Late Ordovician (Caradoc-Ashgill) brachiopod faunas with Foliomena based on data from China

New investigations of mid-Ashgill brachiopod faunas with Foliomena in an on shore to offshore transect in the border region of Zhejiang-Jiangxi provinc es, East China, indicate a remarkable increase in numbers of Foliomena foli um (Barrande) with significant variations of faunal composition, diversity, and abundance from shallow-water to deepwater environments. Based on data from China and elsewhere, faunas with Foliomena are partitioned into typica l and atypical associations. The typical Foliomena fauna is characterized b y Foliomena along with some distinctive constituents (such as Dedzetina, Le ptestiina, Christiania, and Cyclospira), and is essentially located in deep -water environments (mainly BA. 5-6). The atypical Foliomena fauna is repre sented by those assemblages in which rare Foliomena is associated with vari ous genera such as Kassinella at different localities representing shallowe r environments (outer BA 3-BA 4). The Foliomena fauna previously was report ed as latest Caradoc to early Ashgill in age. New Chinese data demonstrate that it ranges from the early Caradoc(Nemagraptus gracilis Biozone) to the mid-Ashgill. It reached its evolutionary acme in the early Ashgill and beca me extinct before the Hirnantian. Paleobiogeographically ly, it is associat ed with eight paleoplates within the Kosov Province, where the shallow-wate r Hirnantia fauna was widely distributed later in the Hirnantian. Continuou s and gradual changes in the taxonomic composition and ecological niches of the Foliomena associations across a range of depths may indicate that the distribution of faunas with Foliomena may not be controlled always by the p osition of the thermocline. Distribution of the typical Foliomena fauna in time and space verifies a successful early Paleozoic ecological experiment int he marine benthos: brachiopods expanded their ranges into vacant deep-w ater benthic niches to exploit soft substrates associated with dark, possib ly oligotrophic conditions.