RESUMOS - UNESP - Rio Claro

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
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