The main generic feature of the hyolithid genus Pterygotheca Novlk, 1891 ‐ the fringe on the lateral edges and on the dorsal side of the conch ‐ is interpreted here as a colony of a tabulate coral, Hyostragulum gen. n. This coral covered the living specimens of different hyolithid species in the Bohemian and Moravian Lower and Middle Devonian and occasionally also of nautiloids and gastropods. Because of this discovery it is necessary to withdraw the order Pterygothecida Syssoiev, 1968 and probably also the family Ptery‐gothecidae Syssoiev, 1958. The genus Pterygotheca is questionable, but further study may prove its validity. The character of the epifaunal coral strongly supports the interpretation of a benthic life of hyolithids.

Abstract:The Odivelas Limestone constitutes one of the few records of Middle Devonian sedimentation in the western Ossa-Morena Zone. Although deformed and metamorphosed the limestones have an abundant fossil content which allows their positioning as late Eifelian/early Givetian in age and to relate the reef fauna with the typical Rhenish facies for the same time period. Magnetic susceptibility analysis was attempted and is in agreement with the biostratigraphy, but the limited extent of sections and the metamorphism precludes firm correlations. The field evidence, petrographic and geochemical analysis point to a close paleogeographical relation and dependence of the reef system on volcanic structures which are included in the Beja Igneous Complex. The age of part of the volcanic and sub-volcanic suite of this complex is thus constrained.

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Development of new stratigraphic techniques has led to better understanding of the compositional variability and quantity of dust-related impurity components in pure marine limestones, with a considerable impact on stratigraphic resolution and explanation of causality. The early Middle Frasnian (E-MF, punctata Zone) stratigraphic interval was selected for this study in order to assess the contribution of atmospheric dust and to distinguish between the robust climatically driven anomalies and the potential distant effect of the Alamo impact. The location of the study in the Moravian Karst area has two advantages: there are no mixed carbonate-siliciclastic sediments, only the pure limestone of a platform reef complex, and the authors have access to voluminous survey and drilling reports. The methodology employed for undertaking the most recent research was based on succession and combination of the following steps: biostratigraphy and facies analysis, magnetic susceptibility (MS), gamma-ray spectrometry (GRS), instrumental neutron activation analysis (INAA), and finally, separation and assessment of rare non-carbonate particles. The natural atmospheric dust burden, deposition, and embedding in pure carbonate traps were, most likely, threefold higher during the Frasnian in the Upper Devonian in comparison with Quaternary platform reef counterparts. Variation of 10-100 ka averages is medium in terms of the Frasnian ranges of MS-GRS values, and the base and top of the E-MF interval are manifested by robust elevations of these values. Forced anomalies in MS, GRS and geochemical signals that defy the normal sequence of rhythms were found: two anomalies disturb the broad middle part of the E-MF interval and one is superimposed on the upper part of the punctata-hassi zones strata. The most significant disturbance was found near the mid-punctata Zone level. In spite of the relatively low magnitude, it shows features that are usually related to major environmental crises which occured in the Devonian, such as the Choteč, Kačák or Kellwasser events. These include a large depression in MS and dust-particle concentration values coupled with a period of sea level lowstand and calm atmospheric conditions (stage A), and an abrupt shift to high MS that has a comb-like pattern that gradually fades upward, developed together with a forced flooding surface, increased detritism, and stormy conditions (stage B). It is a reverse of the normal cyclicity in pure limestone when the high impurity corresponds to lowstands. A very small amount of particulate material of an exotic nature was found at the A-B stage interface and assessed: it contained iron-rich silicate microspherules and drops, devitrified glasses, tiny mineral/rock clasts of hyperbasite compositions, as well as pellets and clumps of glasses and phlogopites. The silt-sized particles show ablated and striated surfaces, flow deformation of devitrified glasses, and layered onion-like structures. Iron-rich lamellae with meshwork crystal patterns occur among decrepitated crystalli...

A specimen of Calceola sandalina (Linné 1771) from the Givetian of the Czech Republic shows severe injury on its right side when observed from its cardinal side. Approximately onehalf of the counter side is missing between the counter septum and the alar corallite angle. The injury is healed within the calice, as visible also on deformed septa close to injury, while the outer flat ventral side shows no signs of healing. The operculum is not preserved but the damage clearly must have affected it. It is difficult to envision how such damage might have occurred by abiotic means in a rather low-energy environment without the influx of grains larger than silt. We consider the injury a result of attack by a predator. When speculating on the animal capable of producing such injury, one must consider preferably a vertebrate with strong jaws: fish-like animals capable of durophagy (placoderms and chondrichthyans) appeared in the Devonian.