Aspidin : The Precursor of Bone

Tarlo, L. B. Halstead

doi:10.1038/199046a0

Cited by 32 publications

(11 citation statements)

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“…L3 incorporates many ply and is extremely thick. P. megalopteryx exhibits typical psammosteid histology, based on comparison to previous studies (Gross, ; Bystrow, ; Tarlo and Tarlo, ; Halstead Tarlo, ; Johanson et al, ). Given that the position of psammosteids within pteraspidiformes is well supported based on the homology of the dermal skeletal plates (Blieck, ; Janvier, ; Pernegre and Elliott, ), it seems likely that the psammosteid dermal skeleton is highly autapomorphic.…”

Section: Resultsmentioning

confidence: 57%

“…Obruchev () later resurrected Rohon's () hypothesis, interpreting the tissue as cellular and the thread‐like cavities as cell lacunae or canaliculi. This interpretation was supported by Halstead (; Halstead Tarlo, , 1964a, b, ) and Novitskaya (). The opposing view, that the elongate spaces represent voids of unmineralised collagen fibres (most frequently identified as Sharpey's fibres), was maintained by Gross (), Bystrow (), Ørvig (, ), and Moss ().…”

Section: Historical Reviewmentioning

confidence: 99%

“…Inevitably, confusion over the identity of the unmineralised aspidin spaces spilled into the wider debate concerning the primitiveness of cellular versus acellular bone. Within this context, aspidin has variously been interpreted as a primitive acellular type of bone (Denison, ; Halstead, ), a secondarily acellular bone (Stensiö, ; Ørvig, ), a primitive type of cellular bone (Obruchev, ; Halstead Tarlo, , 1964a, b; Halstead, ), a type of dentine (Urist, , 1964a, b; Denison, ) and an intermediate grade between dentine and bone (Halstead, ). Urist (, 1964a, b) argued that aspidin could not be a type of bone on the grounds that it did not undergo remodelling, yet tentative evidence of resorption was reported in the psammosteids in the form of scalloping of concentric aspidin lamellae (Gross, ; Halstead Tarlo, , 1964a, b).…”

Section: Historical Reviewmentioning

confidence: 99%

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Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

Keating

Marquart

Donoghue

2015

Journal of Morphology

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Living vertebrates are divided into those that possess a fully formed and fully mineralised skeleton (gnathostomes) versus those that possess only unmineralised cartilaginous rudiments (cyclostomes). As such, extinct phylogenetic intermediates of these living lineages afford unique insights into the evolutionary assembly of the vertebrate mineralised skeleton and its canonical tissue types. Extinct jawless and jawed fishes assigned to the gnathostome stem evidence the piecemeal assembly of skeletal systems, revealing that the dermal skeleton is the earliest manifestation of a homologous mineralised skeleton. Yet the nature of the primitive dermal skeleton, itself, is poorly understood. This is principally because previous histological studies of early vertebrates lacked a phylogenetic framework required to derive evolutionary hypotheses. Nowhere is this more apparent than within Heterostraci, a diverse clade of primitive jawless vertebrates. To this end, we surveyed the dermal skeletal histology of heterostracans, inferred the plesiomorphic heterostracan skeleton and, through histological comparison to other skeletonising vertebrate clades, deduced the ancestral nature of the vertebrate dermal skeleton. Heterostracans primitively possess a four‐layered skeleton, comprising a superficial layer of odontodes composed of dentine and enameloid; a compact layer of acellular parallel‐fibred bone containing a network of vascular canals that supply the pulp canals (L1); a trabecular layer consisting of intersecting radial walls composed of acellular parallel‐fibred bone, showing osteon‐like development (L2); and a basal layer of isopedin (L3). A three layered skeleton, equivalent to the superficial layer L2 and L3 and composed of enameloid, dentine and acellular bone, is possessed by the ancestor of heterostracans + jawed vertebrates. We conclude that an osteogenic component is plesiomorphic with respect to the vertebrate dermal skeleton. Consequently, we interpret the dermal skeleton of denticles in chondrichthyans and jawless thelodonts as independently and secondarily simplified. J. Morphol. 276:657–680, 2015. © 2015 The Authors Journal of Morphology Published by Wiley Periodicals, Inc.

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Section: Resultsmentioning

confidence: 57%

Section: Historical Reviewmentioning

confidence: 99%

Section: Historical Reviewmentioning

confidence: 99%

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Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

Keating

Marquart

Donoghue

2015

Journal of Morphology

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“…Aspidin. Aspidin has been the subject of much debate, much of it focused on whether it represents a form of cellular or acellular bone or, indeed, whether it is in fact a form of dentine (Rohon, 1893, 1901; Gross, 1935; Obruchev, 1941; Bystrow, 1955; Ørvig, 1958, 1965, 1967, 1968; Currey, 1961; Halstead Tarlo, 1963, 1964, 1965; Denison, 1967; Moss, 1968; Halstead, 1969, 1973, 1974, 1987; Smith & Hall, 1990; Smith et al. 1995).…”

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confidence: 99%

Origin and evolution of the integumentary skeleton in non‐tetrapod vertebrates

2009

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Most non-tetrapod vertebrates develop mineralized extra-oral elements within the integument. Known collectively as the integumentary skeleton, these elements represent the structurally diverse skin-bound contribution to the dermal skeleton. In this review we begin by summarizing what is known about the histological diversity of the four main groups of integumentary skeletal tissues: hypermineralized (capping) tissues; dentine; plywood-like tissues; and bone. For most modern taxa, the integumentary skeleton has undergone widespread reduction and modification often rendering the homology and relationships of these elements confused and uncertain. Fundamentally, however, all integumentary skeletal elements are derived (alone or in combination) from only two types of cell condensations: odontogenic and osteogenic condensations. We review the origin and diversification of the integumentary skeleton in aquatic non-tetrapods (including stem gnathostomes), focusing on tissues derived from odontogenic (hypermineralized tissues, dentines and elasmodine) and osteogenic (bone tissues) cell condensations. The novelty of our new scenario of integumentary skeletal evolution resides in the demonstration that elasmodine, the main component of elasmoid scales, is odontogenic in origin. Based on available data we propose that elasmodine is a form of lamellar dentine. Given its widespread distribution in non-tetrapod lineages we further propose that elasmodine is a very ancient tissue in vertebrates and predict that it will be found in ancestral rhombic scales and cosmoid scales.

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“…While one hypothesis suggested that the four tissues all emerged early in vertebrate evolution, the other assumed a long time of tissue plasticity in early mineralized skeletons which preceded differentiation processes that came later on (Tarlo 1963, Halstead 1969). In addition, for many decades, synthesis of paleontological data was influenced by Ernst Haeckel's biogenetic law—that ontogeny recapitulates phylogeny—meaning that skeletons of ancestral adult vertebrates were assumed to be derived from cartilage, analogous to their embryonic skeletons (Hall 2003).…”

Section: Skeletal Evolution: Different Viewsmentioning

confidence: 99%

Where did bone come from?

Wagner

Aspenberg

2011

Acta Orthopaedica

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Bone is specific to vertebrates, and originated as mineralization around the basal membrane of the throat or skin, giving rise to tooth-like structures and protective shields in animals with a soft cartilage-like endoskeleton. A combination of fossil anatomy and genetic information from modern species has improved our understanding of the evolution of bone. Thus, even in man, there are still similarities in the molecular regulation of skin appendages and bone. This article gives a brief overview of the major milestones in skeletal evolution. Some molecular machineries involving members of core genetic networks and their interactions are described in the context of both old theories and modern genetic approaches.

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Aspidin : The Precursor of Bone

Cited by 32 publications

References 1 publication

Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

Origin and evolution of the integumentary skeleton in non‐tetrapod vertebrates

Where did bone come from?

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