grouped in 13 orders and more than a hundred families, and between a third and a quarter of the total number of angiosperm species. Together with the rosids, they constitute the two largest groups of eudicotyledons. They represent the most apotypic clade of the angiosperms, or, as it is inappropriately called, "most evolved". The group most likely originated in the Cenozoic, about 50 million years ago, and its success is related to its adaptation to insect pollinators. Four of the largest families of angiosperms belong to this clade: the Asteraceae, the Rubiaceae, the Lamiaceae and the Apocynaceae. The plants belonging to this clade are characterized by being herbaceous, with hermaphrodite, zygomorphic flowers —that is, they admit only one plane of symmetry— that are pollinated by insects. In addition, the stamens are arranged in a circle and the petals of the corona are joined together forming a tube. The gynoecium is formed by two welded carpels. The flowers are often arranged in tight inflorescences, such as the ears of the labiatae and plantaginaceae or the capitula (heads) of the compositae. Evolution and phylogeny The age of this clade has been estimated at 113 to 116 million years. The oldest macrofossils of eudicots, which unfortunately cannot be attributed to any extant group, belong to the Cretaceous-Cenomanian, just 96-94 million years old. Analyses of complete chloroplast genome sequences allowed us to resolve the relationships among the major Pentapetalae clades. Immediately after diverging from the Gunnerales, the Pentapetalae diverged into three major subclades: (i) the Dileniaceae, (ii) the "superrosid" clade including the Saxifragales, Vitaceae and Rosids, and (iii) the "superasterid" clade composed of the Berberidopsidales, Santalales, Caryophyllales and Asterids. The close relationship demonstrated at the molecular scale between Saxifragales, Vitaceae and rosids is congruent with their morphological affinities. In fact, these clades form the so-called "core of the rosids" in the Cronquist and Takhtajan classification systems. They all have an androcecium with jointed anthers, leaves with stipules, the endosperm with nuclear formation, and a micropyle that forms from the outer integument or both integuments. Several putative synapomorphies may also characterize the superrosid clade. Thus, the "psyllulate" pollen or with a granular structure of the exine, the presence of sclereids in the leaves, the isomerism of the androcecium and the fused carpels unite the santalales, the caryophyllales and the asterids. Likewise, leaves without stipules may be another synapomorphic character, although Berberidopsidaceae have stipules and Aextoxicaceae