Although the underdeveloped embryo, and thus morphological (MD) or morphophysiological (MPD) seed dormancy, is basal in angiosperms, it also occurs in advanced groups. A synthesis of the literature, combining phylogeny and the kind of seed dormancy in the highly evolutionarily advanced order Dipsacales, shows that MPD (or MD) occurs throughout all clades except the most advanced one, Valerina. Seeds of taxa in the Valerina clade have fully developed embryos and physiological dormancy (PD) or are non-dormant (ND); thus, PD and ND are derived conditions in Dipsacales. Assuming that types of seed dormancy have not changed since the Early Tertiary, the fossil record suggests that MPD (or MD) was present in extant genera of Dipsacales by the Palaeocene, but PD (or ND) not until the Miocene. Molecular dating indicates that the ages of dipsacalean lineages with MPD and PD are older than those indicated by the fossil evidence.

Studies were conducted to determine if small embryos (i.e. low embryo length:seed length ratio) in mature dwarf seeds (0.2–2 mm) are underdeveloped. In this case, they would grow (inside the seed) prior to germination, and seeds would have morphological or morphophysiological dormancy. Prior to radicle emergence, embryo length in seeds of Drosera anglica (Droseraceae), Campanula americana, Lobelia appendiculata, L. spicata (Campanulaceae) and Sabatia angularis (Gentianaceae) increased 0, 103, 182, 83 and 57%, respectively. Since embryo growth did not occur in seeds of D. anglica prior to germination, embryos, although small, are fully developed; seeds have only physiological dormancy. The underdeveloped embryo in seeds of C. americana has little or no physiological dormancy; thus, seeds have morphological dormancy. On the other hand, underdeveloped embryos in seeds of L. appendiculata, L. spicata and S. angularis are physiologically dormant, and seeds have morphophysiological dormancy. Therefore, since small embryos in dwarf seeds may or may not be underdeveloped, assignment of seeds to a dormancy class requires that studies be done to determine if embryos grow inside the seed before germination can occur. Such information is important in understanding the evolutionary relationship of the different kinds of seed dormancy.