Alexandra Crisafulli

Maderas gimnospérmicas de la Formación Tres Islas (Pérmico Inferior) de Uruguay

Lenos gimnospermicos picnoxilicos de la Formacion Tres Islas, Permico Inferior, Departamento de Cerro Largo, Uruguay, son analizados por primera vez y correlacionados con otros de unidades permicas y triasicas del Gondwana. Se determinaron las siguientes especies de Coniferales: Agathoxylon allanii (Krausel) Crisafulli y Herbst n. comb., A. kurmarpurensis (Bajpai y Singh) Crisafulli y Herbst, Australoxylon teixeirae Marguerier, una nueva especie, A. acevedoae Crisafulli y Herbst sp. nov., Chapmanoxylon jamuriense (Maheshwari) Pant y Singh, Polysolenoxylon bageense Guerra y una madera afin a las Taxales, Prototaxoxylon brasilianun Krausel y Dolianiti. El analisis anatomico de los lenos estudiados refleja caracteristicas tipicamente araucarioides y el diametro de las punteaduras, de tipo primitivo, como los encontrados en el Permico. Todas las especies tienen anillos de crecimiento bien marcados, sugiriendo periodos climaticos favorables en temperatura y humedad para el periodo de deposicion. Palabras clave: anatomia, maderas, Gimnospermas, Permico, Uruguay.

Leños gimnospérmicos de la Formación Llantenes (Triásico Superior), Provincia de Mendoza, Argentina

GIMNOSPERMOUS WOODS FROM LLANTENES FORMATION (UPPER TRIASSIC), MENDOZA PROVINCE, ARGENTINA. Silicifi ed wood found close to the “dark shales” levels, from the Upper Triassic Llantenes Formation, close to Malargue, southern Mendoza province, Argentina, are described. They are: Agathoxylon dallonii (Boureau) Crisafulli and Herbst nov. comb., Prototaxoxylon intertrappeum Prakash and Srivastava, Podocarpoxylon tikiense Ram-Awata & Rajanikanth and Baieroxylon chilensis Torres and Philippe. The taxa recorded are common with- and frecuently found in different Gondwana sequences, at least one Triassic and two Liassic Formations of Argentina, Triassic and Liassic from Chile, the Tiki Formation of India and Triassic of northern Africa. The anatomic characters refl ecting paleoclimatic conditions of these woods are analized; they show a mesoxerofi tic association that partially shares the conditions proposed by Giraud for other gondwanic wood associations with the same families/orders here recorded.

Contribución a la paleoxiloflora de la Formación Yaguarí, Pérmico superior de Uruguay

This paper is a further contribution to the study of the xyloflora of the Upper Permian Yaguari Formation, from several localities of the Cerro Largo Department, Uruguay. The following taxa are described: Australoxylon teixeirae Marguerier, Zalesskioxylon uniseriatum Pant y Singh, Zalesskioxylon sahnii (Singh) Lepekhina and Araucarioxylon nummularium (White) Maheshwari. The validity of the diagnosis of Australoxylon , a genus found in several formations, is considered and a short analysis of the different species assigned to it is included. This genus is characteristic of the Gondwanic flora due to its limited stratigraphic record and its peculiar anatomical structure. The picnoxylic secondary woods studied here show typical anatomical characters for Paleozoic woods, but have uniseriate and very short rays, a character considered as more advanced; also a reduction in the seriation of pits on the tracheidal walls and mixed and abietinean pits are registered. An evolutive analysis of them indicates an intermediate position between primitive Paleozoic forms and more evolved Mesozoic ones. A comparison with other Gondwanic contemporary formations permits to confirm the Upper Permian age assigned to the Yaguari Formation. The assemblage also allows to infer hydromesophytic to mesoxerophytic climatic conditions, while the analysis of the growth rings suggests the absence of low temperatures for the period.