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A new species of bubble-headed trilobite, Staurocephalus oliveae sp. nov., is described from 250 specimens collected from a recently discovered locality in the Sholeshook Limestone Formation (upper Katian, Upper Ordovician; Ashgill, Cautleyan Zone 1 equivalent) in the village of Llanddowror, Carmarthenshire. Although no fully articulated specimens were found, the material is the most abundant and well-preserved of any Ordovician Staurocephalus species known from Britain and Ireland, and enables the complicated 3D structure of its cephalon to be reconstructed. Staurocephalus oliveae sp. nov. is the earliest representative of the genus recorded in Avalonia, following its presumed migration into the area from Laurentia or Baltica. Recognition of this Cautleyan species resurrects the potential usefulness of the long established, widely distributed, Staurocephalus clavifrons as a latest Katian (= Rawtheyan) indicator.

Floian, Early Ordovician trilobites are systematically described and revised based on new material from the middle part of the Duoquanshan Formation of the Shihuigou area, northern Qinghai Province, northwest China. The fauna that lived on the shallow-water carbonate platform comprises three species belonging to two families, i.e., Tsaidamaspis diarmatus, Zhiyia tsinghaiensis, and Liexiaspis sp. indeterminate. It exhibits a strong endemicity to the Olongbluk terrane. The new isoteline genus Zhiyia is established on the basis of the material from the Olongbluk terrane and South China palaeoplate, and is characterized by its: (i) almost obsolete cephalic and pygidial axial furrows; (ii) flattened anterior border and narrow (sag., exsag.) occipital ring; (iii) bilobed hypostome with a shallow median notch and a small triangular median projection; (iv) subsemicircular pygidium with wide pygidial axis and border. Faunal evidence indicates that the palaeogeographic position of the Olongbluk terrane may have been situated closer to the South China palaeoplate rather than the North China palaeoplate during the Floian.

Species of Catillicephala are known from sites around the mid-Cambrian margin of Laurentian North America, including Vermont, Quebec, Newfoundland and North Greenland. Catillicephala cifellii sp. nov. is from the Downes Point Member of the Shallow Bay Formation (Cow Head Group) in western Newfoundland. It occurs in three shelf margin-derived boulders in debris flow conglomerates that accumulated in a continental slope setting. The associated trilobites and agnostoid arthropods, including Ptychagnostus aculeatus and Megagnostus glandiformis, indicate a correlation with the Lejopyge laevigata Zone. As such, C. cifellii is among the oldest representatives of the genus, and is early Guzhangian in age.

Pilekiines are the earliest diverging members of the successful trilobite family Cheiruridae. The pilekiine genus Anacheirurus is characterized by sub-quadratic to sub-oval glabella, pitted genae, and a distinct trunk with elongated pleural spines in its posterior part. Anacheirurus adserai is a common component of the Fezouata Shale (Lower Ordovician, Morocco), where it was intially included into several species of the genus Lehua. This assignment and taxonomic over-splitting created confusion, overestimated cheirurid diversity at this locality, and simultaneously underestimated morphological variability within A. adserai. In this contribution we examine new material of A. adserai from the Fezouata Shale, clarifying its morphology and systematics. A detailed re-description of the species shows that Anacheirurus is distinct from Lehua, the latter being a more derived member of Cheiruridae. The comparison of Anacheirurus with other pilekiines shows that morphological variability within this subfamily is mostly constrained to the trunk region. Exceptionally preserved specimens of A. adserai from the Fezouata Shale show details of appendages, revealing the endopodite and exopodite morphologies in early members of Cheiruridae. The endopodite of A. adserai is unique among trilobites in possessing comparatively longer distal podomeres 5 and 6, but otherwise, it has the same general morphology as other described trilobite endopodites. The exopodite morphology of A. adserai shows characters typical of some Cambrian species but differs in several aspects from those known in post-Cambrian taxa. It is concluded that trilobite exopodite morphology was probably more variable than the endopodite morphology, which remains rather conservative across different taxa. Morphological diversity of trilobite exopodites in post-Cambrian taxa might be related to ecological escalations during the Ordovician biodiversification and the transition between Cambrian and Ordovician trilobite faunas.

Some exceptional paleontological trilobite sites located in the Sierra Norte de Sevilla UNESCO Global Geopark are presented herein, together with an analysis of their geotourism / geotrail potential and a proposal for geoconservation. The sites are of Marianian age, a regional stage and age of the Cambrian Mediterranean Subprovince which was defined within the territory of the Geopark. This area constitutes the type area of six trilobite genera and twelve trilobite species and other associated faunas (hyolith, serpulid and echinoderm species).

Trilobites achieved their maximum generic diversity in the Cambrian, but the peak of morphological disparity of their cranidia occurred in the Middle to Late Ordovician. Early to middle Cambrian trilobites with a specialized cephalon are rare, especially among the ptychoparioids, a group of libristomates featuring the so-called “generalized” bauplan. Here we describe an unusual ptychopariid trilobite Phantaspis auritus gen. et sp. nov. from the middle Cambrian (Miaolingian, Wuliuan) Mantou Formation in the Shandong Province, North China. This new taxon is characterized by a cephalon with an extended anterior area of double-lobate shape resembling a pair of rabbit ears in later ontogenetic stages; a unique type of cephalic specialization that has not been reported from other trilobites. Such a peculiar cephalon as in Phantaspis provides new insights into the variations of cephalic morphology in middle Cambrian trilobites, and may represent a heuristic example of ecological specialization to predation or an improved discoidal enrollment.

The morphology and ontogeny of the trilobite Changaspis elongata based on 216 specimens collected from the Lazizhai section of the Balang Formation (Stage 4, Series 2 of the Cambrian) in Guizhou Province, South China are described. The relatively continuous ontogenetic series reveals morphological changes, and shows that the species has seventeen thoracic segments in the holaspid period, instead of the sixteen as previously suggested. The development of the pygidial segments shows that their number gradually decreases during ontogeny. A new dataset of well-preserved specimens offers a unique opportunity to investigate developmental traits after segment addition is completed. The ontogenetic size progressions for the lengths of cephalon and trunk show overall compliance with Dyar’s rule. As a result of different average growth rates for the lengths of cephalon, trunk and pygidium, the length of the thorax relative to the body shows a gradually increasing trend; however, the cephalon and pygidium follow the opposite trend. Morphometric analysis across fourteen post-embryonic stages reveals growth gradients with increasing values for each thoracic segment from anterior to posterior. The reconstruction of the development traits shows visualization of the changes in relative growth and segmentation for the different body parts. The new dataset and growth gradient of the trunk suggest that the thoracic segment growth dynamics of early Cambrian to Silurian trilobites follow the same general continuous, steady-state growth gradient decreasing from posterior to anterior.

The lower Cambrian (Series 2) White Point Conglomerate (WPC) on Kangaroo Island, South Australia contains exotic clasts representing a diverse array of lithologies, including metamorphics, chert, sandstone, and abundant carbonates, notably archaeocyath-rich bioclastic limestone. Acetic acid digestion of the WPC bioclastic limestone clasts reveals a diverse shelly fauna. This assemblage includes abundant organophosphatic brachiopods such as Cordatia erinae Brock and Claybourn gen. et sp. nov., Curdus pararaensis, Eodicellomus elkaniformiis, Eohadrotreta sp. cf. E. zhenbaensis, Eoobolus sp., Kyrshabaktella davidii, and Schizopholis yorkensis. Additional shelly taxa include the solenopleurid trilobite Trachoparia? sp., the tommotiids Dailyatia odyssei, Dailyatia decobruta Betts sp. nov., Kelanella sp., and Lapworthella fasciculata, spines of the bradoriid arthropod Mongolitubulus squamifer, and several problematica, such as Stoibostrombus crenulatus and a variety of tubular forms. The upper age limit for the WPC is constrained by biostratigraphic data from the overlying Marsden Sandstone and Emu Bay Shale, which are no younger than the Pararaia janeae Trilobite Zone (Cambrian Series 2, Stage 4). The shelly fossil assemblage from the WPC limestone clasts indicates an upper Dailyatia odyssei Zone (= Pararaia tatei to lower P. janeae trilobite zones), equivalent to the Atdabanian–early Botoman of the Siberian scheme. This contrasts with the previously suggested late Botoman age for the limestone clasts, based on the diverse archaeocyath assemblage. The minor age difference between the WPC and its fossiliferous limestone clasts suggests relatively rapid reworking of biohermal buildups during tectonically-active phases of deposition in the Stansbury Basin.

Euarthropods have a tough exoskeleton that provides crucial protection from predation and parasitism. However, this is restrictive to growth and must be periodically moulted. The moulting sequence is well-known from extant arthropods, consisting of: (i) the long inter-moult stage, in which no changes occur to the hardened exoskeleton; (ii) the pre-moult stage where the old exoskeleton is detached and the new one secreted; (iii) exuviation, when the old exoskeleton is moulted; and (iv) the post-moult stage during which the new exoskeleton starts as soft, thin, and partially compressed and gradually hardens to the robust exoskeleton of the inter-moult stage. Trilobite fossils typically consist of inter-moult carcasses or moulted exuviae, but specimens preserving the post-moult stage are rare. Here we describe nine specimens assigned to Symphysurus ebbestadi representing the first group of contemporaneous fossils collected that preserve all key stages of the moulting process in one taxon, including the post-moult stage. They were collected from a single lens in the Tremadocian part of the Fezouata Shale Formation, Morocco. Based on cephalic displacement and comparison to other trilobite moults, one specimen appears to represent a moulted exoskeleton. Four specimens are typical inter-moult carcasses. Four others are wrinkled and flattened, with thin exoskeletons compared to inter-moult specimens, and are considered post-moult individuals. These S. ebbestadi specimens illuminate the preservation and morphology of the post-moulting stage, characterised by strong anterior-posterior exoskeleton wrinkling, as well as overall body flattening and reduced visibility of thoracic articulations. Being found in the same lens, these specimens likely represent the first preserved in-the-act mass moulting event. The displayed sequence of moulting suggests the moulting process in trilobites was comparable to modern arthropods, and conserved within euarthropod evolutionary history.

Restudy of the Cambrian–Ordovician boundary beds, traditionally assigned to the Mila Formation Member 5 in Mila-Kuh, northern Iran, for the first time provides convincing evidence of the Early Ordovician (Tremadocian) age of the uppermost part of the Mila Formation. Two succeeding trilobite assemblages typifying the Asaphellus inflatus–Dactylocephalus and Psilocephalina lubrica associations have been recognized in the uppermost part of the unit. The Tremadocian trilobite fauna of Mila-Kuh shows close similarity to contemporaneous trilobite faunas of South China down to the species level, while affinity to the Tremadocian fauna of Central Iran is low. The trilobite species Dactylocephalus levificatus and brachiopod species Tritoechia tenuis from the Tremadocian of Mila-Kuh are new to science.

Upper lower Cambrian (provisional Cambrian Series 2) trilobites are described from three sections through the Shuangyingshan Formation in the Beishan area, northwestern Gansu Province, China. The trilobite fauna is dominated by eodiscoid and corynexochid trilobites, together representing at least ten genera: Serrodiscus, Tannudiscus, Calodiscus, Pagetides, Kootenia, Edelsteinaspis, Ptarmiganoides?, Politinella, Dinesus and Subeia. Eleven species are described, of which seven are identified with previously described taxa and four described under open nomenclature. The composition of the fauna suggests biogeographic affinity with Siberian rather than Gondwanan trilobite faunas, and the Cambrian Series 2 faunas described herein and from elsewhere in northwestern China seem to be indicative of the marginal areas of the Siberian palaeocontinent. This suggests that the Middle Tianshan–Beishan Terrane may have been located fairly close to Siberia during middle–late Cambrian Epoch 2.

The brachiopod Hirnantia sagittifera (M’Coy) and trilobite morphs of the genus Mucronaspis from the topmost Ordovician Porkuni Stage of the central East Baltic are described and compared with those from the Hirnantian Stage of other regions. These important Hirnantian taxa occur in the Livonian Tongue of the Central Baltoscandian Facies Belt of the Baltic Basin, where the Porkuni Stage is represented by the non-graptolitic Kuldiga and Saldus formations. Hirnantia sagittifera appears in the lowermost part of the Porkuni Stage and is rather widely distributed in the basin in spite of its rare finds in each locality. Our study of trilobites of the genus Mucronaspis has enabled us to observe morphological changes in its exoskeleton in time and to identify a succession of five morphotypes (morphs). In some characteristics these morphs are similar to those of different alleged species of the genus Mucronaspis (M. olini, M. danai, M. ganabina, M. mucronata) but they cannot be definitely assigned to any of these species due to some variances. However, here for the first time a stratigraphically ordered collection is presented, which deserves attention in revising the taxonomy of highly variable Mucronaspis. The described brachiopods and trilobites occur mainly in the strata correlated with the Normalograptus extraordinarius graptolite Biozone. However, the uppermost finds of both taxa come from strata correlated with the N. persculptus Biozone.

The trilobite order Proetida forms a minor but important faunal element within the Ordovician strata of Baltoscandia. This review follows the current systematic, taxonomic, and stratigraphical usage and discusses the distribution of these trilobites within the context of the Confacies Belt model. A database of species-level information was derived from numerous publications relating to the Scandinavian and Baltic states and relevant neighbouring regions. Important additional information on stratigraphical occurrences of genera has been derived from glacial erratic boulders (geschiebe) from northern Germany and adjacent areas. The representatives from Baltoscandia of three superfamilies, Bathyuroidea, Aulacopleuroidea, and Proetoidea, are listed. The genus level was chosen as the most practicable to plot on the maps, one showing the time interval for the Kukruse Regional Stage (or Global Stage Slice Sa1), the other that for the Pirgu and Porkuni stages (or stage slices Ka4 and Hi1–Hi2). These intervals each show a diversity peak within the ranges of about 30 genera of Proetida and over 70 species from the Ordovician successions of Baltoscandia. Out of these a total of nine genera cross the Ordovician–Silurian boundary.The regional comparisons from within Baltoscandia show differences in facies dependency of certain genera, with possibly also a latitudinal component. During the late Ordovician the faunal resemblance appears to be closest to the neighbouring palaeocontinent Avalonia, suggesting a faunal exchange between or pathways to both continents from elsewhere. Besides climatic and geographical proximity of palaeocontinents, sea-level changes also have to be considered in explaining the distribution of Proetida in Baltoscandia.

Trilobites Calmoniidae (Delo, 1935) constituem o grupo de Phacopida mais abundante e diversificado do registro fóssilda Formação Ponta Grossa, Devoniano, Sub-bacia Apucarana. Embora conhecidos desde o início do século passado, o estudodos trilobites da Formação Ponta Grossa é ainda pouco abrangente, tanto do ponto de vista taxonômico, devido à concentraçãode estudos em certos táxons (calmoniídeos), como paleogeográfico e estratigráfico, em decorrência de concentração dosesforços de coleta nos afloramentos dos municípios de Ponta Grossa e Jaguariaíva. O exame de 398 espécimes, provenientesde rochas litoestratigraficamente correspondentes ao Membro Jaguariaíva, da Formação Ponta Grossa, especialmente daregião de Tibagi – PR, revelou a presença de espécimes atribuíveis à espécie Metacryphaeus rotundatus (Kozlowski, 1923).Trata-se do primeiro registro desta espécie em rochas devonianas, do Brasil. Metacryphaeus rotundatus é uma espécie deocorrência comum em rochas emsianas, da Formação Icla, da Bolívia. Embora no contexto do Domínio Malvinocáfrico, asafinidades paleobiogeográficas mais estreitas da fauna marinha sejam com as faunas das províncias Brasileira e Sul-africana,esse achado reforça outras evidências paleontológicas (e.g., conulários, trilobites homalonotídeos) indicativas da presença deelementos cosmopolitas, da Província Andina, nas assembléias fósseis do Devoniano da Bacia do Paraná. Tais formas viveramsob forte gradiente paleoclimático, desde clima temperado a temperado frio, até subpolar. Finalmente, no Devoniano paranaense,M. rotundatus ocupou, preferencialmente, fundos argilosos, ricos em matéria orgânica, depositados sob condições de águasplataformais, abaixo do nível de base de ondas de tempestades e indicativos de superfícies de inundação marinha.

Trilobites Calmoniidae (Delo, 1935) constituem o grupo de Phacopida mais abundante e diversificado do registro fóssil da Formação Ponta Grossa, Devoniano, Sub-bacia Apucarana. Embora conhecidos desde o início do século passado, o estudo dos trilobites da Formação Ponta Grossa é ainda pouco abrangente, tanto do ponto de vista taxonômico, devido à concentração de estudos em certos táxons (calmoniídeos), como paleogeográfico e estratigráfico, em decorrência de concentração dos esforços de coleta nos afloramentos dos municípios de Ponta Grossa e Jaguariaíva. O exame de 398 espécimes, provenientes de rochas litoestratigraficamente correspondentes ao Membro Jaguariaíva, da Formação Ponta Grossa, especialmente da região de Tibagi - PR, revelou a presença de espécimes atribuíveis à espécie Metacryphaeus rotundatus (Kozlowski, 1923). Trata-se do primeiro registro desta espécie em rochas devonianas, do Brasil. Metacryphaeus rotundatus é uma espécie de ocorrência comum em rochas emsianas, da Formação Icla, da Bolívia. Embora no contexto do Domínio Malvinocáfrico, as afinidades paleobiogeográficas mais estreitas da fauna marinha sejam com as faunas das províncias Brasileira e Sul-africana, esse achado reforça outras evidências paleontológicas (e.g., conulários, trilobites homalonotídeos) indicativas da presença de elementos cosmopolitas, da Província Andina, nas assembléias fósseis do Devoniano da Bacia do Paraná. Tais formas viveram sob forte gradiente paleoclimático, desde clima temperado a temperado frio, até subpolar. Finalmente, no Devoniano paranaense, M. rotundatus ocupou, preferencialmente, fundos argilosos, ricos em matéria orgânica, depositados sob condições de águas plataformais, abaixo do nível de base de ondas de tempestades e indicativos de superfícies de inundação marinha.

The biostratigraphic significance of the latest Cambrian-earliest Ordovician trilobite agnostoids from northwestern Argentina is summarized. A characterization of the faunas recognized below and above the Cambrian-Ordovician boundary is presented on the bases of information from sierra de Cajas (Jujuy Province, Eastern Cordillera; Lampazar and Cardonal Formations), río Volcancito (La Rioja Province, Famatina range; Volcancito Formation) and other localities assigned to the Parabolina frequens argentina Biozone. In addition, the stratigraphic meaning of each agnostoid species from the P. frequens argentina Zone is updated. The uppermost Cambrian is characterized by a distinctive agnostoid assemblage composed of Lotagnostus (Lotagnostus) sp., Lotagnostus (Semagnostus) zuninoi (HARRINGTON and LEANZA), Micragnostus vilonii HARRINGTON and LEANZA, M. calviformis HARRINGTON and LEANZA, Strictagnostus? micropeltis (HARRINGTON and LEANZA), Pseudorhaptagnostus (Machairagnostus) tmetus HARRINGTON and LEANZA, Pseudorhaptagnostus (Machairagnostus) cf. tmetus HARRINGTON and LEANZA, Pseudorhaptagnostus (Machairagnostus) sp., Gymnagnostus bolivianus (HOEK), Gymnagnostus perinflatus HARRINGTON and LEANZA, and Leiagnostus turgidulus HARRINGTON and LEANZA. This fauna is commonly recorded together with the polymeroid Beltella ulrichi (KAYSER), Onychopyge HARRINGTON, Plicatolina scalpta HARRINGTON and LEANZA, Parabolina frequens argentina (KAYSER), Parabolinella coelatifrons HARRINGTON and LEANZA, and Angelina hyeronimi (KAYSER). Based on this agnostoid-polymeroid fauna, a Pseudorhaptagnostus (Machairagnostus) - Gymnagnostus Assemblage Subzone (lower part of the P. frequens argentina Zone) is formally proposed. Agnostoid diversity drastically declines through the Cambrian-Ordovician boundary, probably as a consequence of a regional regressive-transgressive event. In the lowest Tremadoc the agnostoid records are mainly restricted to Trilobagnostus chiushuensis (KOBAYASHI) and some forms described under open nomenclature (Anglagnostus? sp., Micragnostus sp.). The upper part of the P. frequens argentina Zone is better defined by polymeroid trilobites. Jujuyaspis keideli KOBAYASHI is its most characteristic species.

Se estudian los trilobites agnóstidos procedentes de nueve localidades, siete de ellas nuevas para estas faunas, situadas en las pizarras del Llanvirn inferior de la parte meridional de la Zona Centroibérica (Montes de Toledo, Villuercas y región de Almadén). Se determina la presencia de los géneros Geragnostella y Geragnostus, y se describen tres nuevas especies: Geragnostella gilcidae n. sp., Geragnostus hispanicus n. sp. y Geragnostus ninhursagae n. sp. Se proponen también los nuevos nombres Geragnostus pilleti nom. nov. y Geragnostus abdullaevi nom. nov. para designar, respectivamente, las especies G. howelli PILLET, 1978, y G. elongatus ABDULLAEV, 1972, consideradas ambas homónimos objetivos primarios de otras especies definidas con anterioridad.

RESUMO O registro fóssil do Devoniano do estado de Goiás (Sub-bacia Alto Garças, Bacia do Paraná) é ocorrente nos arredores de diversas cidades como Amorinópolis, Iporá, Caiapônia, Rio Verde e Doverlândia. Contudo, os fósseis encontrados em Goiás são, em sua maioria, representados por braquiópodes, comumente pertencentes aos gêneros Derbyina, Australocoelia, Australospirifer, Schuchertella, Orbiculoidea e Lingula. Embora também haja ocorrências, em menor número, de outros grupos como trilobitas, moluscos, tentaculitoideos, anelídeos, equinodermas, lycopsidas e cnidários, além dos microfósseis de quitinozoários, representados pelos gêneros Ramochitina, Ancyrochitina, Sphaerochitina, Angochitina, Conochitina, Lagenochitina e Cyathochitina. No entanto, os trabalhos que tratam de fósseis para esse estado são escassos quando comparados ao grande número de trabalhos realizados no Devoniano do estado do Paraná (Sub-bacia Apucarana, Bacia do Paraná). Tal fato se deve ao baixo número de pesquisadores trabalhando nessa área. Tendo em vista esse défice de artigos, o presente trabalho objetivou instigar o estudo dos fósseis devonianos de Goiás por meio de um levantamento paleontológico, que apresenta os fósseis e as localidades fossilíferas conhecidas no estado, além de apontar novos afloramentos e novos registros fósseis do Devoniano encontrados nas regiões fossilíferas do estado, as quais foram revisitadas pelos autores.