In the northeastern part of Mexico, in the Nuevo Léon region, within the Huasteca Canyon, more than forty species of benthic foraminifera, different species of dacycladales algae and planctonic fauna have been described along a 200-m section of limestone deposits. This micropaleontologic work is based on thin sections observation in which we determined the precise number of each element identified within a reference surface. These results are then reported into a table plotting vertically the numbers of the samples, classified by their stratigraphic order in the natural section, and horizontally the inventory of all the fauna and flora existing in the different samples. Eventually, the elements are classified in function of their deposit environments. The results show that after the Upper Jurassic transgression (Taraises formation), since Upper Valanginian the Cupido platform started to form within normal salinity and oxygen conditions. It lasted until the Lower Aptian. During its evolution, we observe seven periods of exposition of the platform in relationship with eustatic variations associated with the extension phase of Mexico Gulf. However, the proliferation and the quantitative variations of the species strongly depending on the adaptability to the eustatic variations, we can find out layers thickness differences as well as faunistic variations in all its section. This micropaleontologic study allowed recognizing in detail the benthic flora, its associations, and dating approximately the Cupido platform in Huasteca region, with five eustatics variations periods.
