end-Ordovician Mass Extinction Research Articles

Evolution of brachiopod symbiosis in the early Paleozoic

ABSTRACT The evolution of brachiopod symbiosis is closely tied to the evolution of brachiopod faunas and their partner groups during the early Palaeozoic. Brachiopod groups with a larger number of taxa had more symbiotic associations, and there was no specific group that was more prone to symbiosis during this time interval. The first symbiotic associations appeared soon after the emergence of certain brachiopod groups, with Cambrian brachiopods partnering with typical representatives of the Cambrian fauna. Bryozoans and tentaculitoid tubeworms, which became important partners during the Ordovician and Silurian, first diversified in the Ordovician. The gradual decrease in the number of brachiopod partner groups from the Cambrian to the Silurian was likely due to specialisation. However, the number of symbiotic associations did not increase faster than the number of brachiopod taxa. The GOBE-induced diversification of brachiopod taxa did not lead to an escalation in symbiotic relationships. Symbiotic associations involving brachiopods continued after the end-Ordovician mass extinction. Although early Palaeozoic brachiopods were vulnerable to kleptoparasites, the harm caused by these parasites was not enough to drive their associated brachiopods to extinction.

Evolutionary contingency in lingulid brachiopods across mass extinctions

Morphology usually serves as an effective proxy for functional ecology,1,2,3,4,5 and evaluating morphological, anatomical, and ecological changes permits a deeper understanding of the nature of diversification and macroevolution.5,6,7,8,9,10,11,12 Lingulid (order Lingulida) brachiopods are both diverse and abundant during the early Palaeozoic but decrease in diversity over time, with only a few genera of linguloids and discinoids present in modern marine ecosystems, resulting in them frequently being referred to as "living fossils."13,14,15 The dynamics that drove this decline remain uncertain, and it has not been determined if there is an associated decline in morphological and ecological diversity. Here, we apply geometric morphometrics to reconstruct global morphospace occupation for lingulid brachiopods through the Phanerozoic, with results showing that maximum morphospace occupation was reached by the Early Ordovician. At this time of peak diversity, linguloids with a sub-rectangular shell shape already possessed several evolutionary features, such as the rearrangement of mantle canals and reduction of the pseudointerarea, common to all modern infaunal forms. The end Ordovician mass extinction has a differential effect on linguloids, disproportionally wiping out those forms with a rounded shell shape, while forms with sub-rectangular shells survived both the end Ordovician and the Permian-Triassic mass extinctions, leaving a fauna predominantly composed of infaunal forms. For discinoids, both morphospace occupation and epibenthic life strategies remain consistent through the Phanerozoic. Morphospace occupation over time, when considered using anatomical and ecological analyses, suggests that the limited morphological and ecological diversity of modern lingulid brachiopods reflects evolutionary contingency rather than deterministic processes.

Biogeographic dynamics of graptolite species during the end-Ordovician mass extinction in South China

Biogeographic dynamics of graptolite species during the end-Ordovician mass extinction in South China

A diverse Hirnantian scolecodont assemblage from northern Estonia and resilience of polychaetes to the end-Ordovician mass extinction

A diverse Hirnantian scolecodont assemblage from northern Estonia and resilience of polychaetes to the end-Ordovician mass extinction

Ordovician–Silurian true polar wander as a mechanism for severe glaciation and mass extinction

The Ordovician–Silurian transition experienced severe, but enigmatic, glaciation, as well as a paradoxical combination of mass extinction and species origination. Here we report a large and fast true polar wander (TPW) event that occurred 450–440 million years ago based on palaeomagnetic data from South China and compiled reliable palaeopoles from all major continents. Collectively, a ~50˚ wholesale rotation with maximum continental speeds of ~55 cm yr−1 is demonstrated. Multiple isolated continents moving rapidly, synchronously, and unidirectionally is less consistent with and plausible for relative plate motions than TPW. Palaeogeographic reconstructions constrained by TPW controlling for palaeolongitude explain the timing and migration of glacial centers across Gondwana, as well as the protracted end-Ordovician mass extinction. The global quadrature pattern of latitude change during TPW further explains why the extinction was accompanied by elevated levels of origination as some continents migrated into or remained in the amenable tropics.

The oldest complete jawed vertebrates from the early Silurian of China.

Molecular studies suggest that the origin of jawed vertebrates was no later than the Late Ordovician period (around 450 million years ago (Ma))1,2. Together with disarticulated micro-remains of putative chondrichthyans from the Ordovician and early Silurian period3-8, these analyses suggest an evolutionary proliferation of jawed vertebrates before, and immediately after, the end-Ordovician mass extinction. However, until now, the earliest complete fossils of jawed fishes for which a detailed reconstruction of their morphology was possible came from late Silurian assemblages (about 425 Ma)9-13. The dearth of articulated, whole-body fossils from before the late Silurian has long rendered the earliest history of jawed vertebrates obscure. Here we report a newly discovered Konservat-Lagerstätte, which is marked by the presence of diverse, well-preserved jawed fishes with complete bodies, from the early Silurian (Telychian age, around 436 Ma) of Chongqing, South China. The dominant species, a 'placoderm' or jawed stem gnathostome, which we name Xiushanosteus mirabilis gen. et sp. nov., combines characters from major placoderm subgroups14-17 and foreshadows the transformation of the skull roof pattern from the placoderm to the osteichthyan condition10. The chondrichthyan Shenacanthus vermiformis gen. et sp. nov. exhibits extensive thoracic armour plates that were previously unknown in this lineage, and include a large median dorsal plate as in placoderms14-16, combined with a conventional chondrichthyan bauplan18,19. Together, these species reveal a previously unseen diversification of jawed vertebrates in the early Silurian, and provide detailed insights into the whole-body morphology of the jawed vertebrates of this period.

Oceanic anoxia and extinction in the latest Ordovician

The Late Ordovician (Hirnantian) mass extinction (LOME) was marked by two discrete pulses of high species turnover rates attributed to glacial cooling (LOME-1) and subsequent expansion of anoxic marine conditions (LOME-2). However, the mechanisms and extent of global marine anoxia remain controversial. In this study, we present uranium isotope (δ238U) data from a new Ordovician-Silurian (O-S) boundary carbonate section in the Southwest China to explore the extent/duration of the global marine anoxia, and links to the LOME. This section was found to continuously record the characteristic Hirnantian paired carbon isotope excursion (HICE) and complete benthic faunal turnover across the O-S boundary based on detailed stratigraphic constraint. The poor correlations between δ238Ucarb data, local redox proxy (Ce anomalies), and diagenetic indicators (e.g., Mn and Sr contents, Mn/Sr ratio, δ18O), as well as microscopic petrographic examinations of O-S carbonates suggest that most of the δ238U data are not produced by either local redox conditions or post-depositional diagenetic processes. By coupling our new uranium isotope data with a stochastic U isotope mass balance model, we suggest there were two episodes of widespread marine anoxia over this time interval revealed by systematic changes of δ238U with two negative shifts punctuated by one positive one in between. The former took place in the late Katian, predating the LOME-1 episode and the pronounced climatic cooling; while the latter occurred synchronously with the LOME-2 in the mid-late Hirnantian, separated by a potential oceanic oxygenation event. This presents a more complicated picture of anoxia—as inferred from U isotope records—as a driver of the end-Ordovician mass extinction. The insignificant biotic response to late Katian anoxia is consistent with the idea that the effects of anoxia on marine ecosystem can be highly variable. On the other hand, the presence of anoxia in mid-late Hirnantian strengthen the connection between the oceanic deoxygenation and fauna turnover in LOME-2.

An introduction to the Great Ordovician Biodiversification Event: insights from the Tafilalt Biota, Morocco

Abstract The exquisitely preserved, diverse and abundant fossil assemblages yielded by the ‘echinoderm meadows’ of the Tafilalt region of the eastern Anti-Atlas represent a new Konservat-Lagerstätte, one of the few exceptionally preserved Late Ordovician open-marine faunas found globally, giving us an insight into the radiation of life during the later phases of the Great Ordovician Biodiversification Event (GOBE) in high-latitude peri-Gondwana. The GOBE resulted in an unprecedented increase in the diversity of families, classes and orders, at the fastest rate of the entire Phanerozoic and represents one of the most significant events in the evolution of the marine biosphere, preceding the end-Ordovician mass extinction. Nine different phyla and several soft-bodied problematica are represented in the Tafilalt, including several notable echinoderm Lagerstätten. This volume is the culmination of over 20 years of research by several international teams and integrates a series of contributions that look at diverse aspects of the biota, including the stratigraphic distribution of the faunas, depositional environments, systematic palaeontology, preservation, palaeobiogeography and the nature and impact of the international fossil trade on these exceptionally preserved fossil faunas.

Depauperate survival bryozoans following the first episode of the end-Ordovician mass extinction in the Kuanyinchiao Bed (Hirnantian, Upper Ordovician) of northern Guizhou, South China

Depauperate survival bryozoans following the first episode of the end-Ordovician mass extinction in the Kuanyinchiao Bed (Hirnantian, Upper Ordovician) of northern Guizhou, South China

HirnantiaFauna from the Condroz Inlier, Belgium: another case of a relict Ordovician shelly fauna in the Silurian?

AbstractThe end-Ordovician mass extinction, linked to a major glaciation, led to deep changes in Hirnantian–Rhuddanian biotas. TheHirnantiaFauna, the first of two Hirnantian survival brachiopod-dominated communities, characterizes the lower–mid Hirnantian deposits globally, and its distribution is essential to understand how the extinction took place. In this paper, we describe, illustrate, and discuss the first macrofossiliferousHirnantiaFauna assemblage from Belgium, occurring in the Tihange Member of the Fosses Formation at Tihange (Huy), within the Central Condroz Inlier. Six fossiliferous beds have yielded a low-diversity, brachiopod-dominated association. In addition to the brachiopods (Eostropheodonta hirnantensis,Plectothyrella crassicosta,Hirnantiasp., andTrucizetina? sp.), one trilobite (Mucronaspissp.), four pelmatozoans (Xenocrinussp.,Cyclocharax[col.]paucicrenulatus,Conspectocrinus[col.]celticus, andPentagonocyclicus[col.] sp.), three graptolites (Cystograptus ancestralis,Normalograptus normalis, and ?Metabolograptussp.), together with indeterminate machaeridians and bryozoans were identified. The graptolite assemblage, from theAkidograptus ascensus-Parakidograptus acuminatusBiozone, indicates an early Rhuddanian (Silurian) age, and thus, an unexpectedly late occurrence of a typicalHirnantiaFauna. This Belgian association may represent an additional example of relictHirnantiaFauna in the Silurian, sharing characteristics with the only other known from Rhuddanian rocks at Yewdale Beck (Lake District, England), although reworking has not been completely ruled out. The survival of these Hirnantian taxa into the Silurian might be linked to delayed post-glacial effects of rising temperature and sea-level, which may have favored the establishment of refugia in these two particular regions that were paleogeographically close during the Late Ordovician–early Silurian.

Biodiversity changes of the Ordovician trilobites in the middle Yangtze region of South China

The biodiversity changes of trilobites in the middle Yangtze region of South China in the Great Ordovician Biodiversification Event and the end-Ordovician mass extinction have been analysed. The Ordovician trilobites in this region originated in the early Tremadocian and radiated from the late Floian to the early Katian. Two peaks of diversity appeared in the late Dapingian to the early Darriwilian and the early Katian. The extinction occurred in the late Katian, followed by a survival period in the Hirnantian. The Whiterock fauna began to surpass the Ibex fauna during the early Katian and were dominant by the late Katian to the Hirnantian, indicating that Cambrian Evolutionary Fauna was gradually replaced. The study once again confirms the view that the effects of factors such as sea level, climate, oxygen content, nutrient supply, and tectogenesis differ temporally and to different degrees in different regions, resulting in differences in the vertical sequence and horizontal combination of ecosystems, which is the reason for the different evolution patterns of Ordovician trilobites in different regions.

Late Ordovician Mafic Magmatic Event, Southeast Siberia: Tectonic Implications, LIP Interpretation, and Potential Link with a Mass Extinction

A geochronological, isotopic, and geochemical study of the Suordakh event of mafic magmatic intrusions on the southeast Siberian margin was undertaken. U-Pb baddeleyite dating of a mafic sill intruding lower Cambrian rocks, yielded a 458 ± 13 Ma emplacement age. The chemical composition and stratigraphic setting of this dated sill differed from that previously attributed to the Suordakh event, implying that additional intrusions, previously mapped as Devonian, potentially belonged to the Suordakh event. No correlation between L.O.I. and concentration of highly mobile major and trace elements was documented, showing small or no influence of hydrothermal alteration on the chemical composition of the intrusions. A new tectonic reconstruction located an island arc and active margin relatively close to the study area. However, all samples had chemical compositions close to that of OIB and did not display Ta-Nb and Ti-negative anomalies, nor other features typical for subduction-related magmatism. The major and trace element distribution was most characteristic of within-plate basalts with the mantle source composition being transitional from spinel to garnet lherzolite. Combining four U-Pb baddeleyite dates of mafic sills and dykes from southeast Siberia, the age of the Suordakh event was estimated at 454 ± 10 Ma. The area of the Suordakh event was at least 35,000–40,000 km2 (an estimate including sills previously interpreted as Devonian), and could be increased with additional dating in Southeastern Siberia. Similar ages for within-plate intrusions were reported from South Korea, West Mongolia, South Argentina, North Iran and Northwest Canada, and these ca. 450 Ma ages were collectively close in timing with the latest Ordovician (Hirnantian) mass extinction. More high-precision dating is necessary to fully test a link between the Suordakh event (and the other age-correlative events) and the end-Ordovician mass extinction.

Late Ordovician paleoceanographic change: Sedimentary and geochemical evidence from Northwest Tarim and Middle Yangtze region, China

Redox variation during the Late Ordovician were an important driver of palaeoceanographic and ecologic changes that may have eventually facilitated biotic extinction in the end of the Ordovician. Previously, the Late Ordovician paleoredox studies have focused mostly on the last 1–2 million years prior to the end of the Ordovician; redox conditions during the Sandbian–Katian time (early–middle Late Ordovician) are poorly understood. In order to fully evaluate the effects of palaeoceanographic variations on biotic evolutionary trends through the entire Late Ordovician, it is important to fully understand redox variations following the Great Ordovician Biodiversification Event (GOBE) and prior to the end-Ordovician mass extinction. The present study reconstructs paleoredox conditions from the Sandbian–Katian successions of the Dawangou section, northwestern Tarim Basin, northwest China and the Puxihe section of the Middle Yangtze region, South China using pyrite framboidal and redox-sensitive element analyses. The distribution of volcanic microspherules, fossil fragment content and elemental analysis were also applied to reveal possible volcanisms and chemical weathering conditions, and to evoluate their effects on palaeoxygenation and biotic variations. The new results indicate three distinct periods of fluctuating paleoredox conditions during the Late Ordovician in the northwest Tarim and the Middle Yangtze regions, China. Overall, redox conditions varied from mainly oxic but punctuated by short-lived anoxic–dysoxic episodes to rapid fluctuations between reducing and oxidizing conditions, to persistent euxinic conditions. The varition of oxygen minimum zone (OMZ) that developed in the midwater column might be the main cause of anoxic events during the Sandbian–early Katian. Moreover, abundant volcanic microspheres, enhanced chemical weathering, decreasing fossil fragments of benthos, and positive europium anomaly from the study sections collectively indicate that intermittent volcanism during the early–middle Katian may have triggered anoxic-euxinic events during this interval. If integrating the newly obtained redox data with previously published data for the Katian to Hirnantian from the Middle Yangtze area, the long-term, stepwisely accelerated oxyen-poor conditions during the Late Ordovician may have facilitated biotic extinctions in the end of the Ordovician.

Plectatrypinae and other ribbed atrypides succeeding the end Ordovician extinction event, Central Oslo Region, Norway

AbstractStrata of the Solvik Formation in the central Oslo Region (upper Hirnantian through most of Aeronian) are very fossiliferous and provide a good record relating to the survival and recovery faunas after the end-Ordovician mass extinctions. The ribbed atrypide fauna is especially rich with 21 species present. Samples from most of these taxa have been sectioned to reveal internal structures for taxonomic study. Of these, 13 species belong to the family Atrypidae, three of which are described in the present paper;Dihelictera engerensisn. sp.,Gotatrypa vettrensisn. sp., andRhinatrypa henningsmoenin. gen. The family Atrypidae follows a global pattern of recovery with an increase in diversity registered in upper Rhuddanian and further diversification in Aeronian strata. The focus of this paper is the family Atrypinidae, which shows a different pattern. They are common and fairly diverse near the base of the Rhuddanian in deeper waters and rare further up, especially in the Aeronian. One new genus,Bockeliena, and two new species,Plectatrypa rindiandEuroatrypa?sigridiare defined. The relationship between the subfamilies Spirigerininae and Plectatrypinae is clarified through thin sections of material from the Ordovician/Silurian boundary layers. The plectatrypids originated in Baltica through transitional species found in upper Katian to Hirnantian strata leading from the cosmopolitanEospirigerinato thePlectatrypalineage with imbricate ribbing and, separately, toBockelienaand others with lamellose, widely spaced ornamentation. The Oslo Region probably acted as a nexus for survival and spread of brachiopods after the end-Ordovician mass extinction.UUID:http://zoobank.org/95340b41-5537-4192-9338-211a2940bea8.

The repaired durophagous scar in the shell of a lingulid brachiopod immediately after the end Ordovician mass extinction

Repaired shell injuries, widely reported mainly on mollusks, give first hand evidence of biological activity in fossil communities. Scars in fossil brachiopods from predation are rarely found, particularly after major biotic crises. A repair scar on a lingulid brachiopod Pseudolingula? sp. that lived immediately after the end Ordovician mass extinction is reported for the first time here. The specimen, cohabited with other components of Cathaysiorthis fauna, was collected from the basal Shiyang Formation (earliest Rhuddanian, Llandovery, Silurian), Jiangxi, southeast China. The scar’s near-margin position and its drape-like shape, together with the quiet middle to deeper shelf living environment and nearly infaunal lifestyle of the species, suggest that the shell damage was biotic-induced, from a failed predation, possibly by a nautiloid cephalopod. The successful repair supports previous studies showing that environmental conditions ameliorated quickly after the extinction. To analyze its repair mode, another repaired specimen of its living relative Lingula anatina collected from the Yellow Sea, China was examined here as well. Compared to the much more efficient repair for the living lingulids, the drape-like structure of the scar on the shell of Pseudolingula? sp. is more similar to the published repair specimens of Cambrian lingulate brachiopods, which may indicate the evolution of its repair mechanisms.Bing Huang [bhuang@nigpas.ac.cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China; Rongyu Li [lir@brandonu.ca] Department of Geology, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9, Canada.

Constraining the biotic transitions across the end‐Ordovician mass extinction in South China: Bio‐ and chemostratigraphy of the Wulipo Formation in the Meitan area of northern Guizhou

The richly fossiliferous succession of the Wulipo Formation in the Huangjiaba area near Meitan in northern Guizhou, SW China, represents one of the very rare records of shelly fauna across the Ordovician and Silurian transition worldwide. This area is therefore crucial for understanding the pattern and dynamics of the end‐Ordovician mass extinction (EOME). Historically, the Wulipo Formation was dated as middle Rhuddanian (early Silurian). However, its fauna shows a close affinity with Transitional Benthic Fauna 3 (TBF 3), now known to be confined within the late Hirnantian (latest Ordovician) in well‐constrained successions globally. Here we present for the first time, chemostratigraphic data from the Wulipo Formation which confirm the presence of the Hirnantian Isotope Carbon Excursion. A critical review of faunal evidence further indicates a late Hirnantian age for this formation, and thus the hitherto only known anomalous TBF 3 record documented from South China is convincingly redated. The important implication is that the substantial biotic recovery after the EOME commenced globally at the very beginning of the Silurian with an overall amelioration of physical conditions. The new findings also suggest a much wider distribution of postglacial warm‐water benthic faunas on the Yangtze Platform during the late Hirnantian than previously envisaged.

The end Ordovician mass extinction induced by rapid glaciation

The end Ordovician mass extinction induced by rapid glaciation

An extremely brief end Ordovician mass extinction linked to abrupt onset of glaciation

The end Ordovician mass extinction (EOME) was the second most severe biotic crisis in Phanerozoic, and has been widely linked to a major glaciation. However, robust geochronology of this interval is still lacking. Here we present four successive high-precision zircon U–Pb dates by isotope dilution thermal ionization mass spectrometry (ID-TIMS) for biostratigraphically well-constrained K-bentonites of a continuous Ordovician-Silurian boundary section at Wanhe, SW China. They include 444.65 ± 0.22 Ma (middle Dicellograptus complexus Biozone), 444.06 ± 0.20 Ma (lower Paraorthograptus pacificus Biozone), 443.81 ± 0.24 Ma (upper Tangyagraptus typicus Subzone), and 442.99 ± 0.17 Ma (upper Metabolograptus extraordinarius Biozone). Calculations based on sedimentation rates suggest a duration of 0.47 ± 0.34 Ma for the Hirnantian Stage, which is much shorter than previously thought (1.4 ± 2.05 Ma in the International Chronostratigraphic Chart ver. 2019/05). The new data also constrain the Hirnantian glacial maximum to ∼0.2 Ma, supporting that its brevity and intensity probably triggered the EOME.

A nearshore Hirnantian brachiopod fauna from South China and its ecological significance

AbstractThe brachiopods collected from the Kuanyinchiao Beds (Hirnantian, uppermost Ordovician) in Meitan and Zunyi counties, northern Guizhou, include 13 species and one undetermined taxon, dominated by Hirnantia sagittifera (M'Coy, 1851) (which accounts for over one-third of the specimens), together with common Eostropheodonta hirnantensis (M'Coy, 1851). They are assigned to the Hirnantia–Eostropheodonta Community, which probably inhabited a shallow-water, nearshore Benthic Assemblage (BA) 2 to upper BA 3 environment. Population analysis shows that the community was well adapted to this environment after the first phase of the end-Ordovician mass extinction. Representative specimens of all the species are illustrated, and a new species, Minutomena missa, is described herein. The variation in Hirnantia sagittifera was noted in many of previous studies but was not statistically evidenced. Here we have measured representative specimens of that famous species from the major paleoplates and terranes in the world, along with other species assigned to the genus from South China. Having used principal component analysis (PCA), significant variations in the species are documented statistically and revised, and three nominal species, one subspecies, and two morphotypes are now reassigned to Hirnantia sagittifera sensu stricto.UUID: http://zoobank.org/references/3f83fb1e-a6dd-4585-9f9f-9586dad28244

The Brachiopod Dalmanella testudinaria across the End Ordovician Extinction Event in the Cuyania Terrane of Western Argentina

The species Dalmanella testudinaria (Dalman) was reported thirty years ago from the Hirnantian Don Braulio Formation of the Argentinean Precordillera, but its assignment was cast in doubt by a recent revision of the species. Through a detailed morphological analysis of a large collection of specimens, attribution of the Don Braulio Formation material to D. testudinaria is now confirmed. The overlying Rhuddanian sandstones of the La Chilca Formation yielded a dalmanellid which was previously referred to as Dalmanella aff. testudinaria. The minor differences existing between these specimens and the topotype material from Sweden is interpreted as intraspecific variation and consequently they are assigned to D. testudinaria. This implies that in the Precordillera basin this species survived the second pulse of the end-Ordovician mass extinction. In the Don Braulio Formation largest shells occur in shallow-water subtidal carbonate lenses and siltstones, near the base of the posglacial transgression, reflecting deposition in well-oxygenated, nutrient-rich waters. Shell size decreases upsection reaching a minimum in the organic-rich mudstones bearing the graptolite Metabolograptus persculptus (Elles et Wood). Overall evidence suggests that low-richness and low-density of this community could be attributed to unfavorable physical environmental conditions associated with decreased food availability, and such limiting paleoecological factors are considered to be the primary cause of dwarfing. Small specimens of D. testudinaria reappear a few meters above the “extinction level” in the lower part of the La Chilca Formation of Rhuddanian age. Before becoming extinct, D. testudinaria coexisted in the Cuyania terrane with the first representatives of the Afro-South American Realm such as Anabaia Clarke and Heterorthella Harper, Boucot, And Walmsley.