II Encontro dos Programas de Pós-Graduação em Geociências, 2008 PERMIAN PETRIFIED FERTILE FERN LEAVES FROM THE CENTRAL NORTH BRAZIL (PARNAIBA BASIN, ARAGUAINA REGION, MARRATIALLES) TATIANE MARINHO VIEIRA TAVARES E-mail: tatipaleo@yahoo.com.br Orientador: Prof. Dr. Rosemarie Rohn The Natural Monument of Petrified Trees in Tocantin, Central North Brazil, is mainly characterized by the abundant well preserved tree fern stems (mainly Tietea and Psaronius), rare other ferns (Grammatopteris, Dernbachia), as well as gymnosperms (“Dadoxylon” and others). They occur in the southern margin of the Parnaíba Basin in fluvial fine sandstones and siltstones, probably of the Motuca Formation, tentatively positioned close to the Lower-Middle Permian boundary. The Buritirana Farm in the Monument additionally has provided outstanding pinnae preserved as petrifactions. Rare specimens may be included in the compression taxa Pecopteris, Sphenopteris and Lobatopteris, but the majority corresponds to very peculiar ferns of the Scolecopteris type. Their most intriguing characteristic is the pectinate pinnule margin with lobe sinuses very close to the midvein at the adaxial surface and narrow linear lobules curled under, reaching the midvein on the abaxial surface. The lobule lamina is relatively thick. Tangential sections of pinnules show a decurrent strong secondary vein at the middle of each lobule. In some specimens, the lobules were removed from the abaxial surface and the synangia are exposed in 3D. The synangia are borne in one row on each side of the pinnule midrib, disposed very closely, with pedicel apparently attached to the midrib. The shape is broadly oval, slightly acute at the distal part. They are composed of 3 or 4 axially elongate sporangia, fused laterally, not well radially symmetrical. The pinnules are oblong, with rounded tips, closely spaced, attached at 90 o to the pinna rachis, which shows distinct trichomes and a W-shaped vascular trace. Scolecopteris species from the Permo-Carboniferous of Euramerica, Cathaysia and Triassic in Antarctica show pecopterid foliage with smooth to slightly lobed margins, or their shape cannot be determined in sections, being not taken into consideration for classification. The only apparently similar other fertile pectinate pinnules were observed in the Middle Permian of the Paraná Basin, southern Brazil, where Tietea and Psaronius also occur. Up to the moment, it was not possible to substantiate whether the fertile pinnae from both the Parnaíba and Paraná basins are related to Tietea, but their apparent restriction to Western Gondwana is significant. The ecological reason for the deep incisions at the pinnule margins must be further investigated, considering that thick leaf laminae and inrolled margins to the abaxial side may indicate a protection from dehydration. Palavras-chave: Permian, Marattiales, Scolecopteris, Parnaiba Basin. Dados acadêmicos: Nível: Doutorado; Título do Projeto: Estudo de Psaroniales da porcao setentrional de Tocantins, na Bacia do Parnaiba (Permiano, Brasil); Linha de pesquisa: Bacias sedimentares e seus recursos (hídricos e energéticos); data de entrada 91
II Encontro dos Programas de Pós-Graduação em Geociências, 2008 na pós-graduação: 7/8/2007; data prevista de defesa: 6/8/2011; Possui bolsa: Sim; Agência: CNPq. 92