In phylogenetic nomenclature, the Pentapetalae are a large group of eudicots that were informally referred to as the "core eudicots" in some papers on angiosperm phylogenetics. They comprise an extremely large and diverse group that accounting about 65% of the species richness of the angiosperms, with wide variability in habit, morphology, chemistry, geographic distribution, and other attributes. Classical systematics, based solely on morphological information, was not able to recognize this group. In fact, the circumscription of the Pentapetalae as a clade is based on strong evidence obtained from DNA molecular analysis data. The Pentapetalae clade is composed of the orders Berberidopsidales —including the family Aextoxicaceae—Caryophyllales, Santalales and Saxifragales, the families Dilleniaceae and Vitaceae and all members of the clades Asteridae and Rosidae. Phylogenetic analyses of complete chloroplast genome sequences have provided a reliable outline of the relationships among the major Pentapetalae lineages and also provide a framework for investigating the evolutionary processes that generated a large proportion of the diversity of extant angiosperms. In light of these phylogenetic results, the current challenge for scientists in this area of botany is to identify the characters that are unique to the superasterid and superrosid clades and those that arose in parallel in both, and then to explore their evolutionary implications. Description As the name of the clade suggests, the Pentapetalae have a characteristic type of flower made up of whorls of five pieces each. The perianth is formed by a sepal and a corona perfectly differentiated. The sepals are innervated by three or more vascular bundles —called leaf scars— originating in the vascular system of the petiole, while the petals have only one trace. The stamen usually has twice as many pieces as the calyx and corona, which are arranged in two whorls. When the number of stamens is greater than twice the number of pieces of the perianth, they are arranged in fascicles or in a centrifugal spiral. Pollen grains in the Pentapetalae are characteristically tricolpate. This type of pollen grain has three or more pores within grooves called "colpos". In contrast, most other spermatophytes —that is, gymnosperms, monocots and paleodicots— have monoculcate pollen, with a single pore located in a groove called a "sulcus". The gynoecium of Pentapetalae plants is usually composed of five carpels joined together, although gynoeciums formed by three carpels are also quite common. In cases where the gynoecium is composed of only two carpels, they overlap.