Lingulate brachiopod fauna of the Chýnice Limestone (Zlíchov Formation, Emsian; Czech Republic) were examined. Ten species have been observed, of which Acrosaccus vertex, Schizotreta vaneki, Havlicekion frydai, and Opsiconidion coralinus are described here as new taxa. Shell microornaments of several of the taxa were examined and it indicated that some show prominent changes during shell growth. Uniformity of microornaments in particular species is evidenced. Both findings suggest that microornaments can be used as a significant feature in determination of separate species. Composition of the fauna indicates a close relationship to the Eifelian lingulate fauna of the Barrandian area.•

The long-term activities of the International Subcommission on Devonian Stratigraphy have been focused on the division of the Emsian into two new substages. The different stratigraphic levels, close to the Daleje Event, have mostly been discussed as their boundary. The latter event was first recognized in the Barrandian and defined as a bioevent, connected with a pronounced transgression. Its present conception has been inferred from studies of its appearance in deeper environments, with deposition of the calcareous Daleje Shale. We analysed its appearance in shallower environments, with predominantly carbonate sedimentation, using precise qualitative and quantitative biostratigraphic, paleoecological, and sedimentological methods. Our data revealed that the mid-Emsian had a more complex transgression-regression history than previously described. Evaluation of the stratigraphic distribution of more than 1250 newly collected dacryoconarid shells has resulted in the proposal of a new tentaculite biozonation, providing a much higher stratigraphic resolution than the existing biozonations, which are based on goniatites and conodonts. Quantitative analysis of the newly gathered paleoecological data suggests a distinct faunal turnover at the level of the first occurrence of the dacryoconarid tentaculite Nowakia elegans. In addition, our study revealed that the Daleje transgression (and thus the Daleje Event) started at the same time, and that it was preceded by a distinct regression. For these reasons, we propose the first occurrence of the worldwide and easily determinable dacryoconarid Nowakia elegans as a biostratigraphic indicator of the boundary level for the new Emsian substages.

A systematic study of Silurian and Devonian platyceratid gastropods provides new data on their early shell ontogeny. Typical cyrtoneritimorph protoconchs were found in <i>Praenatica cheloti </i>(Oehlert & Oehlert, 1887) from the Lower Devonian strata of Brittany (W France). The same protoconch type, as in <i>Praenatica</i> Barrande in Perner, 1903, was earlier documented in <i>Orthonychia </i>Hall, 1843. Both of the latter taxa have often been considered to be subgenera of <i>Platyceras</i> Conrad, 1840. However, Silurian and Devonian species of <i>Platyceras</i> from the Barrandian area develop quite different protoconchs (orthostrophic and tightly coiled), similar to those found earlier in different species of the family Naticopsidae Waagen, 1880. Current data suggests that Paleozoic platyceratids represent a diphyletic group. The nature of their protoconchs (development of a true larval shell) testifies against the hypothesis that the Paleozoic platyceratids are the stem group for the Patellogastropoda. However, the derivation of modern neritimorphs from Paleozoic “platyceratids” with tightly coiled protoconchs or from the naticopsids seems to be probable. The strongly convolute neritimorph protoconch (apomorphy of neritimorph crown-group) probably originated after the Permian/Triassic mass extinction event, but before the Late Triassic

A new palaeozygopleurid gastropod, Palaeozygopleura vaneki sp. nov., is described from the Emsian Chýnice Limestone (Novakia elegans Zone, upper part of the Zlíchov Formation; late Early Devonian) of the Prague Basin (Bohemia). The phylogeny of the superfamily Loxonematoidea and the origin of planktotrophy are briefly discussed. It is suggested that the large protoconchs of the Palaeozygopleuridae and Loxonematidae might represent a grade before the inception of planktotrophy.•

An unusually complex type of skeletal ornamentation in the new conulariid species, Mesoconularia (?) lukesi sp. nov. from upper Emsian strata of the Prague Basin (Czech Republic) is described. The complex structure of elevated and heavily mineralized tubercles arrayed in transverse rows on the outer surface of the test of this conulariid is interpreted as a protective structure which probably evolved in response to increasing durophagy in the early Devonian. Favourable preservation of M. (?) lukesi sp. nov. revealed several hitherto unknown morphological features which could be important for reconstruction of the organisation and growth of the conulariid test. Polygonal imprints observed on the inner surface of the test laminae may represent epidermal cell moulds. The mineral component of the test of M. (?) lukesi consists of of carbonate-fluorapatite (francolite) and exhibits a homogeneous microstructure in both the outer and the inner layers of the test.•