Trilobite Species Research Articles

Quantified growth and possible heterochronic development of two corynexochid trilobites from the middle Cambrian (Miaolingian Series, Wuliuan Stage) Mount Cap Formation, eastern Mackenzie Mountains, northwestern Canada

Abstract The ontogeny of two species of corynexochid trilobites from the middle Cambrian Mount Cap Formation of the eastern Mackenzie Mountains, northern Canada, is documented. Sahtuia carcajouensis (Dolichometopidae) and Mackenzieaspis parallelispinosa (Zacanthoididae) are both endemic to this formation and only known from one locality. They, along with several other corynexochid taxa, occur in a succession of mudstone with scattered carbonate interbeds, deposited in a weakly storm-agitated setting near the flank of a semi-enclosed basin. The ontogeny of both species is characterized by mainly normal cranidial development, but a unique distribution of segments in their thoraxes and pygidia. The number of trunk segments was typical for their respective families, whereas the final number of segments released into the thorax was reduced. This occurred in both species through timing modifications to segment release, indicating heterochrony. Sahtuia carcajouensis and Mackenzieaspis parallelispinosa are likely derived from two separate clades, and heterochrony probably arose separately but synchronously. The endemicity of both species probably reflects unique paleoecological conditions in this part of the basin. Preliminary results indicate that the fossil-bearing mudstone was deposited under well-oxygenated conditions that underwent high nutrient flux and possibly experienced varying salinity. These factors may have affected the organisms’ physiology, or perhaps provoked an adaptation to achieve early maturation.

A Spectacular Devonian Trilobite Specimen, Dalmanites pratteni, From Illinois Helps Shed Light on How Trilobite Eyes Worked

In 1912, the Field Museum purchased Henry Pratten's collection of fossils. One of the specimens was a dalmanitid trilobite with large eyes (Fig. 1) that Pratten collected from the Devil’s Backbone. In 1933, this specimen was described as a new species of trilobite, Dalmanites pratteni (P 16704) (Roy 1933). Delo (1935) described a new genus of trilobite, Dalmanitoides and assigned it to a new family, Synphorinae. He noted Dalmanites pratteni has similar ornamentation to this genus. Delo (1940) later places D. pratteni in the genus Odontochile. Other authors refer to it as Dalmanites pratteni (Clarkson and Levi-Setti 1975;Levi-Setti 1975; Frankie et al. 2008). Holloway and De Carvalho (2009) refer to it as ‘Dalmanites’ pratteni and state that this species “probably belongs to the Synphoriinae”. The stratigraphic position of this specimen was not recorded. Seid et al. (2009) published a detailed geologic map of the Devil’s Backbone. Most of the ridge is Middle Devonian Grand Tower and St. Laurent formations. However, the southern end of the ridge is faulted, and the Lower Devonian Backbone Limestone and Crystal Creek Chert (Emsian) is exposed. Frankie et al. (2008) and Devera et al. (2020) report Dalmanites pratteni occurring from the Crystal Creek Chert, indicating that the original specimen may have been collected here. One of the most remarkable features of this fossil is the record number of lenses for a Phacopida. Roy (1933) reports 42 rows of eyes, however: “The exact number of lenses cannot be determined, as not all of them are preserved, nor are the areas which they occupied distinctly outlined. It is, however, certain that there are not less than 770 lenses on each eye.” (Roy 1933). I used images of the eyes and illustration software to estimate the number of lenses by filling in the geometric pattern they exhibit. I counted 730 lenses on the right eye and 712 lenses on left eye, which is missing a sizable piece (Fig. 2). The structure of some individual lenses in this specimen can be seen due to differential weathering. Clarkson and Levi-Setti (1975) reported the large round lenses were composed of a doublet structure that followed the principles established by Descartes (1637) and Huygens (1690) to eliminate spherical distortion. This doublet structure allowed the lens to gather more light and focus it on a single point, and strongly indicates that these trilobites had better vision then previously established (Clarkson and Levi-Setti 1975).

Trilobites of the Cranbrook Lagerstätte (Eager Formation, Cambrian Stage 4), British Columbia

Abstract The Eager Formation (Cambrian Stage 4) of the Cranbrook area, British Columbia, contains abundant, sometimes beautifully preserved, trilobites and rare non-biomineralized taxa. Trilobites were first reported just over a century ago but have received little research attention, resulting in uncertainty in the number and identity of species within the assemblage and ambiguity in the age of the fauna. The trilobites of the Eager Formation in the Cranbrook area are described herein based largely upon material collected in 2015. A minimum of eight (and perhaps up to 11) trilobite species are recognized. The four species of olenelloids (Olenellus santuccii Webster n. sp., Olenellus? schofieldi, Mesonacis eagerensis, and Wanneria cranbrookense Webster n. sp.) are by far the most abundant elements of the fauna. At least two, and perhaps as many as five, species of dorypygid are present, as are two species of “ptychoparioids”. Paucity and poor preservational quality of specimens mean that the various dorypygid and “ptychoparioid” species are left in open nomenclature. Trilobite diversity in the Cranbrook Lagerstätte is comparable to that within other Lagerstätten from Cambrian Stage 4 (Series 2) of Laurentia. The diversity and abundance of trilobites, combined with biostratinomic and trace fossil data, suggest that the assemblage is autochthonous and/or parautochthonous, and that the local environment was at least periodically able to support a “typical” benthic trilobite community. The age of the Cranbrook Lagerstätte is constrained to lie within the middle Dyeran Stage of Laurentia, within what was a substantial stratigraphic gap in the distribution of Burgess Shale-type Lagerstätten. UUID: http://zoobank.org/5beab9df-6b6a-4d6d-95e8-57057cd47a66

Trilobites from the Al Rose Formation (Lower Ordovician, Inyo Mountains, California)—faunas marginal to the Great Basin

Abstract The Lower Ordovician (Floian) Al Rose Formation from the Inyo Mountains, California, is a deeper-water, graptolitic equivalent of the well-known and richly fossiliferous successions described from Utah and Nevada. It is considered to have been originally marginal to the Laurentian paleocontinent. It has yielded a low-diversity trilobite fauna that differs strikingly from contemporary faunas to the east in its abundance of raphiophorid, nileid, olenid, and agnostoid trilobites, resembling that of the Nileid Biofacies known from scattered locations marginal to Laurentia. Two new trilobite species are described: Globampyx sexsegmentatus (Raphiophoridae) and Protopresbynileus divergens (Nileidae). Carolinites genacinaca Ross, 1951 is a link with the Great Basin. Other trilobites include the olenid Cloacaspis cf. C. ceryx anataphra Fortey, 1974, metagnostid Geragnostus cf. G. (Novoagnostus) longicollis Raymond, 1925, and pliomerid Hintzeia sp. UUID: https://zoobank.org/19a679ce-968d-4ce1-a590-f7f55bf9d62d

A new Late Ordovician bubble-headed trilobite species from South West Wales and its implications for biostratigraphy

A new Late Ordovician bubble-headed trilobite species from South West Wales and its implications for biostratigraphy

Middle Ordovician trilobites from the Castillejo Formation, Eastern Iberian Range (NE Spain): taxonomic reappraisal, biostratigraphy, and correlation

Middle Ordovician trilobites found in 11 fossil localities from the areas of Alpartir, Aladrén, Luesma and Fombuena (Zaragoza province), and south of Calamocha (Teruel province) are studied. Most records come from the Alpartir Member of the Castillejo Formation, which is dated as Dobrotivian in age (late Darriwilian according to the global scale), with the only exception of two localities that are slightly older, from late Oretanian age (mid−late Darriwilian). In the overlying Sierra Member, three additional localities are recorded, which have estimated age ranges from late early to late Dobrotivian (latest Darriwilian, possibly reaching the Sandbian). A total of 21 different trilobite species were identified including Uralichas hispanicus, Parabarrandia crassa and “Panderia” beaumonti that are recorded for the first time in the Eastern Iberian Range. The main trilobite assemblage from the Alpartir Member belongs to the Placoparia tournemini Biozone, which correlates with numerous areas of southwestern Europe, and here occurs in a biofacies dominated by asaphids. The scarce data derived from the Sierra Member do not allow to distinguish biozones, although the incipient development of a trilobite biofacies adapted to sandy bottoms is recognized, which ends at the top of the Placoparia borni Biozone in the whole of southwestern Europe. The correlation of the trilobite assemblages with those of other formations represented in the Cantabrian, West Asturian-leonese and Central Iberian zones is also discussed, the latter probably related through the enigmatic Central Iberian Arc, a debated orocline of the Iberian Massif.

Funeralaspis n. gen.: a new odontopleurine trilobite from the early Middle Ordovician (Dapingian) of Death Valley, eastern California, USA, and the classification of Ordovician odontopleurines.

Funeralaspis n. gen. (type species F. deathvalleyensis n. sp.) is the oldest known formally named odontopleurine trilobite species, described on the basis of abundant secondarily silicified sclerites of all sclerite types except the rostral plate, from the Dapingian of the Antelope Valley Formation, west flank of the Funeral Range, Death Valley National Park, Inyo County, California. Many Ordovician odontopleurines have been assigned to Diacanthaspis, to the point that it has become something of a taxon of convenience. All of the potential species are listed along with their provenance, preservation, and represented sclerite types. A core group of Diacanthaspis, termed Diacanthaspis (sensu stricto or s.s.) possibly represents a Laurentian clade, consisting of the type species, D. cooperi, and D. lepidus, D. orandensis, D. scitulus, D. secretus, and possibly D. elapsa and D. parvula. This group is characterized by extreme dorsal spinosity, dorsal accessory spines on the base of the genal spine, pygidial spines with lateral fringes of tiny spines, and thoracic and pygidial ring furrows with fringes of tiny spines. Funeralaspis deathvalleyensis has none of the features characteristic of Diacanthaspis and in general scarcely resembles members of this Upper Ordovician group. Remaining species that have been assigned to Diacanthaspis, some of which are very poorly known, should be reclassified as knowledge of Ordovician odontopleurines advances, but for the present are treated as Diacanthaspis (sensu lato or s.l.). A heretofore nearly unknown species described as Ceratocephala maquoketensis from the early Katian of Howard County, Iowa, has not been commented upon in the literature since it was proposed. It is an odontopleurine which in the current state of knowledge should be assigned to the Diacanthaspis (s.l.) group.

New Species of the Genus <i>Oryctocephalus</i> Walcott from the Middle Cambrian of the Siberian Platform

Two new species of trilobites of the Oryctocephalus Walcott, 1886 from the Amgan Stage of the Middle Cambrian of the Siberian Platform were described: Oryctocephalus doliformis sp. nov. and O. molodoensis sp. nov. wich were found in the middle part of the Kuonamka Formation in the Molodo and Muna Rivers sections.

Associations between trilobite intraspecific moulting variability and body proportions: Estaingia bilobata from the Cambrian Emu Bay Shale, Australia

AbstractTrilobites were notably flexible in the moulting behaviours they employed, producing a variety of moult configurations preserved in the fossil record. Investigations seeking to explain this moulting variability and its potential impacts are few, despite abundant material being available for study. We present the first quantitative study on moulting in a single trilobite species using a dataset of almost 500 moult specimens of Estaingia bilobata from the Cambrian (Series 2, Stage 4) Emu Bay Shale, South Australia. Specimens were categorized by moulting mode (Salter's or Sutural Gape) and their associated configurations, and their body proportions measured from both a museum collection (including a bycatch sample) and a randomly‐collected field sample. This enabled analysis of the proportion of E. bilobata specimens displaying the Sutural Gape and Salter's modes of moulting and their different configurations, and tests for association between moulting behaviour and body proportions. The results show a wide range of E. bilobata moulting configurations in all samples, suggesting that configurations represent definable instances in a largely continuous spectrum of variation. Analyses comparing body proportions of specimens showing the two modes of moulting were non‐significant, suggesting there is no true association between moulting behaviour and body proportion, except for a single significant result for body length. All results were relatively consistent between the museum and field samples. However, removing accessioned specimens from the museum sample brought results even further in line with the field sample, supporting the need for consideration of museum collection bias in palaeontological analyses.

Shared patterns of segment size development in trilobites and vertebrates.

The relative sizes of body segments are a major determinant of the shape and functionality of an animal. Developmental biases affecting this trait can therefore have major evolutionary implications. In vertebrates, a molecular activator/inhibitor mechanism, known as the inhibitory cascade (IC), produces a simple and predictable pattern of linear relative size along successive segments. The IC model is considered the default mode of vertebrate segment development and has produced long-term biases in the evolution of serially homologous structures such as teeth, vertebrae, limbs, and digits. Here we investigate whether the IC model or an IC-like model also has controls on segment size development in an ancient and hyperdiverse group of extinct arthropods, the trilobites. We examined segment size patterning in 128 trilobite species, and during ontogenetic growth in three trilobite species. Linear relative segment size patterning is prominent throughout the trunk of trilobites in the adult form, and there is strict regulation of this patterning in newly developing segments in the pygidium. Extending the analysis to select stem and modern arthropods suggests that the IC is a common default mode of segment development capable of producing long-term biases in morphological evolution across arthropods as it does in vertebrates.

Drifting with trilobites: The invasion of early post-embryonic trilobite stages to the pelagic realm

The Ordovician Radiation shaped Paleozoic marine ecosystems and led to an increase in the biodiversity of marine organisms. The onset of the Plankton Revolution in the late Cambrian is an important step within the Ordovician Radiation. During this revolution, various organisms invaded pelagic realms, which affected the marine trophic web through the introduction of phytoplankton, zooplankton, as well as plankton- and suspension-feeding animals. Trilobites, a main Paleozoic group of marine metazoans, played a major role during the Ordovician Radiation. Previous studies showed that some trilobites evolved planktic larvae during the Furongian and Early Ordovician. Herein, we quantify the appearance of trilobite planktic larvae by providing highly resolved Cambrian and Ordovician data on 144 trilobite species with well-known developmental sequences. We show that Cambrian trilobites were dominated by species and families with exclusively benthic early post-embryonic stages. On the contrary, Ordovician seas comprised a remarkable number of trilobites with one or more planktic stages. However, species and families with exclusively benthic early stages still constituted about half of the Ordovician trilobite diversity. The first trilobites with planktic larvae might have been present in the Miaolingian, but their earliest fossil record is from the mid-Furongian. The appearance of planktic forms was accentuated later in the Ordovician with many trilobite lineages adapting a multi-staged planktic mode of life – more than one developmental stage colonizing the water column during ontogeny. Between the Miaolingian and the Middle Ordovician, both species- and family-level data show a progressive increase in the number of taxa incorporating planktic larvae in their development, highlighting a gradual transition in the structure of marine ecosystems during the early Paleozoic.

Modularity in the trilobite head consistent with the hypothesized segmental origin of the eyes.

The trilobite head served multiple functions and was composed of several fused segments. Yet, the underlying organization of the trilobite head, and whether patterns are conserved across trilobites, remains unclear. Modeling the head as being composed of modules, or subunits that vary and thus have the potential to evolve semi-independently can reveal underlying patterns of organization. Hypotheses of modular organization based on the comparative developmental biology of arthropods were evaluated using geometric morphometrics. Two-dimensional (semi)landmark datasets collected from the cranidia of two Ordovician trilobite species, Calyptaulax annulata (Phacopida) and Cloacaspis senilis (Olenida sensu Adrain, 2011) were analyzed. The degree and pattern of modularity were assessed using the covariance ratio (CR), which compares the covariation within putative modules to the covariation between them, and the fit of different models was compared using an effect size measure derived from the CR. When treating the eyes as a distinct module, the best modular hypothesis identified for C. annulata shows the eyes and anteriormost region of the head integrated as a single module. The best modular hypotheses for C. senilis are more complex but the eyes still covary mostly strongly with the anterior part of the head. The latter is also the case for all other well-supported models for both species. These results can be interpreted as a developmental signal corresponding to the anteriormost ocular segment of early arthropods that is retained throughout development, despite any likely selective pressures related to functional needs.

Neoxela: A new replacement name for Xela Botero, Bezark amp; Santos-Silva, 2020 (Coleoptera, Cerambycidae, Lamiinae).

Recently, Botero, Bezark Santos-Silva (2020) described a new genus of Methiini (Cerambycinae), Xela, for their new species Xela tysoni, from Guatemala. Currently, the genus remains monotypic and the species is known only from their type locality. Unfortunately, the authors did not realize that the name had already been used for a trilobite species (Xela drena Jell, 1990). Herein, we propose a new replacement name for the genus.

Cambrian carnage: Trilobite predator-prey interactions in the Emu Bay Shale of South Australia

The Cambrian explosion represents the rapid emergence of complex marine ecosystems on Earth. The propagation of predator-prey interactions within these systems was almost certainly one of the major drivers of this evolutionary event, sparking an arms race that promoted the proliferation of biomineralised exoskeletons and shells, and the evolution of the first durophagous (shell-crushing) predators. The most commonly documented evidence of Cambrian durophagous predation comes from injured trilobites. However, quantitative analysis based on multiple specimens from single localities is lacking. Such studies are required to reveal the dynamics of ancient predator-prey systems at fine ecological scales (e.g. at the population or community level). This study documents injured specimens of two trilobite species, Redlichia takooensis and Redlichia rex, from the Emu Bay Shale Konservat-Lagerstätte (Cambrian Series 2, Stage 4) on Kangaroo Island, South Australia. A total of 38 injured specimens exhibiting various healed cephalic and thoracic injuries are documented, in addition to the mangled remains of two individuals that probably resulted from the activities of a durophagous predator or scavenger. Specimens of both species show that most injuries are located on the posterior portion of the thorax, indicating that predators preferentially attacked from behind and/or prey individuals presented the posterior of the trunk towards the predator when threatened or fleeing. The larger sample of injured R. takooensis shows that while unilateral injuries are more common than bilateral ones, there is no evidence for a left- or right-side bias, contrasting with previous suggestions that Cambrian trilobites exhibit right-sided injury stereotypy. Comparing the position of injured and non-injured R. takooensis and R. rex in bivariate space, we illustrate that injured specimens of both species typically represent some of the largest individuals of these taxa. This suggests that smaller individuals were completely consumed during an attack and/or larger individuals were more likely to survive an attack and thus record a healed injury. We argue that R. rex, rather than radiodonts, was likely the chief producer of exoskeletal injuries and large shelly coprolites in the Emu Bay Shale biota, and represents one of the earliest cannibalistic trilobites.

Extraordinary Ordovician trilobite Fantasticolithus gen. nov. from Peru and its bearing on the trinucleimorph hypothesis

AbstractFantasticolithus isabelae, a new genus and species of trinucleid trilobite from the Lower Ordovician of Peru, developed anterior ventral cephalic ‘props’ that are unique in the Trilobita. Its broad and finely pitted genal prolongations are unlike those of any previously known trinucleid, and closely resemble those invariably present in the unrelated Family Harpetidae, supporting the hypothesis that the two families shared a similar mode of life, as ‘trinucleimorphs’. Fantasticolithus was probably derived from an early trinucleid with a marginal girder, although it resembles younger genera such as Marrolithus in its enlarged anterolateral pits. The new genus provides a natural experiment to test the hypothesis of trinucleimorphs as filter feeders that used a ventral feeding chamber. The role of the pitted marginal fringe as an egress for feeding currents is discussed. Fantasticolithus had an unusual anterior vent that provided a simpler exit mechanism for feeding currents than the pitted fringe. However, the pits were probably important for trinucleids that lacked an anterior arch.

Early Ordovician Seleneceme (Trilobita) in Ziyang Fauna, South China

ABSTRACT Ziyang Fauna is a significant early Ordovician Floian fossil Lagerstätte, recovered from blackish-grey mud limestone and calcareous mudstone of possible slope facies in the Yangtze platform in Ziyang County, Shaanxi Province, China, distinguished by predominate trilobites, accompanied with graptolites, brachiopods, arthropods and some trace fossils. It is marked by high abundance of exceptionally preserved Seleneceme (Trilobita). Two trilobite species named Caputrotundum bashanense and C. ziyangensis, are reassigned here to Seleneceme based on a detailed study of more than one hundred well-preserved specimens. The taxonomic generic and ontogeny characters of Seleneceme are as follows: cephalon semicircular in outline, with axial spine and genal spines; without eye lobes; glabella subcircular in outline, with deep longitudinal glabellar furrows; thorax and pygidium with much parallel segments. The morphological variation during ontogeny of Seleneceme is characterised by the gradual increase of the length/width ratio (L/W) of the body, but with a constant width/length ratio (W/L) of the cephalon, and also a faster growth rate in the pygidium than in the thorax.

Darriwilian (Middle Ordovician) new trilobites from the Upper Yangtze Region, South China, and their macroevolutionary and paleobiogeographic implications

AbstractTwo new genera and six new species of trilobites are systematically documented herein: Sinagnostus mirabilis new genus new species, Yanpingia punctata n. gen. n. sp., Illaenus taoyuanensis n. sp., Panderia striolatus n. sp., Nileus yichongqiaoensis n. sp., and Paratiresias peculiaris n. sp. The materials were collected from the Darriwilian (late Middle Ordovician) strata in the Upper Yangtze Region, South China. Also provided is an emended diagnosis of the genus Paratiresias based on the new species Paratiresias peculiaris, which is the oldest known species of this genus with an extremely narrow (sag. and exsag.) preglabellar field. Those Chinese species previously referred to Nanillaenus are reassigned to Illaenus sensu lato. These trilobites add new data for the Darriwilian trilobite macroevolution and show highly endemic to South China and the faunal exchanges between South China and Tarim, Kazakhstan, Alborz, as well as Sibumasu and North China.UUID: http://zoobank.org/ec3be9be-b003-4367-910d-7a0ac4edc982

Ontogenetic moulting behavior of the Cambrian oryctocephalid trilobite Arthricocephalites xinzhaiheensis.

Moulting behaviors in trilobites are a crucial strategy during development. Previous studies have demonstrated inter-and intraspecific variability of moulting behavior in trilobites. Currently, ecdysial motifs for trilobites are considered not stable even within species and fewer detailed studies dealt with moulting behaviors in a single species of trilobite during development. Here a large sample of meraspid to holaspid exuviae of Arthricocephalites xinzhaiheensis (131 specimens) from the Cambrian Balang Formation of South China has allowed description of the reasonably complete ontogenic moulting sequence. Both ontogenetic stage and body size reveal gradual transition of configuration from Somersault configuration to Henningsmoen’s configuration during development. Somersault configuration is exclusive till meraspid degree five and exists in subsequent growth stages. This suggests that opening of the facial and rostral sutures allowing the emergence forward of the post-ecdysial trilobite was prevalent in early growth stages. In later development, Henningsmoen’s configuration (showing disarticulation of the cranidium) became more dominant. This study indicates that gradual transition of ontogenetic moulting behavior occurred in oryctocephalid trilobites in the early Cambrian.

Middle Ordovician trilobites from the Houping Formation of South China: implications for palaeoecology and palaeobiogeography

ABSTRACT Seventeen trilobite species belonging to 16 genera and 13 families are systematically documented from the Houping Formation (upper Dapingian-lower Darriwilian, Middle Ordovician) at the Datangkou and Dacao sections, Chengkou, northern Chongqing. Of these, a new species, Mioptychopyge chengkouensis sp. nov., is established and described. New morphological information is provided for previously known species on the basis of new specimens. Two trilobite associations based on faunal composition and dominant forms are distinguished from the Houping Formation, in ascending order, the Agerina Association (from the lower and middle members) and the Nileus-Illaenus Association (from the upper member). The Agerina Association lived in an inner shelf margin environment with carbonate substrate above storm wave base (<70 m deep), whereas the Nileus-Illaenus Association developed in a shallow outer shelf environment below storm wave base (>70 m deep), indicating a rise of relative sea level corresponding to the early Darriwilian transgression. The cluster and nonmetric multidimensional scaling analyses of the trilobites in the formation show that the fauna had a strong endemicity to South China and a close biogeographic connection with east Peri-Gondwana, especially Tarim, Annamia and central Iran.LSIDurn:lsid:zoobank.org:pub:E4E6AD0B-417F-4522-83E3-4DC44B647760

The first lower Viséan trilobite association from limestone facies of the Moravian Karst and its relation to the sedimentary environment (Líšeň Formation, Czech Republic)

A lower Visean trilobite association from limestones of the Liseň Formation in the Moravian Karst (Czech Republic) was studied in detail for the first time. The trilobites were obtained from a thin interval in the succession of the HadyŘicka Limestone exposed in the Zetor section situated on the southern margin of the Moravian Karst near Brno. The limestone succession of the Zetor section with prevalently distal calciturbidites was deposited on the lower part of the carbonate ramp. Biostratigraphic data suggest the span of the lower Visean MFZ11 (foraminiferal zone) for the interval rich in trilobites. The trilobites are preserved in at least a partly silicified state. Around twenty trilobite species or subspecies were recorded including one new taxon Bollandia megaira brunensis subsp. nov., various species of ?Namuropyge R. Richter & E. Richter, Liobole R. Richter & E. Richter, Angustibole G. Hahn, ?Cyrtoproetus Reed, Gitarra Gandl, Pseudowaribole (Geigibole) Gandl, Winterbergia G. Hahn & Brauckmann, Bollandia Reed and several taxa of problematic affinity, which are discussed. The recorded taxa show an affinity with associations from the Erdbach Limestone facies in Germany but also with other areas (e.g. Cantabrian Mountains, Spain). The trilobite association shows similarities to the “Shelf Slope” and “Erdbacher Kalke” communities recorded in Germany. In contrast, the previously described lower Visean trilobite associations from the Moravian Karst were restricted to the aleuropelitic facies of the Březina Formation and correspond rather to the “Culm facies” community known from Germany. These associations might represent more distal and deeper basinal settings than the Zetor section or an environment of generally similar depths with a different source area and bottom topography.