, describing a species that has remained more or less unchanged for millions of years. Such species may appear primitive; however when they first appeared they may have represented the end of an increasing trend towards specialization in a particular group. Certain of the present-day gymnosperms, such as Welwitschia, Ginkgo, and Podocarpus are considered bradytelic. The evidence for this comes partly from fossil studies, and also from investigations of the karyotype. Such species have strikingly asymmetrical karyotypes, a feature generally considered to be advanced.