Biogeography of the recent brachiopods

The vertical, latitudinal, and circumcontinental zonality of the distribution of the species, genera, and families of recent brachiopods is considered. The distortions of the latitudinal and meridional symmetry of the biogeographic structure of the ocean are analyzed in view of the patterns of the global circulation of the surface and intermediate waters. Thus ancient faunas may be reconstructed based on data on the structural characteristics of the taxocene of recent brachiopods. The features of the paedomorphic evolution of brachiopods from the different families in extreme habitats (interstitial, underwater caverns, submarine rises, abyssal depths, hydrothermal areas, and margins of habitats) are discussed. The biogeographic structure of bottom dwellers is shown to simplify with depth as well as with simplification of the hydrological structure of the ocean. The important role of the bathyal oceanic zone (slopes of continents, islands, submarine mountains, ridges, and rises) in the preservation of faunal relicts is shown. The historical change from brachiopods to bivalves that occurred from the Paleozoic to the Mesozoic and Cenozoic is shown to have resulted not from competitive exclusion, but from complex and global changes in the plankton composition, which were unfavorable for articulate brachiopods, which had already developed specialized feeding habits, feeding on food that led to the production of almost no metabolic waste products; they had even partly lost their alimentary canal. The development of shelly plankton and, especially, of diatoms hampered the post-Paleozoic revival of large assemblages of articulate brachiopods in shallow-water habitats. The unfilled ecological niches were colonized by bivalves, which were widely adapted to feeding on live phyto-and zooplankton. Recent articulate brachiopods, which are adapted to feeding on the products of decay of dead plankton, form a belt of densely populated settlements of the organic biofilter outside the photic zone on the seaward edge of shelves and on the upper parts of the slopes of continents, islands, and submarine rises throughout the world.     

Predation in the Ordovician and Silurian of Baltica

Signs of predation appear in the Middle Ordovician of Baltica. Shell repair dominates over the predatory borings in the Ordovician and Silurian. Predators attacked molluscs, brachiopods and tentaculitoids in the Ordovician and molluscs, tentaculitoids, brachiopods and ostracods in the Silurian. There is an increase in the number of prey species in the Late Ordovician, which could be related to the Great Ordovician Biodiversification Event. Molluscs are the favourite prey taxon in the Ordovician, but in the Silurian, molluscs became less dominant as the prey. This is probably not an artefact of preservation as Ordovician and Silurian molluscs are equally well preserved.     

A spinose stem group brachiopod with pedicle from the Middle Cambrian Burgess Shale

A new genus and species of a Middle Cambrian stem group brachiopod, Acanthotretella spinosa n. gen. and n. sp., is described from the Burgess Shale Formation. Most of the 42 specimens studied came from the Greater Phyllopod bed (Walcott Quarry) and were collected from five bed assemblages, each representing a single obrution event. Specimens are probably preserved within their original habitat. In contrast to all brachiopods known from the Burgess Shale, the shells of the new stem group brachiopod are often deformed and do not show signs of brittle breakage, which suggests that the valves were originally either entirely organic in composition or, more likely, had just a minor mineral component. Acanthotretella spinosa differs from all the other described Cambrian brachiopods in that it is covered by long, slender and possibly partly mineralized spines that are posteriorly inclined at an oblique angle away from the anterior margin. The spines penetrate the shell and are mainly comparable with the thorn‐like organic objects that have been inferred from early siphonotretoid brachiopods. The pedicle was slender and was composed of a central coelomic region and emerged from an apical foramen at the end of an internal pedicle tube. The finding of a pedicle attached to the macrobenthic algae Dictyophycus and other epibenthos implies that A. spinosa did not have an infaunal mode of life. The visceral region and interior characters are poorly preserved.     

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.     

New Carboniferous brachiopods from the eastern Great Basin, Nevada, USA: implications for loop ontogeny and evolution in Late Palaeozoic terebratuloids

Terebratuloid brachiopods from two localities in the eastern Great Basin, Nevada, USA, include the new taxa Cryptacanthia savagei sp. nov., Fletcherithyris infrequens sp. nov., Cryptonella simplex sp. nov., and Albelenina alvarezi gen. et sp. nov. The faunas are considered to be mid Desmoinesian (late Moscovian) in age. The brachiopods were found associated in clusters, and many of the specimens are well preserved. Records of Pennsylvanian terebratuloid brachiopods are uncommon, and these faunas have enabled an understanding of internal features previously unknown or poorly understood. Systematic analyses of the faunas have generated some new concepts on the ontogeny and evolution of the loop in Late Palaeozoic terebratuloids. From ontogenetic analyses, it is inferred that the stage of loop development may be the most important aspect in taxonomic classification. Analyses of loop evolution suggest the possibility of a transition from a teloform stage to long-flanged deltiform and deltiform stages. These transitions may be possible through reduction in length of the descending lamellae of the crura by resorption of calcium carbonate or posteroventral folding of flanges. Subsequently, these changes in loop morphology are retained by paedomorphosis within long-term evolutionary processes.     

Do brachiopods show substrate‐related phenotypic variation? A case study from the Burgess Shale

As sessile, benthic filter feeders, brachiopods share an intimate relationship with their chosen substrate. Individuals of Micromitra burgessensis in the Burgess Shale Formation are preserved in life position, attached to a range of hard substrates, including skeletal debris, conspecific brachiopods, sponges and enigmatic tubes. Here we investigate the phenotypic variability of M. burgessensis associated with differing substrate attachments. We apply geometric morphometrics to test for variation by plotting landmarks on the exterior of ventral and dorsal valves of M. burgessensis specimens that are preserved attached to different substrates. Using principal component, canonical variate analyses and anova , we determine that there is some variation in shape related to substrate. Canonical variate analyses, for ventral valves and dorsal valves, indicate that specimens attached to the same substrate are recognizable in shape from specimens attached to other substrate types. The strength of differentiation however, is not robust and combined with our discriminate analysis of separate populations suggests that there is the potential for substrates to exercise only weak control over the morphology of Brachiopoda.     

An ecologically mixed brachiopod fauna from Changhsingian deep-water basin of South China: consequence of end-Permian global warming

The Late Permian Shaiwa Group of the Ziyun area of Guizhou, South China is a deep-water facies succession characterized by deep-water assemblages of pelagic radiolarians, foraminifers, bivalves, ammonoids and brachiopods. Here we report 20 brachiopod species in 18 genera from the uppermost Shaiwa Group. This brachiopod fauna is latest Changhsingian in age and dominated by productides. The palaeoecologic and taphonomic analysis reveals that the brachiopod fauna is preserved in situ. The attachment modes and substratum preference demonstrate that the Shaiwa brachiopod fauna comprises admixed elements of deep-water and shallow-water assemblages. The presence of the shallow-water brachiopods in the Shaiwa faunas indicates the involuntary settlement of shallow-water brachiopods. The stressed ecologic pressure, triggered by warming surface waters, restricted ecospace and short food sources, may have forced some shallow-water elements to move to hospitable deep-water settings and others to modify their habiting behaviours and exploit new ecospace in deep-water environments. We infer that the end-Permian global warming and subsequent transgression event may have accounted for the stressed environmental pressure in the shallow-water communities prior to the end-Permian mass extinction.     

Epithelial cell moulds in acrotretoid brachiopods

The preservation of polygonal imprints of epithelial cells in acrotretoid brachiopods is reviewed and supplemented by new data from the Cambrian of southern Great Britain. The imprints are confirmed as representing moulds of epithelial cells rather than an artefact of microstructure or preserved soft tissues, as they are (1) recorded in most taxa reviewed, (2) best preserved in areas where the shell has been thickened and (3) similar in size to cells recorded in Lingula, the closest living relative to the now extinct acrotretoids. Analysis of the morphology and sizes of epithelial cell moulds demonstrates that there is no consistent relationship between cell width and valve size, and that epithelial cells are not a useful taxonomic character within this group.     

Earliest ontogeny of the Silurian orthotetide brachiopod Coolinia and its significance for interpreting strophomenate phylogeny

Well‐preserved juvenile specimens of the orthotetide brachiopod Coolinia pecten (Linnaeus, 1758 ) from the Silurian of Gotland, Sweden, demonstrate evidence of a planktotrophic larval habit. Larval shell morphology indicates the absence of a pedicle sheath: this character is otherwise typical of derived billingsellides, strophomenides and productides, which form the conventional strophomenide clade. The presence of a rudimentary colleplax structure in the larval shell of Colinia suggests instead a phylogenetic link to chiliate brachiopods and the enigmatic genus Salanygolina. This relationship suggests an early divergence of rhynchonellate and strophomenate brachiopods.     

First records of brachiopods of the family Discinidae (Class Lingulata) from the Upper Jurassic of West Siberia

The organophosphatic brachiopods of the superfamily Discinoidea, family Discinidae are described from the Upper Jurassic of West Siberia. The protegulum (embryonic shell) preserved in adult shells is for the first time discovered in Mesozoic discinids. The shell microstructure is studied. A new species, Discinisca undata Smirnova, sp. nov., is established.     

Morphology of gametes of mollusks, echinoderms, and brachiopods in systematics and phylogeny

The morphology of eggs and sperm of echinoderms, mollusks, and brachiopods was studied and compared. The gametes of inarticulate brachiopods (two classes Lingulata and Craniata and two subphyla Linguliformea and Craniaformea) are shown to have significant morphological differences from those of articulate brachiopods (extant class Rhynchonellata, subphylum Rhynchonelliformea). Inarticulate brachiopods have similar sperm morphology to that of primitive brachiopods, bivalves and some polychaetes that have external fertilization. Sperm morphology of articulate brachiopods is similar to that of echinoderms, which are considered to be typical deuterostomate invertebrates. This similarity supports an early deviation of lophophore-bearing animals from Bilateria, before this lineage branched into Protostomia and Deuterostomia. Similar gamete morphology in Lingulata and Craniata supports the view that inarticulate brachiopods should be retained as a supraclass taxon for comparison with other Lophotrochozoa, in particular with phoronids, bryozoans, and mollusks. Based on the new data on the gamete morphology in inarticulate brachiopods, we propose the name Lingulophyles with the type genus Lingula, and for articulate brachiopods Coptothyrophyles with the type genus Coptothyris.     

Geochemical investigation of growth in selected Recent articulate brachiopods

Buening, N. & Carlson. S. J. 1992 07 15: Geochemical investigation of growth in selected Recent articulate brachiopods.
Growth increments have traditionally been used to determine age and growth rates of shelled organisms, particularly bivalves. Brachiopod growth increments and the time span they represent are rather poorly understood, however. Geochemical analyses of trace element concentrations preserved in skeletal calcite may provide an alternative method to determine the age of Recent brachiopods and to interpret their patterns of growth. Magnesium is a particularly important trace element in skeletal calcite because it is thought to vary with temperature, growth rate. and taxonomic affiliation. Electron microprobe analyses of Mg concentrations in the Recent articulate, temperate water brachiopods Terebratulina unguicula and Terebrotalia transversa , have revealed two distinct ontogenetic patterns of Mg concentration. The primary ontogenetic pattern is characterized by elevated and more variable levels of Mg concentration during early growth. followed by lower, more stable Mg concentrations during growth after sexual maturity. This pattern appears to be related to a predictable decrease in growth rate through ontopeny. Secondary peaks of Mg superimposed on this primary pattern may represent growth spurts related to annual cycles of productivity. Preliminary Fourier analyses of patterns of Mg concentration provide additional support for this hypothesis. Thus, a record of productivity characterized by annual peaks of Mg concentration may well allow us to age individual brachiopods by means other than size-frequency histograms. growth lines, and other less precise and accurate methods. Brachiopods, growth. biomineralization, calcification, Terebratali transversa, Terebratulina Unogicui.a, magnesium, Calcium, geochemical. ontogeny .     

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.     

Deciphering the exceptional preservation of the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

After the end-Permian mass extinction, the Early Triassic (∼251.9 to 247 Ma) is characterized by several biotic crises that particularly affected marine faunas; accordingly, marine ecosystems from this unstable interval have been often described as heavily depauperate. This assumption, however, may relate to a biased fossil record. The discovery of taphonomic windows, like Konservat-Lagerstätten, in the Early Triassic would help to better understand the composition and diversity of ecosystems at that time. The Paris Biota (Idaho, USA) is a highly diverse fossil assemblage from the earliest Spathian (early late Olenekian, ∼250.6 Ma), indicating a rapid rediversification for many groups after the end-Permian crisis and pointing toward a remarkably complex marine ecosystem ∼1.3 m.y. after the Permian-Triassic boundary. However, its detailed taphonomy has not yet been investigated. Here we present the mineral characterization of four of its most abundant taxa: discinoid and linguloid brachiopods, leptomitid sponges, and caridean shrimps. For this purpose, we combined data from Raman microspectroscopy, Fourier Transform InfraRed spectroscopy, and SEM-EDXS. Although all taxa were preserved in calcium phosphate, the morphology, structuring and size of crystals are highly dissimilar at a nano- to micrometric scale. In brachiopods, the ultrastructure of calcium phosphate shows unorganized bacillary-like crystals, while in crustaceans their size is considerably smaller and round-shaped. Similar small crystals are observed in sponges. However, the ultrastructure of calcium phosphate in sponges exhibits a well-defined preferential orientation. In addition, sponges show some compressed but preserved three-dimensional features, with an inner surface better preserved. Such analyses are essential to understand the taphonomic pathways enabling exceptional preservation. The further comprehension of preservation features would help to understand potential bias on observed diversity signals and their interpretation.     

Über Nahrung und Ernährungsweise von Ammoniten

Until only a few years ago, the majority of ammonites were considered to have been rather swift nectonic swimmers of little ecologic bondage. About their food, nothing was known with certainty. Comparison with recent Coleoids and withNautilus suggests, however, that most ammonoids were poor swimmers. It is not even certain that the hyponome was used for locomotion as much as inNautilus. Slow locomotion made it impossible for ammonites to hunt for fish or other highly agile prey. Their lower jaws, which are identical to the structures known as aptychi and anaptychi (formerly considered to be opercula), are like shovels and make it impossible for their bearers actually to bite and cut with them. Consequently the structure of their jaws also prevented their hunting large and active prey. Their jaws were probably actually used like shovels along the bottom of the sea. They may have gathered small or slow benthonic organisms like foraminifers, ostracodes, small crustaceans, young brachiopods, corals, bryozoa, but also drifting or slowly swimming and dead organisms. Several unusually well preserved stomachs of ammonites contained foraminifers, ostracodes, crinoids, smaller ammonites, and possibly inarticulate brachiopods. It is concluded that, ecologically, ammonites inhabited the place of modern bottom-feeding gastropods.     

Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossil Mickwitzia muralensis Walcott, 1913

Exceptionally preserved carbonate- and shale-hosted Mickwitzia muralensis from the Lower Cambrian Mural Formation, southern Canadian Rocky Mountains, complement one another to yield an unusually complete account of its ontogeny, ecology and phylogenetic relationships. The shell of M. muralensis is composed of dense phosphatic layers interspersed with porous organic-rich layers. At the insertion of shell-penetrating tubes, shell layers deflect inwards to produce inwardly pointing cones. The tubes are interpreted as having hosted setae that were secreted by outer-epithelial follicles. Follicular setae also occurred at the mantle margin, where they were oriented within the plane of the shell as in modern brachiopods. During ontogeny, the initial setae oriented in the plane of the shell occurred before the first shell-penetrative setae. In the juvenile and early-mature stages of shell secretion, a posterior opening was present between both valves and was used for the protrusion of an attachment structure. In the late-mature shell, this opening became fixed in the ventral valve. Based on the posterior margin and the shell microstructure, a close relationship between Mickwitzia and the paterinids is proposed with differences interpreted as heterochronic. The shell-penetrative setal apparatus of M. muralensis is distinct from that previously described of Micrina, though both types are conceivably homologous to adult and juvenile setae of modern brachiopods.     

Epizoic bryozoans and corals as indicators of life and post-mortem orientations of the Devonian brachiopod Meristella

The in-life and post-mortem orientations of the Lower Devonian brachiopod Meristella atoka from the Haragan Formation (Lower Devonian; south-central Oklahoma) are inferred from the distribution of epizoic bryozoans and the orientations of base plates of epizoic corals. Three bryozoans, Cyphotrypa corrugata, Fistuliporella maynardi and Leioclema pulchellum, and one coral, Favosites conicus, are considered. Most zoaria that contact the commissure terminate at the commissurc, and a few zoaria terminate at growth lines. This suggests that the bryozoans were primarily life associates of Meristella atoka. Collectively, these three bryozoan species most extensively encrusted marginal sectors of the brachial valve and are very rare on the posteromedian sector (the umbo) of the pedicle valve. This distributional pattern indicates that the preferred living orientation of Meristella atoka was umbo-down (posteromedian sector of the pedicle valve resting on or buried in the substratum) with the commissure steeply inclined to the sediment water interface. Most coralla of Favosites conicus that contacted the commissure encrusted over the commissure. This indicates that Favosites conicus either preferentially encrusted Meristella atoka post-mortem or colonized living brachiopods but subsequently caused them to die. Furthermore, Favosites conicus most extensively encrusted anterior sectors of the brachial valve, especially the fold. The lateral and anterior orientations of the commissure with respect to the base plates (holothecae) of Favosites conicus indicates that the brachiopods were oriented approximately horizontal with respect to the base plates. This suggests that the preferred post-mortem orientation of Meristella atoka was resting nearly horizontally on the substratum. These data and interpretations confirm previously inferred in-life orientations of Meristella atoka and are consistent with post-mortem orientations hypothesized for elongate-oval athyrid brachiopods. □Brachiopoda, Athyridacea, Meristella atoka , palaeoecology, autecology, epizoans, bryozoans, corals, sedimentology, Lower Devonian, North America, Oklahoma.     

Determination of paleoseasonality of fossil brachiopods using shell spiral deviations and chemical proxies

Brachiopods have been extensively used in paleoclimatic and paleoecological reconstructions, but their utility would greatly increase if paleoseasonality information could be obtained from their shells. Determining seasonal seawater temperature variations from fossil brachiopods requires knowledge of specimen ontogenetic ages, which is difficult to determine compared to other organisms secreting a shell by accretion. In this study, the combination of the spiral deviation methodology and chemical proxies is tested for determining specimen ontogenetic ages and paleoseasonality using two species of fossil brachiopods, Laqueus rubellus and Terebratula terebratula, of Pleistocene and Late Miocene age, respectively. Spiral deviations were obtained for Laqueus and Terebratula using an R program developed for modern taxa, and well-preserved shells were analyzed using oxygen isotopes and Mg/Ca ratios as chemical proxies for past seawater temperature. Results reveal that locations of spiral deviations on shells of L. rubellus displayed a strong direct relationship with Mg concentrations, and resulting Mg/Ca-derived paleotemperatures were seasonal. Conversely, specimens of T. terebratula did not show a consistently strong relationship between Mg concentrations and spiral deviations, although resulting paleotemperatures agreed with those from previous studies. Overall, the results from this study indicate that the spiral deviation methodology combined with chemical proxies presents great potential for utility in past seasonal seawater temperature reconstructions in pristinely preserved, biconvex fossil brachiopods.     

The monophyletic origin of the Brachiopoda

Although it is commonly acepted that the brachiopods descended from phoronid-like ancestors there is dispute over their origin. Traditionally they have been regarded as a monophyletic group, a clade. More recently it has been claimed that brachiopods are polyphyletic and that several of the orders arose independently from separate phoronid-like stocks. The latter point of view implies that brachiopods are not a taxon but merely a grade of organization. Traditional stratophenetic approaches do little to resolve the problem, which may be outside their domain. It is possible, even probable, that the initial radiation involved organisms that lacked mineralized shells. Cladistic analysis of both living forms and Lower Paleozoic taxa strongly supports the contention that brachiopods are monophytetic and closely related to the phoronids. It suggests, however, that the 'inarticulate' Paterinida and Kutorginida are genealogically more closely related to the Articulata than they are to the remaining Inarticulata. □ Brachiopoda, Lophophorata, cladistics, Cambrian.     

Discovery of soft parts of a fossil brachiopod in the “Hunsrückschiefer” (Lower Devonian, Germany)

The author recently discovered among 16 discinid brachiopods from the Lower Devonian Hunsrück Slate, by using the X-ray technique, two specimens with mineralized soft parts and pedicle. These are truly unique finds, as previously no bodily preserved pedicle of fossil discinids has been described. Also, they prove that in the Hunsriick Slate soft parts can be pyritized. New shell observations give rise to doubts on the generic assignment ofOrbiculoidea mediorhenana Fuchs 1915. By comparing the anatomy of the related, livingLingula with the extinct discinid in question, a reconstruction of the latter is presented.