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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.

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) Letna 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 nektobenthic lifestyles was probably achieved early in the evolution of Thylacocephala.

Upper Ordovician shallow marine fine-grained sandstones and siltstones exposed in the Loděnice – vinice locality yielded a distinct and well-preserved tiering pattern of trace fossils. The two uppermost tiers are composed mainly of Bifungites and Nereites. Deeper in the sediment, tiers dominated by Thalassinoides, Zoophycos and Teichichnus occur. Most of the succession is completely bioturbated; however, several storm layers enabled study of a well-preserved frozen tiering pattern. Large portions of the bedding planes (ichnologic snapshots) showed a considerable patchiness of intensive surface bioturbation and a preferred orientation of Bifungites. The identified tiering pattern is one of the earliest examples of a well-documented complex tiering of burrows documented in detail.

A review of all currently known Ordovician trilobites with soft parts described or figured from West-Gondwana, European peri-Gondwana and Avalonia shows remains of the digestive system in 19 species. In comparison, remains of antennae and/or walking legs are known only in five species. Soft parts are known in Asaphidae, Bathycheilidae, Calymenidae, Cheiruridae, Dalmanitidae, Harpidae, Lichidae, Nileidae, Odontopleuridae and Trinucleidae. Exceptionally preserved trilobites originate from the Late Tremadocian Mílina Formation and Fezouata Shale, Middle Darriwilian Šárka and Llanfallteg formations, early Sandbian Tafilalt and Letná Konservat-Lagerstätten and Katian Bohdalec Formation. Levels containing exceptionally preserved trilobites in these units are characterized by prevailing fine-grained sediments with the exception of the Early Sandbian Lower Tafilalt and Letná Lagerstätten.

The trilobite assemblage of Calceola-bearing beds in the upper part of Acanthopyge Limestone (Choteč Formation, Eifelian) in the Koněprusy area, the Czech Republic, is described. Together with occurrence of Calceola, it indicates absence of significant palaeogeographic barriers restricting the distribution of the Rhenish-Type faunas in the Middle Devonian. The generic composition of the gathered trilobite assemblage somewhat differs from typical Acanthopyge-Phaetonellus assemblage characteristic for the Acanthopyge Limestone facies in possible absence and/or very rare occurrence of Phaetonellus, and only infrequent occurrence of Acanthopyge. Phacopid Chotecops cf. hoseri (Hawle et Corda, 1847) distinctly dominates; all other taxa are rather rare. Important is an occurrence of scutelluids of the Scutellum sensu lato group (preservation of remains does not enable more precise determination) and Longiproetus(?). Trilobite remnants are generally poorly preserved and very fragmented (only minute shields are not affected), which support a high-dynamic, shallow-water original environment.

The dark pelbiodetrital limestone beds of the ‘upper dark interval’ in the Koněprusy area, Central Bohemia, the Czech Republic, the assumed manifestation of the Kačák Event in this area, yielded a moderately diverse faunule of rhynchonelliform brachiopods and trilobites. In total, 15 species have been recognized (13 brachiopods and 2 trilobites), but the majority of them are only tentatively determined to generic level due to fragmentation, rarity or poor preservation. Brachiopod genera Leptaenopyxis, Protodouvillina, Douvillinella, Holynetes, Poloniproductus, Iridistrophia, Mystrophora, Pentamerella, Quasidavidsonia, Carinatina, Mimatrypa, Leptathyris, Eoreticularia and a single trilobite Astycoryphe were determined. The mode of preservation indicates transport of skeletal bioclasts from shallower parts of the basin and their fragmentation in debris flows together with fragments of terrestrial plants, crinoid detritus and numerous pelagic fossils, especially the dacryoconarid Nowakia ex gr. otomari. Associated conodonts (as well as trilobites) indicate a late Eifelian age for the fauna (Polygnathus ensensis Zone).

A large sample of postembryonic specimens ofDalmanitina proaeva elfridaandD. socialisfrom the Upper Ordovician (Sandbian to Katian) Prague Basin allows for the first reasonably complete ontogenetic sequence of Dalmanitoidea (Phacopina). The material provides an abundance of morphological information, including well-preserved marginal spines in protaspides and meraspides, and hypostome external surfaces throughout. The development ofD. proaeva elfridais unusual due to variability in timing of the first trunk articulation. This broadens our developmental understanding of Phacopina, a diverse group of phacopid trilobites, and also allows us to study the evolution of their specializations in exoskeletal molting behavior. Adult phacopines, unlike most other trilobites, had fused facial sutures. This means that rather than molting through the sutural gape mode, characterized by opening of the facial sutures and separation of the librigenae, they disarticulated the entire cephalon in Salter’s mode of molting. For other phacopine clades (Phacopoidea) the transition to Salter’s mode occurs during the meraspid period or at the onset of holaspis, and its developmental timing is intraspecifically fixed. However, owing to the large sample size, we can see that facial suture fusion likely occurred later inDalmanitina, usually during the holaspid period, and was intraspecifically variable with holaspides of varying sizes showing unfused sutures. Further,D. proaeva elfridaspecimens showed an initial librigenal–rostral plate fusion event, where the librigenae began as separate entities but appear fused with the rostral plate as one structure (the “lower cephalic unit”) from M1, and are discarded as such during molting. Dalmanitoidea is considered to represent the first phacopine divergence, occurring earliest in the fossil record. This material therefore provides insight into how linked morphologies and behaviors evolved, potentially suggesting the timing of facial suture fusion in Phacopina moved earlier during development and became more intraspecifically fixed over geological time.

Objective To analyze anomalies of a biomineralized exoskeleton of a trilobite. Materials A specimen of Dalmanitina socialis from the Upper Ordovician Letna Formation at Vesela near Beroun, Czechoslovakia, curated at the Czech Geological Survey in Prague. Methods The internal mold and external mold and latex casts were coated with ammonium chloride sublimate and photographed. Results A substantial reduction of the eye surface associated with changes in morphology and surface structure was noted. Conclusions 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. Significance 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. Limitations Post-mortem damage rendered analysis difficult. Suggestionsfor further research Exploration of other cases of healed trauma in order to understand Ordovician ecosystems.

Graphical working paper concerning morphology of Dacryoconarida, its surface structures and planned landmarks for geometrical-morphological studies of Placoparia and "odontochilinid" trilobites.

Graphical working paper concerning paleogeography and stratigraphy of Placoparia and "odontochilinid" trilobites in today's Europe.

The temporarily exposed rocks of the Dobrotivá Formation (Middle Ordovician, upper Darriwilian) accessible, due to lower water levels, in Džbán water reservoir (Praha-Vokovice area) have produced common fauna. The newly obtained trilobite-dominated fossil associations enable a more detailed discussion of faunal changes in the lower and lower-middle portions of the Dobrotivá Formation - a transition from the Placoparia Association to the newly recognized Degamella-Zeliszkella Association, dominated by mesopelagic forms.

The illaenid trilobite Vysocania is widely represented in the Upper Ordovician of the Czech Republic, Portugal and Spain, and is one of the most characteristic taxa in the high-latitude peri-Gondwana palaeobiogeographical region to which it is endemic. Three species of the genus that were formerly assigned to Stenopareia and Zetillaenus, from the Czech Republic and Spain respectively, are herein revised, and a new species is described from the Czech Republic. The genus Octillaenus, of which a new species is described from the Upper Ordovician of Morocco, is considered to have arisen from Vysocania through paedomorphic (neotenic) processes. The relationships between Vysocania, Octillaenus, Stenopareia and Zetillaenus are reviewed and the criteria used in the definition of these taxa discussed. Species assigned to Vysocania are V. vaneki (type-species), V. iberica, V. moraveci sp. nov. and V. panderi; species assigned to Octillaenus are O. hisingeri (type-species) and O. marocanus sp. nov. Vysocania appears for the first time in the lower Berounian (Sandbian) and has its last undoubted record in the upper Berounian (upper Katian); Octillaenus is presently restricted to the Kralodvorian (upper Katian)., Departamento de Geologia and Instituto Dom Luiz, Universidade de Lisboa, Portugal, Departamento de Geologia, Universidade de Trás-os-Montes e Alto Douro, Portugal, Faculdade de Direito, Universidade Nova de Lisboa, Portugal, Czech Geological Survey, República Checa, Department of Palaeontology, National Museum Prague, República Checa, Museo Geominero, Instituto Geológico y Minero de España, España

The middle Cambrian Jince Formation of the Přibram–Jince Basin is globally renowned as a classical repository of well-preserved skeletal marine fauna, including abundant remains of trilobites. An exceptionally preserved articulated exoskeleton of middle Cambrian trilobite Conocoryphe sulzeri (Schlotheim, 1823) exhibits a prominent palaeopathological anomaly interpreted here as a healed traumatic injury. We suggest to attribute the extensive damage of the right side of the cephalon and three anterior-most right thoracic pleurae to a failed predatory attack. The anomalocaridid genus Hurdia and the large bivalved arthropod Tuzoia represent two potential candidates for durophagous predators responsible for the described trilobite injury. The large size of healed injury demonstrates a high level of exoskeletal regeneration in trilobites.

Arthropods are known to display a variable number of eye lenses and this number mostly increases during their development. In trilobites, most species possessing schizochroal eyes exhibit a notable intraspecific variation in the number of dorso ventral files of eye lenses that can be age related (i.e., growth) or not (i.e., living environment). Several previous studies have shown that some trilobite groups (e.g. phacopids) tend to have fewer lenses/files in representatives from the deeper habitats than those from shallower habitats. In this study, we analyzed the pattern of variation in the number of dorso ventral files of eye lenses in two Devonian phacopid trilobites from the Prague Basin of the Czech Republic. We quantified their intraspecific variability. To better understand the patterning, we compared more than 120 individuals. Data first reveal evidence of a bimodal distribution of lens/file number without intermediate forms among each of two studied populations ofProkops prokopi(Chlupáč, 1971) and throughout the ontogeny ofPedinopariops insequens(Chlupáč, 1977). Our results indicate that caution must be taken for taxonomical affiliation and biodiversity analyses of taxa in which the intraspecific variability is unclear. Additionally, we investigated possible relations of these bimodalities to the stratigraphical position of studied populations and to the paleoenvironment. InProkops prokopi, a slightly different age of both populations, together with supposed differences in the local environments can be responsible for observed variability. InPedinopariops insequens, stress conditions possibly related to the approaching onset of the Basal Choteč Event can be responsible for surprising intrapopulation variability. We speculate that the stress conditions could cause a bimodal selection and possibly also the change of ontogenetic trajectory within this species.Pedinopariops insequenswas the only phacopid in the Prague Basin that crosses the Lower/Middle Devonian boundary and survived also the onset of Basal Choteč Event.

Laibl, L., Fatka, O., Budil, P., Ahlberg, P., Szabad, M., Vokac, V. & Kozak, V., 24.3.2015. The ontogeny of Ellipsocephalus (Trilobita) and systematic position of Ellipsocephalidae. Alcheringa 39, 477–487. ISSN 0311-5518.Well-preserved early holaspid stages of the Cambrian Series 3 trilobites Ellipsocephalus hoffi (Schlotheim, 1823) and Ellipsocephalus polytomus Linnarsson, 1877 have been discovered in the Přibram-Jince Basin (Czech Republic) and Jamtland (Sweden), respectively. Both species show remarkable morphological changes during late ontogeny. The earliest holaspides share long genal spines, and long macrospines on the second thoracic segment. Whereas macrospines disappear abruptly in later stages, genal spines are progressively shortened. Consequently, the ontogeny of trilobites of Ellipsocephalidae is revised. The morphology of early meraspid cranidia and ontogenetic patterns in the disappearance of macrospines suggest that this family is closely related to members of Redlichiida rather than Ptyc...

A systematically undetermined protaspid larva is described from the upper stratigraphical levels of the Buchava Formation in the Skryje–Týřovice Basin, Czech Republic. The specimen is simple in morphology, with forwardly expanding glabella, prominent anterior pits, sagittal furrow in L2-L3 and distinct palpebral lobes. It is presumed to represent the protaspid stage of a ptychopariid trilobite.

Remains of the digestive system are described in the holotype of the rare harpidid trilobite Harpides grimmi Barrande, 1852 collected from the Lower Ordovician Milina Formation of the Prague Basin. The intestine (post-stomach alimentary canal) starts just behind the glabellar poste- rior margin and extends through the narrow axial region in all nineteen thoracic segments of this exceptionally preserved specimen. The anterior-most part of the digestive system is masked by the in situ hypostome preserved under the missing glabella. Similarly, also the posterior-most part of the post-stomach alimentary canal is absent, as the pygidium is not preserved. This specimen constitutes the first example of preserved digestive structures in the family Harpididae. Earlier finds of digestive system in Ordovician trilobites are briefly assessed.

Complete early ontogenetic stages of phacopid trilobites are very rare in the fossil record worldwide. Although phacopid trilobites were a common component of the Devonian communities inhabiting the Prague Basin, only two articulated juvenile individuals have been described so far. However, rich and diverse fauna, including common remains of meraspid and young holaspid specimens of the phacopid Pedinopariops superstes superstes, has been found in the late Emsian Daleje Shale (Daleje-Třebotov Formation) at the Ceřinka Quarry near Bubovice. The rather unusual association of skeletal fauna in the Daleje Shale collected from the Ceřinka Quarry probably reflects the specific position of the locality, which corresponds to the transition from shale facies to carbonate facies. This newly described association contains common molted young holaspids, one entire meraspid specimen, and one poorly preserved but entire late meraspid–early holaspid specimen. The young individuals of P. superstes superstes strongly resemble the ancestral Pedinopariops degener; with the exception of their smaller eyes, they are somewhat reminiscent of the coarsely tuberculated descendent Pedinopariops superstes superior. The principal differences between the early stages of P. superstes superstes and the adult specimens include the relatively coarse tuberculation of the dorsal exoskeleton, which is more strongly vaulted and shows a less advanced level of eye development in young specimens. However, co-occurring adult specimens appear to be typical P. superstes. Here, the newly collected material is supplemented with a description of two as yet unreported remains of juvenile Pedinopariops superstes from other localities, and one well preserved specimen of an entire meraspid of Reedops cf. bronni, as well as a detailed discussion of the two previously described specimens of Pedinopariops insequens and Prokops hoeninghausi. Possible causes of an obvious paucity of articulated meraspid and young holaspid specimens when compared with adult and subadult ontogenetic stages in phacopid trilobites are discussed.

* �Correspondingauthor The Lower Permian volcano-sedimentary complexes of the Khar Argalant and Delger Khangay formations in the Khar Argalant Mts. in south-western Mongolia are products of postorogenic within-plate magmatic activity. They consist of terrestrial lavas and pyroclastic flows with local intercalations of clastic sedimentary rocks. Vascular plants in volcano- clastic layers correspond to typical Lower to Middle Permian terrestrial associations formed under dry to intermediate conditions of temperate to colder climatic zones. The plant communities of all three formations show affinities to the Siberia (Angara) - "Cordaitean taiga". Relationships of volcanic rocks suggest simultaneous eruptions of mafic (basalt to trachyandesite) and felsic (trachyte to rhyolite) lavas. The rocks of both formations have similar major- and trace-element contents as well as volcanological character. The granite of the Shar Oroy Massif, with zircon concordia age of 285 ± 1 Ma, was roughly contemporaneous with the volcanic rocks of the Delger Khangay Fm. The Early/Late Permian clastic sedimentary rocks of the Butnaa Khudag Fm. in the hanging wall of the Delger Khangay Fm. postdated the terrestrial volcanic events. Geochemical and structural characteristics suggest that the Shar Oroy Massif and the surrounding Permian volcanic suite represent an eroded, shallow-level plutonic centre and its eruptive cover, which evolved during a crustal extension.

A complete list of fossils originating from the Cambrian of the Barrandian area and housed in the Musee d'Histoire Naturelle de Lille is compiled. The collection includes two agnostids, ten trilobites, one brachiopod and one echinoderm species, all collected at ten outcrops in the Buchava Formation of the Skryje-Týřovice Basin and most probably also at two outcrops in the Jince Formation of the Přibram-Jince Basin. A large part of the material was collected by Prof. Charles Barrois and Dr. Louis Dolle (both University of Lille) during the excursion organised before the Ninth International Geological Congress in Vienna in 1903. Other, poorly documented specimens were purchased from the enterprise Krantz towards the end of the 19th century and in the first years of 20th century. The geographic position and stratigraphy of outcrops, from which the material originates, are briefly discussed.

International audience; A rare, complete specimen of Zlichovaspis (Zlichovaspis) rugosa rugosa (Hawle & Corda, 1847) with in situ articulated hypostome is described from the locality Tetín Hill near Beroun (Bohemia). This unique sample is stored in the Musée d'Histoire Naturelle de Lille (France). Dalmanitid trilobites with articulated hypostome represent very rare findings worldwide, although these trilobites show the conterminant type of the hypostome. Although these trilobites are a common component of Devonian communities inhabiting Prague Basin, only eight specimens with hypostome attached to the doublure and/or hypostome preserved very close to the doublure have been described; they all belong to the common species Zlichovaspis (Zlichovaspis) rugosa rugosa and Odontochile cristata Hawle & Corda, 1847, respectively. The newly described specimen represents most probably a carcass. It is the best preserved specimen of this species with hypostome in situ and provides the opportunity to reconstruct the 3D orientation of the hypostome and its relation to the cephalon for the first time. The possible causes of the apparent paucity of specimens with hypostome in situ in Devonian dalmanitid trilobites are discussed.; Un rare spécimen complet de Zlichovaspis (Zlichovaspis) rugosa rugosa (Hawle & Corda, 1847) avec son hypostome articulé provenant de la localité de Tetín Hill près de Beroun (Bohême) est décrit. Cet exemplaire unique est conservé au Musée d'Histoire Naturelle de Lille (France). Les trilobites dalmanitides avec un hypostome articulé représentent de rares découvertes à l'échelle mondiale, malgré la présence d'un hypostome de type conterminant. Bien que constituant une composante commune des communautés dévoniennes du Bassin de Prague, seuls huit spécimens avec un hypostome attaché à la doublure et/ou un hypostome préservé à proximité de la doublure ont été décrits ; ils appartiennent tous à l'espèce commune Zlichovaspis (Zlichovaspis) rugosa rugosa. Le nouveau spécimen représente très probablement une carcasse. C'est le spécimen le mieux préservé de cette espèce avec son hypostome in situ. Il fournit ainsi pour la première fois l'opportunité de reconstruire l'orientation 3-D de l'hypostome et sa relation avec le céphalon. Les causes possibles de cette rareté apparente de trilobites dalmanitides dévoniens ayant conservé un hypostome in situ sont également discutées.

A review of the supposed moulting positions of the Bohemian Ordovician dalmanitoid and acastoid trilobites is presented. Five main moulting positions are described, but some combinations of these are also widespread. The variability of the supposed moulting mechanisms is surprisingly high, especially in Middle Ordovician taxa. All and/or almost all moulting positions may occur together even within a single species. In advanced representatives, only a few of the described mechanisms prevail. Nevertheless, the occurrence of the moulting positions in the Bohemian Ordovician dalmanitoid and acastoid trilobites is considered to be constrained by the overall body morphology, rather than the result of phylogenetical relations. Functionality of the facial suture in these groups during the ontogeny and phylogeny is discussed.

International audience; A complete list of fossils originating from the Cambrian of the Barrandian area and housed in the Musée d'Histoire Naturelle de Lille is compiled. The collection includes two agnostids, ten trilobites, one brachiopod and one echinoderm species, all collected at ten outcrops in the Buchava Formation of the Skryje-Týřovice Basin and most probably also at two outcrops in the Jince Formation of the Příbram-Jince Basin. A large part of the material was collected by Prof. Charles BARROIS and Dr. Louis DOLLÉ (both University of Lille) during the excursion organised before the Ninth International Geological Congress in Vienna in 1903. Other, poorly documented specimens were purchased from the enterprise KRANTZ towards the end of the 19 th century and in the first years of 20 th century. The geographic position and stratigraphy of outcrops, from which the material originates, are briefly discussed.; Une liste complète des fossiles provenant du Cambrien de la région barrandienne déposés au Musée d'Histoire Naturelle de Lille a été établie. La collection comprend deux espèces d'agnostidés, dix trilobites, un brachiopode et un échinoderme ; les fossiles récoltés dans dix affleurements proviennent tous de la Formation Buchava du bassin de Skryje–Týřovice et probablement également de deux affleurements de la Formation Jince du bassin de Příbram-Jince. Une grande partie du matériel a été récoltée par le Professeur Charles BARROIS et par le Dr. Louis DOLLÉ (de l'Université de Lille) au cours de l'excursion organisée avant le VIIIème Congrès géologique national à Vienne en 1903. Les autres spécimens, mal documentés, ont été achetés à l'entreprise KRANTZ à la fin de 19ème siècle et dans les premières années du 20ème siècle. La situation géographique et la stratigraphie des affleurements d'où provient le matériel sont brièvement discutées.