As estruturas integumentares dos vertebrados terrestres, as penas sao mais complexas e diversificadas. Apesar de abundantes, sua ocorrencia no registro f6ssil e rara , uma vez que possuem baixo potencial de preservacao. Embora limitadas, as ocorrencias sao cosmopolita. No Brasil, duas unidades geol6gicas se destacam: a Formacao Crato (Bacia do Araripe, NE, Cretaceo) e a Formacao Tremembe (Bacia de Taubate, SE, Pale6geno). 0 padrao de coloracao das penas, e produzido pela presenca de pigmentos naturais (i.e., biocromosy, pelo arranjo das ultraestruturas na matriz de queratina. Dentre essas, se destacam os melanossomos, que sao organelas especializadas em sintetizar e armazenar 0 biocromo melanina. Com uma dirnensao entre 0.2 it 2.0 urn, sua morfologia varia de acordo com 0 tipo de melanina, podendo ser divididos em dois grupos: os eumelanossomos com formato de bastonetes sao responsaveis pelas cores escuras e, os f eomelanossomos de forma esferica que responsaveis pelas cores acastanhadas. Embora ja publicadas na Formacao Crato, a presenca dessas estruturas na Formacao Tremernbe permanece desconhecida. Seis penas f6sseis oriundas dessas duas unidades foram caracterizadas macro e microscopicamente e, sua preservacao reconhecida atraves da aplicacao de tecnicas geoquirnicas e de microscopia. Morfologicamente, essas estruturas foram classificadas como penas penaceas e plurnulaceas, e a sua inclusao no registro geol6gico ocorreu por transporte e6lico. Analises de MEV indicam a preservacao por eumelanossomos e por molde extemo, enquanto as analises geoquimicas sugerem uma cornposicao carbonosa e por goetita. Com posse desses resultados e, baseado em dados da literatura, e possivel concluir que nas duas unidades 0 paleoambiente era habitado por dinossauros de porte medio a pequeno que possuiam baixa (Formacao Crato) e alta (Formacao Tremembe) relacao com 0 corpo dagua. A presenca de eumelanossomos sugere padrao de coloracao escura, refletindo as condicoes climaticas serniaridas dessas unidades. Alem disso, os gradientes geoquimicos (e.g., niveis de pH e O2) a presenca de esteiras microbianas no fundo dos paleolagos, propiciaram urn ambiente favoravel para preservacao dessas estruturas. Deste modo, este trabalho revela a viabilidade de arnpliacao deste tipo de estudo, sobretudo em outros organismos, proporcionando assim, visao mais abrangente da paleobiologia e paleoambiente.

The feathers are the most complex and diversified structures of terrestrial vertebrates integuments. Despite their abundance, they are scanty due to low preservational potential. Nevertheless, their occurrence is worldwide, and in Brazil, two geological units are responsible for most ofthe records: the Crato Formation (Araripe Basin, NE, Cretaceous) and Tremernbe Formation (Taubate Basin, SE, Paleogene). In extant feathers, the diverse colour patterns are produced by the presence of natural pigments (i.e., biochromes) as well as by ultrastructural arrangements in the keratin matrix. Among these structures, the melanosomes stand out since they are specialized organelles that synthesizes and stock the biochrome melanin, ranging between 0.2 to 2.0 urn in size, their morphology varies according to the melanin type. Anyway, it is possible to join them in two groups: rod shaped eumelanosomes that confers darkish colours, and spherical pheomelanosomes with reddish colour patterns. The eumelanosomes have been reported in the Crato Formation, but not yet in the Tremernbe. Six fossil feathers from these units were characterized macro and microscopically, and its preservation was inferred through geochemical and microscopical techniques. Morphologically, these structures were classified as pennaceous and plumulaceous feathers occurring in geological record through aeolian transport. SEM analysis revealed the preservation by eumelanosomes and by external molds, whereas geochemical analysis suggests their carbonaceous and goethite chemistry. According to these results, and based on the published literature, it is possible to conclude that in both units, the paleoenvironments was inhabited by medium to small sized dinosaurs, with low (at Crato Formation) and high (at Tremembe Formation) relation with the body of water. The presence of eumelanosomes suggests a darkish colouration, reflected mainly by its semi-arid climatic conditions. Besides that, the geochemical gradients (e.g., pH and O2 levels) and the presence of microbial mats in paleolake bottom, enabled a favourable environment for the preservation of these structures. In this way, this work reveals the feasibility of expanding this type of study, especially in other organisms, which allows a more comprehensive view of palaeobiology and palaeoenvironments.