Ultrastructure in Palmatolepis sp. and Polygnathus sp

Pierce, Richard W.; Langenheim, Ralph L.

doi:10.1130/0016-7606(1969)80[1397:uipsap]2.0.co;2

Cited by 7 publications

(6 citation statements)

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“…In contrast, specimen preparation techniques used in earlier studies, being microtome sections of block‐mounted conodont elements (Pietzner et al . 1968; Szaniawski 1987; Kemp 2002) and examination of peels and acid‐etched surfaces of block‐mounted specimens (Pierce & Langenheim 1969; Barnes et al . 1970), most likely modified the tissues to some extent and complicated characterization of their crystalline structure.…”

Section: Discussionmentioning

confidence: 99%

“…The present study has examined sections of conodont elements that were Ar-ion-milled, and produced what we suggest are the first published images of undisrupted crystalline structure of basal body, hyaline, and albid crown tissues. In contrast, specimen preparation techniques used in earlier studies, being microtome sections of block-mounted conodont elements (Pietzner et al 1968;Szaniawski 1987;Kemp 2002) and examination of peels and acid-etched surfaces of block-mounted specimens (Pierce & Langenheim 1969;Barnes et al 1970), most likely modified the tissues to some extent and complicated characterization of their crystalline structure. While excellent images of superficially similar apatitic materials (e.g.…”

Section: Histological Artefactsmentioning

confidence: 91%

“…Transmission electron microscopy (TEM) has the potential to reveal nanometre‐scale details of crystal geometry, morphology, alignment, and composition, yet to date there are only five such published studies of conodont apatite (Pietzner et al . 1968; Pierce & Langenheim 1969; Barnes et al . 1970; Szaniawski 1987; Kemp 2002).…”

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New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

Trotter

Gerald

Kokkonen

et al. 2007

LET

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2007: New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy. Lethaia , Vol. 40, New crystalline structures have been observed in argon ion-milled conodont elements from a diverse suite of Ordovician taxa (' Cordylodus robustus ', Drepanoistodus suberectus , Panderodus gracilis , Plectodina ? sp., Aphelognathus sp., Periodon aculeatus ), using transmission electron microscopy (TEM). Electron diffraction patterns of albid tissue reveal that the component crystals are extraordinarily large, in the order of hundred(s) of microns. These large albid crystals show typical cancellate porosity, although a distinctly lamellar structure has also been observed within a large albid crystal positioned between hyaline lamellar and cancellate albid tissues. There is a distinct absence of 'interlamellar space' within all hyaline tissues examined, which are characterized by a polycrystalline matrix of micron-scale elongate crystals that are both strongly aligned and tightly bound within a broader lamellar structure. Optical opacity, caused by light scattering within large ( ≥ 0.5 µ m) pores, is also a feature of both albid and polycrystalline lamellar crown tissues. Accordingly, conodont hard tissues are differentiated by crystal size and shape, as well as inter-and intracrystalline porosity.These new observations highlight the structural complexities of conodont histologies and the need for more comprehensive investigations particularly of transitional crown tissues, which are not well defined by terms typically used in the literature. Their histological structures are interpreted to be a product of in vivo crystallization and thus provide new insights into the relative porosity, permeability, and inherent integrity of the tissues as well as their growth relationships. Accordingly, these data not only have implications for earlier histological and palaeobiological interpretations of conodont hard tissues but are also fundamental in determining their chemical integrity, which is crucial for characterizing palaeoseawater composition and palaeoenvironmental change. The potential for conodont apatite to retain primary chemical information depends on crystal size and permeability, so the large albid crystal domains are consistent with parallel geochemical studies that suggest that cancellate albid crown is more resistant to diagenetic modification. ᮀ Apatite, conodont, histology, TEM, transmission electron microscopy, palaeoseawater chemistr y.

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Section: Discussionmentioning

confidence: 99%

Section: Histological Artefactsmentioning

confidence: 91%

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New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

Trotter

Gerald

Kokkonen

et al. 2007

LET

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“…The advent of the transmission and, especially, the scanning electron microscopes has allowed considerable advances in our knowledge of conodont ultrastructure. Studies using these more advanced techniques have been published by Pietznerand others (1968), Pierce andLangenheim (1969, 1970), and Barnes and others (1970).…”

Section: Introduction Previous Workmentioning

confidence: 99%

Ultrastructure of Some Ordovician Conodonts

Barnes¹,

Sass²,

Monroe³

1972

Geological Society of America Special Papers

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The ultrastructure of 24 form-species of Ordovician conodonts has been examined with the scanning electron microscope. The conodonts represent two provincial and three subprovincial faunas and include hyaline forms, neurodonts (a subgroup of the hyalines), and cancellate forms (conodonts with white matter).The robust neurodont elements are constructed of cone-in-cone lamellae separated by distinct interlamellar spaces. There is limited fusion between adjacent lamellae and between the long, needle-like crystallites within each lamella. Crystallites become granular in form near the base in some neurodonts. A sheet-like septum bisects the elements longitudinally, but does not pass through the central growth canal. The latter is surrounded by fused lamellae producing a strengthened wall. Minute spheres occur along crystallites in some neurodonts. In the non-neurodont hyaline conodonts, greater fusion occurs between lamellae and between crystallites, and white matter may develop along the central growth canal; no septum or spheres have been noted within this group. Increased fusion is considered to have produced stronger elements capable of acquiring lateral compression, costae, and keels. Cancellate conodonts develop white matter primarily in their cusps and denticles. White matter is finely crystalline with no lamellar structure, but with abundant circular and linear voids. There is no pattern to the occurrence of the holes, but most linear voids are oriented transversely. White matter is formed by secondary transformation from lamellar material; this change is reflected in a transitional zone of incipient white matter, where 1 2 BARNES, SASS, AND MONROE a reorientation of the hard tissue is evident. Minute spheres occur in white matter; the central growth canal is destroyed and does not penetrate beyond the transition zone. White matter is believed to provide extra strength to the element allowing marked lateral compression and sharp margins.Although separated on structural criteria, these three conodont groups appear to occupy distinct and evolving ecosystems during the Ordovician. Three theories are proposed which, individually or in combination, may indicate the functional advantages conveyed by the development of white matter:(1) that the factors of element weight and phosphate availability were important, (2) that greater strength to cope with variable stresses was achieved, and (3) that white matter was induced by a disruption in vascular supply, possibly resulting from a partial eruption through the secreting tissues.

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“…As a rule, lamellar tissue, white matter and interlamellar tissue are recognized (see Pierce & Langenheim 1969;Müller & Nogami 1971;Barnes et al 1973; Barnes & Slack 1975;Donoghue 1998, among others). These hard-tissue types are well known and are described in a number of works.…”

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confidence: 99%

A new type of conodont hard tissue

Журавлев

2002

LET

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Ultrastructure in Palmatolepis sp. and Polygnathus sp

Cited by 7 publications

References 0 publications

New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

Ultrastructure of Some Ordovician Conodonts

A new type of conodont hard tissue

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