FIG. 6.—The evolutionary origin and loss of key courtship traits in Rhŋacotriton and plethodontid genera. Character origins are shown with solid rectangles; character losses are shown with open rectangles: sff ¼ spermatophore deposition in front of the female, TSW ¼ tail-straddling walk, tpd ¼ transdermal pheromone delivery (tpd1 and tpd2), tbf ¼ turning back towards the female during TSW, tm ¼ tail massage during spermatophore pickup, opd ¼ olfactory pheromone delivery. The question marks on the Amphiuma and Hŋdromantes branches indicate that courtship behavior has not been adequately described. Dendrotriton is not shown on this tree but is the sister group to the Bolitoglossa-Pseudoeurŋcea lineage. The time of origin for each trait is bounded by the times at the ends of the branch on which it resides. Arrowhead pointing to the right indicates that the origin of traits on that branch precedes the date for the right end of the branch. Time-calibrated phylogeny based on Shen et al. (2016), using an independent-rate model (clock ¼ 2). Time scale shown in millions of years.