Permian–Triassic phylogenetic and morphologic evolution of rhynchonellide brachiopods

Abstract The Rhynchonellida is a major group of brachiopods that survived the “big five” mass extinctions and flourished after Permian/Triassic (P/Tr) crisis. However, phylogenetic character evolution in across P/Tr transition poorly understood. In view widespread homoplasy this order, we employ tip-dated Bayesian analysis to reconstruct relationships for late Permian–Triassic rhynchonellides. same data were also analyzed using three other methods: undated Bayesian, equal-weighting, implied-weighting parsimony. Compared with trees generated by methods, those constructed tip-dating best account are closer previous assumptions on order. Based analyses multiple trees, increase lineage richness occurred Early early Middle Triassic. Also, Anisian almost reached highest level seen According fossil records, pronounced reduction shell size development ornamentation extinction, which largely due loss large highly sculptured genera diversification small-sized weakly ornamented genera. Ancestral-state estimation ornamentation, coupled comparisons characters, indicate Early–Middle Triassic mature “small-sized taxa” may have characters displayed juveniles their ancestors. This suggests these genera, paedomorphosis was possibly strategy survive diversify harsh environment extinction.