Lenhos de coníferas do Mesocretáceo do norte do Maranhão, Brasil

Abstract

-CONIFER WOODS FROM THE MIDDLE CRETACEOUS OF NORTHERN MARANHÃO STATE, BRAZIL.In the present work, 13 silicified logs collected in the fossiliferous levels of the Alcântara Formation (Upper AlbianLower Cenomanian estuarine deposits in northern Maranhão State, NE Brazil) were analyzed through petrographic slides applying parataxonomic approach. The gymnospermous araucarioid pattern is the prevailing pattern observed in the wood association, suggesting a possible relation to the Araucariaceae. Considering that pollen grains of Araucariacites australis were previously reported from the same sedimentary deposits where the sample came from, the presence of Araucariacea is assumed, mainly in the estuarine environment inferred for the region of Alcântara and São Luís. Conifers with abietoid wood pattern may be related to Taxaceae and probably throve in inland areas. The absence of angiospermous woods in the assemblage, opposed to the expressive representation in palynological analyses, can be attributed to a combination of taphonomic factors or, alternatively, to the development of conifer and angiosperm plants in distinct paleoenvironment during the middle Creataceous. The predominance of uninterrupted wood growth and rare evidences of partially interrupted wood growth patterns and the presence of radial desiccation cracks led to the inference of a stable paleoclimate, but with sporadic drought episodes during growing season, included in global scale in the equatorial humid belt in the boundary with the northern hot arid belt.

Exploring the First Appearance of the Main Derived Conifer Families of Gondwana: Evidence Provided by the Triassic Woods from Argentina

“…2.10). Unlike the helical thickening, the microfibrillar patterns produced by decay and fossilization consist of several closely parallel strikes at a variable angle with the longitudinal axis which usually do not curve towards the tracheid face rim (Araujo et al, 2011;Philippe et al, 2019).…”

Diversidade e aspectos paleobiológicos do registro de Dicynodontia no Brasil

“…Entre outros detalhes anatômicos, Jachaleria (comprimento máximo do crânio estimado em ~ 50cm) pode ser diagnosticado pela presença de um arco zigomático acentuadamente inclinado e dorsoventralmente estreito (Kammerer & Ordoñez, 2021). Duas espécies são geralmente consideradas válidas: a espécie-tipo Jachaleria colorata Bonaparte, 1971 e a espécie referida Jachaleria candelariensis Araújo & Gonzaga, 1980. Até o presente momento, J. colorata é endêmica da Argentina, enquanto J. candelariensis (figura 6) é endêmica do Brasil.…”