Myracrodruon urundeuva Fr. Allem. (syn Astronium urundeuva (Fr. Allem) EngI.) known as ?aroeira? belongs to the family Anacardiaceae. It is widely distributed in the South Arnerica and is an importam hardwood. This work aims to describe the morphological and anatomical structure of the seed development. The ovule is anatropous, bitegmic, crassinucellar, with a well-developed raphe; at the chalazal end of the embryo sac has a weakly developed hypostase. Both inner and out teguments are discernible only in the micropylar region. The ovule has a long and bent funicle. The tanuiniferous hypostase results from the chalazal and nucellar tissues. The strong development of the funicle may be described as vestiges of an aril. The membranous seed coat has two different constructive regions, one that is chalazal or partially pachychalazal and another that is tegumentary. The partial pachychalaza manifests externally as a dark-brown patch and the tegumentar is pale-brown and formed by remaining teguments.