A new holocrinid sea lily from the Anisian (Middle Triassic) of Qingyan, south-western China, and the morphological variability of the distal nodal facets in the genus Holocrinus

Holocrinus hagdorni sp. nov. (Crinoidea, Holocrinida) is described based on well-preserved, disarticulated stem remains from latest middle to early late Anisian (early Middle Triassic) deposits of the north-eastern outskirts of Qingyan, Guizhou Province, south-western China. The columnals exhibit a well-differentiated articulation facet sculpture, and the distal nodal facets show a conspicuous variability. They generally are symplectial as typical for Holocrinus, but in many nodals, the distal facet is slightly to distinctly weaker sculptured than the proximal facet, and sometimes cryptosymplectial to more or less synostosial distal nodal facets occur. The morphological variability of the distal nodal facets in the genus Holocrinus is discussed with regard to holocrinid and isocrinid evolution and life mode. Cryptosymplectial to synostosial nodal–infranodal articulations have only been documented in a minority of the Holocrinus species and their occurrence appears to be random with regard to stratigraphical age and ontogenetic stage, whereas the isocrinids, descended from holocrinids and co-existing with them in Triassic times, show always cryptosymplectial to synostosial nodal–infranodal articulations. The predisposition for weaker sculptured nodal–infranodal articulations probably developed in early holocrinids prior to or during the early Olenekian (late Early Triassic) in the far-eastern part of the Palaeotethys. Furthermore, the isocrinid genus Bakonycrinus is documented from China for the first time.