OBJECTIVE: To analyze anomalies of a biomineralized exoskeleton of a trilobite. MATERIALS: A specimen of Dalmanitina socialis from the Upper Ordovician Letná Formation at Veselá 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.

• Klíčová slova
• Barrandian area, Cephalon, Czech Republic, Late Ordovician, Trauma,
• MeSH
• členovci * MeSH
• ekosystém MeSH
• pitva MeSH
• regenerace MeSH
• zkameněliny * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Early Palaeozoic sites with soft-tissue preservation are predominantly found in Cambrian rocks and tend to capture past tropical and temperate ecosystems. In this study, we describe the diversity and preservation of the Cabrières Biota, a newly discovered Early Ordovician Lagerstätte from Montagne Noire, southern France. The Cabrières Biota showcases a diverse polar assemblage of both biomineralized and soft-bodied organisms predominantly preserved in iron oxides. Echinoderms are extremely scarce, while sponges and algae are abundantly represented. Non-biomineralized arthropod fragments are also preserved, along with faunal elements reminiscent of Cambrian Burgess Shale-type ecosystems, such as armoured lobopodians. The taxonomic diversity observed in the Cabrières Biota mixes Early Ordovician Lagerstätten taxa with Cambrian forms. By potentially being the closest Lagerstätte to the South Pole, the Cabrières Biota probably served as a biotic refuge amid the high-water temperatures of the Early Ordovician, and shows comparable ecological structuring to modern polar communities.

• MeSH
• členovci * MeSH
• Echinodermata MeSH
• ekosystém * MeSH
• společenstvo MeSH
• zkameněliny MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

The Fezouata Biota (Morocco) is a unique Early Ordovician fossil assemblage. The discovery of this biota revolutionized our understanding of Earth's early animal diversifications-the Cambrian Explosion and the Ordovician Radiation-by suggesting an evolutionary continuum between both events. Herein, we describe Taichoute, a new fossil locality from the Fezouata Shale. This locality extends the temporal distribution of fossil preservation from this formation into the upper Floian, while also expanding the range of depositional environments to more distal parts of the shelf. In Taichoute, most animals were transported by density flows, unlike the in-situ preservation of animals recovered in previously investigated Fezouata sites. Taichoute is dominated by three-dimensionally preserved, and heavily sclerotized fragments of large euarthropods-possibly representing nektobenthic/nektic bivalved taxa and/or hurdiid radiodonts. Resolving whether this dominance reflects a legitimate aspect of the original ecosystem or a preservational bias requires an in-depth assessment of the environmental conditions at this site. Nevertheless, Taichoute provides novel preservational and palaeontological insights during a key evolutionary transition in the history of life on Earth.

• MeSH
• biologická evoluce MeSH
• ekosystém * MeSH
• minerály MeSH
• společenstvo MeSH
• zkameněliny * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• minerály MeSH

The Fezouata Biota (Morocco) is a Burgess Shale-type (BST) assemblage that provides a wealth of information on Early Ordovician ecosystems. Much work has been done to compare the preservation of the Fezouata Biota to other BSTs. However, studies investigating preservation variations within the Fezouata Biota are rare. Here, we use probabilities to investigate the preservation of various ecological categories of Fezouata eumetazoans. Complex taphonomic processes and phylum-specific constraints have led to the better preservation of predators/scavengers in this biota. However, no differences in preservation are observed between vagile and sessile taxa. Importantly, Tremadocian taxa are better preserved than Floian ones. As such, this study highlights the gradual closure of the BST window of preservation in the Zagora region of Morocco and constitutes a benchmark for future palaeoecological and evolutionary studies on the Fezouata Biota.

• Klíčová slova
• Early Palaeozoic, Gondwana, Invertebrates, Statistics,
• MeSH
• biodiverzita MeSH
• biologická evoluce MeSH
• ekosystém MeSH
• společenstvo * MeSH
• zkameněliny MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Maroko MeSH

Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (∼447-444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.

• Klíčová slova
• abundance, climate change, extinction, macroevolution, selection,
• MeSH
• Bayesova věta MeSH
• bezobratlí klasifikace   růst a vývoj   MeSH
• biodiverzita MeSH
• biologické modely MeSH
• časové faktory MeSH
• extinkce biologická * MeSH
• geologické sedimenty MeSH
• klimatické změny * MeSH
• oceány a moře MeSH
• vodní organismy klasifikace   růst a vývoj   MeSH
• zkameněliny * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geografické názvy
• oceány a moře MeSH

The Palaeozoic sediments of the Barrandian area are globally well-known as a classic example of rocks characterised by an abundant skeletal marine fauna, including well-preserved remains of hyoliths. Several tens specimens of malformed invertebrates such as trilobites, cephalopods and gastropods have been collected and documented from Cambrian to Devonian clastic sediments and carbonates in this area. However, no malformed hyolith specimen has yet been recorded. Hyoliths are Palaeozoic animals with small calcium carbonate shells composed of the conch (= oblong, conical and bilaterally symmetrical shell of diverse cross section and aperture at its wide end) and the operculum (= cap closing the conch aperture). Here we describe an operculum showing regeneration after non-lethal predatory attack in the Ordovician hyolith Elegantilites custos. This is the first record of regeneration in a hyolith operculum that has been repaired after a failed durophagous attack. Epibenthic/infaunal predatory echinoderms, such as ophiuroids, are considered as potential culprits.

• Klíčová slova
• Failed predation, Hyolitha, Ordovician, Prague Basin,
• MeSH
• bezobratlí * MeSH
• zkameněliny * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Trilobites represent a model for 'evo-devo' studies in fossil euarthropods, owing to a rare developmental trait: the biomineralization of the dorsal exoskeleton soon after hatching. Many fossilized trilobite ontogenies thus feature early stages - the protaspides - characterized by non-articulated, calcified dorsal exoskeletons. The recent discovery of a protaspid-like fossil occurring with aglaspidid remains in Middle Ordovician strata of Siberia has been interpreted as evidence for the presence of protaspides in these distant relatives of trilobites. In this contribution, we demonstrate that this Siberian protaspis actually belongs to the asaphid trilobite Isotelus (or a related taxon), a genus likely present in the same bed. We conclude that protaspid larvae still represent a developmental trait unique to Trilobita.

• Klíčová slova
• Aglaspidida, Euarthropoda, Larval ecology, Ordovician, Protaspis, Trilobita,
• MeSH
• členovci * MeSH
• larva MeSH
• zkameněliny MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Studies of micrometeorites in mid-Ordovician limestones and impact craters on Earth indicate that our planet witnessed a massive infall of ordinary L chondrite material about 466 million years ago1-3 that may have been at the origin of an Ordovician ice age and major turnover in biodiversity4. The breakup of a large asteroid in the main belt is the likely cause of this massive infall. Currently, material originating from this breakup still dominates meteorite falls (>20% of all falls)5. Here we provide spectroscopic observations and dynamical evidence that the Massalia collisional family is the only plausible source of this catastrophic event and the most abundant class of meteorites falling on Earth today. This family of asteroids is suitably located in the inner belt, at low-inclination orbits, which corresponds to the observed distribution of L-chondrite-like near-Earth objects and interplanetary dust concentrated at 1.4° (refs. 6,7).

• Publikační typ
• časopisecké články MeSH

Organisms with external phosphatic shells diversified and became abundant at the beginning of the Early Paleozoic but gradually declined and were rare by its end. The decreasing availability of phosphorus in oceans is thought to be responsible for this evolutionary trend. Responses of organisms to changes in the phosphorus cycle can be traced to the late Neoproterozoic, and likely had a significant role in the Cambrian explosion, the Great Ordovician Biodiversification Event (GOBE), and the Devonian nekton revolution. Effective use of phosphorus by vertebrates during the Devonian nekton revolution caused the phosphorus pool to shift from benthic external shells to the skeletons of pelagic vertebrates, and moved the marine faunas toward the dominance patterns and ecological structure of the Modern Evolutionary Fauna.

• Klíčová slova
• Devonian, GOBE, phosphate, phosphorus cycle, shells,
• MeSH
• biodiverzita * MeSH
• biologická evoluce MeSH
• fosfor MeSH
• obratlovci MeSH
• zkameněliny * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• fosfor MeSH

The second pulse of the Late Ordovician mass extinction occurred around the Hirnantian-Rhuddanian boundary (~444 Ma) and has been correlated with expanded marine anoxia lasting into the earliest Silurian. Characterization of the Hirnantian ocean anoxic event has focused on the onset of anoxia, with global reconstructions based on carbonate δ238U modeling. However, there have been limited attempts to quantify uncertainty in metal isotope mass balance approaches. Here, we probabilistically evaluate coupled metal isotopes and sedimentary archives to increase constraint. We present iron speciation, metal concentration, δ98Mo and δ238U measurements of Rhuddanian black shales from the Murzuq Basin, Libya. We evaluate these data (and published carbonate δ238U data) with a coupled stochastic mass balance model. Combined statistical analysis of metal isotopes and sedimentary sinks provides uncertainty-bounded constraints on the intensity of Hirnantian-Rhuddanian euxinia. This work extends the duration of anoxia to >3 Myrs - notably longer than well-studied Mesozoic ocean anoxic events.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH