First record of Cupressaceae s.l. from the Jurassic of Patagonia, Argentina.

ESCAPA, IGNACIO; CÚNEO, RUBÉN; AXSMITH, BRIAN

Chicago, USA

Congreso; Botany 2007; 2007

Middle to Upper Jurassic conifers from Patagonia are traditionally recognized as species of Araucaria/Pararaucaria, which are classically represented by permineralized seed cones. However, recent findings from northern Patagatonia recognize new conifer types that substantially enlarge the diversity of the group. As a result, fossils of the Cupressaceae s.l. can now be added to the classical representatives of the families Araucariaceae, Podocarpaceae and Cheirolepideaceae In the present contribution, micro and megasporangiate cones organically attached to leafy shoots of the Elatocladus morphotype are described from the Callovian-Oxfordian Cañadón Asfalto Fm. in the Chubut Province. The material consists of impressions and compressions including vegetative branches of at least two orders, both with helically arranged, flattened leaves. The female cones are single or in pairs -always on the apex of the branches- and composed of rhomboidal bract-scale complexes helically disposed with one or two anatropous ovules on the adaxial surface. The pollen cones are disposed in terminal clusters with modified leaves at the base, and show helically arranged sporophylls with abaxial pollen sacs. These materials share characters with other conifers known from the Paleozoic (e.g., Ferugliocladus, Ugartecladus), Mesozoic (e.g., Elatides, Seardiodendron) and modern ones, such as Cunninghamia. In this regard, homology hypotheses based on the most relevant characters are discussed, especially those related to the structure of the megasporangiate cones. On this basis, the new fossils are interptreted as occupying a basal phylogenetic position within the Cupressaceae.