Dunbarella marine marker horizon has significant stratigraphical importance for the Lublin Coal Basin LCB (Poland). It sets the boundary between Westphalian A (Langsettian) and B (Duckmantian) and between paralic and limnic sedimentation at the same time. This marker horizon is also the base of the Lublin formation deposits where a main multi-seam coal deposits can be found. The horizon correlates with the Clay Cross Marine Band (England), the Katharina horizon (Germany, The Netherlands) and the Quaregnon horizon (Belgium). The paleontological material taken from recent boreholes provides new data about development of the Dunbarella horizon of the LCB. 32 bivalve species have been encountered and can be assigned to 28 genera. Edmondia, Posidonia, Sanguinolites, Polidevcia, Phestia and Dunbarella are the most abundant in all profiles. Slightly less numerous are gastropods (9 genera), represented mainly by Glabrocingulum and Euphemites, and cephalopods (4 genera), represented mainly by Gastrioceras and Anthracoceras. Very frequent, although not so diverse, are the brachiopods, primarily inarticulate and represented almost exclusively by Lingula. Studies of macrofauna showed the presence of marker species and faunal assemblages typical of the Dunbarella horizon. A distinctive feature of this horizon which was observed was the cyclic sedimentation and associated variability of the fauna spectrum. This is typical for Westphalian marine horizons of Northwestern Europe, including those correlated with the Dunbarella horizon. (C) 2015 Elsevier B.V. All rights reserved.