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Sophie Sanchez - One of the best experts on this subject based on the ideXlab platform.
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The developmental relationship between teeth and dermal Odontodes in the most primitive bony fish Lophosteus.
eLife, 2020Co-Authors: Donglei Chen, Sophie Sanchez, Henning Blom, Paul Tafforeau, Tiiu Märss, Per E. AhlbergAbstract:Human teeth are an example of Odontodes: hard structures made of a material called dentine that are sometimes coated in enamel. Teeth are the only Odontodes humans have, but other vertebrates (animals with backbones) have tooth-like scales on their skin. These structures are called dermal Odontodes, and sharks and rays, for example, are covered with them. How these structures evolved, and whether teeth or dermal Odontodes developed first, continues to spark great discussion among palaeontologists. Some researchers think that teeth evolved from dermal Odontodes, a theory known as the ‘scales-to-teeth’ hypothesis. Others think dermal Odontodes are distinct from teeth because they lack the same spatial organization. To investigate this further, palaeontologists are looking at the earliest examples of Odontodes they can find: fossils of early vertebrates that carry both teeth and dermal Odontodes. Here, Chen et al. have studied Lophosteus, one of the earliest bony fishes that lived more than 400 million years ago, to explore early tooth evolution and growth patterns. Chen et al. digitally dissected a fossilized Lophosteus jawbone using submicron X-ray imaging, a technique with resolution to less than one millionth of a metre. Imaging thin sections of the specimen, found in Estonia, Chen et al. reconstructed the entire sequence of Odontode development in the bony fish in 3D. The analysis showed that teeth and dermal Odontodes initially take shape together but differentiate as they grow, presumably instructed to do so by various developmental signals. However, at a later stage, the two types of Odontodes become similar in appearance again, suggesting that they respond to each other’s signals. For example, as the jawbone grows, dermal Odontodes overgrow the earliest formed teeth. These younger Odontodes resemble teeth, while the new teeth developing near the dermal Odontodes take after dermal Odontodes. These findings suggest that teeth and dermal Odontodes are not wholly separate systems but, instead, are closely related on a molecular level. The results also show that contrary to the ‘scale-to-teeth’ hypothesis, teeth do not evolve from fully formed dermal Odontodes, rather the two types of Odontodes form out of one founder. This research builds on our knowledge from modern sharks and points to a previously unrecognised evolutionary relationship between teeth and dermal Odontodes. It also furthers our understanding of how molecular regulation controls development.
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Dental ontogeny in the most primitive bony fish Lophosteus reveals the developmental relationship between teeth and dermal Odontodes
2020Co-Authors: Donglei Chen, Sophie Sanchez, Henning Blom, Paul Tafforeau, Tiiu Märss, Per AhlbergAbstract:Ontogenetic data obtained by synchrotron microtomography of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically basalmost stem osteichthyan, reveal developmental relationships between teeth and ornament that are not obvious from the adult morphology. The earliest Odontodes are two longitudinal founder ridges formed at the ossification center. Subsequent Odontodes that are added lingually to the ridges turn into conical teeth and undergo cyclic replacement, while those added labially achieve a stellate appearance. The stellate Odontodes deposited directly on the bony plate are aligned with the alternate files of the teeth. Successive Odontodes overgrowing the labial tooth rows become tooth-like and the replacement teeth near to them are ornament-like. We propose that teeth and ornament are modifications of a single Odontode system regulated and differentiated by the oral and dermal signals; signal cross-communication between the two domains can occur around the oral-dermal boundary.
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Virtual thin sections in transverse view of the dorsal ridge spine of Romundina stellina (P.11714).
2017Co-Authors: Anna Jerve, Sophie Sanchez, Per Erik Ahlberg, Tatjana HaitinaAbstract:(A1-A3) Three-dimensional reconstruction created from low-resolution (7.46 micron) synchrotron data. Red lines on B1 indicate approximate locations of A1-A3. (B1-B4) 3D reconstructions of the spine illustrating its overall morphology in (B1) left lateral, (B2) right lateral, (B3) anterior, and (B4) posterior, (C) dorsal, and (D) ventral views. Scale bars are 1500 μm. Abbreviations are: cc, central canal; eo, embedded Odontode; pch.b, perichondral bone; s, sediment; vc, vascular canal; vco, vascular canal opening.
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Right oblique view of the spine reconstructed from low-resolution data (7.46 μm).
2017Co-Authors: Anna Jerve, Sophie Sanchez, Per Erik Ahlberg, Tatjana HaitinaAbstract:(A) Shows the approximate location of the area of interest examined at high-resolution (0.678 μm). Scale bar is 1500 μm. (B) Virtual thin section of the spine, showing its overall histological organization, with generations of Odontodes highlighted in different shades of pink. Yellow arrows indicate the presence of poorly mineralized bone. Blue is bone with many vascular canals, green is bone with few vascular canals, and red is the outer layer of dentine ornamentation. Scale bar is 300 μm. (C) Closer view of an Odontode. Scale bar is 70 μm. (D1-D3) 3D reconstruction of Odontode morphology, showing relative distribution of Odontodes in three generations (go1, pink; g0 2. dark purple; go3, light purple). Scale bar is 300 μm. Abbreviations are: cc, central canal; go1, 2, 3, first, second, third generation Odontodes; n, node; o, osteocyte spaces; s, sediment; sd, semidentine; vc, vascular canal; vco, vascular canal opening.
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Vascularization of the Romundina dorsal ridge spine using high-resolution synchrotron data (0.678 μm).
2017Co-Authors: Anna Jerve, Sophie Sanchez, Per Erik Ahlberg, Tatjana HaitinaAbstract:(A) 3D reconstructions of the four individual layers of vascular canals beginning with the innermost layer (yellow). Scale bar is 300 μm. (B) Virtual thin-section of the reconstructed vascularization that illustrates how the different layers of canals relate to each other. Scale bar is 350 μm. (C) and (D) Virtual thin sections with the different vascular layers highlighted to correspond to the reconstructed data. Scale bar is 350 μm. Abbreviations are: bvc, bone vascular canals; cc, central cavity; dvc, dentine vascular canals; eo, embedded Odontode; o, osteocyte spaces; s, sediment; sd, semidentine; vc, vascular canal.
Miquelarena, Amalia María. - One of the best experts on this subject based on the ideXlab platform.
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A new species of Hisonotus (Siluriformes, Loricariidae) of the upper río Uruguay basin
2013Co-Authors: Aquino, Adriana Elbia, Schaefer, Scott A., Miquelarena, Amalia María.Abstract:A new species of the hypoptopomatine genus Hisonotus (Loricariidae) is described from a small tributary of the upper río Uruguay basin near the border between Uruguay and Brazil. The new species can be distinguished from all other congeners by the following combination of characters: (1) presence of serrae along distal two thirds of posterior margin of pectoral-fin spine (versus serrae absent, posterior margin smooth); (2) Odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow Odontode-free area covered by pad of soft tissue; (3) caudal peduncle short (27–34% SL, versus > 34% SL) and deep (13–15 % SL, versus 34) y alto (13–15 % LE, versus usualmente < 13); (4) ojo grande (15–19 % in HL, versus usualmente < 13), y (5) patrón de coloración de la aleta caudal, cuando se encuentra bien definido, marrón oscuro, con un par de manchas blanquecinas sobre los lóbulos superior e inferior de la aleta. La distribución geográfica de la nueva especie es discutida en relación al grado de endemismo registrado en otros grupos de peces de la cuenca del río Uruguay.Facultad de Ciencias Naturales y Muse
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A new species of Hisonotus (Siluriformes, Loricariidae) of the upper Río Uruguay Basin. American Museum novitates ; no. 3333
New York NY : American Museum of Natural History, 2001Co-Authors: Aquino, Adriana E., Schaefer, Scott Allen 1958-, Miquelarena, Amalia María.Abstract:12 p. : ill. ; 26 cm.Includes bibliographical references (p. 11-12).A new species of the hypoptopomatine genus Hisonotus (Loricariidae) is described from a small tributary of the upper río Uruguay basin near the border between Uruguay and Brazil. The new species can be distinguished from all other congeners by the following combination of characters: (1) presence of serrae along distal two thirds of posterior margin of pectoral-fin spine (versus serrae absent, posterior margin smooth); (2) Odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow Odontode-free area covered by pad of soft tissue; (3) caudal peduncle short (27-34% SL, versus > 34% SL) and deep (13-15% SL, versus < 13% SL); (4) eye large (15-19% HL, versus < 13% HL); and (5) caudal-fin pigmentation, when well defined, dark brown with a pair of whitish blotches on upper and lower lobes. The significance of the distribution of the new species is discussed relative to the degree of endemism of other fish groups in the Uruguay basin
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Redescription of Hypoptopoma inexspectata (Holmberg, 1883), with notes on its anatomy (Siluriformes: Loricariidae)
2001Co-Authors: Aquino, Adriana Elbia, Miquelarena, Amalia María.Abstract:Se presenta una diagnosis y redescripción de Hypoptopoma inexspectata sobre la base del examen de material adicional y comparación con sus congéneres. Esta especie de Hypoptopoma, pobremente conocida, se distribuye en las cuencas de los ríos Paraná y Paraguay. Hypoptopoma inexspectata se diagnostica sobre la base de la autapomorfía ordenamiento bi-serial de los Odontodes del margen rostral del hocico, extendiéndose lateralmente desde el extremo anterior hasta el límite entre los infraorbitales 2 y 3; la serie dorsalmente orientada se separa de la ventralmente orientada por un área angosta libre de Odontodes. Esta especie se distingue además por la combinación (1) bajo número de la serie media de placas laterales (2022, típicamente 21), (2) presencia de placas prepectorales, (3) dos series de 3-5 placas abdominales, (4) distancia interorbital mínima 48-56 % longitud cabeza, (5) diámetro horizontal de la órbita 17-20% longitud cabeza, y (6) distancia mínima órbita-narina 8-12% longitud cabeza. Se reporta variación intraespecífica en relación con los huesos dérmicos de la cabeza, neuracráneo y suspensorio, placas dérmicas, y aleta adiposa.Hypoptopoma inexspectata is diagnosed and redescribed based on the examination of additional material and comparison with its congeners. This poorly known hypoptopomine species is distributed in the Paraguay and Paraná river draínages. Hypoptopoma inexspectata is diagnosable based on the autapomorphy biserial arrangement of anterior snout rostral margin Odontodes, laterally extended to limit between second and third infraorbital plates, with dorsally directed dorsad series separated from ventrally directed ventrad series by a narrow Odontode-free area, which at the level of first and second infraorbital plates is reduced to a dividing line of the series. The species can be further distinguished by the combination (1) low number of canal-bearing lateral plates (20-22, typically 21), (2) presence of a shield of prepectoral dermal plates, (3) arrangement of abdominal plates in one paired series of 3-5 plates, (4) shorter least interorbital distance 4856% head lengh, (5) larger horizontal eye diameter 17-20% head lengh, and (6) least orbit-nare distance 812% head lengh. Intraspecific variation skull dermal bones, neuracranium and suspensorium bones, dermal plates, adipose fin is reported.Facultad de Ciencias Naturales y Muse
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A new species of Hisonotus (Siluriformes, Loricariidae) of the upper río Uruguay basin
2001Co-Authors: Aquino, Adriana Elbia, Schaefer, Scott A., Miquelarena, Amalia María.Abstract:A new species of the hypoptopomatine genus Hisonotus (Loricariidae) is described from a small tributary of the upper río Uruguay basin near the border between Uruguay and Brazil. The new species can be distinguished from all other congeners by the following combination of characters: (1) presence of serrae along distal two thirds of posterior margin of pectoral-fin spine (versus serrae absent, posterior margin smooth); (2) Odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow Odontode-free area covered by pad of soft tissue; (3) caudal peduncle short (27–34% SL, versus > 34% SL) and deep (13–15 % SL, versus < 13% SL); (4) eye large (15–19% HL, versus < 13% HL); and (5) caudal-fin pigmentation, when well defined, dark brown with a pair of whitish blotches on upper and lower lobes. The significance of the distribution of the new species is discussed relative to the degree of endemism of other fish groups in the Uruguay basin.Una nueva especie de Hypoptopomatinae del género Hisonotus (Loricariidae) es descripta para un pequeño tributario del río Uruguay superior, cerca del límite entre Uruguay y Brasil. La nueva especie puede distinguirse de todas las otras especies nominales del género por la siguiente combinación de caracteres: (1) presencia de sierra a lo largo del margen posterior de los dos tercios distales de la espina pectoral (versus margen posterior liso), (2) Odontodes del margen anterior del hocico ordenados biserialmente, las series dorsal y ventral separadas por una banda angosta libre de Odontodes, cubierta por tejido blando; (3) pedúnculo caudal corto (27–34 % LE, versus usualmente > 34) y alto (13–15 % LE, versus usualmente < 13); (4) ojo grande (15–19 % in HL, versus usualmente < 13), y (5) patrón de coloración de la aleta caudal, cuando se encuentra bien definido, marrón oscuro, con un par de manchas blanquecinas sobre los lóbulos superior e inferior de la aleta. La distribución geográfica de la nueva especie es discutida en relación al grado de endemismo registrado en otros grupos de peces de la cuenca del río Uruguay.Facultad de Ciencias Naturales y Muse
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A New Species of Hisonotus (Siluriformes, Loricariidae) of the Upper Río Uruguay Basin
'American Museum of Natural History (BioOne sponsored)', 2001Co-Authors: Aquino, Adriana E., Schaefer, Scott A., Miquelarena, Amalia María.Abstract:A new species of the hypoptopomatine genus Hisonotus (Loricariidae) is described from a small tributary of the upper rı´o Uruguay basin near the border between Uruguay and Brazil. The new species can be distinguished from all other congeners by the following combination of characters: (1) presence of serrae along distal two thirds of posterior margin of pectoral-fin spine (versus serrae absent, posterior margin smooth); (2) Odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow Odontode-free area covered by pad of soft tissue; (3) caudal peduncle short (27–34% SL, versus . 34% SL) and deep (13–15 % SL, versus , 13% SL); (4) eye large (15–19% HL, versus , 13% HL); and (5) caudal-fin pigmentation, when well defined, dark brown with a pair of whitish blotches on upper and lower lobes. The significance of the distribution of the new species is discussed relative to the degree of endemism of other fish groups in the Uruguay basin.Fil: Aquino, Adriana E.. American Museum of Natural History; Estados UnidosFil: Schaefer, Scott A.. American Museum of Natural History; Estados UnidosFil: Miquelarena, Amalia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología ; Argentin
Per E. Ahlberg - One of the best experts on this subject based on the ideXlab platform.
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The developmental relationship between teeth and dermal Odontodes in the most primitive bony fish Lophosteus.
eLife, 2020Co-Authors: Donglei Chen, Sophie Sanchez, Henning Blom, Paul Tafforeau, Tiiu Märss, Per E. AhlbergAbstract:Human teeth are an example of Odontodes: hard structures made of a material called dentine that are sometimes coated in enamel. Teeth are the only Odontodes humans have, but other vertebrates (animals with backbones) have tooth-like scales on their skin. These structures are called dermal Odontodes, and sharks and rays, for example, are covered with them. How these structures evolved, and whether teeth or dermal Odontodes developed first, continues to spark great discussion among palaeontologists. Some researchers think that teeth evolved from dermal Odontodes, a theory known as the ‘scales-to-teeth’ hypothesis. Others think dermal Odontodes are distinct from teeth because they lack the same spatial organization. To investigate this further, palaeontologists are looking at the earliest examples of Odontodes they can find: fossils of early vertebrates that carry both teeth and dermal Odontodes. Here, Chen et al. have studied Lophosteus, one of the earliest bony fishes that lived more than 400 million years ago, to explore early tooth evolution and growth patterns. Chen et al. digitally dissected a fossilized Lophosteus jawbone using submicron X-ray imaging, a technique with resolution to less than one millionth of a metre. Imaging thin sections of the specimen, found in Estonia, Chen et al. reconstructed the entire sequence of Odontode development in the bony fish in 3D. The analysis showed that teeth and dermal Odontodes initially take shape together but differentiate as they grow, presumably instructed to do so by various developmental signals. However, at a later stage, the two types of Odontodes become similar in appearance again, suggesting that they respond to each other’s signals. For example, as the jawbone grows, dermal Odontodes overgrow the earliest formed teeth. These younger Odontodes resemble teeth, while the new teeth developing near the dermal Odontodes take after dermal Odontodes. These findings suggest that teeth and dermal Odontodes are not wholly separate systems but, instead, are closely related on a molecular level. The results also show that contrary to the ‘scale-to-teeth’ hypothesis, teeth do not evolve from fully formed dermal Odontodes, rather the two types of Odontodes form out of one founder. This research builds on our knowledge from modern sharks and points to a previously unrecognised evolutionary relationship between teeth and dermal Odontodes. It also furthers our understanding of how molecular regulation controls development.
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New genomic and fossil data illuminate the origin of enamel.
Nature, 2015Co-Authors: Tatjana Haitina, Min Zhu, Per E. AhlbergAbstract:Enamel, the hardest vertebrate tissue, covers the teeth of almost all sarcopterygians (lobe-finned bony fishes and tetrapods) as well as the scales and dermal bones of many fossil lobe-fins. Enamel deposition requires an organic matrix containing the unique enamel matrix proteins (EMPs) amelogenin (AMEL), enamelin (ENAM) and ameloblastin (AMBN). Chondrichthyans (cartilaginous fishes) lack both enamel and EMP genes. Many fossil and a few living non-teleost actinopterygians (ray-finned bony fishes) such as the gar, Lepisosteus, have scales and dermal bones covered with a proposed enamel homologue called ganoine. However, no gene or transcript data for EMPs have been described from actinopterygians. Here we show that Psarolepis romeri, a bony fish from the the Early Devonian period, combines enamel-covered dermal Odontodes on scales and skull bones with teeth of naked dentine, and that Lepisosteus oculatus (the spotted gar) has enam and ambn genes that are expressed in the skin, probably associated with ganoine formation. The genetic evidence strengthens the hypothesis that ganoine is homologous with enamel. The fossil evidence, further supported by the Silurian bony fish Andreolepis, which has enamel-covered scales but teeth and Odontodes on its dermal bones made of naked dentine, indicates that this tissue originated on the dermal skeleton, probably on the scales. It subsequently underwent heterotopic expansion across two highly conserved patterning boundaries (scales/head-shoulder and dermal/oral) within the Odontode skeleton.
Henning Blom - One of the best experts on this subject based on the ideXlab platform.
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The developmental relationship between teeth and dermal Odontodes in the most primitive bony fish Lophosteus.
eLife, 2020Co-Authors: Donglei Chen, Sophie Sanchez, Henning Blom, Paul Tafforeau, Tiiu Märss, Per E. AhlbergAbstract:Human teeth are an example of Odontodes: hard structures made of a material called dentine that are sometimes coated in enamel. Teeth are the only Odontodes humans have, but other vertebrates (animals with backbones) have tooth-like scales on their skin. These structures are called dermal Odontodes, and sharks and rays, for example, are covered with them. How these structures evolved, and whether teeth or dermal Odontodes developed first, continues to spark great discussion among palaeontologists. Some researchers think that teeth evolved from dermal Odontodes, a theory known as the ‘scales-to-teeth’ hypothesis. Others think dermal Odontodes are distinct from teeth because they lack the same spatial organization. To investigate this further, palaeontologists are looking at the earliest examples of Odontodes they can find: fossils of early vertebrates that carry both teeth and dermal Odontodes. Here, Chen et al. have studied Lophosteus, one of the earliest bony fishes that lived more than 400 million years ago, to explore early tooth evolution and growth patterns. Chen et al. digitally dissected a fossilized Lophosteus jawbone using submicron X-ray imaging, a technique with resolution to less than one millionth of a metre. Imaging thin sections of the specimen, found in Estonia, Chen et al. reconstructed the entire sequence of Odontode development in the bony fish in 3D. The analysis showed that teeth and dermal Odontodes initially take shape together but differentiate as they grow, presumably instructed to do so by various developmental signals. However, at a later stage, the two types of Odontodes become similar in appearance again, suggesting that they respond to each other’s signals. For example, as the jawbone grows, dermal Odontodes overgrow the earliest formed teeth. These younger Odontodes resemble teeth, while the new teeth developing near the dermal Odontodes take after dermal Odontodes. These findings suggest that teeth and dermal Odontodes are not wholly separate systems but, instead, are closely related on a molecular level. The results also show that contrary to the ‘scale-to-teeth’ hypothesis, teeth do not evolve from fully formed dermal Odontodes, rather the two types of Odontodes form out of one founder. This research builds on our knowledge from modern sharks and points to a previously unrecognised evolutionary relationship between teeth and dermal Odontodes. It also furthers our understanding of how molecular regulation controls development.
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Dental ontogeny in the most primitive bony fish Lophosteus reveals the developmental relationship between teeth and dermal Odontodes
2020Co-Authors: Donglei Chen, Sophie Sanchez, Henning Blom, Paul Tafforeau, Tiiu Märss, Per AhlbergAbstract:Ontogenetic data obtained by synchrotron microtomography of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically basalmost stem osteichthyan, reveal developmental relationships between teeth and ornament that are not obvious from the adult morphology. The earliest Odontodes are two longitudinal founder ridges formed at the ossification center. Subsequent Odontodes that are added lingually to the ridges turn into conical teeth and undergo cyclic replacement, while those added labially achieve a stellate appearance. The stellate Odontodes deposited directly on the bony plate are aligned with the alternate files of the teeth. Successive Odontodes overgrowing the labial tooth rows become tooth-like and the replacement teeth near to them are ornament-like. We propose that teeth and ornament are modifications of a single Odontode system regulated and differentiated by the oral and dermal signals; signal cross-communication between the two domains can occur around the oral-dermal boundary.
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Three-dimensional paleohistology of the scale and median fin spine of Lophosteus superbus (Pander 1856)
PeerJ, 2016Co-Authors: Anna Jerve, Sophie Sanchez, Henning Blom, Per Erik AhlbergAbstract:Lophosteus superbus is one of only a handful of probable stem-group osteichthyans known from the fossil record. First collected and described in the late 19th century from the upper Silurian Saaremaa Cliff locality in Estonia, it is known from a wealth of disarticulated scales, fin spines, and bone fragments. In this study we provide the first description of the morphology and paleohistology of a fin spine and scale from Lophosteus using virtual thin sections and 3D reconstructions that were segmented using phase-contrast synchrotron X-ray microtomography. These data reveal that both structures have fully or partially buried Odontodes, which retain fine morphological details in older generations, including sharp nodes and serrated ridgelets. The vascular architecture of the fin spine tip, which is composed of several layers of longitudinally directed bone vascular canals, is much more complex compared to the bulbous horizontal canals within the scale, but they both have distinctive networks of ascending canals within each individual Odontode. Other histological characteristics that can be observed from the data are cell spaces and Sharpey's fibers that, when combined with the vascularization, could help to provide insights into the growth of the structure. The 3D data of the scales from Lophosteus superbus is similar to comparable data from other fossil osteichthyans, and the morphology of the reconstructed buried Odontodes from this species is identical to scale material of Lophosteus ohesaarensis, casting doubt on the validity of that species. The 3D data presented in this paper is the first for fossil fin spines and so comparable data is not yet available. However, the overall morphology and histology seems to be similar to the structure of placoderm dermal plates. The 3D datasets presented here provide show that microtomography is a powerful tool for investigating the three-dimensional microstructure of fossils, which is difficult to study using traditional histological methods. These results also increase the utility of fin spines and scales suggest that these data are a potentially rich source of morphological data that could be used for studying questions relating to early vertebrate growth and evolution
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Scales and Tooth Whorls of Ancient Fishes Challenge Distinction between External and Oral ‘Teeth’
PloS one, 2013Co-Authors: Sophie Sanchez, Henning Blom, Paul Tafforeau, Per AhlbergAbstract:The debate about the origin of the vertebrate dentition has been given fresh fuel by new fossil discoveries and developmental studies of extant animals. Odontodes (teeth or tooth-like structures) can be found in two distinct regions, the ‘internal’ oropharyngeal cavity and the ‘external’ skin. A recent hypothesis argues that regularly patterned Odontodes is a specific oropharyngeal feature, whereas Odontodes in the external skeleton lack this organization. However, this argument relies on the skeletal system of modern chondrichthyans (sharks and their relatives), which differ from other gnathostome (jawed vertebrate) groups in not having dermal bones associated with the Odontodes. Their external skeleton is also composed of monoOdontode 'placoid scales', whereas the scales of most early fossil gnathostomes are polyOdontode, i.e. constructed from several Odontodes on a shared bony base. Propagation phase contrast X-ray Synchrotron microtomography (PPC-SRµCT) is used to study the polyOdontode scales of the early bony fish Andreolepis hedei. The Odontodes constructing a single scale are reconstructed in 3D, and a linear and regular growth mechanism similar to that in a gnathostome dentition is confirmed, together with a second, gap-filling growth mechanism. Acanthodian tooth whorls are described, which show that ossification of the whorl base preceded and probably patterned the development of the dental lamina, in contrast to the condition in sharks where the dental lamina develops early and patterns the dentition.The new findings reveal, for the first time, how polyOdontode scales grow in 3D in an extinct bony fish. They show that dentition-like Odontode patterning occurs on scales and that the primary patterning unit of a tooth whorl may be the bony base rather than the Odontodes it carries. These results contradict the hypothesis that oropharyngeal and external Odontode skeletons are fundamentally separate and suggest that the importance of dermal bone interactions to Odontode patterning has been underestimated.
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The reconstructed growth pattern of Odontodes in the scanned scale of Andreolepis, crown view.
2013Co-Authors: Sophie Sanchez, Henning Blom, Paul Tafforeau, Per Erik AhlbergAbstract:A–J. The referred sequential addition of Odontodes – in the crown of the scale. The first generation Odontodes (Odontodes – , see text) form a growth series, but the other younger Odontodes ( – ) do not necessarily fall neatly into the same sequence even though they generally continue to get larger; the yellow horizontal vascular canal system is used as landmark to show the positions of the Odontodes K. Crown view of the scale with buried Odontodes, showing the actual surface composition of the scale. Note that the most dorsal denticles compose the enamel layers from both Odontode and , Odontode is partially overlapped by ; Odontode is only overlapped by and posteriorly and exposed to the surface otherwise.
Mélanie Debiais-thibaud - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary developmental genetics of teeth and Odontodes in jawed vertebrates: a perspective from the study of elasmobranchs.
Journal of fish biology, 2019Co-Authors: Fidji Berio, Mélanie Debiais-thibaudAbstract:Most extant vertebrates display a high variety of tooth and tooth-like organs (Odontodes) that vary in shape, position over the body and nature of composing tissues. The development of these structures is known to involve similar genetic cascades and teeth and Odontodes are believed to share a common evolutionary history. Gene expression patterns have previously been compared between mammalian and teleost tooth development but we highlight how the comparative framework was not always properly defined to deal with different tooth types or tooth developmental stages. Larger-scale comparative analyses also included cartilaginous fishes: sharks display oral teeth and dermal scales for which the gene expression during development started to be investigated in the small-spotted catshark Scyliorhinus canicula during the past decade. We report several descriptive approaches to analyse the embryonic tooth and caudal scale gene expressions in S. canicula. We compare these expressions wih the ones reported in mouse molars and teleost oral and pharyngeal teeth and highlight contributions and biases that arise from these interspecific comparisons. We finally discuss the evolutionary processes that can explain the observed intra and interspecific similarities and divergences in the genetic cascades involved in tooth and Odontode development in jawed vertebrates.
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Skeletal Mineralization in Association with Type X Collagen Expression Is an Ancestral Feature for Jawed Vertebrates
Molecular Biology and Evolution, 2019Co-Authors: Mélanie Debiais-thibaud, David Muñoz, Paul Simion, Stéphanie Ventéo, Sylvain Marcellini, Sylvie Mazan, Tatjana HaitinaAbstract:In order to characterize the molecular bases of mineralizing cell evolution, we targeted type X collagen, a nonfibrillar network forming collagen encoded by the Col10a1 gene. It is involved in the process of endochondral ossification in ray-finned fishes and tetrapods (Osteichthyes), but until now unknown in cartilaginous fishes (Chondrichthyes). We show that holocephalans and elasmobranchs have respectively five and six tandemly duplicated Col10a1 gene copies that display conserved genomic synteny with osteichthyan Col10a1 genes. All Col10a1 genes in the catshark Scyliorhinus canicula are expressed in ameloblasts and/or odontoblasts of teeth and scales, during the stages of extracellular matrix protein secretion and mineralization. Only one duplicate is expressed in the endoskeletal (vertebral) mineralizing tissues. We also show that the expression of type X collagen is present in teeth of two osteichthyans, the zebrafish Danio rerio and the western clawed frog Xenopus tropicalis, indicating an ancestral jawed vertebrate involvement of type X collagen in Odontode formation. Our findings push the origin of Col10a1 gene prior to the divergence of osteichthyans and chondrichthyans, and demonstrate its ancestral association with mineralization of both the Odontode skeleton and the endoskeleton.
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Evolution of dental tissue mineralization: an analysis of the jawed vertebrate SPARC and SPARC-L families
BMC Evolutionary Biology, 2018Co-Authors: Sébastien Enault, Jean-yves Sire, David Muñoz, Paul Simion, Stéphanie Ventéo, Sylvain Marcellini, Mélanie Debiais-thibaudAbstract:Background: The molecular bases explaining the diversity of dental tissue mineralization across gnathostomes are still poorly understood. Odontodes, such as teeth and body denticles, are serial structures that develop through deployment of a gene regulatory network shared between all gnathostomes. Dentin, the inner Odontode mineralized tissue, is produced by odontoblasts and appears well-conserved through evolution. In contrast, the Odontode hypermineralized external layer (enamel or enameloid) produced by ameloblasts of epithelial origin, shows extensive structural variations. As EMP (Enamel Matrix Protein) genes are as yet only found in osteichthyans where they play a major role in the mineralization of teeth and others skeletal organs, our understanding of the molecular mechanisms leading to the mineralized Odontode matrices in chondrichthyans remains virtually unknown. Results: We undertook a phylogenetic analysis of the SPARC/SPARC-L gene family, from which the EMPs are supposed to have arisen, and examined the expression patterns of its members and of major fibrillar collagens in the spotted catshark Scyliorhinus canicula, the thornback ray Raja clavata, and the clawed frog Xenopus tropicalis. Our phylogenetic analyses reveal that the single chondrichthyan SPARC-L gene is co-orthologous to the osteichthyan SPARC-L1 and SPARC-L2 paralogues. In all three species, odontoblasts co-express SPARC and collagens. In contrast, ameloblasts do not strongly express collagen genes but exhibit strikingly similar SPARC-L and EMP expression patterns at their maturation stage, in the examined chondrichthyan and osteichthyan species, respectively.
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Evolution of dental tissue mineralization: an analysis of the jawed vertebrate SPARC and SPARC-L families
BMC evolutionary biology, 2018Co-Authors: Sébastien Enault, Jean-yves Sire, David Muñoz, Paul Simion, Stéphanie Ventéo, Sylvain Marcellini, Mélanie Debiais-thibaudAbstract:Background The molecular bases explaining the diversity of dental tissue mineralization across gnathostomes are still poorly understood. Odontodes, such as teeth and body denticles, are serial structures that develop through deployment of a gene regulatory network shared between all gnathostomes. Dentin, the inner Odontode mineralized tissue, is produced by odontoblasts and appears well-conserved through evolution. In contrast, the Odontode hypermineralized external layer (enamel or enameloid) produced by ameloblasts of epithelial origin, shows extensive structural variations. As EMP (Enamel Matrix Protein) genes are as yet only found in osteichthyans where they play a major role in the mineralization of teeth and others skeletal organs, our understanding of the molecular mechanisms leading to the mineralized Odontode matrices in chondrichthyans remains virtually unknown.
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Evolution of dental tissue mineralization: an analysis of the jawed vertebrate SPARC and SPARC-L families
BMC, 2018Co-Authors: Sébastien Enault, Jean-yves Sire, David Muñoz, Paul Simion, Stéphanie Ventéo, Sylvain Marcellini, Mélanie Debiais-thibaudAbstract:Abstract Background The molecular bases explaining the diversity of dental tissue mineralization across gnathostomes are still poorly understood. Odontodes, such as teeth and body denticles, are serial structures that develop through deployment of a gene regulatory network shared between all gnathostomes. Dentin, the inner Odontode mineralized tissue, is produced by odontoblasts and appears well-conserved through evolution. In contrast, the Odontode hypermineralized external layer (enamel or enameloid) produced by ameloblasts of epithelial origin, shows extensive structural variations. As EMP (Enamel Matrix Protein) genes are as yet only found in osteichthyans where they play a major role in the mineralization of teeth and others skeletal organs, our understanding of the molecular mechanisms leading to the mineralized Odontode matrices in chondrichthyans remains virtually unknown. Results We undertook a phylogenetic analysis of the SPARC/SPARC-L gene family, from which the EMPs are supposed to have arisen, and examined the expression patterns of its members and of major fibrillar collagens in the spotted catshark Scyliorhinus canicula, the thornback ray Raja clavata, and the clawed frog Xenopus tropicalis. Our phylogenetic analyses reveal that the single chondrichthyan SPARC-L gene is co-orthologous to the osteichthyan SPARC-L1 and SPARC-L2 paralogues. In all three species, odontoblasts co-express SPARC and collagens. In contrast, ameloblasts do not strongly express collagen genes but exhibit strikingly similar SPARC-L and EMP expression patterns at their maturation stage, in the examined chondrichthyan and osteichthyan species, respectively. Conclusions A well-conserved odontoblastic collagen/SPARC module across gnathostomes further confirms dentin homology. Members of the SPARC-L clade evolved faster than their SPARC paralogues, both in terms of protein sequence and gene duplication. We uncover an osteichthyan-specific duplication that produced SPARC-L1 (subsequently lost in pipidae frogs) and SPARC-L2 (independently lost in teleosts and tetrapods).Our results suggest the ameloblastic expression of the single chondrichthyan SPARC-L gene at the maturation stage reflects the ancestral gnathostome situation, and provide new evidence in favor of the homology of enamel and enameloids in all gnathostomes
