The discovery of a crinoid community in the Late Triassic Zhuganpo Formation of Guizhou province and its geological significance

Recently a rich and well-preserved crinoid community including Traumatocrin us and Encrinus has been found in the Late Triassic Zhuganpo Formation in G uanling and Xingyi, Guizhou province, China. Among the fossils Traumatocrin us is the richest, and most of it occurs as clusters, with each cluster con taining 3-42 crinoid branches. Study of the stem and calyx of Traumatocrinu s shows that the number of stem-joints (columnals) is equal to the total st em length x K (5.85 per cm x stem-diameter). There are about 376 first- and second-order columnals on the whole stem. This number seems to coincide wi th the number of days in a year at that time. According to the present stud y of the palaeoecological environment of the crinoid community, it is consi dered that the reproduction and preservation of the crinoid community were controlled by the Late Triassic regression and the restricted bay of an int erior sea behind the S-shaped shoal zone.