Recent brachiopods from the southern Brazilian shelf: palaeontological and biogeographical implications

Until recently, the rhynchonelliform (articulated) brachiopod fauna from the Brazilian continental shelf (western South Atlantic) was represented only by the endemic species Bouchardia rosea (Mawe), reported from coastal waters of the states of São Paulo and Rio de Janeiro. The present study, based on samples from coastal (<30 m), shelf, and continental slope waters (99–485 m), documents the South Atlantic brachiopod fauna and shows that this fauna is more widespread, diverse, and cosmopolitan than previously thought. Based on a total of 16,177 specimens, the following brachiopods have been identified: Bouchardia rosea (Family Bouchardiidae), Platidia anomioides (Family Platidiidae), Argyrotheca cf. cuneata (Family Megathyrididae), and Terebratulina sp. (Family Cancellothyrididae). In coastal settings, the fauna is overwhelmingly dominated by Bouchardia rosea . Rare juvenile (<2 mm) specimens of Argyrotheca cf. cuneata were also found at two shallow-water sites. In shelf settings (100–200 m), the fauna is more diverse and includes Bouchardia rosea , Terebratulina sp., Argyrotheca cf. cuneata , and Platidia anomioides . Notably, Bouchardia rosea was found in waters as deep as 485 m, extending the known bathymetric range of this genus. Also, the record of this brachiopod in waters of the state of Paraná is the southernmost known occurrence of this species. The genera Platidia and Terebratulina are documented here for the first time for the western South Atlantic. The Brazilian brachiopod fauna shares similarities with those from the Atlantic and Indian shelves of southern Africa, and from the Antarctic, Caribbean and Mediterranean waters. The present-day brachiopods of the western South Atlantic are much more cosmopolitan than previously thought and their Cenozoic palaeobiogeographic history has to be reconsidered from that perspective.     

Paleoecology of Auloporida: an example from the Devonian of the Holy Cross Mts., Poland

Substrate specificity of Auloporida (Tabulata) from the Ska?y Fm. (Upper Eifelian-Lower Givetian) of the Holy Cross Mts., Poland, has been recognized. Kyrtatrypa sp., a rare species in the formation (under 5%), was the most often encrusted brachiopod (59% of investigated specimens), while the most often occurring brachiopod, Aulacella eifeliensis (de Verneuil) was nearly not encrusted. The majority of encrusted brachiopods were larger than 20 mm, while smaller brachiopods occur abundantly in the Formation. The substrate specificity has been caused mainly by the ornamentation of the host's shell. The position of corallites along the commissure of the brachiopod shell proves that auloporids often encrusted living hosts. The epizoan probably used water currents produced by brachiopod's lophophore impoverishing the host's food composition, their relationship can therefore be described as scramble competition.     

Molecular phylogeny of brachiopods and phoronids based on nuclear-encoded small subunit ribosomal RNA gene sequences

Brachiopod and phoronid phylogeny is inferred from SSU rDNA sequences of 28 articulate and nine inarticulate brachiopods, three phoronids, two ectoprocts and various outgroups, using gene trees reconstructed by weighted parsimony, distance and maximum likelihood methods. Of these sequences, 33 from brachiopods, two from phoronids and one each from an ectoproct and a priapulan are newly determined. The brachiopod sequences belong to 31 different genera and thus survey about 10% of extant genus-level diversity. Sequences determined in different laboratories and those from closely related taxa agree well, but evidence is presented suggesting that one published phoronid sequence (GenBank accession UO12648) is a brachiopod-phoronid chimaera, and this sequence is excluded from the analyses. The chiton, Acanthopleura, is identified as the phenetically proximal outgroup; other selected outgroups were chosen to allow comparison with recent, non-molecular analyses of brachiopod phylogeny. The different outgroups and methods of phylogenetic reconstruction lead to similar results, with differences mainly in the resolution of weakly supported ancient and recent nodes, including the divergence of inarticulate brachiopod sub-phyla, the position of the rhynchonellids in relation to long- and short-looped articulate brachiopod clades and the relationships of some articulate brachiopod genera and species. Attention is drawn to the problem presented by nodes that are strongly supported by non-molecular evidence but receive only low bootstrap resampling support. Overall, the gene trees agree with morphology-based brachiopod taxonomy, but novel relationships are tentatively suggested for thecideidine and megathyrid brachiopods. Articulate brachiopods are found to be monophyletic in all reconstructions, but monophyly of inarticulate brachiopods and the possible inclusion of phoronids in the inarticulate brachiopod clade are less strongly established. Phoronids are clearly excluded from a sister-group relationship with articulate brachiopods, this proposed relationship being due to the rejected, chimaeric sequence (GenBank UO12648). Lineage relative rate tests show no heterogeneity of evolutionary rate among articulate brachiopod sequences, but indicate that inarticulate brachiopod plus phoronid sequences evolve somewhat more slowly. Both brachiopods and phoronids evolve slowly by comparison with other invertebrates. A number of palaeontologically dated times of earliest appearance are used to make upper and lower estimates of the global rate of brachiopod SSU rDNA evolution, and these estimates are used to infer the likely divergence times of other nodes in the gene tree. There is reasonable agreement between most inferred molecular and palaeontological ages. The estimated rates of SSU rDNA sequence evolution suggest that the last common ancestor of brachiopods, chitons and other protostome invertebrates (Lophotrochozoa and Ecdysozoa) lived deep in Precambrian time. Results of this first DNA-based, taxonomically representative analysis of brachiopod phylogeny are in broad agreement with current morphology-based classification and systematics and are largely consistent with the hypothesis that brachiopod shell ontogeny and morphology are a good guide to phylogeny.     

Study of fossil and recent brachiopods,using a skyscan 1172 X-ray microtomograph

Fossil and recent brachiopods were studied with the aid of a Skyscan 1172 microtomograph. The capabilities of this method at different stages of studying, X-ray scanning and producing slices and 3D models are described. The method enables the study of punctuation, microornamentation, and inner structures of the brachiopod shells and soft tissues. The contrast of shell structures of fossil brachiopods is discussed; it depends on differences in the mineral composition of the shell and surrounding matter. This method allows studying the inner structure of the holotypes of brachiopod species without damaging their shells. The data on the efficiency of the method are provided.     

WUCHIAPINGIAN (LOPINGIAN, LATE PERMIAN) BRACHIOPODS FROM THE EPISKOPI FORMATION OF HYDRA ISLAND, GREECE

Abstract:  Twenty-three species of silicified brachiopods are described from four samples in the middle and upper parts of the Episkopi Formation from Hydra Island, Greece. These brachiopods are newly recorded from the region and together with previously described brachiopods from the same localities constitute the most diverse Lopingian (Late Permian) brachiopod fauna reported in southern Europe. The brachiopod fauna is Wuchiapingian as indicated by the associated conodonts. The fauna from Hydra exhibits strong palaeobiogeographical links with the faunas from South China. In addition, palaeobiogeographical affinities with the faunas of Thailand and the northern peri-Gondwanan region are also present, which implies a peri-Gondwanan origin for Hydra. Palaeoecologically, the brachiopod assemblage from sample EP in the middle part of the Episkopi Formation is dominated by pedically-attached and cementing genera and reflects moderate energy conditions above storm wave base and an abundance of hard substrates provided by sponges in the biohermal habitat. By contrast, the brachiopod assemblage in the other three samples from the upper part of the Episkopi Formation is dominated by spinose genera with a free-resting life habit, suggesting soft substrates in a quiet water environment below storm wave base on the outer part of the shelf. New taxa are Petinospiriferina gen. nov., Hustedia episkopiensis sp. nov., Waterhouseiella hydraensis sp. nov. and Xenosaria tenuis sp. nov.     

Substrate specific associations of epebionts on Middle Devonian brachiopods: Implications for paleoecology

A detailed study of over 2500 host brachiopods, from the Middle Devonian Hamilton Group of New York State, revealed distinct patterns of epibiont encrustation, that provide insight into taphonomy and paleoautecology of the host brachiopod shells and depositional environments. The concavo‐convex orthid, Tropidoleptus carinatus (Conrad), as well as strophomenid, and smooth athyrid brachiopods are among the most heavily encrusted. However, terebratulids of nearly identical size and shape are relatively clean of epibionts. This selective distribution strongly suggests that epibionts were discouraged from settling on punctate brachiopods. Brachiopods with small spines and frills were also nearly clean of epibionts, possibly because of entrapment of a mud layer, which made the outer layer of the host inhospitable for larval settling. Concavo‐convex taxa reveal high percent coverage and diversity of epibionts on the convex valve, which probably rested on the substrate during the life of brachiopod. This pattern is observed even on brachiopods that were buried with the convex valve downward. This implies complex post‐mortem histories involving multiple episodes of reorientation and colonization.     

Thick brachiopod shell concentrations from prodelta and siliciclastic ramp in a Tortonian Atlantic–Mediterranean strait (Miocene, Guadix Basin, southern Spain)

Carbonate production by brachiopods in shallow-water habitats is generally expected to be not sufficiently high and temporally persistent to allow them to form very thick and densely packed shell concentrations. The formation of thick brachiopod concentrations requires long-term persistence of populations with high density of individuals, and such circumstances are assumed to be rare especially during the Cenozoic. However, here we show that the large-sized brachiopod Terebratula terebratula, the most common species in benthic assemblages with epifaunal bivalves and irregular echinoids, formed several decameter- to meter-thick, densely packed concentrations in shallow siliciclastic, high-energy environments, in a seaway connecting the Atlantic Ocean with the Mediterranean Sea during the Latest Tortonian (Late Miocene, Guadix Basin, southern Spain). This brachiopod formed (1) meter-scale, thick, parautochthonous concentrations in a prodelta setting and (2) thin, mainly allochthonous, tide- and storm-reworked concentrations in megaripples and dunes. The abundance of brachiopods at the spatial scale of the Guadix Basin seems to be mainly related to intermediate levels of sedimentation rate and current velocity because abundance and thickness of shell concentrations decline both (1) in onshore direction towards delta foresets with high sedimentation rate generated by debris flows and (2) in offshore direction with increasing levels of tide- and storm-induced substrate instability. Although brachiopods in dune and megaripple deposits are more fragmented, disarticulated, and sorted, and have a higher pedicle/brachial valve ratio than in prodelta deposits, taphonomic damage is still relatively high in prodelta deposits. Terebratula terebratula thus formed thick concentrations in spite of that disintegration processes were relatively intense along the whole depositional gradient. Therefore, population dynamic of this species was probably characterized by production maxima that were comparable to some Cenozoic molluscs in terms of their productivity potential to form thick shell concentrations in shallow subtidal environments. We suggest that temporal changes in brachiopod carbonate production have a significant spatial and phylogenetic component because multiple large-sized species of the family Terebratulidae, which underwent radiation during the Cenozoic, attained high abundances and formed shell concentrations in temperate regions.     

Size-frequency and population structure of brachiopods

The living terebratulids, Terabratulina unguicula, Terebratalia transversa, Laqueus vancouverensis, and the rhynchonelid Hemithiris psittacea were studied in the San Juan Islands, Washington, U.S.A. Those results and a review of a the literature lead to the conclusion that most brachiopod populations experience episodic recruitment at intervals which may be irregular. The occurrence of juveniles attached to adults, brooding, and bi- or multimodal size-frequency distributions demonstrate that, contrary to a previously suggested hypothesis, adult brachiopods do not generally exclude juveniles from the same area. The commony observed rarity of small individuals is regarded as a product of local recruitment failure due to patchy distribution of larvae; it does not justify the assumption that brachiopods are unaffected by high post-larval juvenile mortality. However, the frequent rarity of small individuals confirms that this cannot be used as a criterion of transport in assemblages of fossil brachiopods.     

Architecture and function of the lophophore in the problematic brachiopod Heliomedusa orienta (Early Cambrian, South China)

The detailed structure of the lophophore is a key diagnostic character in the definition of higher brachiopod taxa. The problematic Heliomedusa orienta Sun and Hou, from the Lower Cambrian Chengjiang Lagerstätte of Yunnan, southwestern China, has a well-preserved lophophore, which is unlike that of any known extant or extinct brachiopods. Based on a comparative study of lophophore disposition in H. orienta and the extant discinid Pelagodiscus atlanticus, the in- and excurrent pattern and shell orientation of H. orienta are described and discussed. Reconstructions of lophophore shape and function are based on numerous specimens and comparison with P. atlanticus. The lophophore is composed of a pair of lophophoral arms that freely arch posteriorly rather than coiling anteriorly as commonly seen in fossil and recent lingulids. The lophophore is attached to the dorsal lobe of the mantle; it has neither calcareous nor chitinous supporting structures, and is disposed symmetrically on either side of the valve midline. The mouth can be inferred to be located at the base of the two brachial tubes, slightly posterior to the anterodorsal projection of the body wall. The lophophoral arms bear laterofrontal tentacles with a double row of cilia along their lateral edge, as in extant lingulid brachiopods. The main brachial axes are also ciliated, which presumably facilitated transport of mucous-bound nutrient particles to the mouth. The unique organization of the lophophore in Heliomedusa is not like any known fossil and living brachiopods. This clearly demonstrates that H. orienta is not a member of any crown group. It is here considered as a member of the brachiopod stem group, which challenges recent interpretations of a close discinid affinity.     

BILLENGSELLIDE AND ORTHIDE BRACHIOPODS: NEW INSIGHTS INTO EARLIEST ORDOVICIAN EVOLUTION AND BIOGEOGRAPHY FROM NORTHERN IRAN

Abstract:  The eastern Alborz Mountains of Iran comprise a significant peri-Gondwanan terrane relevant to the early evolution of late Cambrian – early Ordovician brachiopods incorporated into the emerging benthic biota of the Paleozoic Evolutionary Fauna. A low diversity brachiopod assemblage from the late Tremadocian unit of the Lashkarak Formation contains six new species including the polytoechioideans Polytoechia and Protambonites and the orthoideans Paralenorthis, Ranorthis, Tarfaya and Xianorthis . The fauna preserves the earliest records of Polytoechia , unknown previously outside Laurentia and the Uralian margin of Baltica, and of Paralenorthis and Ranorthis , which were widespread along Gondwanan margins and in Baltica from the Floian (Arenig), plus Xianorthis , known hitherto only from the Floian of South China. The enigmatic Tarfaya has an impunctate shell fabric and setigerous perforations along the posterior margin, indicating placement within the Orthoidea in a new Family Tarfayidae. New species of Polytoechia , Protambonites , Paralenorthis, Ranorthis , Tarfaya , Xianorthis are described.     

The brachiopod fold: a neglected body plan hypothesis

Attention is drawn to Nielsen's radical body plan concept, here named the 'brachiopod fold hypothesis', under which brachiopods and phoronids are recognized to be transversely folded across the ontogenetic anterior–posterior axis so that, to make useful comparisons with other phyla, these organisms must be conceptually unfolded. Under the hypothesis brachiopod brachial and pedicle shell valves are respectively 'anterior' and 'posterior' rather than 'dorsal' and 'ventral' as traditionally described. The hypothesis makes sense of the symmetry axes of the brachiopod shell, is consistent with various indications from fossil and Recent brachiopods, and gives rise to predicted patterns of axis–determining gene expression that differ from those obtaining under the traditional view of the body plan, whilst the variety of folding movements in different lineages implies that superficially dissimilar morphogenetic folds may be fundamentally homologous. Convergent folding patterns are noted in some other organisms. A previous conjecture that inarticulate linguloid brachiopods were derived from halkieriid–like ancestors is elaborated with proposals that recognize possible functional continuities of coelomic and marginal sclerite functions, and it is noted that an ancestrally facultative fold could have become incorporated by genetic assimilation into the brachiopod developmental program. An experimental approach is outlined to test the possibility that some members of the 'small shelly fauna' may have been members of the halkieriid–like brachiopod stem lineage and it is also suggested that buoyancy modification may have been an important function of mineralization amongst Lower Cambrian floaters and swimmers, since negative buoyancy would facilitate access to the benthic niche.     

The life and death of torquirhynchia inconstans (brachiopoda,upper jurassic) in England

Torquirhynchia inconstans, a rhynchonellid brachiopod, shows a curious asymmetric commissure. This is interpreted as an adaptation to life in tidal environments. Type of preservation, growth line, and size frequency analysis indicate that the population analyzed consist of dominantly mature individuals, which by analogy with recent brachiopod populations is a primary feature of the original population, and not due to selective destruction, selective transport, or selective predation of smaller individuals. The possible functions of the asymmetry of Torquirhynchia inconstans are considered, and it is concluded that the brachiopod was adapted to life in tidal environments, a conclusion supported by sedimentological evidence. Asymmetric brachiopods are considered to have developed from colonies of partly asymmetric, variable brachiopods by selection of extreme variants.     

PHYLOGENETIC RELATIONSHIPS AMONG EXTANT BRACHIOPODS

Abstract— The monophyletic status of the Brachiopoda and phylogenetic relationships within the phylum have long been contentious issues for brachiopod systematists. The relationship of brachiopods to other lophophore-bearing taxa is also uncertain; results from recent morphological and molecular studies are in conflict. To test current hypotheses of relationship, a phylogenetic analysis was completed (using PAUP 3.1.1) with 112 morphological and embryological characters that vary among extant representatives of seven brachiopod superfamilies, using bryozoans, phoronids, pterobranchs and sipunculids as outgroups. In the range of analyses performed, brachiopod monophyly is well supported, particularly by characters of soft anatomy. Arguments concerning single or multiple origins of a bivalved shell are not relevant to recognizing brachiopods as a clade. Articulate monophyly is very strongly supported, but inarticulate monophyly receives relatively weak support. Unlike previous studies, the nature of uncertainties about the clade status of Inarticulata are detailed explicitly here, making them easier to test in the future. Calcareous inarticulates appear to share derived characters with the other inarticulates, while sharing many primitive characters with other calcareous brachiopods (the articulates). Experimental manipulation of the data matrix reveals potential sources of bias in previous hypotheses of brachiopod phylogeny. Although not tested explicitly, lophophorate monophyly is very tentatively supported. Molecular systematic studies of a diverse group of brachiopods and other lophophorates will be particularly welcome in providing a test of the conclusions presented here.     

A Stem Group Brachiopod From The Lower Cambrian: Support For A Micrina (Halkieriid) Ancestry

The shell structure of the Lower Cambrian Mickwitzia , a bilaterally symmetrical bivalve hitherto doubtfully assigned to the Brachiopoda, confirms that the genus shares characters with linguliform brachiopods. The columnar lamination of its organophosphatic shell is homologous with that characterizing acrotretides. The shell, however, is also pervaded by striated apatitic tubes indistinguishable from those permeating the sclerites of the problematic organophosphatic, laminar–shelled Micrina which is close to Halkieria . No crown group brachiopods have such tubes that are presumed to have contained setae. The presence of both these features in the Mickwitzia shell suggests that the stock is a stem group brachiopod with a halkieriid ancestry.     

A three‐dimensional geometric morphometric study of the development of sulcus versus shell outline in Permian neospiriferine brachiopods

The morphological variation of the sulcal development and shell outline in large Permian neospiriferine brachiopods including Fasciculatia Waterhouse, 2004 is investigated using geometric morphometrics. The sulcal tongues of spiriferide brachiopods can be, in a qualitative sense, categorized into three types according to the degree of their development: short sulcal tongue, long sulcal tongue and geniculated sulcal tongue. All three types have been noted within Fasciculatia striatoparadoxa, regardless of the nature of the substrate which they originally inhabited. To quantify its morphological variation both in sulcal development and shell outline, 51 brachiopod shells were scanned with a three‐dimensional (3‐D) surface imaging device, and their 3‐D models were reconstructed. Using two landmarks and 58 semilandmarks designated on the surface of the reconstructed 3‐D models, a landmark‐based morphometric analysis was performed. Our result demonstrates a significant intraspecific variation of sulcal development in F. striatoparadoxa and its relatives. Local environmental factors, especially the intensity of ambient water flow, are invoked as the most likely cause for this intraspecific variation. Additionally, this study also shows that there are considerable interspecific distinctions in shell outline among Fasciculatia species, independent of the high variation in the sulcal development. The strong stability of overall shell outline at species level implies a decoupled morphological development between sulcal tongue and whole shell outline. The 3‐D morphometric approach applied here demonstrates its great utility as a tool for quantifying and analysing the morphological variation of highly convex brachiopod shells.     

New insights into the larval development of Macandrevia cranium (Müller, 1776) (Brachiopoda: Rhynchonelliformea)

The terebratulid Macandrevia cranium (Müller, 1776) is a representative of articulate brachiopods. However, little is known about its embryology and larval development. In order to obtain reproducible results we used a strict protocol of artificial fertilization under controlled temperature conditions as a basis for our morphological study. Sampling of embryos or developing larvae at frequent intervals led to the most comprehensive collection of preserved developmental stages, ranging from early zygotes to late three-lobed stage larvae. SEM studies of all these stages showed that the development of M. cranium is similar to that of other terebratulid brachiopods. This includes the presence of four bundles of larval setae in three-lobed stage larvae. Our results contradict earlier observations on the development of M. cranium and show that this species exhibits more typical features of articulate brachiopod development than previously thought.     

Microborings in Recent brachiopods and the functions of caeca

Microborings in the primary shell layer of Recent brachiopods are clearly seen to avoid endopunctamicroscopic canals pervading the shell fabric and housing papillose extcnlions of the mantle (the caeca). This avoidance confirms the suggestion that the caecal contents inhibit boring organisms (Owen & Williams 1969; Proc. R. Soc. Loud. B, 172 ), and as such the caecum can be considered as an important instrument in protecting the brachiopod shell. A comparison of the relative fecundity of co-habitating impunctate and cndopunctate New Zealand brachiopods provides indirect evidence that the caecum may indeed also function in a nutrient storage capacity. Brachiopods, microborings, primary shell layer, endopuncta, defence, storage.     

A HISTORY OF SKELETAL SECRETION AMONG ARTICULATE BRACHIOPODS

Studies of the ultrastructure of the exoskeleton of Notosaria nigricans (Sowerby), which can be used as the standard succession for articulate brachiopods, show that shell secretion involves six distinct operations giving rise to the following layers: mucopolysaccharide, outer fibrillar triple-layered membrane, mucoprotein, inner fibrillar triple-layered membrane, calcareous primary layer and calcareous-organic secondary layer. Comparison with the secretory régimes of terebratulids like Waltonia inconspicua (Sowerby) suggests that only four of these operations are fundamental, those controlling secretion of mucopolysaccharide, outer fibrillar membrane and the primary and secondary shell. An endoskeletal secretory phase giving rise to spicules in the mantle and lophophore is also found in many terebratulids. In the geological record, the orthodox primary-secondary shell can be traced back to the billingsellaceans and is presumed to have been associated with the mucopolysaccharide layer and a fibrillar membrane which together might well have constituted the prototypic organic exoskeleton. Deviation from this pattern during brachiopod evolution was relatively minor and was, so far as is known, limited to the strophomenids, some spiriferids and thecideidines.     

RHYNCHONELLIFORMEAN BRACHIOPODS WITH SOFT-TISSUE PRESERVATION FROM THE EARLY CAMBRIAN CHENGJIANG LAGERSTÄTTE OF SOUTH CHINA

Abstract:  Cosmopolitan kutorginates, the most abundant Early Cambrian rhynchonelliformean brachiopods, became extinct at the end of the Middle Cambrian. Consequently, any information concerning the anatomy of this peculiar lineage of brachiopods has great phylogenetic significance with regard to their extant relatives for analogies with the stem-group clade. Such data have been supplied from fossils of which the soft parts have been preserved in exceptional detail. A new brachiopod, Kutorgina chengjiangensis sp. nov., from the Early Cambrian Chengjiang Lagerstätte of southern China, is described here. It is the first articulated brachiopod species collected from this deposit. The specimens preserve a set of soft-body parts, i.e. lophophore, digestive tract and pedicle, all previously poorly known in almost all Palaeozoic calcareous brachiopod taxa. The lophophore attains an early spirolophe stage, clearly homologous to that in the coeval lingulids. The digestive tract consists of a mouth, oesophagus, swollen stomach, intestine and a terminal anus. The pedicle protruding between the valves is stout and elongate, with annulated lamellae on the surface, and contains a putative cœlomic cavity. K. chengjiangensis displays the characteristics of the stem group of calcareous brachiopods, and illustrates anatomical similarities between Cambrian phosphatic- and calcareous-shelled brachiopods, thus corroborating that the Brachiopoda are a monophyletic group.