New Middle-Late Jurassic Conifers from Chubut province, Patagonia, Argentina.

ESCAPA, IGNACIO; CÚNEO, RUBÉN

Chico, California, USA

Congreso; Botany 2006; 2006

JURASSIC conifers in Patagonia are mainly known from the classical Cerro Cuadrado locality in Santa Cruz province, where tons of Araucaria mirabilis and Pararaucaria patagonica seedcones have been recorded. Recently, new localities from northern Patagonia, Chubut province, have provided of a new flora that includes permineralized and compression/impression fossil conifers. These materials are represented by leafy shoots, branches, seedcones, pollen cones and seedlings that allow inferring the presence of at least three conifer families. Some compression-impression leafy shoots, seedcones and pollen cones show morphological characters –including the record of isolated Classopollis pollen- that resemble members of the Cheirolepideaceae. On the other hand, representatives of the family Araucariaceae have also been found, in particular through the presence of huge permineralized seedcones recognized for the first time in northern Patagonia. These araucarian permineralized seedcones, as well as associated compressed ones, appear different –especially in size- from the well-known Araucaria mirabilis and correspond to a new species. Associated wood and seedlings could also be related. Smaller seedcones also occur in the same site and they closely resemble Pararaucaria, a possible taxodiaceous or pinaceous taxon. Interestingly, this generic association –Araucaria/Pararaucaria- is coincident with the same one recognized from Jurassic beds in the Santa Cruz province.Additionally, other possible conifers represented by leafy shoots (e.g., Pagiophyllum, Elatocladus and Brachiphyllum) are also present, suggesting a high degree of diversity during the middle-late Jurassic in northern Patagonia.Finally, it must be emphasized that extended conifers forest or woodlands, with a fern-dominated understorey, covered Patagonia during the Jurassic suggesting homogeneous climatic conditions along an extended latitudinal gradient.