Leños fósiles de Boraginaceae de la Formación Peñas Coloradas (Paleoceno superior), Puerto Visser, Chubut Argentina
Abstract
Resumen. Se describe una nueva especie de madera petrificada, la cual es asignada a la familia Boraginaceae. Los ejemplares provienen de las sedimentitas del Paleoceno superior de Puerto Visser, Chubut. La comparación con miembros de las Boraginaceae muestra que Cordioxylonprototrichotoma sp. nov. es similar a la especie actual Cordiatrichotoma (Vell.) Arráb. ex Steud. La especie fósil muestra los siguientes caracteres diagnósticos: anillos de crecimiento ausentes; porosidad difusa; poros agrupados y solitarios, raramente múltiples radiales de 2 elementos y ocasionalmente múltiples radiales de 3, 4 y 5 elementos; placa de perforación simple; punteaduras intervasculares alternas; radios cortos, anchos y numerosos, heterocelulares y heterogéneos, multiseriados raramente uniseriados y biseriados; parénquima axial apotraqueal difuso y difuso agregado y paratraqueal escaso y en bandas de una célula de ancho. La presencia en el Paleoceno superior de este nuevo elemento florístico, Cordioxylonprototrichotoma, sugiere la existencia de pluviselvas que se habrían desarrollado bajo condiciones de clima cálido y húmedo. Abstract. FOSSIL WOODS OF BORAGINACEAE FROM THE PEÑAS COLORADAS FORMATION (UPPER PALEOCENE), PUERTO VISSER, CHUBUT, ARGENTINA.Petrified woods of a new species of the family Boraginaceae from Upper Paleocene sediments of Puerto Visser locality, Chubut are described. The comparison within members of Boraginaceae shows that Cordioxylonprototrichotoma sp. nov. is similar to the extant Cordiatrichotoma (Vell.) Arráb. ex Steud. The fossil species shows the following diagnostic features: growth rings absent; diffuse porous; pores in clusters and solitary, rarely in radial multiples of 2 elements and occasionally in radial multiples of 3, 4 and 5 elements; perforation plate simple; alternate intervascular pitting; rays short, broad and numerous, heterocellular and heterogenous, multiseriate, rarely uniseriate and biseriate; axial parenchyma apotracheal diffuse and diffuse-in-aggregates and paratracheal scanty and banded of one cell wide. The presence in the Upper Paleocene of this new floristic element, Cordioxylon prototrichotoma, suggests the existence of rainforests, with a warm and humid climate for this region.Downloads
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