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Cuticular remains of the phyllocarid crustaceans Caryocaris? and Ceratiocaris? obtained via maceration of macrofossil remains in hydrofluoric acid are compared with dispersed fragments isolated using both the low-manipulation HF extraction and the standard HCl–HF–HCl method. The studied specimens were obtained from Ordovician and Silurian shales of the Šárka and Požáry formations (Prague Basin, Barrandian area, Czech Republic). This methodological approach allows a direct comparison of macrofossil remains with microfossils in residue. The differences in residues obtained through the two bulk-rock extraction methods are also discussed. [ABSTRACT FROM AUTHOR]

Preservation of digestive structures in trilobites is generally rare; remains of the alimentary tract have been documented in about eighty of more than twenty thousand described species. Several tens of specimens belonging to five Cambrian and nine Ordovician species from the Barrandian area, Czech Republic, have markedly contributed to the knowledge of the trilobite digestive system. Here, we describe seven exceptionally preserved late holaspid trilobite specimens of species of the genus Dalmanitina collected from Upper Ordovician strata of the Barrandian area. All studied specimens are preserved as internal moulds and exhibit a narrow strip-like structure that runs sagitally or sub-sagitally under the axial lobe of the thoracopygon. These strip-like structures are markedly different from scavenger burrows and are interpreted as remains of the alimentary canal. A slightly expanded anterior-most part of the digestive system is preserved in the cephalic shield of six specimens and is interpreted as a remainder of the anterior midgut. A dark area is seen in the glabellar lobes of three specimens. These dark areas do not represent pyrite concentrations in the hypostome-glabellar cavity, because they contain only small amounts of Fe and S. These areas are interpreted as the remainder of cephalic digestive midgut diverticula, or the "perigastric organ". Quantitative chemical analyses show that in species of Dalmanitina the digestive system is preserved as dark matter containing partly digested food particles and most probably also a higher amount of clay minerals. The described specimens constitute the first well-documented example of digestive structures in the subfamily Dalmanitininae. [ABSTRACT FROM AUTHOR]

Remains of agnostid hypostomes are rare and have only been reported in about fifty specimens assigned to ten Cambrian species. A large collection of several thousand specimens of a Cambrian skeletal fauna from the Barrandian area includes articulated agnostids with in situ preserved hypostomes in two species from the Příbram-Jince Basin and in one species from the Skryje-Týřovice Basin. Unequivocal remains of hypostomes are described in Condylopyge rex (Barrande, 1846), Peronopsis integra (Beyrich, 1845) and Onymagnostus hybridus (Brøgger, 1878). The material provides the first information on the hypostomal morphology in the superfamily Condylopygoidea Raymond, 1913 and adds new data in two other Cambrian agnostid genera. The chemical composition and placement of agnostid hypostomes are briefly discussed. [ABSTRACT FROM AUTHOR]

Monogeneric clusters of five acritarch genera (Adara, Cymatiosphaera, Eliasum, Synsphaeridium and Timofeevia) were discovered in palynological residues obtained from fine-grained siliciclastic samples from the middle Cambrian (Miaolingian) Jince Formation of the Příbram–Jince Basin (Czech Republic). The clusters consist of two to more than 100 individual specimens and lack a common pattern of organisation. Acritarchs within clusters fall within a similar size range, regardless of generic affinity. Proposed mechanisms for the formation of these acritarch clusters are discussed: for the Jince Formation clusters, aggregation within algal blooms or primary colonial behaviour are the most plausible explanations. In addition, a summary of reports of acritarch clusters from lower Palaeozoic strata is included: clusters of a variety of acritarch genera have been documented from rocks of early Cambrian to Late Devonian age. [ABSTRACT FROM AUTHOR]

Cheloniellida is a rare but significant clade of artiopod euarthropods, and a major component of Vicissicaudata alongside aglaspidids. The first cheloniellid to be described was Triopus draboviensis, based on a single specimen from the Upper Ordovician Letná Formation in Bohemia. Because this specimen was believed to be missing its anterior, Triopus draboviensis has been the subject of considerable speculation regarding its affinities, with several authors combining various isolated cephalic shields with its trunk. Notwithstanding, Triopus draboviensis has eluded detailed restudy in the 150 years since its first description. Here we provide a redescription of the holotype and hitherto only known specimen of Triopus draboviensis, and describe a recently discovered second partial specimen as Triopus sp. It is shown that the holotype of Triopus draboviensis preserves the complete cephalic shield, while the trunk reveals a likely articulating device, which may represent an apomorphy for Cheloniellida. Further information on the trunk morphology provided by the new specimen has allowed a complete reconstruction of the dorsal exoskeleton of Triopus. An assessment is made of fossils previously suggested to represent the cephalic shield of Triopus draboviensis; while it is shown that none of those fossils can be attributed to Triopus, it is reaffirmed that Drabovaspis complexa likely does belong to Cheloniellida, making Drabovaspis the third cheloniellid genus known from the Letná Formation, after Triopus and Duslia. A revised diagnosis for Cheloniellida is provided, and the recently described problematic euarthropod Parioscorpio venator from the Silurian of Wisconsin is firmly rejected from this clade. [ABSTRACT FROM AUTHOR]

The Lower Paleozoic sediments of the Barrandian area are globally renowned as a classical example of well-preserved skeletal marine fauna, including abundant remains of trilobites. Several tens of morphologically anomalous exoskeletons of trilobites have been collected and documented from Cambrian to Devonian clastic sediments and carbonates. One of them, an exceptionally well preserved, articulated and partly enrolled exoskeleton of the Ordovician nektobenthic trilobite Parabarrandia bohemica (NOVÁK, 1884) exhibits a prominent palaeopathological anomaly in its pygidium. We interpret this anomaly as a healed traumatic injury and attribute this damage to a failed predatory attack. The subsequently healed injury is classified as the ichnogenus Oichnus BROMLEY, 1981. The structure on the pygidium is strongly reminiscent of injuries caused by octopods and a large cephalopod is proposed as a potential durophagous predator responsible for the herein described trilobite injury. However, an attack from an unknown arthropod while the trilobite was in a soft-shelled stage cannot be excluded. [ABSTRACT FROM AUTHOR]

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]

To analyze anomalies of a biomineralized exoskeleton of a trilobite. A specimen of Dalmanitina socialis from the Upper Ordovician Letná Formation at Veselá near Beroun, Czechoslovakia, curated at the Czech Geological Survey in Prague. The internal mold and external mold and latex casts were coated with ammonium chloride sublimate and photographed. A substantial reduction of the eye surface associated with changes in morphology and surface structure was noted. The anomaly is believed to be the result of a healed injury after an unsuccessful predatory attack. Based on the presumed mechanism of injury, a 'large arthropod' is proposed to be the potential attacker. The low incidence of sublethal attack to cephala in collections of Cambrian to Carboniferous trilobites implies that most such attacks were fatal, rendering this specimen unique and capable of providing insight into healing processes. Post-mortem damage rendered analysis difficult. Exploration of other cases of healed trauma in order to understand Ordovician ecosystems. [ABSTRACT FROM AUTHOR]

Thylacocephala is a clade of marine bivalved euarthropods generally considered to belong to Eucrustacea, although their affinities within this group remain unsettled. Detailed thylacocephalan anatomy and tagmosis is poorly known, and the majority of taxa have been described based only on the valves of the carapace. While some thylacocephalans are considered to have been fully nektic, others probably had a nekto‐benthic mode of life. The group makes its last appearance in the Upper Cretaceous of Lebanon, while the previously oldest definite record is from the Silurian of Wisconsin, USA. This paper describes two new thylacocephalans, Pseudoprotozoea irenae gen. et sp. nov. and Bohemiacaris libori gen. et sp. nov. from the Sandbian (Upper Ordovician) Letná Formation of Bohemia (Czech Republic). Apart from the carapaces, both fossils preserve some evidence of the appendages. Remarkably, even though the newly described taxa represent the oldest unequivocal thylacocephalans, their carapaces display several characters most similar to those of Mesozoic groups. Whether these similarities reflect true close relationships and Ordovician origins for these groups or are only the result of convergent evolution is uncertain. Regardless, the new finds show that ecological differentiation between fully nektic and nekto‐benthic lifestyles was probably achieved early in the evolution of Thylacocephala. [ABSTRACT FROM AUTHOR]

The lepidocystoid echinoderm Vyscystis is known from the mid-Cambrian (Drumian) Jince Formation of the Příbram-Jince Basin (Czech Republic). Recently collected specimens of this genus, which are very well preserved, provide important new information, resulting in an improved understanding of their morphology (particularly the oral surface), growth trends and an assessment of their phylogenetic position and palaeoecology. Vyscystis is characterized by an aboral imbricate cup and a flattened tessellate oral surface, bearing exotomous curved ambulacra supporting coiled brachioles. A phylogenetic analysis suggests a basal position of lepidocystoids among blastozoans. Vyscystis shares plesiomorphic characters with other lepidocystoids (e.g. calyx) and some edrioasteroids (curvature of the ambulacra). It shows homoplasies (exotomous ambulacral pattern and coiled brachioles) with more derived eocrinoids (e.g. Gogia). Vyscystis was probably a low-level suspension feeder, living attached to hard debris on a soft substrate. Attachment to skeletal fragments was probably achieved by some sort of 'biogluing'. [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]

This contribution briefly summarizes the history of research, modes of preservation and stratigraphie distribution of 51 trilobite and five agnostid taxa from the Barrandian area, for which the early developmental stages have been described. [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]