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A small skeletal fossil assemblage is described for the first time from the bioclastic limestone interbeds of the siltstone-dominated Guojiaba Formation, southern Shaanxi, China. The carbonate-hosted fossils include brachiopods (Eohadrotreta zhujiahensis, Eohadrotreta zhenbaensis, Spinobolus sp., Kuangshanotreta malungensis, Kyrshabaktella sp., Lingulellotreta yuanshanensis, Eoobolus incipiens, and Eoobolus sp.), sphenothallids (Sphenothallus sp.), archaeocyaths (Robustocyathus sp. and Yukonocyathus sp.), bradoriids (Kunmingella douvillei), chancelloriids sclerites (Onychia sp., Allonnia sp., Diminia sp., Archiasterella pentactina, and Chancelloria cf. eros), echinoderm plates, fragments of trilobites (Eoredlichia sp.), and hyolithelminths. The discovery of archaeocyaths in the Guojiaba Formation significantly extends their stratigraphic range in South China from the early Tsanglangpuian at least to the late Chiungchussuan. Thus, the Guojiaba Formation now represents the lowest known stratigraphic horizon where archaeocyath fossils have been found in the southern Shaanxi area. The overall assemblage is most comparable, in terms of composition, to Small skeletal fossil (SSF) assemblages from the early Cambrian Chengjiang fauna recovered from the Yu’anshan Formation in eastern Yunnan Province. The existing position that the Guojiaba Formation is correlated with Stage 3 in Cambrian Series 2 is strongly upheld based on the fossil assemblage recovered in this study.

Abstract Phosphate-shelled brachiopods differ in filter-feeding lifestyle, with Lingula anatina an active infaunal burrower, and Discinisca tenuis a shallow marine epibenthic animal. The shells of these animals are built of organophosphatic constituents, the organic fibres/sheets reinforced with calcium phosphate to provide a sophisticated ultrastructural robustness. This investigation examined the nature of the organic fibres in order to improve understanding of how living organisms produce hierarchically structured biomaterials. Unlike powdered samples commonly used in previous studies, organic fibres were isolated for the first time and the shell fractions were purified, in order to study the content and nature of the biopolymer fibres. Biochemical methods including Calcofluor staining revealed a chitin matrix. Ultrastructural analysis, thermal gravimetric analysis, and spectroscopic analyses show that the core polysaccharide framework is composed of layers of β-chitin sheets and/or fibrils that are coated with a fibrous organic matrix. There is more chitin matrix in the L. anatina shells (26.6 wt.%) compared to the D. tenuis shells (12.9 wt.%). Taken together, the data show that the chitin matrix contributes to increased skeletal strength, making L. anatina highly adapted for life as an active burrower. In comparison, D. tenuis contains less chitin and lives as attached epibenthos in a shallow marine environment. Graphical abstract First spectroscopic evidence of β-chitin sheets in recent organophosphatic brachiopods

Summary 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.

Diverse and abundant fossil taxa have been described in the lower Cambrian Shipai Formation in the Three Gorges area of Hubei Province, South China, but the taxonomy and diversity of the co-occurring brachiopod fauna are still far from clear. Here we describe the brachiopod fauna recovered from the Shipai Formation in the Three Gorges area of South China, including representatives of the subphylum Linguliformea: linguloids (Lingulellotreta ergalievi, Eoobolus malongensis, and Neobolidae gen. indet. sp. indet.), and an acrotretoid (Linnarssonia sapushanensis); and representatives from the subphylum Rhynchonelliformea: the calcareous-shelled Kutorginates (Kutorgina sinensis, Kutorgina sp., and Nisusia liantuoensis). This brachiopod assemblage and the first occurrence of Linnarssonia sapushanensis shell beds permit correlation of the Shipai Formation in the Three Gorges area of Hubei Province with the Stage 4 Wulongqing Formation in the Wuding area of eastern Yunnan. This correlation is further strengthened by the first appearance datum (FAD) of the rhynchonelliform brachiopod Nisusia in the upper silty mudstone of both the Shipai and Wulongqing formations. The new well-preserved material, derived from siliciclastic rocks, also gives critical new insights into the fine shell structure of L. sapushanensis. Microstructural studies on micromorphic acrotretoids (like Linnarssonia) have previously been restricted to fossils that were acid-etched from limestones. This is the first study to carry out detailed comparative ultrastructural studies on acrotretoid shells preserved in siliciclastic rocks. This work reveals a hollow tube and solid column microstructure in the acrotretoid shells from the Shipai Formation, which is likely to be equivalent of traditional column and central canal observed in shells dissolved from limestones.

The Silurian (Aeronian) post-extinction recovery brachiopod fauna of Iran and Afghanistan is characterized by a proliferation of the Stegocornu Brachiopod Association, which includes prominent ende...

Rare Oichnus simplex drill holes occur in mature obolid shells from the Cambrian/Ordovician boundary beds of northern Estonia (Iru and Ülgase) and the uppermost Cambrian of NW Russia (Lava River). The drill holes are significantly more common in the central rather than the marginal regions of the obolid valves. Drilling predators attacked Ungula ingrica in the Kallavere Formation and Ungula convexa in the Ladoga Formation. Failed predatory attacks on obolids were relatively common in the latest Cambrian-earliest Tremadocian of Estonia. Presumably drilling predators at Lava River and Iru differed from those at the Ülgase as indicated by significant differences in drill hole sizes at these locations. Most likely some types of worms preyed on obolids in the latest Cambrian-earliest Tremadocian of Estonia and latest Cambrian of NW Russia. The predation rate (6% to 9%) of studied obolids indicates that they likely had an epibenthic life mode. In addition to Oichnus drill holes in the obolids, there are also common pseudoborings caused by mineral dissolution.

Limestones of the Xihaoping Member of the Dengying Formation in the Xiaoyangba section, South China, yield the oldest known Cambrian brachiopod–trilobite association. In this member, the trilobite Parabadiella cf. huoi co-occurs with the new brachiopod species Eoobolus incipiens sp. nov. The association provides potential for correlation of lower Cambrian successions and gives novel insights into the origin, palaeobiogeographic distribution and early evolution of linguliform brachiopods. Parabadiella occurs in shallow marine clastic and carbonate rocks in South China, demonstrating a broad distribution for this taxon. The new discovery indicates an early Chiungchussuan age (Parabadiella trilobite Zone, Cambrian Age 3) for the longstanding problematic Xihaoping Member. Furthermore, this earliest Parabadiella–Eoobolus association helps to establish close links with the oldest known trilobite–brachiopod assemblage from the upper Micrina etheridgei Zone (Parabadiella huoi trilobite Zone) in Australia. Eoobolus incipiens represents one of the earliest known linguliform brachiopods, with a distinctive mixture of characters shared with both problematic tommotiids, as well as paterinide, lingulide and acrotretide brachiopods, indicating that these features may be plesiomorphic for the Linguliformea. An age-constrained dispersal mode for early lingulate brachiopods is proposed, indicating that the Subphylum Linguliformea may have originated in East Gondwana and South China during Cambrian Age 3, and only subsequently dispersed to other major Cambrian palaeocontinents (e.g. Siberia, Laurentia, Antarctica, Baltica, Avalonia, West Gondwana, North China) during the late stage of the Cambrian evolutionary radiation of animals.

Brachiopod shell accumulations are abundant and diverse in the lower Cambrian strata of Yunnan Province, South China, but most commonly they are composed of linguloid and acrotheloid brachiopods. Here, we describe the first record of shell beds with high-density accumulations of microscopic acrotretoid brachiopods (usually Linnarssonia sapushanensis n. sp., which differs from other species of Linnarssonia mainly in having a well-developed internal pedicle tube, as well as a relatively longer dorsal median septum. The occurrence of Linnarssonia sapushanensis n. sp. in the Wulongqing Formation in eastern Yunnan extend the oldest record of the genus on the Yangtze Platform of South China back to at least Cambrian Stage 4.UUID: http://zoobank.org/3e0c3878-6ce2-4eed-87bf-e39647c310c4

A moderately diverse assemblage of micromorphic linguliform brachiopods, including Tapuritreta gribovensis sp. nov., Wahwahlingula? pankovensis sp. nov., Acrothele sp., Anabolotreta? sp., Orbithele? sp. and Stilpnotreta sp., is for the first time described from the Cambrian Karpinsk Formation (Miaolingian, Guzhangian) of the South Island of Novaya Zemlya. The morphology of the metamorphic shell in Acrothele and Wahwahlingula? suggest that both taxa had a single pair of larval setal sacs, similar to the recent discinids, but their metamorphosis was completed only at the end of the pelagic stage and shows that they did have direct development, which is characteristic of all recent lingulides. The biogeographical signature of the new Cambrian brachiopod fauna from Novaya Zemlya is discussed, and the new fauna gives new information on the poorly known Cambrian margins of the Baltica palaeocontinent.

The origin of Cambrian brachiopods and their phylogenetic relationship with other lophotrochozoans is far from clear. Lingulellotretidae, the oldest family of lingulate brachiopods, is typified by ...

Brachiopods from Cambrian Series 2, Stage 4 carbonate strata of the Byrd Group in the Central Transantarctic Mountains, East Antarctica, are described for the first time. These include six lingulate, one paterinate, and one rhynchonelliform taxa, including the new lingulate brachiopod Plicarmus wildi gen. et sp. nov. The biostratigraphy correlates closely to the brachiopods recently reported from the Xinji Formation (Shuiyu section) in North China, as well as brachiopods recovered from the Dailyatia odyssei Zone across the Arrowie Basin of South Australia. These findings also support the previously identified close palaeobiogeography of these regions. The first unambiguous example of the acrotretid brachiopod Eohadrotreta zhenbaensis Li and Holmer outside South China is also identified in the context of its ontogenetic stages. Well preserved specimens of the acrotheloid Schizopholis yorkensis (Holmer and Ushatinskaya in Gravestock et al.) facilitates a new reconstruction of its musculature and visceral region. This data is synthesised into a new cladistic analysis that resolves Acrotheloidea as a well-supported monophyletic clade and supports previous hypotheses of a morphocline in acrotheloid evolution.

The shells of linguloid brachiopods such as Lingula and Discinisca are inorganic–organic nanocomposites with a mineral phase of calcium phosphate (Ca-phosphate). Collagen, the main extracellular matrix in Ca-phosphatic vertebrate skeletons, has not previously been clearly resolved at the molecular level in organophosphatic brachiopods. Here, modern and recently-alive linguliform brachiopod shells of Lingula and Discinisca have been studied by microRaman spectroscopy, Fourier transform infrared spectroscopy, field emission gun scanning electron microscopy, and thermal gravimetric analysis. For the first time, biomineralized collagen matrix and Ca-phosphate components were simultaneously identified, showing that the collagen matrix is an important moiety in organophosphatic brachiopod shells, in addition to prevalent chitin. Stabilized nanosized apatitic biominerals (up to ∼50 nm) permeate the framework of organic fibrils. There is a ∼2.5-fold higher wt% of carbonate (CO32−) in Lingula versus Discinisca shells. Both microRaman spectroscopy and infrared spectra show transient amorphous Ca-phosphate and octacalcium phosphate components. For the first time, trivalent moieties at ∼1660 cm−1 and divalent moieties at ∼1690 cm−1 in the amide I spectral region were identified. These are related to collagen cross-links that are abundant in mineralized tissues, and could be important features in the biostructural and mechanical properties of Ca-phosphate shell biominerals. This work provides a critical new understanding of organophosphatic brachiopod shells, which are some of the earliest examples of biomineralization in still-living animals that appeared in the Cambrian radiation.

The Ediacaran–Cambrian transition, one of the major turning points in Earth’s history, is characterized by an epoch-making change in biosphere. In South China, the late Ediacaran Dengying Formation (ca. 551–538 Ma) is an important stratigraphic unit yielding trace fossils, tubular skeletal fossils and some complex forms that represent possible bilateral animals. The fossil-bearing Ediacaran strata of eastern Yunnan is hitherto known from the Jiucheng Member containing the Jiangchuan Biota, together with the enigmatic cosmopolitan taxon Shaanxilithes. Here, we present for the first time cavity-dwelling filamentous microorganisms accommodated within a valve-like fossil from the upper Baiyanshao Member of the Dengying Formation at the Sujiawa Section in Huize County, eastern Yunnan of China. SEM scanning and Micro-CT reconstruction indicate that the well-preserved filaments were characterized by mycelial network structures with abundant branching pattern. Preservation of filamentous microorganisms might result from the decay process of soft parts that were originally accommodated and enclosed within the valve-like organism, and subsequently preserved by early diagenetic phosphatization, which obscures their original organic identity and chemical composition. This paper potentially presents the first fossil evidence of a saprophytic relationship between microorganisms as decomposers and a valve-like organism prior to the eve of the Cambrian Explosion of metazoan animals.

A moderately diverse assemblage of brachiopods from the Latham Shale Lagerstätte (Cambrian Series 2, upper Stage 4) and the upper Cadiz Formation (Miaolingian, Wuliuan), California is described in detail for the first time. The fauna includes both linguliform and rhynchonelliform brachiopods—Hadrotreta primaea(Walcott, 1902),Paterina prospectensis(Walcott, 1884),Dictyonina pannula(White, 1874), andMickwitzia occidensWalcott, 1908; andNisusia fulleriMount, 1981 andWimanella highlandensis(Walcott, 1886), respectively—together with olenellid trilobites and hyolithids. The fauna differs from other Cambrian Konservat-Lagerstätten (notably Cambrian Series 2 Chengjiang and Guanshan Lagerstätten, eastern Yunnan) in that the brachiopod shell valves in many cases are still preserved with their original mineralization. Moreover, the excellently preserved shale-hosted valves even include cases with exquisite epithelial cell molds, otherwise only seen in acid-etched material from carbonate rocks. The pitted ornamentation inD. pannulaclosely resembles that described from Ordovician linguliforms. The unusual preservation ofN. fulleriprovides important clues for ancestral composition of the brachiopod shell. The two articulated rhynchonelliform species probably represent the oldest records of this group from the west Laurentia. The fauna could also represent the earliest onset of the transition from the Cambrian Evolutionary Fauna (CEF) to the Paleozoic Evolutionary Fauna (PEF).

A comprehensive review and phylogenetic analysis of genera and species presently assigned to the rhynchonelliform superfamily Nisusioidea and family Nisusiidae suggests that this short‐lived but important group of brachiopods first appeared in peri‐Gondwana during the second half of the Cambrian Series 2, before going extinct by the end of Drumian times. Nisusiides achieved their maximum morphological disparity and geographical distribution during the Wuliuan Age, and Laurentia was probably the major centre of their dispersal. A new phylogenetic analysis suggests an early separation of the lineages of spinose and non‐spinose nisusiids. The non‐spinose nisusiids probably evolved in Laurentia by the end of Cambrian Series 4. The new nisusiid genus Bellistrophia is described. The new species Nisusia multicostata represents the first documented rhynchonelliform (kutorginide) brachiopod from the Miaolingian (Drumian) of the Alborz Mountains, Iran., LH's work is supported by the Zhongjian Yang Scholarship from the Department of Geology, Northwest University, Xi'an. Mohammad‐Reza Kebria‐ee Zadeh thanks the Payam‐Noor University for support via a research fellowship. LEP acknowledges support from the National Museum of Wales and the Payam‐Noor University for work in Iran. MGP thanks the Uppsala University for logistical support and Golestan University for her visit on sabbatical to Sweden. ZZ sincerely acknowledges the National Natural Science Foundation of China (41425008, 41621003, 41720104002 and 41890844) and the 111 Centre (D17013) for the continuous financial support for the palaeobiology group in Xi'an.

Recent excavations of the Guanshan biota at the Shijiangjun section in the eastern Yunnan Province, South China, have revealed many well-defined faecal pellets and related trace fossils. These can be assigned to three morphotypes, which have affinities with the ichnogenera Tomaculum, Alcyonidiopsis and Tubulichnium. Morphotype 1 is an unbranched burrow filled with randomly distributed faecal pellets. Morphotype 2 is a string-shaped burrow without branching, containing intensely compacted faecal pellets. Morphotype 3 comprises unbranched burrows with a fill of faecal pellets and a central cavity. The ellipsoidal faecal pellets in morphotype 1 and 2 can be assigned to Coprulus oblongus. They are morphologically similar to the excrements produced by modern deposit-feeding polychaetes, as well as the gut content of early Cambrian polychaete worms (Guanshanchaeta felicia) from the Guanshan biota and priapulid worms (Selkirkia) from the Xiaoshiba Lagerstatte. This analogy suggests polychaetes and priapulid worms as potential producers of these burrows and that a diverse range of digestive methods had already been established in the Cambrian Stage 4 ca. 510 Ma ago. Morphotype 3 is interpreted to be related to the storage of faecal pellets and possibly for cultivation of bacteria, which would represent an early case of this behaviour. The discovery of this diverse suite of burrows with faecal pellets indicates that the origin of diverse deposit-feeding strategies in worms can be traced back to at least the Cambrian Stage 4.

Acrotretides are extinct micromorphic brachiopods that exhibited considerable morphological variation during their rapid evolution in the early Palaeozoic. The plano-conical shells of acrotretides are distinct in comparison to other brachiopod groups and despite their diversity and abundance in early Palaeozoic communities, their origins, early evolution, life history and phylogeny are poorly understood. Here, we employ advanced geometric morphometrics to quantitatively investigate ontogenetic variation and allometry in the ventral valve of the oldest known acrotretide species from the early Cambrian of South China. Our results identify substantial shape variation for Eohadrotreta zhenbaensis, along with a parabolic morphological trajectory through ontogeny, demonstrating a remarkable reversal to PC1 values equivalent to those obtained for juveniles, during later ontogenetic stages. The evolutionary novel body plan (diminutive and plano-conical) of Acrotretida was established gradually during two phases of allometry, formed initially during the final stage of the Cambrian evolutionary radiation from an ancestral low, equivalved lingulide body plan. The development of a conical shaped valve seems to have resulted in an overall smaller body size, when compared with non-conical forms. The heterochronic processes responsible for generating these ontogenetic modifications at different allometric phases may have facilitated the evolutionary diversification of acrotretide brachiopods during the early Palaeozoic.

Cambrian Series 2 shelly fossils from thick carbonate successions in East Antarctica have received limited systematic treatment through the 20th century. Described here are the East Antarctic camenellan tommotiids from the Shackleton Limestone in the Central Transantarctic Mountains and the Schneider Hills limestone in the Argentina Range. This material comes from both newly sampled collections and incompletely described material from older collections. The assemblage supports correlation to the Dailyatia odyssei Zone and Pararaia janeae Trilobite Zone of South Australia, with the newly examined specimens of Dailyatia decobruta from the Shackleton Limestone providing direct correlation to the Mernmerna Formation of the Ikara-Flinders Ranges and White Point Conglomerate of Kangaroo Island. These East Antarctic assemblages include five species referred to Dailyatia, in addition to an undetermined kennardiid species and fragments of the problematic Shetlandia multiplicata. The results further corroborate the notion that fossiliferous carbonate clasts found on King George Island were sourced from the same carbonate shelf as the Shackleton Limestone, with the taxon S. multiplicata found in both units. The Schneider Hills limestone in the Argentina Range has yielded sclerites of Dailyatia icari sp. nov., currently only known from this location. New taxa described in the preprint manuscript are not considered valid until final publication of reviewed article, according to the rules of the ICZNTitle in thesis list of papers: New and previously undescribed camenellan tommotiids From The Cambrian Series 2, Stages 3-4, East Antarctica: Biostratigraphy, palaeobiogeography, and systematics

Phosphate-shelled brachiopods differ in filter-feeding lifestyle, with Lingula anatina an active infaunal burrower, and Discinisca tenuis a shallow marine epibenthic animal. The shells of these biomineralized organisms are built of organophosphatic constituents, the organic fibres/sheets reinforced with calcium phosphate (Ca-phosphate) to provide a sophisticated ultrastructural robustness. This investigation studied the nature of organic fibres in order to improve our understanding of how design principles are relevant to biominerals. Unlike the powdered samples that were commonly used in previous studies, for the first time organic fibres were isolated and the shell fractions were purified, in order to study the content and nature of the biopolymer fibres. Ultrastructural analysis, thermal gravimetric analysis and spectroscopic analyses reveal that the core polysaccharide framework is composed of layers of β-chitin sheets that are coated with a fibrous protein matrix. The chitin matrix in Lingula shells, 26.6 wt.%, is about two-fold higher wt.% compared to Discinisca shells,12.9 wt.%. After thermal gravimetric analysis, skeletal imaging of these shells shows important differences. Discinisca contains just a single layer that is ~21.0 µm thick. In contrast, Lingula exhibits two separate layers: the thicknesses of the primary- and secondary-layers are ~20.3 µm and ~8.1 µm, respectively. Taken together, the data shows that the chitin matrix contributes to increased skeletal strength, making Lingula highly adapted for life as an active burrower. In comparison, Discinisca contains less chitin and lives as attached epibenthos in a shallow marine environment.

Abundant and diverse small shelly fossils have been reported from Cambrian Series 2 in North China, but the co-occurring brachiopods are still poorly known. Herein, we describe seven genera, five species and two undetermined species of organophosphatic brachiopods including one new genus and new species from the lower Cambrian Xinji Formation at Shuiyu section, located on the southern margin of North China Platform. The brachiopod assemblage comprises one mickwitziid (stem group brachiopoda), Paramickwitzia boreussinaensis n. gen. n. sp., a paterinide, Askepasma toddense Laurie, 1986 , an acrotretoid, Eohadrotreta cf. zhenbaensis Li and Holmer, 2004 , a botsfordiid, Schizopholis yorkensis (Holmer and Ushatinskaya in Gravestock et al., 2001 ) and three linguloids, Spinobolus sp., Eodicellomus cf. elkaniiformis Holmer and Ushatinskaya in Gravestock et al., 2001 and Eoobolus sp. This brachiopod assemblage suggests a late Age 3 to early Age 4 for the Xinji Formation and reveals a remarkably strong connection with coeval faunas from East Gondwana, particularly the Hawker Group in South Australia. The high degree of similarity (even at species level) further supports a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian as indicated by small shelly fossil data.

Micromorphic acrotretide brachiopods first appeared during Cambrian Epoch 2 and subsequently experienced a rapid diversification. However, our knowledge of acrotretide origins and early evolution is hampered by our poor understanding of their earliest representatives. Here, we describe one of the oldest known acrotretides from the Cambrian Series 2 Shuijingtuo Formation of southern Shaanxi and western Hubei, South China. The new genusPalaeotretagen. nov. can be distinguished from all other genera, mainly by its unusual ontogeny and morphology; inPalaeotretathe pedicle foramen is located mostly outside of the metamorphic shell, the ventral intertrough is very short and the inclination of the ventral pseudointerarea changes from catacline to apsacline. Two ontogenetic stages (T1-T2) of post-metamorphic shell growth can be distinguished in the low cap-likePalaeotreta shannanensisgen. et sp. nov.; this type of development with a relatively long pedicle foramen forming stage (T1), a simple pedicle opening, weakly developed ventral apical process and dorsal median septum, can be considered to represent a plesiomorphy for the acrotretides. By contrast, the more derivedPalaeotreta zhujiahensis(Li & Holmer, 2004) is characterized by paedomorphosis, expressed in an early enclosure of pedicle foramen and greatly decreased growth of the ventral intertrough during the intertrough-increasing stage (T3), producing a cap-like shape and retaining catacline inclination of the ventral pseudointerarea. Thus, heterochrony may have played an important role in the morphological divergence of acrotretides during the Cambrian evolutionary radiation, and promoted the subsequent radiation of acrotretides. The ontogenetic study ofPalaeotretagen. nov. also supports the notion that the ventral intertrough of acrotretide brachiopods may have formed by the 'rolling up' of the lingulide propareas.

First report of brachiopods with soft parts from the Lower Cambrian Latham Shale (Series 2, Stage 4), California

The origin of the Brachiopoda has long been a hotly debated topic, and various models have been proposed following the latest finds of exceptionally preserved material. The lower Cambrian (Stage 3) Heliomedusa orienta from the Chengjiang Konservat-LagerstÀtte, eastern Yunnan of South China, is an important example of exceptional preservation. A wide variety of affinities have been proposed for Heliomedusa, but recently it has been suggested to reside within the mickwitziids, which may form a stem group to the Brachiopoda. Detailed studies of exceptionally preserved Heliomedusa have increased our knowledge of the soft-part anatomy of this important early brachiopod, but unfortunately, almost nothing is known about its shell structure. Here, we describe new exceptionally preserved specimens from the Chengjiang biota to better reveal both shell structure and ornamentation. Its reticulate–pustulose ornament and tubular structure are reminiscent of traits seen in other mickwitziid brachiopods. In addition, two types of setae can be observed. Apart from the pyritized marginal mantle setae, some tubules are filled with iron oxides, potentially representing thinner and shorter penetrative setae. Both valves of H. orienta appear to have been less mineralized as compared to Mickwitzia monilifera, and the two species differ in diameter and density of tubules and pustules, and in terms of slightly less projected profile of ventral valve with lower umbo posteromedially placed. Although Heliomedusa clearly is closely related to Mickwitzia, their different preservational modes (compacted poorly mineralized/noncompacted mineralized) make detailed comparison difficult; they are provisionally kept as separate genera pending further studies of better-preserved Chinese material.

New records of the poorly known acrotretid (Biernatidae) microbrachiopod Opsiconidion minor Popov are described from middle Emsian strata of the Ogilvie Formation in east-central Alaska and the adjacent Yukon Territory, Canada, and compared with new better-preserved topotypes from the late Early Devonian (Emsian) of Novaya Zemlya, Russia. In Alaska O. minor occurs together with fragmentary material of Lingulipora sp. and an indeterminate discinid. The only other previous record of O. minor, outside the type area, comes from the Early to ?Middle Devonian (Pragian to ?Givetian) of Australia (Victoria and NSW). Opsiconidion Ludvigsen is a stratigraphically extremely long-ranging and cosmopolitan acrotretid, which exhibits a remarkable conservatism; the morphology of the ventral valve remains essentially unchanged from the earliest Ordovician (Darriwilian) records to the Devonian.

Exceptionally preserved, silicified and articulated complete shells of the rhynchonelliform kutorginate brachiopod Nisusia sulcata are redescribed from the middle Cambrian (Series 3) Marjum Limesto ...

Laser micropyrolysis gas chromatography-mass spectrometry enables researchers to selectively obtain chemical information about the organic matter in specific parts of a variety of specimens, such as coals and fossils, in order to elucidate chemical composition. This paper briefly reviews the history of this type of pyrolysis and examines whether the technique can be used to isolate and recover biogeochemical signatures directly from the mineralised organophosphatic sclerites of Cambrian tommotiids—a group of enigmatic lophotrochozoans—and potentially related organophosphatic brachiopods. We analysed specimens of two tommotiids (Micrina etheridgei and Dailyatia sp.) and the paterinate brachiopod Askepasma toddense from the lower Cambrian of South Australia. Pyrolysate hydrocarbons from the sclerites of these species were detected and compared. Results indicate that A. toddense is more chemically complex than either of the two tommotiid taxa, but that M. etheridgei is compositionally more similar to A. toddense. Importantly, this study has demonstrated that laser micropyrolysis gas chromatography-mass spectrometry of Cambrian organophosphatic small shelly fossils yields detectable pyrolysates that have geochemical significance. It will be analytically possible and useful in the future to apply this technique to a larger sample set to elucidate deep time biogeochemical homologies, and to test intra-shell heterogeneity.

The earliest growth of post-metamorphic (post-larval) shells in two species of Eohadrotreta is described from the Cambrian Shuijingtuo Formation of South China. Two different growth patterns can be observed by quantifying developmental variations in size and shape of successive stages of post-metamorphic shell growth (including the pedicle foramen forming stage, pedicle foramen enclosing stage and intertrough increasing stage) of Eohadrotreta zhenbaensis and Eohadrotreta? zhujiahensis. The pedicle foramen is never enclosed within the metamorphic shell of E. zhenbaensis, while the enclosed pedicle foramen of E.? zhujiahensis is located directly outside the metamorphic shell after the pedicle foramen enclosing stage. A strongly allometric growth pattern of E. zhenbaensis is demonstrated by the early enclosure of the pedicle foramen; an accelerated lengthening of the ventral intertrough is associated with the development of a more complex dorsal median septum during the intertrough increasing stage. By contrast, E.? zhujiahensis demonstrates possible paedomorphic development by delayed enclosure of pedicle foramen and an associated decreased lengthening of ventral intertrough during the intertrough increasing stage. This ontogenetic developmental sequence represents the marginal accretionary formation and growth of the pedicle foramen, which resembles that of linguloid brachiopods. Furthermore, the developmental process of the pedicle foramen of Eohadrotreta seems to recapitulate the likely evolutionary transition from the Botsfordiidae, with open delthyrium, to the Acrotheloidea, with an enclosed foramen. This study provides a unique opportunity to obtain a complete understanding of the ontogenetic development of the earliest acrotretoids, and casts new light on the phylogeny of lingulate brachiopods.

The kutorginates are commonly the most abundant rhynchonelliform brachiopod found in the early Cambrian; they are also some of the oldest known rhynchonelliforms, first appearing in the Unnamed Series 2 (Atdabanian equivalent) and becoming extinct sometime in Cambrian Series 3 (Amgaian equivalent). Moreover, kutorginates are the first known member of the rhynchonelliforms for which we have a detailed knowledge of their soft-part anatomy, including the lophophore, digestive tract, and pedicle—all exceptionally preserved inKutorgina chengjiangensisZhang et al., 2007 from the early Cambrian Chengjiang Lagerstätte of southern China. The stout and annulated pedicle in the original report was described as protruding between the valves; however, newly collected better-preserved material now clearly shows that the pedicle actually protrudes from the apical perforation ofKutorgina chengjiangensis.This type of apical pedicle has also been described from other early Cambrian rhynchonelliforms, including the problematic chileateLongtancunella chengjiangensis(Zhang et al., 2011a). Exceptionally preserved similar pedicles are also known to emerge apically from the Silurian chileate dictyonellidEichwaldia subtrigonalisBillings, 1858, as well as from the recently described Silurian chileateTrifissura rigidaHolmer, Popov, and Bassett, 2014. However, it is clear that the only other exceptionally preserved kutorginate—a silicifiedNisusia—was provided with an adult pedicle emerging between the valves from a posterior gap; thus,Nisusiahas two pedicle openings. However, the apical foramen may represent the earliest attachment of the larvae, which subsequently became nonfunctional through ontogeny. It is suggested that both types of attachment strategies may have appeared early in the stem lineage of the Rhynchonelliformea.

Karlsorusn. gen. is proposed in this study as a large, smooth-shelled pentameride brachiopod of the family Pentameridae, based onPentamerus gothlandicusLebedev, 1892, from the Wenlock (Silurian) Slite beds of Gotland, Sweden. This species is transferred fromPentamerusto the new genus because of the combination of aPentamerus-like shell shape and the development of a brachiophorium through fusion of the outer hinge plates in the middle portion, like a dorso-ventrally inversed cruralium. The first appearance of brachiophorium in pentamerids is in the late Wenlock, known also inBrooksina,Pentamerifera, and other related pentamerid genera, marking a significant stage in morphological transformation of dorsal internal structures, as part of the Silurian pentameride diversification in both level-bottom and reefal depositional environments.

A characteristic coarsely pitted ornamentation (with pits larger than 0.015 mm across) can be found on some very enigmatic and rare Lower Ordovician phosphatic-shelled linguliform brachiopods, including the paterinid Lacunites balaschovae Gorjansky and the obolid Foveola maarduensis Gorjansky. Both of these species are poorly understood and known from only a few specimens from the Floian of the East Baltic. Here we describe the Ordovician species Lacunites ivantsovi sp. nov. from the lower Darriwilian of the St Petersburg region and Foveola ivari sp. nov. from the Sandbian of Estonia, representing the last known survivors of these genera in the area. The new Darriwilian species of Lacunites is also one of the last members of the Class Paterinata, which most importantly includes some of the earliest known brachiopods from the early Cambrian. The coarsely pitted ornamentation of Foveola ivari is associated with the formation of asymmetrical so-called terrace lines in the umbonal area. The latter may indicate a burrowing life style. The pits in Lacunites and Foveola are directly comparable to the more or less identical coarse pits in the discinoid Trematis. Unlike the microscopic pits found in many fossil linguliforms, it is most likely that the coarse pits were empty in life; the minute surface ornamentation of irregular wrinkles in the outer primary layer continues across the bottom of the depressions in Foveola and Trematis; in the latter the cementing attachment discs of an attached phosphatic tubular Byronia-like organism also extend down into the pits.

The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40 °C. In the mid-latitude Baltoscandian Basin, conodonts displaying low δ O values, which suggest high temperatures (>40 °C) in the water column, are in contrast with the discovery of contemporaneous glendonite clusters, a pseudomorph of ikaite (CaCO ·6H O) traditionally considered as indicator of near-freezing bottom-water conditions. The massive precipitation of this temperature sensitive mineral is associated with transgressive conditions and high organic productivity. As a result, the lower Tremadocian sediments of Baltoscandia apparently contain both “greenhouse” pelagic signals and near-freezing substrate indicators. This paradox points to other primary controlling mechanisms for ikaite precipitation in kerogenous substrates, such as carbonate alkalinity, pH and Mg/Ca ratios, as recently constrained by laboratory experiments. Preservation of “hot” conodonts embedded in kerogenous shales rich in δ O-depleted glendonites suggests both the onset of sharp thermal stratification patterns in a semi-closed basin and the assumed influence of isotopically depleted freshwater yielded by fluvial systems.

An assemblage of Cambrian Series 2, Stages 3–4, conchiferan mollusks from the Shackleton Limestone, Transantarctic Mountains, East Antarctica, is formally described and illustrated. The fauna includes one bivalve, one macromollusk, and 10 micromollusks, including the first description of the speciesXinjispira simplexZhou and Xiao, 1984 outside North China. The new fauna shows some similarity to previously described micromollusks from lower Cambrian glacial erratics from the Antarctic Peninsula. The fauna, mainly composed of steinkerns, is relatively low diversity, but the presence of diagnostic taxa, including helcionelloidDavidonia rostrata(Zhou and Xiao, 1984), bivalvePojetaia runnegariJell, 1980, cambroclavidCambroclavus absonusConway Morris in Bengtson et al., 1990, and bradoriidSpinospitella coronataSkovsted et al., 2006, as well as the botsfordiid brachiopodSchizopholis yorkensis(Ushatinskaya and Holmer in Gravestock et al., 2001), in the overlying Holyoake Formation correlates the succession to theDailyatia odysseiZone (Cambrian Stages 3–4) in South Australia.

The Yangtze platform of South China offers evidence within its Ediacaran–Cambrian geological record of the Cambrian explosion and diversification events in metazoan history. To understand the explosive radiation of animals and the environments in which it took place, the basal Cambrian fauna succession of the Aijiahe section in the Three Gorges area, western Hubei Province, has been studied, revealing the earliest brachiopod fauna (Tsunyidiscus trilobite Zone) in this region, which was dominated numerically by acrotretoids. This is accompanied by abundant skeletal fossils including minute well-preserved phosphatized archaeocyath cups and an assortment of abundant sponge spicules, chancelloriids, mollusks, hyoliths, and bradoriids, retrieved by acid-etching limestone interbeds in the black shale-dominated Shuijingtuo Formation (Series 2). The brachiopods comprise two species of acrotretoids, two types of botsfordiids (Botsfordiidae gen. et sp. indet. A and B), and four species of linguloids. Of the latter, Spinobolus popovi n. gen. n. sp. is strikingly distinctive and typified by spine-like ornamentation seen for the first time in the lower Cambrian; the remaining three linguloid genera, Palaeobolus, Eoobolus, and Lingulellotreta, have a trans-paleocontinental distribution. The Three Gorges Shuijingtuo brachiopod assemblage differs from that of the upper Atdabanian Stage (Cambrian Stage 3) in Siberia and South China, but shows great similarities with those discovered in the Tsanglangpuan (equivalent to Botoman or Stage 4) Stage of eastern Yunnan Province, Siberia, and South Australia, suggesting a much more prolonged sedimentary hiatus in basalmost Shuijingtuo Formation of the Three Gorges area than previously expected. The presence of such unconformities provides a caveat to stable isotope-based correlations that involve a number of discussions of global ocean geochemical changes across the time interval that witnessed Cambrian explosion of metazoans.

The Early Triassic (late Induan to early Olenekian) Lingula borealis Bittner, from the Russkii Island on the Pacific cost of south-eastern Russia is revised, based on re-examination of the type material. Although this species, like most described Triassic lingulids, has remained very poorly understood due to the lack of information on important characters, such as musculature and mantle canals, it has been commonly recorded in subsequent studies and included in attempts at understanding the patterns of extinction and recovery at around the Permian–Triassic boundary. Linguliform brachiopods are some of the notable survivors of this significant mass extinction event. Lingula borealis has previously been referred to Lingularia and provisionally synonymised with Lingularia similis Biernat & Emig. Here, it is shown that it differs from Lingularia similis mainly in characters of mantle canals, musculature and most importantly in details of the pedicle nerve impression. In Lingularia borealis, the impres...