[3] It shows the evolutionary relationships of a group of organisms in a temporal framework.
[4] As with a phylogenetic tree, timetrees can be drawn in different shapes: rectangular, circular,[3] or even spiral.
[2] The only figure in Darwin's On the Origin of Species,[5] one of the earliest printed evolutionary trees, is a hypothetical timetree.
[6] In the past, timetrees were sometimes called "chronograms,"[7] but that term has been criticized because it is imprecise, referring to any graph that shows time, and not indicating that evolutionary relationships are involved.
[3] The first use of the single word "timetree," in the context of an evolutionary tree scaled to time, was in 2001.