CECOAL   02625
CENTRO DE ECOLOGIA APLICADA DEL LITORAL
Unidad Ejecutora - UE
artículos
Título:
Ginkgoaleans woods from the Jurassic of Argentina: taxonomic considerations and palaeogeographical distribution
Autor/es:
GNAEDINGER, S.
Revista:
GEOBIOS
Editorial:
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
Referencias:
Año: 2011
ISSN:
0016-6995
Resumen:
Abstract. A specimen of Baieroxylon rocablanquense Gnaedinger nov. sp. from the Roca  Blanca Formation (Early Jurassic), and a specimen of Ginkgomyeloxylon tanzanii Giraud and Hankel from the La Matilde Formation (Middle Jurassic), both located in the Santa Cruz province, Argentina, are described in detail. Identification of the morphogenus Baieroxylon is based upon secondary xylem characteristics (cross-field tracheid pitting and ray characteristics), while identification of Ginkgomyeloxylon is based upon pith, primary xylem, and secondary xylem features. A synthesis of Ginkgoalean woods is also presented, which combines diagnostic anatomical evidence with data related to stratigraphic and paleogeographical distributions. Based on the results of this analysis, a key for genus-level identification is provided, and is used to elucidate global patterns of historical distribution over the course of geological time. In Gondwana, a greater diversity of ´mixed-type´ woods is present during the Mesozoic, especially during the Upper Triassic. In contrast, in Laurasia a low diversity of the mixed type is recorded during the Paleozoic and Mesozoic, with increases in ´abietinoid-type´ wood – similar to extant Ginkgo – taking place at the beginning of the Cretaceous. During the Jurassic and Lower Cretaceous in both Laurasia and Gondwana, mixed-type and abietinoid-type woods co-existed. Therefore it is possible to infer that important evolutionary changes in wood anatomy occurred during the Mesozoic (Jurassic- Cretaceous).