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Fossils preserved in Cambrian to Devonian sediments of the Barrandian area (Czech Republic) have contributed significantly to our knowledge of numerous invertebrate groups. With respect to trilobites, important data has been discovered on the construction of eyes, healing of exoskeletal injuries, as well as on the morphology of soft parts. The generally rarely preserved frontal auxiliary impressions (FAIs) on the glabellar surface of trilobites were first described in Devonian examples from this area in the mid-nineteenth century by Barrande. Such impressions have only rarely been documented in a few trilobite species in the Lower Palaeozoic of the Barrandian area. Here we describe twelve exceptionally preserved holaspid cephalic shields of Dalmanitina socialis Barrande, 1846. These specimens are internal moulds and were collected at three localities in the Upper Ordovician Letná Formation. This material documents a high level of variability in the disposition of FAIs within the glabella. However, the FAIs show a common pattern at the anterior glabellar margin and are arranged in two pairs around a medial impression and are also associated with a third pair situated more posterolaterally. This current study is the first to focus on the distribution of FAIs within the Dalmanitidae. Dalmanitina socialis specimens with FAIs from the Letná Formation indicate that the depositional environment at the several localities in that unit was favourable to exceptional preservation. Excellently preserved cephalic shields of Dalmanitina demonstrate the presence of the posterior median impression (pmi) of Eldredge (1972) and enable new terminology to be proposed for other FAIs. [ABSTRACT FROM AUTHOR]

About 100-1 50 m thick intercalation of dark micaceous siltstone to black clayey shale can be distinguished in the middle part of the Letná Formation (Upper Ordovician, Lower Sandbian) at several localities in the NW and NE parts of the Prague Basin. Sandstone and greywacke, dominant elsewhere in this formation, form only a subordinate part of the sequence. In the NW belt of the Letná Formation, N of the Prague Fault (see Fig. 1C), this thick intercalation has been previously known from Bulovka -Bílá Skála Rock and from Rudolfova Štola Gallery (Rohlich 1956, 1960; Mikuláš 1994). A comparable, slightly thinner, and locally discontinuous intercalation of dark siltstone and black clayey shale was described also in the middle belt of the Letná Formation, S. of the Prague Fault (see Fig. 1C) by Rohlich (1956, 1960); such lithology is known from the Praha - Žižkov, Kyje and Malešice areas. An equivalent of this interlayer was documented by Budil (1996) in the middle part of the Letná Formation from the Černý Most area. No such interlayer of dark, fine-grained sediments has been reported from the southern belt of the Letná Formation (Fig. 1C), most probably because of its much poorer exploration. New borehole documentation at Praha - Střešovice extends our knowledge on the above - discussed dark siltstone and claystone intercalation in the NW belt of the Letná Formation. In two boreholes (HJ 11 and HJ 16), more than 60 m thick sequence of dark, fine-grained sediments has been documented in the middle part of the Letná Formation. The presence of these sediments was confirmed also by the study of archive data - previous geotechnical documentation of this area. The archive data documented the presence of a second, thinner and rather lenslike body of dark, fine-grained sediments which can be traced in the lower third of the Letná Formation in the Střešovice area. It is suggested that the sedimentation of relatively thick sequences of dark siltstones and shales reflects short-time periods of decrease in the input of clastic material. Alternatively, it could correspond to a partial, synsedimentary tectonic-related deepening of respective parts of the sedimentary basin. Locally bioturbated black siltstone and shale sequence is barren of benthos and contains only rare remains of indeterminable linguliformean brachiopods. It is supposed that such association corresponds to the Paterula Community of Havlíček (1982), so far only poorly documented from the Letná Formation (Van Roy et al. 2021). [ABSTRACT FROM AUTHOR]

The preservation of digestive structures of trilobites is not unique but recognition and reporting about these remains are rare. Here we describe a specimen of Lioparia bassleri Resser & Endo, 1937, recently collected from the Weifang Biota in the Manto Formation (Cambrian, Miaolingian, Shandong, North China). This exceptionally preserved specimen displays the remains of the digestive system in the cephalon as well as in thoracic and pygidial parts of the body. The morphology of the remains of soft parts preserved in the specimen agrees with a simple digestive tract which included a simple gut tube in the thorax and pygidium associated with four pairs of cephalic gut diverticulae in the glabella. The morphology of the digestive tract of L. bassleri compares favourably with earlier observations on trilobites that had gut diverticulae. The preservation of the digestive system in the studied trilobite confirms that the depositional environment of the Manto Formation was favourable to soft-tissue preservation. Earlier papers on trilobites with preserved soft parts from China are summarized. Exceptional preservation of sponges, palaeoscolecids, radiodonts, bivalved arthropods, trilobites, and echinoderms in the Manto Formation is briefly discussed. [ABSTRACT FROM AUTHOR]

Imperfectly preserved specimen of a supposed hydrozoanMedusitescf.radiatusLinnars., originally described by Pompeckj (1896) from the “Pod trním” locality near Týřovice (Slapnice Member of the Buchava Formation, Skryje–Týřovice Basin) is revised. Recent study of the original specimen and a more complete topotype specimen testify the affiliation to the pineapple-shaped ichnogenusAstropolichnusCrimes and Anderson, 1985. A new ichnospeciesA. bohemicusis established on the material from the Buchava Formation. This material is the first occurrence ofAstropolichnusin the middle Cambrian as well as the first report of this ichnogenus in the Barrandian area of Czech Republic. [ABSTRACT FROM AUTHOR]

One of the important outcrops in the Upper Ordovician Letná Formation - the Kazín section - has been examined for chitinozoans. All studied samples contained a highly diverse chitinozoan assemblage including specimens classified within more than thirty taxa. A significant number of them has been previously unknown from the Prague Basin. Despite a comparatively poor to moderate preservation of chitinozoan vesicles, detailed observation based on SEM together with morphometric measurement enables determination, up to the species level, in about one third of the studied specimens. Belonechitina micracantha, Cyathochitina campanulaeformis, C. kuckersiana and Desmochitina minor are typical representatives of Ordovician Chitinozoans and represent the so called "long-ranging" taxa, but without any significant contribution to the age of the Letná Formation at the Kazín section. Linochitina pissotensis represents the index species of the Upper Darriwilian, its LAD marks the upper boundary of the Middle Ordovician Series. Only seven specimens of L. pissotensis have been reported from two lowermost samples at the Kazín section. The Darriwilian age is supported also by Euconochitina vulgaris, a species that is restricted exclusively to the Middle Ordovician. Twenty-seven specimens of E. vulgaris have been documented from four different samples in the upper part of the Kazín section. The third species, Conochitina chydaea, ranges from the latest Middle to the Upper Ordovician. This species is the most abundant in the Kazín section, with a total of fifty-nine specimens distributed in all samples. The abnormally high diversity and unexpected Middle Ordovician age apparently indicated by some of chitinozoans in samples from the Kazín section could be explained, most probably, by a re-deposition of typically Middle Ordovician chitinozoan species into the Upper Ordovician Letná Formation. The exact time for sedimentation of the Letná Formation cannot be established due to the absence of stratigraphically important Upper Ordovician chitinozoan taxa. [ABSTRACT FROM AUTHOR]

The gogiid eocrinoid Akadocrinus jani Prokop, 1962 is known from the mid-Cambrian (Drumian) Jince Formation of the Příbram-Jince Basin (Barrandian area, Czech Republic). Excellently preserved specimens of this species are described in detail. Our primary focus was on juvenile specimens, described here for the first time. Detailed comparison among juvenile specimens makes it possible to establish changes in morphology during ontogeny. Juvenile specimens differ considerably from adult specimens in (1) a lower number of thecal plates, (2) a complete absence of epispires, (3) comparatively shorter brachioles, comprising a small number of brachiolar plates, (4) a comparatively shorter stem, comprising a small number of columnals and (5) a relatively large attachment disc. Study of the Jince material makes it possible to establish two basic phases in the development of Akadocrinus: the pre-epispire bearing phase and the epispire bearing phase. [ABSTRACT FROM AUTHOR]

Two recently discovered specimens of the abundant calymenoid trilobite Colpocoryphe Novák in Perner, 1918 from the Middle Ordovician Šárka Formation and one specimen of Flexicalymene (Flexicalymene) pragensis Vaněk & Vokáč, 1997 from the Upper Ordovician Bohdalec Formation, all from the Prague Basin, display remains of the digestive system. In Colpocoryphe, an internal mould of an articulated exoskeleton contains a post-stomach part of the alimentary canal preserved through the narrow axial region of the occipital ring, all thoracic segments as well as in the axial part of the pygidial shield. The anterior part of the digestive system is poorly known as the specimen shows the hypostome preserved in situ and the space between the glabella and the hypostome is represented by an empty cavity associated with probable remains of gut diverticulae on both sides of the cephalon. The second, incomplete specimen consists of five posterior thoracic segments articulated with the pygidium. The axial region of this specimen is preserved with a clearly discernible segmented intestine which terminates at the axial tip and then bends ventrally. In an enrolled specimen of Flexicalymene pragensis, supposed remains of the alimentary tract are comparatively poorly preserved but discernible in the middle and posterior parts of the thoracic axis and in the anterior part of the pygidial axis. Digestive structures within the family Calymenidae have not been described previously. Earlier discoveries of the digestive system in Ordovician trilobites of the Barrandian area are briefly reviewed. [ABSTRACT FROM AUTHOR]

Rare remains of Reussiana cf. brevispicula Horbinger, 2000 have been collected near the Praha-Lochkov, together with a rich faunal association characteristic of the upper part of the Lochkov Formation (Lower Devonian, Lochkovian, Monograptus hercynicus graptolite Biozone). This occurrence confirms the earlier assumption that large Devonian dalmanitids ("odontochilinids") appear in the Prague Basin below the Basal Pragian Regressive Event. The unique discovery represents one of the earliest occurrences of Devonian dalmanitids worldwide and sheds light on the migration and early radiation of dalmanitids within the Rheic Ocean realm during the Early Devonian. [ABSTRACT FROM AUTHOR]

Previously published biostratigraphical subdivisions of the "middle" Cambrian succession of the Příbram-Jince Basin in the Barrandian area are summarized and a modified subdivision of twelve biozones proposed. Nine of the biozones are delimited by the first appearance of the eponymous species; five of these are interval zones and four are taxon-range zones. The youngest stratigraphical levels of the fossiliferous sequence in the Litavka River Valley, which lack any characteristic taxa, are assigned to one assemblage zone that is subdivided into two levels defined by the presence of two trilobites and two lingulate brachiopods. The Kodymirus vagans, Hypagnostus parvifrons and Dawsonia bohemica zones, and the Barren interzone between Paradoxides (Eccaparadoxides) pusillus-Paradoxides (Paradoxides) paradoxissimus gracilis, are newly established; the other zones are redefined or the earlier definitions retained. [ABSTRACT FROM AUTHOR]

Preservation of ontogenetic stages of trilobites from the Cambrian of the Skryje-Týřovice Basin (Barrandian area) has been known from several localities in the upper part of the Buchava Formation. The most complete information on exoskeletal changes during ontogeny was based on material assigned by Barrande (1852) to Sao hirsuta. Based on quantitative methods and detailed study of the morphology of the exoskeleton, we recognize three protaspid and two early meraspid instars of Sao hirsuta. We also describe the protaspid stages of two indeterminate taxa of Ptychopariida, one originally determined as the protaspides of Sao hirsuta and the other referred to by Růžička (1943) as "Barrande's larva". Protaspides of Sao hirsuta have an adult-like morphology, and their presumed benthic mode of life is consistent with the restricted palaeogeographic distribution of this genus. [ABSTRACT FROM AUTHOR]

The preservation of digestive structures of trilobites is extremely rare. Here we describe two new examples of trilobites from the Upper Ordovician Letná Formation (Prague Basin, Czech Republic), which display remains of the digestive system. The first specimen, assigned to Selenopeltis buchi (Barrande, 1846), exhibits cavities under the posterior part of the glabella and the axis of most thoracic segments. These cavities are interpreted as remains of metamerically paired digestive caeca and constitute the first example of preserved digestive structures in the order Odontopleurida. The second specimen belongs to Birmanites ingens (Barrande, 1852) and displays a tube-like structure, filled with a finely-grained material, that runs under the axial lobe of the entire trunk. We interpret this structure as a gut infilling similar to that repeatedly observed in the Moroccan Basilicus calzadai. These specimens confirm that the depositional environment of the Letná Formation was locally favourable to soft-tissue preservation. They also further document the presence of two different types of digestive systems in trilobites. The possibility that different processes might have been involved in the preservation of different parts of the trilobite gut is discussed, and several criteria to differentiate genuine gut remains from scavenger burrows are proposed. [ABSTRACT FROM AUTHOR]

Two orthothecid hyoliths Probactrotheca briketa new genus and new species and Circotheca smetanai new species are described from the Middle Cambrian Buchava Formation of the Skryje-Týlřovice Basin in the Czech Republic. The new forms are based on about twenty well-preserved external and internal moulds of opercula and conchs. The stratigraphic range and geographic distributions for both taxa are well known. [ABSTRACT FROM AUTHOR]

An introduction to the article is presented in which the authors focus on the Precambrian-Cambrian biosphere revolution based on changes seen in the Chinese Yangtze platform and discusses reports published within the issue, including one by Bernd Weber and colleagues which describes the diverse trace fossil communities of Guanshan Community, another by Shixue Hu and colleagues which presents palaeontological data on the diversity of priapulid worms and lobopodians and Jianni Liu and colleagues which describes an occurrence of the Guanshan fossil assemblage from the Huize County of eastern Yunnan, China.

Isolated sclerites of the genus Wiwaxia are reported from shale interlayers in lower levels of middle Cambrian (unnamed 3rd Series of Cambrian) Buchava Formation in the Skryje-Týrovice Basin in the Czech Republic interpreted as shallow-water sediments. Geographic distribution of Wiwaxia indicates latitudinal control as all occurrences are obviously restricted to tropical belt. [ABSTRACT FROM AUTHOR]

Two specimens of rare trilobites from the Middle Ordovician Šárka Formation (= Darriwilian, Oretanian), both coming from Osek near Rokycany locality, are shortly described. An excellently preserved entire proetide specimen substantially differs from all other Middle Ordovician representatives of this order known from the Prague Basin. We place it tentatively in the genus Mezzaluna as a new species Mezzaluna? xeelee sp. n. Malformed exoskeleton of the rare cheirurid Areiaspis barrandei shows atypically developed left 9th pleural tip. Possible mechanisms of this malformation are shortly discussed and unpublished observations on the morphology of the species are added. [ABSTRACT FROM AUTHOR]