The Permian-Triassic Merrillina (conodont) in South China and its ecological significance

Conodonts from Permian-Triassic Boundary (P-TB) beds have been intensively investigated in recent years. Many species survived the end-Permian mass extinction, and some became cosmopolitan in the earliest Triassic. Most studies have focused on common families such as the Gondolellidae and the Achignathodidae, whilst the Ellisonidae is understudied due to the difficulties of reconstructing their multi-element apparatus. Here, we focus on the Ellisonidae from the Meishan, Shangsi and Gaohua sections in South China and find Merrilina (M.) spp. are common taxa. A representative species, M. ultima, previously regarded as a Changhsingian cool-water species, is found in warm, shallow platform settings of the earliest Triassic. Biostratigraphically, M. ultima ranges from the Hindeodus parvus Zone to the Isarcicella staeschei Zone at Meishan and to the I. isarcica Zone at Gaohua, whilst it only occurred in the Clarkina taylore Zone at Shangsi. A compilation of all published data suggests M. ultima firstly appeared in the C. meishanensis-H. praeparvus Zone and went extinct in the I. isarcica Zone. Merrillina spp. occur in various settings and latitudes, indicating that the species were likely cosmopolitan taxa that favoured surface-water habitats and were not restricted to cool waters.