2022 Volume 33 Issue 1 Pages 3-12
We propose a new graphical expression to show time ranges of species and their chronological relations. Let So be the set of species forming a higher rank of taxon Σ that lived in the true range T in time. Information that a species appeared at t=a and became extinct at t=b is represented by a point (a, b) on a two-dimensional coordinate diagram where the abscissa and the ordinate denote the appearance time and the extinction time, respectively. The coordinate diagram provides a new method to show time ranges of species in So on one diagram and further to represent the chronological relation of time ranges as a directed graph. As an application example, an algorithm is proposed to select a subset S of So such that S satisfies two constrains: (1) S is a totally ordered under the chronological relation and (2) at least one species lived at any time within T. The algorithm guarantees the existence of a subset S satisfying two constraints.
