fauna: distinguishing ancient from recent associations in bark beetles. Proceedings of the Royal Society B: Biological Sciences.
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