Fossil Brachiopods Research Articles

Automatic identification and morphological comparison of bivalve and brachiopod fossils based on deep learning.

Fossil identification is an essential and fundamental task for conducting palaeontological research. Because the manual identification of fossils requires extensive experience and is time-consuming, automatic identification methods are proposed. However, these studies are limited to a few or dozens of species, which is hardly adequate for the needs of research. This study enabled the automatic identification of hundreds of species based on a newly established fossil dataset. An available "bivalve and brachiopod fossil image dataset" (BBFID, containing >16,000 "image-label" data pairs, taxonomic determination completed) was created. The bivalves and brachiopods contained in BBFID are closely related in morphology, ecology and evolution that have long attracted the interest of researchers. We achieved >80% identification accuracy at 22 genera and ∼64% accuracy at 343 species using EfficientNetV2s architecture. The intermediate output of the model was extracted and downscaled to obtain the morphological feature space of fossils using t-distributed stochastic neighbor embedding (t-SNE). We found a distinctive boundary between the morphological feature points of bivalves and brachiopods in fossil morphological feature distribution maps. This study provides a possible method for studying the morphological evolution of fossil clades using computer vision in the future.

Properties of Conglomerates from the Middle Ordovician Dongchong Formation and Its Response to the Yunan Orogeny in the Yunkai Area, South China

The strata in the Shita Mountain, Yunkai region, are predominantly composed of clastic rocks with intercalated limestones. However, the precise stratigraphic age remains uncertain due to the scarcity of fossils. Previously, conglomerate layers in this region were considered indicative of the Yunan Orogeny during the Cambrian–Ordovician transition. However, through the identification of 12 lithofacies types and 5 lithofacies combinations in the conglomerate layers of the Shita Mountain section, it has been confirmed that these layers represent a fan delta depositional environment characterized by debris flow, traction flow, torrent, and rock flow. Based on the presence of brachiopod fossils dating to the Early–Middle Ordovician, we propose a novel two-episode model for the Yunan Orogeny. The first episode corresponds to submarine fan deposition, while the second episode involves tectonic uplift and a short-term sedimentary hiatus. Further analysis of the detrital zircon provenance reveals a strong affinity among the Yunkai area, India, Antarctica, the Lhasa, the Himalayas, Southern Qiangtang, and Western Australia during the Early–Middle Ordovician transition under the Gondwana assemblage background.

Nova ocorrência de Crinoidea no Pensilvaniano da Formação Itaituba, Pedreira Caltarém, norte da Bacia do Amazonas

Crinoidea from the Pennsylvanian deposits of the Itaituba Formation, Northern Amazonas Basin. The Itaituba Formation comprises part of the marine section of the Tapajós Group in the Amazonas Basin. This unit mainly comprises Pennsylvanian carbonate deposits associated with various marine invertebrate fossils. In this work, we present new records of crinoids in the Itaituba Formation in the Caltarém quarry, north platform of the Amazonas Basin. There are described and taxonomically identified, two genera of crinoids, through the study of columnals and pluricolumnals, in addition to the interpretation of the depositional environment through the analysis of carbonate microfacies. The identified specimens correspond to the species Cyclocaudex aff. typicus Moore & Jeffords, and to the genus Pentaridica Moore & Jeffords (first record in the Itaituba Formation). The textural, compositional, and paleontological analysis suggests four standard microfacies MPF 09, 10, 16, 23) and two faciological zones (ZF 7 E 8). The bioturbated bioclastic wackestones (MFP 09) and bioclastic wackestones/packstones (MFP 10) microfacies, with fossils of brachiopods, crinoids, echinoids, miliolid and fusulinid foraminifera, trilobites, and bryozoans, characterize an interior shelf environment, with a connection to an open marine circulation (ZF 7). The peloidal wackestones (MFP 16) and mudstones (MFP 23) microfacies, with a fossiliferous assemblage limited to brachiopods, echinoids and miliolid foraminifera, characterize a restricted lagoon environment (ZF 8). Paleontological data and microfacies analysis indicate the development of a lagoon environment with a diverse paleofauna of marine invertebrates in the carbonate platform of the northern bord of the Amazonas Basin, in the Monte Alegre County, during the Pennsylvanian. Keywords: taxonomy, echinoderms, microfacies, paleoenvironment, Pennsylvanian.

Niche conservatism and ecological change during the Late Devonian mass extinction.

Studies of the fossil record can inform our understanding of not only the causes of mass extinctions, but also their effects on biodiversity, ecology and evolution. Here, we examine regional-scale ecological changes resulting from a Late Devonian mass extinction event using brachiopod fossil assemblages from the Appalachian Basin. About half of the species went extinct, but were largely replaced by new immigrant taxa. Both before and after the extinction, the primary gradient in faunal composition was correlated with onshore-offshore position, with a second gradient attributed to frequency of disturbance. Survivors of the extinction displayed a strong degree of niche conservatism along these gradients. Despite these indicators of ecological stability, the pre- and post-extinction faunas were quite distinct at the order level, with atrypids and strophomenids largely replaced by productids, whose spiny shells may have provided greater resistance to disturbance and/or predation. Thus, extinction survivors persisted in similar ecological niches despite environmental perturbations and considerable change in the taxonomic and ecological composition of the regional species pool.

Variation of shell ornamentation with latitude and water depth-A case study using living brachiopods.

As a potential anti-predatory defensive structure, the shell ornamentation of marine calcifiers is usually used to understand the macro coevolution of the interactions between predators and preys. Marine calcifiers' shell ornamentation complexity is generally believed to vary negatively with latitude and water depth. In this paper, we explored the association between shell ornamentation and latitude/bathymetry using the latest global database of living brachiopods. We found that (1) ~59% of living brachiopods species are characterized by smooth shells and that (2) there is no statistically significant linear trend, either positive or negative, between the ornamentation index and latitudes nor with water depths. Both findings are puzzling for living brachiopods as they are sharply contrasted to the patterns of fossil brachiopods whereby the latter, especially Paleozoic brachiopods, are known to exhibit (1) a much greater ornamentation diversity and (2) (at least for the geological periods that have been studied) a linear latitudinal gradient of ornamentation complexity existed. The reasons why living brachiopods have such a high proportion of smooth or weakly ornamented shells and fail to demonstrate an unequivocal linear latitudinal ornamentation gradient were explored and are linked to a multitude of potential factors rather than uniquely only to the predation pressure. Among these, the most plausible factor seems to be the cryptic (refuge-type) habitats (e.g., deep waters, cold polar regions, and submarine rock caves) that living brachiopods have been adapted to due to their low metabolism, where predation pressure is low, allowing brachiopods to enact the predator avoidance strategy rather than having to manufacture robust shell ornamentation to survive in an otherwise highly engaged predator-prey global marine ecosystem.

Diagenetic and Biological Overprints in Geochemical Signatures of the Gigantoproductus Tertiary Layer (Brachiopoda): Assessing the Paleoclimatic Interpretation

Variations in the geochemical signatures of fossil brachiopod shells may be due to diagenesis and/or biological processes (i.e., 'vital effects'). It is critical to characterise them in order to identify reliable shell areas suitable for paleoclimate studies. This investigation contributes to an in-depth understanding of geochemical variations in Gigantoproductus sp. shells (SW Spain, Serpukhovian age), throwing light onto the Late Paleozoic Ice Age interpretation. Microstructural, crystallographic, cathodoluminescence and geochemical (minor and trace elements, δ18O, δ13C, and strontium isotopes) characterisations have been performed on the tertiary layer of the ventral valve, to assess the preservation state. Poorly preserved areas exhibit microstructural and geochemical changes such as recrystallisation, fracturing and higher Mn and Fe enrichment. Moreover, these areas have a higher dispersion of ⁸⁶Sr, ⁸⁷Sr, δ18O and δ13C than well-preserved areas. Three structural regions have been identified in well-preserved areas of the ventral valve by differences in valve curvature and thickness, such as the umbonal and thick and thin regions. These regions have different proportions of Mg, S, Na, δ18O, and δ13C, which are interpreted as 'vital effects' and probably related to growth-rate differences during shell growth. The Gigantoproductus tertiary layer seems the most suitable for paleoclimate studies, because it retains the original microstructure and geochemical composition.

БРАХИОПОДЫ ИМТАЧАНСКОЙ СВИТЫ ВЕРХНЕЙ ПЕРМИ ЮЖНОГО ВЕРХОЯНЬЯ, СЕВЕРО-ВОСТОК РОССИИ

An extensive collection of fossil brachiopods, all assigned to the Wuchiapingian Stage, was recovered from the lower part of the Imtachan Formation along the Ustupnyi Creek (right tributary of the Setorym River) in the Southern Verkhoyanie. It comprises strophalosiids (Strophalosia? aff. vollossovitschi (Fredericks), Strophalosia? sp., Subtaeniothaerus lungersgauzeni Solomina, Marginalosia? magna Abramov et Grigorjeva), spiriferids (Crassispirifer monumentalis Abramov et Grigorjeva, Crassispirifer cf. monumentalis Abramov et Grigorjeva, Crassispirifer sp.), athyridids (Cleiothyridina nikolaevi Grunt, Cleiothyridina sp. 1, Bajtugania sp.), and terebratulids (Marinurnula? aff. mantuanensis (Campbell), Marinurnula? sp.). The identified assemblage is associated with brachiopods from the lower part of the Khalpirki Formation of the Western Verkhoyanie, the appearance of which marks the boundary between the Dulgalakhian and Khalpirkian Regional Stages and also substantiates the lower boundary of the Crassispirifer monumentalis Zone. Single finds of Crassispirifer cf. monumentalis in the lower part of the Middle Imtachan Subformation indicate that the entire lower subformation and the lower part of the middle subformation belong to the C. monumentalis Zone. There are no reliable finds of brachiopods at higher levels of the Imtachan Formation.

Texture and microstructure of the outer layer of a brachiopod fossil from the Terebratulida order (−155 My)

Texture and microstructure of the outer layer of a brachiopod fossil from the Terebratulida order (−155 My)

Constraining marine anoxia under the extremely oxygenated Permian atmosphere using uranium isotopes in calcitic brachiopods and marine carbonates

The redox chemistry change in ancient oceans has profoundly shaped the evolutionary trajectories of animals. Uranium isotopes (δ238U) in marine carbonate sediments have widely been used to place quantitative constraints on the oxygenation state of the oceans through geological history. However, syndepositional and post-depositional diagenesis impose a positive and variable δ238U offset in the carbonate sediments relative to contemporaneous seawater, leaving uncertainties on quantification of anoxic seafloor areas in the past. Studies from modern settings suggest that Low-Magnesium Calcite (LMC) in articulate brachiopod shells are diagenetic resistant materials that may faithfully record the δ238U value of ancient seawater. However, this notation has not yet been validated in geological records. Here, we test this hypothesis by analyzing paired brachiopod shells and the host carbonate rocks from several Permian stratigraphic successions in South China. Forty-nine articulate brachiopod fossil shells and twenty-six host carbonate rocks from the Early Permian to the Late Permian were investigated. We performed a rigorous screening to monitor the diagenetic process that might have influenced the δ238U of the shells using a scanning electronic microscope, cathodoluminescent microscopy, and major and trace elements. We estimate that 53% of the shells preserve the primary seawater δ238U signals. Using the screened δ238U values of shells and bulk carbonates, we suggest there were four episodes of expanding marine anoxia during the Permian that are temporally coincident with periods of volcanism. The first two oceanic anoxic events occurred at a time when atmospheric pO2 levels were predicted to be higher than today. The last two events are temporally coincident or immediately preceding the end-Guadalupian and the end-Permian mass extinctions, respectively, confirming previous suggestions that marine anoxia was a critical factor in driving marine animal extinctions.

Reassessment of ocean paleotemperatures during the Late Ordovician

Abstract The Late Ordovician is a paradox, with a greenhouse climate shifting to an icehouse climate during a time of presumably high CO2 levels. We used clumped isotope (Δ47) microanalysis of fossil brachiopod shells to determine paleotemperatures of North America (Cincinnati Arch) during the Katian (453–443 Ma). Microanalyses of fossil brachiopods yielded a right-skewed distribution of clumped isotope temperatures [T(Δ47)] ranging from 25 °C to 55 °C with a mode of 32 °C and a mean of 36 °C. To test the impact of Δ47 reordering (reequilibration of 13C-18O bonding) at burial temperatures on T(Δ47), we applied a Monte Carlo simulation to a Δ47 reordering model based on the burial history. Because the reordering simulation indicated partial reordering, we used the simulation results to back-calculate T(Δ47) and correct the reordering effect. Correcting for reordering decreased the mean T(Δ47) by only ~1 °C, to 35 °C, and did not change the mode (32 °C). These temperatures are lower than those of previous studies, but still suggest that the Late Ordovician climate of the Cincinnati Arch was warmer than the modern subtropical seas. However, carbonate facies in these strata argue for upwelling of cool water; thus, typical subtropical surface waters may have been as warm as 35 °C approaching the Hirnantian glaciation. Seawater δ18O values derived from back-calculated T(Δ47) and brachiopod δ18O values average −0.3‰ ± 0.6‰ relative to Vienna standard mean ocean water (VSMOW), consistent with the value expected for subtropical surface waters in a greenhouse Earth, assuming a constant seawater-δ18O model.

Mass extinction or extirpation: Permian biotic turnovers in the northwestern margin of Pangea

Abstract The Capitanian (Middle Permian) mass extinction event, prior to and separate from the end-Permian mass extinction, has been suggested as a severe biotic crisis comparable to the big five mass extinctions of the Phanerozoic. However, there is still controversy about its global significance. In particular, this purportedly disastrous event in the Capitanian was mostly documented in the eastern Tethys, especially South China and Japan, whereas its extent in higher latitudinal regions remains unclear. A few recent studies have reported biostratigraphic and chemostratigraphic evidence for the Capitanian extinction at the northwestern marginal shelf of Pangea, including in the Kapp Starostin Formation in Spitsbergen. However, we here report a different result from these previous studies based on a study of abundant brachiopod fossils collected from eight geological sections that represent the same formation in western and central Spitsbergen, Arctic Norway. Our biostratigraphic investigation recognizes a total of five brachiopod assemblages from the type section of the Kapp Starostin Formation at Festningen in Spitsbergen. The most striking biotic change in species composition is observed at the interval between the lowermost Vøringen Member (late Artinskian) and its overlying member (Kungurian) of the Kapp Starostin Formation in Spitsbergen, which makes it much earlier than the Capitanian. A similar faunal shift at the same stratigraphic interval is also observed from bryozoan-based biostratigraphic data. This faunal turnover could be linked to a significant climatic shift (cooling) along the northwestern margin of Pangea during the Artinskian−Kungurian. Specifically, it is inferred that a climatic perturbation (cooling) likely drove the extirpation (emigration) of marine faunas out of Spitsbergen and dispersal eastward into some lower latitudinal and climatically more habitable areas. Our result indicates that the Capitanian interval in Spitsbergen does not record a catastrophic event that corresponds to the Capitanian mass extinction in Tethyan regions but rather marks gradual faunal transitions throughout the Middle to Late Permian. This faunal transition, driven by continuous cooling, was accompanied by major changes in regional lithology, which suggest a degree of local environmental control, especially in the changes of substrate and water depth, on the composition of the benthic faunas. The Wegener Halvø and Schuchert Dal Formations (Lopingian) in central East Greenland contain a diverse brachiopod fauna that is comparable to that of the post-Vøringen Member in Spitsbergen. This implies that the brachiopods in the northwestern marginal shelf of Pangea did not suffer a severe mass extinction in the Capitanian; instead, many of them migrated southward with the development of the Zechstein seaway.

First Record of Brachiopod Species in Myanmar

The Paleozoic rocks are well exposed in the Taungnyo area and the main purpose of classification is taxonomic status of the invertebrate fossils and describing the systematic paleontology of brachiopod fossils from Taungnyo Formation. Mainly distributed clastic sedimentary rocks of Taungnyo Formation (Early Carboniferous) and carbonate rocks of Moulmein Limestone Group (Permian to Middle Triassic) are well exposed in the Taungnyo area. In this study, mainly, a total of five species are recognized in the clastic sediments of Taungnyo Formation. Most brachiopods are generally found abundant and well preserved in the mudstone unit. Among them, most of the taxa have not been recorded previously. The brachiopods include: Fimbrispirifer venustus, Ovetensispirifer ovetensium, Aullacella sp., Kayserellae emanuelensis, and Chonopectus sp. All of the species are first recorded in Myanmar.

Fossil brachiopod identification using a new deep convolutional neural network

The identification of brachiopods requires specialist knowledge held by a limited number of researchers and is very time-consuming. The new technique of deep learning by artificial intelligence offers promising tools to break these shackles to develop computer automatic identification. However, we found that the traditional convolution neural network is not sufficient to automatically identify brachiopod species. Thus, we propose a new tailored Transpose Convolutional Neural Network (TCNN) in order to automatically identify brachiopod fossils with high efficiency. In this network, we add an “upsampling” Transpose Convolutional Layer and synthesize the data of this layer with the data of a Convolutional Layer to fully mix the small and large scales features extracted by the neural network. Compared with the traditional Convolution Neural Network (CNN), the Transpose Convolutional Neural Network (TCNN) can achieve a high identification accuracy using a smaller training data set of images of brachiopods. Results from this study show that the TCNN can achieve 98%, 98% and 97% identification accuracy respectively, with training data sets of 400 images of 3 species, 484 images of 4 species and 630 images of 5 species. In contrast, the traditional CNN can achieve only a low identification accuracy (67%) with 400 images of 3 species and requires 3000 images per 3 species to achieve a 95% identification accuracy. For most of brachiopod species, it is almost an impossible task to collected thousands of samples and as more brachiopod species are fitted into automatic identification, it is significant to have a reliable network which can achieve high accuracy on a small data set. In summary, the TCNN is a more efficient neural network that could be better applied to automatically identify brachiopod fossils.

Analysis of the juvenile shell ofLingula anatina(Brachiopoda: Linguliformea) provides insight into the evolution of life cycles of fossil brachiopods

AbstractInferences on the development and morphology of extinct brachiopods must be informed by the ontogeny and shell ornamentation of extant brachiopods. Although the adult shells of extant brachiopods are well studied, detailed descriptions of the embryonic and juvenile shells of extant lingulides are lacking. Here, we describe in detail the shells of juveniles ofLingula anatinaLamarck, 1801 from Vietnam and the Republic of the Philippines. The following previously unknown properties of the lingulide shell are described: (1) a distinct border between the protegulum and the brephic shell; (2) drapes that develop on both the protegulum and brephic shell; and (3) the notched anterior margin of the brephic shell. The drapes and cogs on the brephic shell may be caused by the formation of setal follicles during the planktonic stage. Specimens ofL. anatinafrom the Philippines have larger brephic shells than those from Vietnam, probably because the former have a longer planktonic stage. Based on comparisons of the first-formed shells of extant brachiopods with published data on fossil brachiopods, we suggest that the life cycle of extant lingulides, in which planktotrophic juveniles with a shell hatch from the egg envelope, is the most evolutionarily advanced brachiopod life cycle and appeared in the early Silurian. We suggest criteria for determining the type of life cycle based on the structure of the first-formed shell of brachiopods. Finally, we consider hypothetical scenarios of life cycles of fossil brachiopods, including true planktotrophic larvae in the Cambrian linguliforms.

Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations

The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinction. The end-Permian mass extinction was linked with ocean acidification due to carbon degassing associated with Siberian Trap emplacement, according to boron isotopes from fossil shells and reconstruction of the carbon cycle.

The Brachiopod δ11B Record Across the Carboniferous‐Permian Climate Transition

AbstractWe present the δ11B of well‐preserved brachiopod fossils coupled with geochemical modeling to examine how seawater boron responded to abrupt and dynamic climate changes in the Late Paleozoic. The Late Carboniferous, a time of major coal formation and glacioeustatic sea level changes, is characterized by relatively stable brachiopod δ11B of 15–17‰, similar to values seen in modern brachiopods. Brachiopod δ11B dropped by ~5‰ in the early Permian and then restabilized at a new value of 10‰ within a few million years. Mass balance models of seawater δ11B reproduced the overall trends in our brachiopod data but failed to capture the large drop in δ11B in the early Permian. Published seawater 87Sr/86Sr and δ44/40Ca data based on brachiopod shells also shift to lower values in the early Permian, suggesting a common control on all three seawater isotope systems. The Permian terrestrial record of evaporites and eolian deposits suggests a prolonged reduced delivery of dissolved weathering products to the ocean, accounting for the change in seawater 87Sr/86Sr. This reduced weathering, in turn, led to increased atmospheric CO2 and lowered seawater pH, which may have significantly decreased major removal mechanisms for seawater calcium and boron leading to declines in both isotope systems. We propose that boron removal via coprecipitation in carbonates and adsorption onto clay minerals was significantly diminished due to a reduction in the availability of the borate aqueous species caused by lowered seawater pH.

Oichnus taddeii, a new fossil trace produced by capulids on brachiopod shells

We describe the new ichnospecies Oichnus taddeii, a bioerosion trace left by parasitic capulids on fossil brachiopods, prevalently Quaternary Terebratula species. We present the diagnosis of the new ichnospecies and discuss its status. The trace was previously attributed to either Oichnus or Lacrimichnus ichngenera. We provide a statistical assessment of the trace distribution on brachiopod shells, in order to infer the capulid behaviour, and the parasitic activity the trace represents

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

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

Linnaeocaninella nomen novum for the Middle Permian fossil Caninella Liang, 1990 (Brachiopoda: Productida: Richthofenidae), preoccupied by Caninella Gorsky, 1938 (Cnidaria: Anthozoa: Bothrophyllidae).

Liang (1990) erected the monospecific genus Caninella for a Middle Permian fossil brachiopod species, Caninella zhinanensis, from the Lengwu Formation, Tonglu, Zhejiang, in China. This genus was included within the family Richthofenidae Waagen, 1885. Thus, Caninella zhinanensis, Liang, 1990, collected in strata of Middle Permian (Capitanian) age, was the type species by monotypy. Subsequently, Williams, Harper Grant (2000) placed Caninella Liang, 1990 in the superfamily Permianelloidea, family Uncertain, subfamily Loczyellinae, but expressed doubt about the validity of Caninella since it was based on three poorly preserved specimens. Nevertheless, Shen et al. (2017) retain the placement in Richthofenidae on the basis of its somewhat bilobate outline and deep incisive sulcus in anterior or posterior views, but suggest that the genus is "highly likely a subjective synonym of either Richthofenia Kayser, 1881 or Permianella He Zhu, 1979".

Geochemistry of recent and fossil brachiopod calcite of Megathiris detruncata (Terebratulida, Megathyrididae): A modern baseline study to trace past environmental conditions

Modern and fossil calcareous shells of the terebratulide brachiopod Megathiris detruncata have been investigated for stable oxygen and carbon isotope and elemental (Mg, Sr, Mn, Fe, Ba) compositions to assess the possibility of using this species to trace past environmental conditions. Modern shells were collected from the Mediterranean Sea and the Atlantic Ocean, while fossil specimens were sampled from late Eocene to Pleistocene deposits in Europe. We mainly analysed bulk shells (i.e., primary and secondary layers together) but, in some cases, their single median and lateral septa, ventral and dorsal valves. The oxygen and carbon isotope compositions of the modern shells indicate that M. detruncata mineralizes the bulk of its calcite shell in equilibrium with seawater. In addition, their Mn, Ba, and Fe concentrations are low with few exceptions from the Atlantic Ocean where high Fe/Ca ratios can probably be related to locally enhanced Fe availability. The Sr/Ca ratio ranges narrowly between 1.4 and 1.7mmol/mol, while the Mg/Ca ratio has larger variability from about 23 to 45mmol/mol. The δ18O derived temperatures do not correlate with Mg/Ca, suggesting that Mg is likely affected by greater vital effects. Physiological control on biomineralization might also explain the somewhat larger spread of δ13C between different valves of the same individual and will require further testing by in situ analyses.The fossil M. detruncata shells have a compositional range much larger than modern specimens, with large intra-shell and intra-site variabilities indicative of partial or full alteration. Altered fossils, characterized by low δ18O and δ13C values, low Mg/Ca and Sr/Ca, and high Mn/Ca and Fe/Ca ratios are often associated with clear signs of re-crystallization and/or secondary calcite precipitation within the shells.We used fossil samples without obvious recrystallization features and chemical and isotopic compositions similar to modern specimens to discuss environmental parameters such as temperature and δ18Oseawater at the given time. We recognized variable local controls on seawater isotopic compositions in the Paratethys from the Oligocene until the Middle Miocene, and we propose somewhat warmer habitats for the M. detruncata in the Aquitaine Basin in southwestern France during the Late Oligocene. Isotope variation recorded in the Plio-Pleistocene Mediterranean shells are instead best explained by changing glacial-interglacial conditions.