Stratigraphic column of the Xiazhen Formation with the 18 stromatoporoid-bearing intervals

<p>A diverse labechiid stromatoporoid assemblage that includes 16 species in 8 genera was found in the Upper Ordovician Xiazhen Formation (mid-late Katian) at Zhuzhai, Jiangxi Province of South China. The assemblage is characterized by a combination of: a) North China provincial species succeeding from their origination in the Darriwilian, including <i>Pseudostylodictyon </i><i>poshanense</i> Ozaki, 1938, <i>Labechia shanhsiensis</i> Yabe and Sugiyama, 1930, <i>Lb</i>. <i>variabilis</i> Yabe and Sugiyama, 1930 and <i>Labechiella regularis</i> (Yabe and Sugiyama, 1930), and b) South China endemic species, including three new species (<i>Lb. zhuzhainus</i> Jeon sp. nov., <i>Lblla</i>. <i>beluatus</i> Jeon sp. nov., <i>Sinabeatricea </i><i>luteolus</i> Jeon gen. et sp. nov.), and four species in open nomenclature (<i>Rosenella</i> sp., <i>Cystostroma </i>sp., <i>Pseudostylodictyon</i> sp. and <i>Labechia </i>sp.). The finding of <i>Lblla</i>. <i>gondwanense</i> Jeon sp. nov., <i>Stylostroma </i><i>bubsense</i> Webby, 1991, <i>Sty</i>.<i> ugbrookense</i> Webby, 1991 and <i>Thamnobeatricea gouldi</i> Webby, 1991 in the formation indicates that Tasmania was closely related to South China, and had a closer paleobiogeographical relation with peri-Gondwanan terranes than Laurentia. In addition, the occurrences of <i>Labechia altunensis</i> Dong and Wang, 1984 and <i>Stylostroma</i> species support a close biogeographic link between Tarim and South China through the Middle to Late Ordovician interval, corresponding with the results from other fossil groups such as brachiopods, conodonts and chitinozoans. The diverse labechiids from the Xiazhen Formation improve our understanding of the diversity of Ordovician stromatoporoids in peri-Gondwanan terranes and the biogeographic affinities among Australia (especially Tasmania rather than central New South Wales), Tarim and South China.</p>