Shell biomechanics in the bivalve Laternula

The ligament in Laternula is modified into a complex mechanical structure composed of rigid and flexible parts with multiple connection points. Rather than allowing the valves to move with respect to each other, this ligament tends to keep them immobile. Providing space inside the shell for the modified ligament requires a secondary increase in shell curvature of the umbones. This is achieved by the shell flexing by muscular contraction and stiffening while flexed through the construction of a rigid buttress. A vertical slit in each valve, produced by secondary resorption and breakage of shell material, confines mechanical stress to the posterior slope of the shell. □ Mollusca, Bivalvia, Laternulidae, Holocene, Indo-Pacific, functional morphology.     

Shell microstructure of the early bivalve Pojetaia and the independent origin of nacre within the mollusca

Abstract: Pojetaia and Fordilla are the oldest bivalve molluscs, occurring in roughly co‐eval rocks from the Tommotian, and are the only undisputed, well‐known bivalves from the Cambrian. New specimens reveal that Pojetaia had a laminar inner shell microstructure reminiscent of the foliated aragonite of modern monoplacophorans, and the same is true for Fordilla. A similar shell microstructure is seen in Anabarella and Watsonella, providing support for the hypothesis that they are the ancestors of bivalves. Foliated aragonite shares many similarities with nacre, and it may have been the precursor to nacre in bivalves. No cases of undisputed nacre occur in the Cambrian, in spite of much shell microstructure data from molluscs of this time period. Thus, although considered by many to be homologous among molluscs, we conclude that nacre convergently evolved in monoplacophorans, gastropods, bivalves, and cephalopods. This independent origin of nacre appears to have taken place during, or just prior to, the Great Ordovician Biodiversification Event and represents a significant step in the arms race between predators and molluscan prey.     

Revision of the Permian ammonoid family Cyclolobidae

The development of views on the phylogeny of the family Cyclolobidae Zittel, 1895 is discussed. The generic composition is emended, phylogenetic links are indicated, a new version of the phylogenetic scheme is proposed, and phylogeny of the key genera is traced at species level. The sutural ontogeny of the genus Mexicoceras is examined, its placement in the family Cyclolobidae is supported, and its position in the phylogenetic reconstruction of the family is determined.     

New generic names for Permian plants of Cathaysia

New generic names Szecalamitina nom. nov., Gigantogramme nom. nov., and Gigantocladus nom. nov. are proposed here for the Permian plants of Cathaysia to replace illegitimate names Siella Yang, 2006, Acanthocladus Yang, 2006, and Hallea Yang et Wu, 2006, which are later homonyms respectively of flowering plants Siella Pimenov, 1978 (Rubiaceae) and Acanthocladus Hasskarl, 1864 (Polygalaceae), Hallea Mathews, 1948, used for fossil seeds. New combinations are made to transfer all described species of these Chinese fossil plants into new genera, Szecalamitina, Gigantogramme, and Gigantocladus.     

Shell microstructure in mesozoic articulate brachiopods

The shell microstructure was studied based on extensive material of Triassic, Jurassic, and Cretaceous brachiopods from the orders Rhynchonellida, Terebratulida, and Thecideida. Evolutionary changes in relationships between the shell layers of thecideids were revealed; the narrowing of fibers in historical development of rhynchonellids was established; the importance of the prismatic layer for taxonomy was recognized; and differences in width and shape of fibers within the superfamilies of rhynchonellids and terebratulids were determined.     

New species of the Inoceramus-like bivalve genus Maitaia Marwick from the Permian of northeastern Asia

Historical development of Permian Inoceramus-like bivalves of the bipolar genus Maitaia Marwick in northeastern Asia is briefly considered. Five new species (Maitaia vedernikovi sp. nov., M. kusnezovi sp. nov., M. orulganica sp. nov., M. regularicostatum sp. nov., and M. tobonnoensis sp. nov.) from the Middle and Upper Permian of the Omolon Massif, northern, western, and southern Verkhoyansk Region are described.     

Shell microstructure and mineralogy of the Littorinidae: ecological and evolutionary significance

An examination of the shell microstructure and mineralogy of species from 30 of the 32 genera and subgenera of the gastropod family Littorinidae shows that most species have a shell consisting of layers of aragonitic crossed-lamellar structure, with minor variations in some taxa. However, Pellilitorina, Risellopsis and most species of Littorina have partly or entirely calcitic shells. In Pellilitorina the shell is made entirely of calcitic crossed-foliated structure, while in the other two genera there is only an outer calcitic layer of irregular-prismatic structure. A cladistic analysis shows that the calcitic layers have been independently evolved in at least three clades. The calcite is found only in the outermost layers of the shell and in species inhabiting cooler waters of both northern and southern hemispheres. Calcium carbonate is more soluble in cold than warm water and, of the two polymorphs, calcite is about 35% less soluble than aragonite. We suggest that calcitic shell layers are an adaptation of high latitude littorinids to resist shell dissolution.     

Revision of Late Permian Nonmarine Bivalves of the Genus Opokiella Plotnikov, 1949

Paleontological Journal - The genus Opokiella occurs in the Upper Permian (upper part of the Guadalupian–Lopingian) of the East European Platform, sharply differing from members of the...     

Revision of trilobites of the genus Paraphillipsia Tumanskaya from the Permian Olistoliths of Crimea

The genus Paraphillipsia Tumanskaya, 1935 is revised and the species P. taurica Tumanskaya, 1935 from the Middle Permian of Crimea is redescribed. The age distribution of species of the genus Paraphillipsia from Crimea is emended based on new stratigraphic data on the locality (species previously considered Artinskian became Roadian). As a result of analysis of a rather large number of new records of trilobites, the species P. kussicum, P. tauricum var. anfensis, and P. netschaewi are synonymized under P. taurica.     

Shell layers of the black-lip pearl oyster Pinctada margaritifera: matching microstructure and composition

The nacre-prism transition of the mollusc shell Pinctada margaritifera was studied using scanning electron microscopy, electron probe micro-analysis (EPMA) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Mineralogical change is correlated with a change in organic matrix. Previous analyses had shown that sugars were involved in the transition layer (fibrous aragonite). The new Energy Dispersive Spectrometry (EDS) and TOF-SIMS maps show that the modifications at the layer boundary are complex, and that proteins and lipids are also involved. Detailed TOF-SIMS maps show that the thick organic envelopes surrounding the prisms, and between the prisms and the fibrous aragonitic layer, are not composed by regular layers, but are a patchwork of various molecules. The amino acid compositions of the nacreous and prismatic layer are compared thanks to the TOF-SIMS localized analyses.     

The cranial anatomy,ontogeny, and relationships of Karpinskiosaurus secundus (Amalitzky) (Seymouriamorpha,Karpinskiosauridae) from the Upper Permian of European Russia

The Upper Permian seymouriamorph tetrapod Karpinskiosaurus from European Russia includes two species: Karpinskiosaurus secundus and Karpinskiosaurus ultimus. Karpinskiosaurus secundus is represented by two specimens with skull lengths of about 75 mm. All specimens of K. ultimus are smaller than those of K. secundus. Revision of the cranial anatomy of all previously known and several new specimens of Karpinskiosaurus shows that the specimens of K. secundus and most of the specimens of K. ultimus represent the ontogenetic series of one species: K. secundus. The holotype specimen of K. ultimus requires revision, with the aim to find out whether it represents a second species of Karpinskiosaurus or not. The available material permits new reconstructions of the largest, holotype skull, and one smaller skull with a length of about 36 mm. Karpinskiosaurus secundus is included in a cladistic analysis for the first time here. The analysis shows it to form a sister taxon to Discosauriscidae. The clade comprising Karpinskiosaurus secundus plus Discosauriscidae forms a sister group to Seymouriidae. Karpinskiosaurus secundus has a large postorbital and a short preorbital region, and the orbits are placed in the posterior portion of the anterior half of the skull length. Among all seymouriamorphs, such cranial proportions are exhibited only by the largest known specimens of Discosauriscus austriacus. None of the specimens of K. secundus described here exhibits the presence of sensory grooves; thus, all specimens composing the ontogenetic sequence of K. secundus are considered to be terrestrial. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010.     

Revision of generic limits in Hyptis Jacq. (Labiatae) and its allies

The primarily neotropical sub-tribe Hyptidinae (Labiatae: tribe Ocimeae) consists of six or seven genera of which the largest is the genus Hyptis with over 300 species. Over the last 12 years, work on the group at the Royal Botanic Gardens, Kew, examining macro-morphological and anatomical characters, as well as pollen surface and chromosome number, has indicated that the genus Hyptis is paraphyletic, with a few of the larger-flowered sections apparently being more closely related to the neighbouring genus Eriope than to the smaller-flowered sections of Hyptis . This has been confirmed by preliminary cladistic studies now in progress. In order to provide a working classification for the group, prior to the publication of the more detailed study, two new genera: Hypenia and Hyptidendron are created. A key to genera of South American Hyptidinae is provided, as well as one to distinguish the two new sections of Hyptidendron . Forty-five new combinations are made.     

To the Revision of Freshwater Permian and Triassic Ostracods of the Genus Gerdalia Belousova, 1961

Paleontological Journal - Partial revision of the Permian–Triassic freshwater ostracod genus Gerdalia Belousova, 1961 is performed. The genus is shown to be a collective group. The holotype...     

Revision of the family Idelinellidae,with a review of the Permian Eoblattida (Insecta)

Permian Eoblattida, which include the families Tillyardembiidae, Protembiidae (=Sylvardembiidae), Soyanopteridae, and Idelinellidae, are reviewed. The latter family is revised; it includes Idelinella macroptera Storozhenko, 1997 from the Middle Permian (Lower Kazanian Substage) of northern European Russia, Permostriga augustalis Novokshonov, 1999, Sylvastriga miranda Aristov, 2004, Strigulla cuculiophora (Aristov, 2002) comb. nov., Cucullistriga cucullata Aristov et Rasnitsyn, gen. et sp. nov., Scutistriga scutata Aristov et Rasnitsyn, gen. et sp. nov. from the Lower Permian (Kungurian Stage) of the Urals, Permeoblatta borealis Rasnitsyn et Aristov, 2010 from the Upper Permian (Upper Severodvinian Substage) of northern European Russia, and probably also Rasstriga americana Aristov et Rasnitsyn, gen. et sp. nov. from the Upper Carboniferous (Desmoinesian Stage) of Illinois.     

A microstructure study on silicified wood from the Permian Petrified Forest of Chemnitz

Three typical plant taxa from the fossil assemblage of the 290-million-year-old Chemnitz Petrified Forest (Zeisigwald Tuff Horizon, Leukersdorf Formation) were studied with regard to the microstructure of the petrifactions: samples of the tree fern Psaronius sp., the seed fern Medullosa stellata, and the gymnosperm Dadoxylon sp. The plant’s tissues are anatomically preserved by silica exhibiting different crystalline order and by other mineralisations. Specimens were studied by means of electron backscatter imaging and electron backscatter diffraction in a scanning electron microscope. The cell walls were largely preserved by quartz crystals, the cell lumina by cryptocrystalline silica. The former organisation and chemical composition of the vascular tissue are mirrored by varying grain formation and grain size. Results are discussed in terms of extant xylem cell wall organisation showing highly hydrophilic cellulose and hemicellulose cross-linked by hydrophobic lignin. The effect of polar and non-polar wood components on the precipitation of silica from aqueous solution and on the formation of crystals is convincing, and the reported results provide a better understanding of how silica replaced organic matter during the petrifaction process.     

Revision of Late Permian tetrapod tracks from the Dolomites (Trentino-Alto Adige,Italy)

The Val Gardena Formation of the Dolomites region in northern Italy preserves the most significant assemblage of Late Permian tetrapod footprints in the world. More than 120 years of collecting resulted in about 900 publicly accessible specimens from the study area. This huge amount of data is comprehensively revised in the light of recent advances in the study of Late Palaeozoic – Early Mesozoic tetrapod ichnofossils. According to our analyses, the Val Gardena Sandstone Formation includes tracks that can be assigned to cf. Batrachichnus isp. (temnospondyl amphibian), Capitosauroides isp. (amphibian), Dicynodontipus isp. (cynodont therapsid), Dolomitipes accordii n. igen. n. comb. (dicynodont therapsid), cf. Dromopus isp. (neodiapsid), Pachypes dolomiticus (pareiasaurian parareptile), Paradoxichnium problematicum (archosauromorph neodiapsid), Procolophonichnium tirolensis n. comb. (procolophonoid parareptile), cf. Protochirotherium isp. (archosauriform neodiapsid) and Rhynchosauroides pallinii (neodiapsid). The ichnoassociation is dominated by tracks of neodiapsid and parareptilian tetrapods, whereas synapsid and anamniote tracks are rather minor components. It includes 10 out of 12 tetrapod ichnogenera known from Lopingian deposits and thus it constitutes a reference for the Paradoxichnium biochron. It shows striking similarities with other low-latitude non-aeolian contemporaneous ichnoassociations of Europe and North Africa, differences may be linked to the palaeoenvironment. Moreover, it shows a clear Triassic affinity.

The new ichnogenus Dolomitipes was registered in Zoobank.org. urn:lsid:zoobank.org:act:5B4D871C-D16A-4E93-8211-CEE08019BA60     

A new possible bivalve burrow Oblongichnus solodukhoi from the late Kazanian (middle Permian) stratotype section in Russia

A burrow previously assigned to the ichnotaxon Palaeophycus insignis is redescribed, and a new ichnotaxon Olongichnus solodukhoi n. igen. n. isp is erected for this flattened, slightly curved, multi-oriented, smooth burrow that has a thick lining with internal and external very fine-grained mucuous layers. It shows subrectangular to oblong form in cross section. O. solodukhoi is collected from the lowermost part of the Member D (Seryi Kamen Member, Pechishchi Beds) of the late Kazanian (middle Permian) stratotype section (East European Platform). It occurs in yellowish grey dolostone formed within open shallow-marine environments. O. solodukhoi records combined feeding and dwelling behaviours of a suspension-feeding organism. It could be produced by burrowing organisms with a simple flattened morphology, such as flatworms or polychaetes; however, we favour elongate and ultra-elongate bivalves as the potential tracemakers of the reported burrows.