Figure 4. Maximum Clade Credibility tree of early to middle Paleozoic crinoids. Posterior probabilities (>.50) are located next to nodes and expressed in percent; blue node bars represent the 95% highest posterior density age estimates; thick black bars represent genus-level stratigraphic ranges. Note the inclusion of stratigraphic ranges gives the appearance of sister taxon relationships where zero-length branches were sampled (e.g., Cupulocrinus). The Cladida (sensu Simms and Sevastopulo, 1993) are sister to the Disparida. Crinoid taxa depicted represent the major clades discussed in the text: (from top to bottom) the disparid Eustenocrinus springeri Ulrich, 1925, redrawn from Ubaghs (1978); representative porocrinoid and hybocrinid (see text), Hybocrinus conicus Billings, 1857, redrawn from Sprinkle and Moore (1978); the flexible Protaxocrinus laevis (Billings, 1857), redrawn from Springer (1911); representative eucladid Dictenocrinus, redrawn from Bather (1900).
