Cretaceous conifers from the Araripe Basin, with emphasis on cone analyses

• Ano de defesa: 2018
• Autor(a) principal: Westerkamp, Ana Paula de Assis Oliveira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Palavras-chave em Português: Cones; Coníferas; Bacia do Araripe
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/38664

Conifers have played a major role in terrestrial ecosystems since the end of the Carboniferous. The arrival of angiosperms in the Aptian (Early Cretaceous) triggered a competition from the Late Cretaceous onwards, finally resulting in an exclusion of conifers from certain regions or habitats. Nowadays, conifers are the most dominant and remarkable gymnosperms in floras throughout the world; they have a high economic and ecological importance. Cones, the conifer reproductive organs, are conspicuous and reflect the adaptive traits developed during the evolutionary process of the group. In the Crato Formation (Santana Group, Araripe Basin) diversity and preservation types of conifer-related fossils were investigated, giving special emphasis on cone structures. Information on whole-plant aspects and pollen records were taken from current literature. Cone data were obtained studying external aspects of the fossils. Vegetative shoot SEM analyses confirmed the presence of charcoal. A total of 140 cone specimens were encountered in the palaeontological collections visited. They were grouped into 26 morphotypes. Conifer macrofossils and palynology prove the occurrence of five conifer families: Araucariaceae, Cheirolepidiaceae, Cupressaceae, Pinaceae, and Podocarpaceae. The number of coalified cones exceeded the sum of all other preservation modes. Iron oxide was second followed by charcoal and impression. All types of preservation were observed in both greyish and yellowish sediments, with higher numbers in the first. Aspects of plant and animal diversity as well as their ecological relationships are presented for the Crato biome. The morphological diversity of the studied cones indicates a richness hitherto unsuspected for conifer species/families in the Araripe Basin. The variety of fossil taxa found in exceptional state of preservation in the Crato Formation reflects the intricate ecological relationships that existed in the Early Cretaceous in northeastern Brazil.