Rhynchonelliform Brachiopods Research Articles

Morphological variation in first-formed shells of the Ordovician Paucicrura–Diceromyonia brachiopod lineage of North America

Abstract First-formed shells of several species of Dalmanellidae (Brachiopoda) from the Ordovician (Katian) of North America were measured and compared: Cincinnetina multisecta, Diceromyonia tersa, Diceromyonia storeya, Paucicrura corpulenta, Paucicrura rogata, and Paucicrura sillimani. Sizes and structures of the first-formed shells suggest that members of this family had planktotrophic subadults, with some species showing indications of only an unshelled larval stage and others showing both a larval stage and a shelled juvenile stage. This differs from modern rhynchonelliformean brachiopods, which all possess only a lecithotrophic larval stage. The range of sizes of first-formed shells of most studied species are similar, but P. sillimani of Baffin Island, Canada (middle Katian), has a significantly larger first-formed shell that formed during an extended juvenile stage. This may have enabled the species to colonize newly exploitable habitats during an interval of rapid sea level rise in Laurentia during the Katian. This plasticity of developmental modes in the Dalmanellidae shows not only that using distantly related modern brachiopods as an analog for extinct Paleozoic lineages may be misleading, but also that development can vary within a single lineage and that timing of developmental stages should not be considered a reliable character for use in phylogenetic studies of brachiopods.

The demise of large tropical brachiopods and the Mesozoic marine revolution.

Changes in predator-prey interactions are often implicated as drivers of major evolutionary change. A prominent example is the dramatic changes in shallow marine assemblages during the Mesozoic Marine Revolution (MMR) when major clades, including rhynchonelliform brachiopods, became restricted and less diverse. Currently, shallow-water temperate and polar brachiopods can be large, but in the tropics, they are small. By contrast, we demonstrate that throughout the Jurassic large brachiopods occurred in shallow sites, from polar to tropical latitudes, but are absent in later periods from tropical areas. These changes occurred in parallel in both major orders (Rhynchonellida and Terebratulida) and also independently within the two sub-ordinal lineages within the Terebratulida (terebratulinids and terebratellinids). Increases in both grazing and predation pressures associated with the MMR might account for this pattern. However, we note that many current environments support both large brachiopods and high densities of grazing species and suggest that the pattern fits more closely to the intensification of durophagous predation in shallow tropical waters.

Population dynamics of shoreface to upper offshore occupation of the lower Ordovician brachiopod Tarfaya purmamarcaensis (Benedetto)

Occupation of shallow environments by rhynchonelliform brachiopods is rare during the early late Tremadocian (Tr2). However, in the NW Argentina basin the plectorthoidean Tarfaya purmamarcaensis occupied high-energy environments during this time interval. This species forms up to 15 cm thick monospecific concentrations in shoreface and offshore transition settings, and polytypic pavements in relatively deeper water offshore environments. Generation of such concentrations could be linked to the population dynamics of T. purmamarcaensis. A geometric morphometrics analysis allowed us to recognize four growth stages in the ontogeny of the species. The juvenile phases are absent in high-energy proximal environments and are scarce in the shoreface; in contrast, no representatives of the fourth phase (hypermature adults) have been found in the open platform deposits, and adults are almost absent. Although shell concentrations are usually linked to physical processes (i.e., storm events), the low taphonomic alteration of the shells suggests that transport was not a highly influential factor. Morphological differences (i.e., development of cardinal canals, ribs incurved posterolaterally) in specimens from different environments suggest that the population dynamics could have been the main cause in generating different concentrations. According to the source-sink model, high productivity of brachiopods in the shoreface environment and a passive transport of larvae to the offshore might explain not only the thicker shallow-water concentrations but also the differences in shell growth of populations inhabiting these environments.

Revision of the Llandovery (lower Silurian) trimerellide brachiopod Yidurella in South China

Although a minor group of brachiopods in the Ordovician and Silurian, the trimerellides include some of the largest known brachiopods in the Early Paleozoic. Yidurella Zeng, a monospecific genus of moderate size from the Shamao Formation of Tizikou, Yidu City, Hubei Province, was originally described as having a solid platform. However, new material collected from the type locality (Tizikou Section), the Kapeng Reservoir Section in Hunan Province, and from the Yangjiawanzi and Hongyan sections in Yunnan Province reveal that its platform is vaulted. A new, emended diagnosis is therefore proposed for Yidurella. All specimens of Yidurella studied were collected from a single thin layer in Telychian rocks between the Lower Red Beds and the Upper Red Beds, suggesting its potential for biostratigraphic correlation. Associated rhynchonelliform brachiopods and corals in each section, together with a population analysis of Yidurella yiduensis Zeng from the Kapeng Reservoir Section, indicate that this trimerellide inhabited in inner to outer shelf environments (Benthic Assemblages (BA) 2 to 3) in warm water. The genus is also tentatively recognized in contemporaneous rocks from Severnaya Zemlya in Russia.

Brachiopod and mollusc biomineralisation is a conserved process that was lost in the phoronid–bryozoan stem lineage

BackgroundBrachiopods and molluscs are lophotrochozoans with hard external shells which are often believed to have evolved convergently. While palaeontological data indicate that both groups are descended from biomineralising Cambrian ancestors, the closest relatives of brachiopods, phoronids and bryozoans, are mineralised to a much lower extent and are comparatively poorly represented in the Palaeozoic fossil record. Although brachiopod and mollusc shells are structurally analogous, genomic and proteomic evidence indicates that their formation involves a complement of conserved, orthologous genes. Here, we study a set of genes comprised of 3 homeodomain transcription factors, one signalling molecule and 6 structural proteins which are implicated in mollusc and brachiopod shell formation, search for their orthologs in transcriptomes or genomes of brachiopods, phoronids and bryozoans, and present expression patterns of 8 of the genes in postmetamorphic juveniles of the rhynchonelliform brachiopod T. transversa.ResultsTranscriptome and genome searches for the 10 target genes in the brachiopods Terebratalia transversa, Lingula anatina, Novocrania anomala, the bryozoans Bugula neritina and Membranipora membranacea, and the phoronids Phoronis australis and Phoronopsis harmeri resulted in the recovery of orthologs of the majority of the genes in all taxa. While the full complement of genes was present in all brachiopods with a single exception in L. anatina, a bloc of four genes could consistently not be retrieved from bryozoans and phoronids. The genes engrailed, distal-less, ferritin, perlucin, sp1 and sp2 were shown to be expressed in the biomineralising mantle margin of T. transversa juveniles.ConclusionsThe gene expression patterns we recovered indicate that while mineralised shells in brachiopods and molluscs are structurally analogous, their formation builds on a homologous process that involves a conserved complement of orthologous genes. Losses of some of the genes related to biomineralisation in bryozoans and phoronids indicate that loss of the capacity to form mineralised structures occurred already in the phoronid–bryozoan stem group and supports the idea that mineralised skeletons evolved secondarily in some of the bryozoan subclades.

Palaeobiogeography of the family Nisusiidae (Cambrian rhynchonelliform brachiopods) using the ‘area‐transition count’ method and systematic revision of Korean species

AbstractNisusiidae is a rhynchonelliform brachiopod family that was widely distributed in low‐latitude regions during the middle Cambrian (Stage 3 of Series 2 to the Drumian Stage of the Miaolingian Series). Cladistic analysis of 24 nisusiid species including two species from South Korea (Nisusia paucicostellata and Nisusiidae gen. et sp. indet.) demonstrates that the nisusiids consist of two sister clades (Clade 1 and 2) whose common ancestor was derived from a paraphyletic ‘basal’ group. Non‐spinose taxa are all included in Clade 1, while spinose Nisusia species are found throughout the three groups including Clade 1, indicating paraphyly of Nisusia. The optimized ancestral area(s) are assigned to internal nodes of the taxon area cladogram using both the Fitch algorithm and the DIVALIKE+J model of BioGeoBEARS, and then the relationship between cladogenetic area transition types and palaeogeographical areas is examined using the ‘area‐transition count’ method. Of 10 possible cladogenetic area transitions, which are combinations of range contraction (C), expansion (E), switch (S) and no range change (N), six (CC, CE, CN, EN, NN and NS) are observed in the two optimization results. It is proposed that the nisusiids originated in Laurentia as a strongly spinose form and dispersed into high‐latitude peri‐Gondwana during Stage 3 and then strongly diversified into other areas during Stage 4, and that non‐spinose forms evolved later, mainly in Laurentia. The nisusiid palaeobiogeographical pattern is interpreted to reflect distributional range changes that were probably caused by palaeo‐oceanic currents with the aid of island arcs as stepping stones, and pumice, produced by volcanic activity, as the means of dispersal.

A new rhynchonelliform brachiopod Longtancunella with soft-part preservation from the Hongjingshao Formation (Cambrian Stage 3) in Yunnan, South China

Rhynchonelliform brachiopods made their first appearance in early Cambrian, and became a major group within the palaeozoic evolutionary fauna since late Cambrian. Exceptionally preserved fossils from the early Cambrian Lagerstätten provide valuable chances to investigate their phylogeny and ecology. Longtancunella is one of the most interesting early rhynchonelliforms, and has been mainly recovered from the Chengjiang Lagerstätte (Series 2, Stage 3). Here, we report a new rhynchonelliform Longtancunella xiazhuangensis n. sp. from the lower Hongjingshao Formation (upper Stage 3) in Yunnan Province, China. These specimens were well preserved with soft parts, including pinnate mantle canal system and a pedicle. It is identified as a new species based mainly on its difference in shell ornamentations, pinnate mantle canals and pedicle morphology from the type species. Its pedicle looks unusually stout with distinct annulated lamellae on the surface, and reveals crucial evidence in illustrating its ecology and settling strategy as an early marine epifauna. The ecological interaction between L. xiazhuangensis and other marine animals also provides insights into the food web structure in the early Cambrian.

Brachiopods from the Latham Shale Lagerstätte (Cambrian Series 2, Stage 4) and Cadiz Formation (Miaolingian, Wuliuan), California

AbstractA 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).

Earth science collections of the Centre Grégoire Fournier (Maredsous) with comments on Middle Devonian–Carboniferous brachiopods and trilobites from southern Belgium

Although the Centre Grégoire Fournier of the Maredsous Abbey is especially famous for the fossils and minerals from the Carboniferous (Viséan) ‘black marble’ of Denée, a marine conservation-Lagerstätte, its palaeontological collections likewise include some types and illustrated specimens of invertebrates (cystoids, goniatites, ostracods, trilobites) and fishes from the Ordovician, Devonian and Carboniferous of Belgium. These specimens are discussed and/or illustrated as is the case of the fragments of two Belgian meteorites (Lesves and Tourinnes-la-Grosse chondrites) that are part of the CGF mineralogical and petrological collections. Moreover, the type material of 30 species and subspecies of Upper Devonian–Pennsylvanian linguliformean and rhynchonelliformean brachiopods (described by de Koninck (1847), J. Fraipont (1888a), Ch. Fraipont (1908), Demanet (1923, 1934), Demanet (in Demanet & Van Straelen, 1938), and Grimm (1998)) and that of two Middle–Upper Devonian species of trilobites (Stainier, 1887; Richter & Richter, 1933), almost all from the Namur–Dinant Basin (southern Belgium), are re-investigated and/or fully figured for the first time in order to facilitate future taxonomic revision. The obscure Tournaisian genus Anomianella de Ryckholt (1851) is rejected from the bivalves and transferred to the brachiopods (Craniida). It is probably related to Petrocrania Raymond, 1911. The lectotype (hereby selected) of Orthis latissima M‘Coy, 1844 and that of Producta corrugata M‘Coy, 1844, both from the Viséan of Ireland, are photographically illustrated (for the first time for the former). The lectotype of Productus murchisonianus de Koninck, 1847 from the Upper Palaeozoic of Tasmania (Australia) is also designated.

Early Cambrian (Stage 4) brachiopods from the Shipai Formation in the Three Gorges area of South China

AbstractDiverse 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,Kutorginasp., andNisusia liantuoensis). This brachiopod assemblage and the first occurrence ofLinnarssonia sapushanensisshell 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 brachiopodNisusiain 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 ofL.sapushanensis. Microstructural studies on micromorphic acrotretoids (likeLinnarssonia) 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.

Silurian (Aeronian) rhynchonelliform brachiopods of Shabdjereh, south-west Central Iran and their significance for early spiriferide evolution

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 endemic rhynchonellide and spiriferide components. A local variety of that association, recently recovered from the Shabdjereh Formation of Kerman Province, East-Central Iran, contains eight brachiopod species, including the rhynchonellide Kermanirhyncha granulata gen. et sp. nov., and the spiriferides Levanispirifer alatus gen. et sp. nov. and Mictospirifer obtusus sp. nov. A new phylogenetic analysis of the earliest Late Ordovician to Aeronian spiriferides, within the general context of the Ordovician radiation of rhynchonelliform brachiopods with calcified brachial supports, reveals the following two major centres of biodiversification and dispersal: (1) the Laurentian palaeocontinent, which is the likely place of origin and initial diversification of the atrypide suborders Lissatrypidina and Anazygidina; and (2) the assemblage of Kazakh island arcs and microplates (known also as Kazakh Archipelago), which was the centre of origin and initial dispersal of the atrypid suborder Atrypidina and the order Spiriferida. South China represents a major refuge, where spiriferides survived the terminal Ordovician extinction and from where they dispersed towards adjacent parts of Gondwana including the Iranian terranes. The latter areas were an important secondary centre of spiriferide biodiversification during the Aeronian Age. http://zoobank.org/urn:lsid:zoobank.org.pub:B8726A08-7D90-4AAF-8ECF-B81E78119712

Victims of ancient hyperthermal events herald the fates of marine clades and traits under global warming.

Organismic groups vary non-randomly in their vulnerability to extinction. However, it is unclear whether the same groups are consistently vulnerable, regardless of the dominant extinction drivers, or whether certain drivers have their own distinctive and predictable victims. Given the challenges presented by anthropogenic global warming, we focus on changes in extinction selectivity trends during ancient hyperthermal events: geologically rapid episodes of global warming. Focusing on the fossil record of the last 300 million years, we identify clades and traits of marine ectotherms that were more prone to extinction under the onset of six hyperthermal events than during other times. Hyperthermals enhanced the vulnerability of marine fauna that host photosymbionts, particularly zooxanthellate corals, the reef environments they provide, and genera with actively burrowing or swimming adult life-stages. The extinction risk of larger sized fauna also increased relative to non-hyperthermal times, while genera with a poorly buffered internal physiology did not become more vulnerable on average during hyperthermals. Hyperthermal-vulnerable clades include rhynchonelliform brachiopods and bony fish, whereas resistant clades include cartilaginous fish, and ostreid and venerid bivalves. These extinction responses in the geological past mirror modern responses of these groups to warming, including range-shift magnitudes, population losses, and experimental performance under climate-related stressors. Accordingly, extinction mechanisms distinctive to rapid global warming may be indicated, including sensitivity to warming-induced seawater deoxygenation. In anticipation of modern warming-driven marine extinctions, the trends illustrated in the fossil record offer an expedient preview.

Early–Middle Ordovician brachiopod diversification in the middle Yangtze region of South China

The evolution of the Early–Middle Ordovician brachiopod diversity in the middle Yangtze region of South China has been analyzed. The brachiopods in this region originated in the early Tremadocian and radiated from the late Floian to the late Dapingian. The composition of rhynchonelliformean brachiopods underwent major changes in the late Floian, and endemic genera migrated from the upper Yangtze region to replace the cosmopolitan genera. A global comparison of the brachiopod diversity curves of South China, Laurentia, and Baltica reveals that (1) the processes and scales of brachiopod radiation in different paleocontinents were distinct; (2) unlike the global evolution of graptolites and chitinozoans, the correlation between brachiopod diversification and regional habitat change was more obvious, and the impact of habitat heterogeneity was reflected not only between plates but also in the interior of the plates, such as the closely connected middle and upper Yangtze regions of South China; and (3) geographical isolation was a key factor in the differential radiation on different paleocontinents.

Early parasitic drilling in a rhynchonelliform brachiopodRongatrypa xichuanensisfrom the Katian (Upper Ordovician) of central China

AbstractAn example of parasitic drilling in a rhynchonelliform brachiopod is described from the Shiyanhe Formation (Katian, Upper Ordovician) of Henan, central China. The boring extends into the shell almost perpendicular to the surface. The shell has been serially sectioned, and the trace (including boring and bioclaustration) has been modeled in three dimensions. Healing of the shell evident in serial sections supports a long-term relationship between the brachiopod and borer that we interpret as parasitic. Platyceratid gastropods, found at the same locality as these brachiopods, are the most likely drilling organism. Previous reports of Paleozoic brachiopod parasitic traces can be classified into two main groups, constructive association and destructive association, depending on whether parasites damage brachiopod shells. The example in this study belongs to the second type as the brachiopod shell has been partly damaged by the borer.

A brachiopod biotope associated with rocky bottoms at the shelf break in the central Mediterranean Sea: Geobiological traits and conservation aspects

Abstract In the Recent, brachiopods only seldom occur in benthic communities. A biotope dominated by Megerlia truncata was identified in 2013 by exploration of the south‐easternmost Adriatic margin by Remotely Operated Vehicle (ROV). Emerging rocky substrates next to the shelf break at approximately 120 m appear intensively exploited by this eurybathic rhynchonelliformean brachiopod, attaining a population of more than 300 individuals per m2. Calcareous red algae are almost ubiquitous at this site and preferentially encrust sectors of the substrate where brachiopods are minimal. This Megerlia biotope is a novel finding for this part of the Mediterranean Sea, similar to a situation previously observed in the Western Basin, off the Mediterranean French coast. It is proposed that this remarkable brachiopod biotope and the adjacent rhodolith bed are considered important for conservation management.

Molecular patterning during the development of Phoronopsis harmeri reveals similarities to rhynchonelliform brachiopods

BackgroundPhoronids, rhynchonelliform and linguliform brachiopods show striking similarities in their embryonic fate maps, in particular in their axis specification and regionalization. However, although brachiopod development has been studied in detail and demonstrated embryonic patterning as a causal factor of the gastrulation mode (protostomy vs deuterostomy), molecular descriptions are still missing in phoronids. To understand whether phoronids display underlying embryonic molecular mechanisms similar to those of brachiopods, here we report the expression patterns of anterior (otx, gsc, six3/6, nk2.1), posterior (cdx, bra) and endomesodermal (foxA, gata4/5/6, twist) markers during the development of the protostomic phoronid Phoronopsis harmeri.ResultsThe transcription factors foxA, gata4/5/6 and cdx show conserved expression in patterning the development and regionalization of the phoronid embryonic gut, with foxA expressed in the presumptive foregut, gata4/5/6 demarcating the midgut and cdx confined to the hindgut. Furthermore, six3/6, usually a well-conserved anterior marker, shows a remarkably dynamic expression, demarcating not only the apical organ and the oral ectoderm, but also clusters of cells of the developing midgut and the anterior mesoderm, similar to what has been reported for brachiopods, bryozoans and some deuterostome Bilateria. Surprisingly, brachyury, a transcription factor often associated with gastrulation movements and mouth and hindgut development, seems not to be involved with these patterning events in phoronids.ConclusionsOur description and comparison of gene expression patterns with other studied Bilateria reveals that the timing of axis determination and cell fate distribution of the phoronid shows highest similarity to that of rhynchonelliform brachiopods, which is likely related to their shared protostomic mode of development. Despite these similarities, the phoronid Ph. harmeri also shows particularities in its development, which hint to divergences in the arrangement of gene regulatory networks responsible for germ layer formation and axis specification.

Macroinvertebrates of the Capivari marine bed, late Paleozoic glacial Itararé Group, northeast Paraná Basin, Brazil: Paleoenvironmental and paleogeographic implications

A 2-m-thick silty shale bed within the Taciba Formation, Itararé Group, Paraná Basin, State of São Paulo, southeastern Brazil, records marine sedimentation in a siliciclastic-dominated, low-energy, shelf setting, during a short-lived deglacial event. The bed is located 100–150 m below the base of the lower Permian, post-glacial Tatui Formation. The marine assemblage is dominated by rhynchonelliform brachiopods, with subordinate bivalves, gastropods and crinoids, recording the highest phylum-level diversity so far identified within a given fossil-bearing horizon in the uppermost portion of the Itararé Group. Two new species are described, one brachiopod Biconvexiella saopauloensis and one gastropod Peruvispira brasilensis. Additionally, shells of Lyonia rochacamposi, Rhynchopora grossopunctata, Quinquenella rionegrensis, Phestia tepuelensis, Streblopteria aff. S. lagunensis, Limipecten capivariensis, Praeundulomya cf. subelongata and Mourlonia (Woolnoughia)? sp. are identified. Crinoid columns were assigned to øPentaridica sp. (a genus based on elements of the columnal). This is the first systematic description of members of the Eurydesma-Lyonia fauna in the northeastern part of the Paraná Basin, Brazil. The overwhelming majority of brachiopods belong to Biconvexiella saopauloensis, followed by Rhynchopora grossopunctata. The record of Lyonia rochacamposi closely resembles that of the uppermost part of the Taciba Formation in southern Brazil. Hence, the Capivari marine fauna correlates approximately with that of the upper part of the Taciba Formation. Lyonia rochacamposi also indicates correlation with Permian units of the Sauce Grande-Colorado (Argentina), Huab (Hardap shale of the Dwyka Group), Aranos area (Namibia), southwest Africa, and the Carnavon (Western Australia) basins. These correlations support a latest Asselian-earliest Sakmarian age for the fauna.

Rhynchonelliform brachiopods and trilobites of the ‘upper dark interval’ in the koněprusy area (Devonian, Eifelian, Kačák Event; the Czech Republic)

Abstract The dark pelbiodetrital limestone beds of the ‘upper dark interval’ in the Koněprusy area, Central Bohemia, the Czech Republic, the assumed manifestation of the Kačák Event in this area, yielded a moderately diverse faunule of rhynchonelliform brachiopods and trilobites. In total, 15 species have been recognized (13 brachiopods and 2 trilobites), but the majority of them are only tentatively determined to generic level due to fragmentation, rarity or poor preservation. Brachiopod genera Leptaenopyxis, Protodouvillina, Douvillinella, Holynetes, Poloniproductus, Iridistrophia, Mystrophora, Pentamerella, Quasidavidsonia, Carinatina, Mimatrypa, Leptathyris, Eoreticularia and a single trilobite Astycoryphe were determined. The mode of preservation indicates transport of skeletal bioclasts from shallower parts of the basin and their fragmentation in debris flows together with fragments of terrestrial plants, crinoid detritus and numerous pelagic fossils, especially the dacryoconarid Nowakia ex gr. otomari. Associated conodonts (as well as trilobites) indicate a late Eifelian age for the fauna (Polygnathus ensensis Zone).

Cambrian rhynchonelliform nisusioid brachiopods: phylogeny and distribution

AbstractA 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.

Hox gene expression in postmetamorphic juveniles of the brachiopod Terebratalia transversa

BackgroundHox genes encode a family of homeodomain containing transcription factors that are clustered together on chromosomes of many Bilateria. Some bilaterian lineages express these genes during embryogenesis in spatial and/or temporal order according to their arrangement in the cluster, a phenomenon referred to as collinearity. Expression of Hox genes is well studied during embryonic and larval development of numerous species; however, relatively few studies focus on the comparison of pre- and postmetamorphic expression of Hox genes in animals with biphasic life cycle. Recently, the expression of Hox genes was described for embryos and larvae of Terebratalia transversa, a rhynchonelliformean brachiopod, which possesses distinct metamorphosis from planktonic larvae to sessile juveniles. During premetamorphic development, T. transversa does not exhibit spatial collinearity and several of its Hox genes are recruited for the morphogenesis of novel structures. In our study, we determined the expression of Hox genes in postmetamorphic juveniles of T. transversa in order to examine metamorphosis-related changes of expression patterns and to test whether Hox genes are expressed in the spatially collinear way in the postmetamorphic juveniles.ResultsHox genes are expressed in a spatially non-collinear manner in juveniles, generally showing similar patterns as ones observed in competent larvae: genes labial and post1 are expressed in chaetae-related structures, sex combs reduced in the shell-forming epithelium, whereas lox5 and lox4 in dorso-posterior epidermis. After metamorphosis, expression of genes proboscipedia, hox3, deformed and antennapedia becomes restricted to, respectively, shell musculature, prospective hinge rudiments and pedicle musculature and epidermis.ConclusionsAll developmental stages of T. transversa, including postmetamorphic juveniles, exhibit a spatial non-collinear Hox genes expression with only minor changes observed between pre- and postmetamorphic stages. Our results are concordant with morphological observation that metamorphosis in rhynchonelliformean brachiopods, despite being rapid, is rather gradual. The most drastic changes in Hox gene expression patterns observed during metamorphosis could be explained by the inversion of the mantle lobe, which relocates some of the more posterior larval structures into the anterior edge of the juveniles. Co-option of Hox genes for the morphogenesis of novel structures is even more pronounced in postmetamorphic brachiopods when compared to larvae.