Material and methods
- Gymnospermous woods from Jejenes Formation, Carboniferous of San Juan, Argentina: Abietopitys petriellae (Brea and Césari) nov. comb.
Wood taxonomy is based on Lepekhina (1972), who revised the nomenclature and taxonomy of Paleozoic woods worldwide. The wood has been described, when possible, in accordance with the list of microscopic features for softwood identification (Richter et al ., 2004) and the Greguss' glossary of terms (Greguss, 1955).
The new material consists of 5 specimens which were collected in the fossiliferous locality known as Quebrada de la Mina, located at 31°50´34´´ S and 68°37´57´´ W in the eastern margin of the Sierra Chica de Zonda (figure 1). These specimens were compared with the holotype from Las Lajas locality (see Brea and Césari, 1995). Stratigraphically, the fossiliferous bearing strata correspond to the upper part of the Jejenes Formation, which is suggested to be early late Carboniferous in age. All the specimens are silicified (chalcedony) displaying fissures filled with carbonatic material.
Wood fragments were cut in thin sections in the three planes usually used to study their anatomy. Cellulose acetate peels were also made, with poor results compared to thin sections. Good results were obtained from macerations of small wood fragments. Samples were first placed in HF 75%, washed with water, and then mounted in glycerine-jelly. These preparations allowed the observation of fine details such as cross-field pits and ray cell walls thickenings (figures 2.J, 2.K, 2.L).
The studied material is deposited in the Paleobotany collection of the Museo Argentino de Ciencias Naturales (BAPb for fossil wood fragments and BAPbPm for thin sections): BAPb 12906 (with slides BAPbPm 441 to 445), BAPb 12907 (with slides BAPbPm 446 to 449), BAPb 12908 (with slides BAPbPm 450 and 451), BAPb 12909 (with slides BAPbPm 452 and 453) and BAPb 12905. The holotype, BAPB 244 (from Las Lajas locality) includes thin sections (BAPb 244a to 244f, 244l and 244m) and cellulose acetate peels (BAPb 244g to 244j).
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