Part H, Brachiopoda (Revised), vol. 1, ch. 4, p. 321–440

Williams, Alwyn; Mackinnon, David I.; Brunton, C. H. C.

doi:10.17161/dt.v0i0.5556

Cited by 23 publications

(33 citation statements)

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“…A detailed study across the secondary layer has been conducted in three regions, with the same structure but differences in shell thickness, along the dorsal valve length (figure 5). For all regions, nanoindentations often came across punctae (perforations penetrating the shell; see Williams et al 1997), with the resultant drop in the values of hardness (less than 2 GPa) and elastic modulus (less than 40 GPa). The posterior (figure 5a) and anterior (figure 5c) regions are of equal thickness (360 mm), but the values of hardness and elastic modulus are quite different.…”

Section: Novocrania Anomalamentioning

confidence: 99%

Material properties of brachiopod shell ultrastructure by nanoindentation

Pérez‐Huerta

Cusack

Zhu

et al. 2006

J. R. Soc. Interface.

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Mineral-producing organisms exert exquisite control on all aspects of biomineral production. Among shell-bearing organisms, a wide range of mineral fabrics are developed reflecting diverse modes of life that require different material properties. Our knowledge of how biomineral structures relate to material properties is still limited because it requires the determination of these properties on a detailed scale. Nanoindentation, mostly applied in engineering and materials science, is used here to assess, at the microstructural level, material properties of two calcite brachiopods living in the same environment but with different modes of life and shell ultrastructure. Values of hardness (H) and the Young modulus of elasticity (E) are determined by nanoindentation. In brachiopod shells, calcite semi-nacre provides a harder and stiffer structure (H approximately 3-6 GPa; E=60-110/120 GPa) than calcite fibres (H=0-3 GPa; E=20-60/80 GPa). Thus, brachiopods with calcite semi-nacre can cement to a substrate and remain immobile during their adult life cycle. This correlation between mode of life and material properties, as a consequence of ultrastructure, begins to explain why organisms produce a wide range of structures using the same chemical components, such as calcium carbonate.

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Section: Novocrania Anomalamentioning

confidence: 99%

Material properties of brachiopod shell ultrastructure by nanoindentation

Pérez‐Huerta

Cusack

Zhu

et al. 2006

J. R. Soc. Interface.

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“…The latter seems more convincing because these genera bearing Type-IV brachidia are phylogenetically closely related to Crurithyris , and the brachidial morphology of Cruricella is very similar to that of Crurithyris except for the initial direction or course of the primary lamellae. Such morphological change can be achieved in the secretion and resorption processes controlled by the sheathed outer epithelium during growth of the brachidia (Williams et al, 1997b) to produce the simplest Type-IV brachidium, as in Cruricella from that in Crurithyris .…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, Type-III and Type-IV brachidia are closely associated with prolongation of the crura, indicating not only a change in morphology of the brachidia but also a possible change in the position of the esophagus. The crura grow forward on either side of the esophagus to connect with the anterior body wall and posterior part of the lophophore on either side of the mouth in living brachiopods, therefore all processes so named in fossil rhynchonellides, terebratulides, and many spire-bearing brachiopods are thought to perform a similar function (Williams et al, 1997b). If so, the prolongation of crura in the modified group would indicate a displacement of the mouth to the anterior part of mantle cavity, accompanied by the forward extension of the esophagus along the dorsal mantle lobe (Fig.…”

Section: Discussionmentioning

confidence: 99%

Brachial supporting structure of Spiriferida (Brachiopoda)

et al. 2020

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The filter-feeding organ of some extinct brachiopods is supported by a skeletal apparatus called the brachidium. Although relatively well studied in Atrypida and Athyridida, the brachidial morphology is usually neglected in Spiriferida. To investigate the variations of brachidial morphology in Spiriferida, 65 species belonging to eight superfamilies were analyzed. Based on the presence/absence of the jugal processes and normal/modified primary lamellae of the spiralia, four types of brachidium are recognized. Type-I (with jugal processes) and Type-II (without jugal processes), both having normal primary lamellae, could give rise to each other by losing/re-evolving the jugal processes. Type-III, without jugal processes, originated from Type-II through evolution of the modified lateral-convex primary lamellae, and it subsequently gave rise to Type-IV by evolving the modified medial-convex primary lamellae. The evolution of brachidia within individual evolutionary lineages must be clarified because two or more types can be present within a single family. Type-III and Type-IV are closely associated with the prolongation of the crura, representing innovative modifications of the feeding apparatus in response to possible shift in the position of the mouth towards the anterior, allowing for more efficient feeding on particles entering the mantle cavity from the anterior gape. Meanwhile, the modified primary lamellae adjusted/regulated the feeding currents. The absence of spires in some taxa with Type-IV brachidium might suggest that they developed a similar lophophore to that in some extant brachiopods, which can extend out of the shell.

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“…Seven morphological terms are commonly used in the description of platystrophiid cardinalia: brachiophores, brachiophore plates, sockets, fulcral plates, cardinal process, notothyrial platform, and sessile septalium. In general, we follow the terminology used by Williams & Brunton (1997; see also discussion in Brunton et al 1996), but some of these terms have not always been used consistently and may have contributed to misinterpretations of the morphology of the platystrophiid brachiopods.…”

Section: Remarks On the Cardinalia In Platystrophiid Brachiopodsmentioning

confidence: 99%

Platystrophia (Orthida) and new related Ordovician and Early Silurian brachiopod genera

Harper¹,

Zuykov²

2007

EJES

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More than 150 Ordovician and Early Silurian brachiopod species have been assigned to the genus Platystrophia King, 1850 mainly on the basis of their Spirifer-like shell exteriors. King's concept of the genus was based on Platystrophia biforata King, which is not conspecific with Terebratulites biforatus Schlotheim, traditionally regarded as the type species of Platystrophia. Porambonites costatus Pander, 1830 is formally proposed as the type species of the genus to replace P. biforata; the latter is considered to be a nomen dubium. In our revised diagnosis, Platystrophia is restricted to a group of Arenig to upper Caradoc species from Baltica and Avalonia, whereas the Ashgill and lower Silurian taxa of these regions, hitherto assigned to Platystrophia, are placed in the new genus Neoplatystrophia. Platystrophia ponderosa Foerste, 1909 from the Upper Ordovician of North America is proposed as the type species of a new genus Vinlandostrophia. Two new species, Platystrophia baltica and Platystrophia pogrebovi from the Llanvirn-Caradoc of the East Baltic are also described.

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Part H, Brachiopoda (Revised), vol. 1, ch. 4, p. 321–440

Abstract: FIG. 295. Finely lamellose, parvicostellate exterior of the Middle Devonian Xystostrophia umbulacrum (SCHLO-THEIM) with shell margin to the right of the micrograph, ×55 (new).

Cited by 23 publications

References 0 publications

Material properties of brachiopod shell ultrastructure by nanoindentation

Material properties of brachiopod shell ultrastructure by nanoindentation

Brachial supporting structure of Spiriferida (Brachiopoda)

Platystrophia (Orthida) and new related Ordovician and Early Silurian brachiopod genera

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