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Gegenbaur's classic and almost universally accepted view of the primitive visceral skeleton of vertebrates, envisioning gill, hyoid, and mandibular arches as uniform, serially homologous (homonomous) structures separated by gill clefts, has not been actually demonstrated among either recent or fossil forms. In all cases the mandibular and hyoid arches are specialized in various ways to meet the functional requirements of the mandibular arch that frames the mouth opening.

• Read more about New evidence on the nature of the jaw suspension in Palaeozoic anacanthous sharks

A shelly fauna occurring in the Arra Mountains near Ballina, Co. Tipperary, is correlated with a fauna from Ballycar in the Cratloe Hills inlier, South Clare, and assigned to the upper Wenlock. The faunas are considered to have been derived from a shelf area situated to the south-east, and to have been transported north-westwards towards a basin limited south-eastwards and southwards by the Nenagh-Navan Line and by the Gallowshill-Silvermines Fault.

• Read more about Palaeogeographical implications of two Silurian shelly faunas from the Arra Mountains and Cratloe Hills, Ireland

A reconstruction of the apparatus of Ozarkodina sagitta (Walliser) is proposed, consistent with the composition of other apparatuses of the genus Ozarkodina and based on collections of disjunct conodont elements from Bohemia, Britain, Ireland, and the Carnic Alps of Austria. Descriptions of the apparatuses of the three subspecies of O. sagitta include details of the previously undescribed hindeodellan, plectospathodontan, and trichono-dellan elements.The stratigraphical distribution of O.

• Read more about The Silurian conodont Ozarkodina sagitta and its value in correlation

Broken pieces of a huge thick-shelled myalinid forming a calcirudite in the Kinta Valley, West Malaysia, show that the live shells rested on spectacular flanges formed by acute bends in the lateral flanks of the valves. Consequently the shells had a large permanent posterior gape, and must therefore have lived below low-tide level. The flanges may have acted like snowshoes to support the animals on the surface of a fine carbonate substrate, or they may have acted as outriggers to prevent overturning.

• Read more about Tanchintongia gen. nov., a bizarre Permian myalinid bivalve from West Malaysia and Japan

Ammonites (Crioceras) occultum Seeley and Hamites phillipsi Phillips, the type species of Paracrioceras and Hoplocrioceras Spath, 1924, are redescribed and the original concept of the genera is reviewed. The 'Tethyan' forms Emericiceras and Aspinoceras are regarded as junior subjective synonyms of Paracrioceras and Hoplocrioceras respectively. As defined by Spath, Hoplocrioceras embraces small forms with weakly aspinoceratid coiling together with larger, crioceratitid species; this definition cuts completely across existing generic classification of related Tethyan forms.

• Read more about The interpretation of the lower Cretaceous heteromorph ammonite genera Paracrioceras and Hoplocrioceras Spath, 1924

The classical separation of Cainozoic long-looped brachiopods into two groups of genera, dallinid and terebratellid, according to certain early developmental features of the loop, does not withstand critical examination. These studies confirm the high taxonomic value of developing loop patterns but consider features of the developing loop, used previously to separate families, to be invalid. The dallinid sequence as defined previously is shown herein to include two groups of genera differing in the loop patterns exhibited during intermediate phases of development.

• Read more about Loop development and the classification of terebratellacean brachiopods

Several species of Mesozoic and Tertiary serpulids from Europe and the Middle East were infested by a colonial organism which is preserved as the mould of a stolonal network with polyp chambers buried in the peripheral zone of the calcareous tube. The polyp chambers open to the outer surface of the tube through small, usually semicircular apertures. The mould is the result of incorporation of the organism into the worm tube during calcification by the serpulid: it is not a boring.

• Read more about Hydroid-serpulid symbiosis in the Mesozoic and Tertiary

Three species of Jurassic freshwater ostracods representing the genera Timiriasevia, Darwinula, and (?)Limnocythere are described from the limestone of the Kola Formation of the Pranhita-Godavari Valley. India. Of these Timiriastvia digitalis sp. nov. is new, (?)Limnocythere sp, A is left under open nomenclature, and Darn-inula cf. D. sarytirmenensis compared with the Middle Jurassic species of that name recorded from the Mangishlaka Peninsula, U.S.S.R.

• Read more about Jurassic freshwater ostracods from the Kota Limestone of India

Since its appearance near the beginning of the Cretaceous, the family Glycymerididae has retained the same simple shell form. Variation among species is largely restricted to differences in size and external sculpture. This evolutionary conservatism can be explained in terms of the morphology and ecology of Glycymeris. Bivariate and multivariate studies of interactions among shell characters show that individual parameters of the shell are closely interrelated; there are rigid geometrical and mechanical constraints on deviations from the simple form.

• Read more about Functional morphology, ecology, and evolutionary conservatism in the Glycymerididae (Bivalvia)

Studies on some species of the Ambocoeliidae from the Devonian of Poland have shown that their micro-ornamentation may be completely changed by secondary factors such as weathering, which leads to the separation of initially invisible coarse-crystalline structures, known as microspines, from the primary shell layer. Thus, secondary microspinosity appears on the surface of originally smooth or radially ornamented specimens. The recognition of primary and secondary micro-ornamentation is shown to be important in taxonomic studies.

• Read more about Secondary changes in micro-ornamentation of some Devonian ambocoeliid brachiopods