Early Silurian chondrichthyans from the Tarim Basin (Xinjiang, China)

Andreev, Plamen S.; Zhao, Wei; Wang, Nian-Zhong; Smith, Moya Meredith; Li, Qiang; Cui, Xindong; Zhu, Min; Sansom, Ivan J.

doi:10.1371/journal.pone.0228589

Cited by 20 publications

(13 citation statements)

References 36 publications

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“…Some of the earliest‐reported stem chondrichthyan fossils are isolated mongolepid scales and sinacanthid spines from China (Early Silurian, ca . 430–440 bp ; Andreev et al ., 2020, and references therein). Sinacanthid spines are described as consisting of atubular lamellar dentine with traces of calcospheritic mineralization, lined internally by a biomineralized tissue which has been interpreted as GCC, based on the presence of mineralized spherites and Liesegang waves.…”

Section: Discussionmentioning

confidence: 99%

Architectural and ultrastructural features of tessellated calcified cartilage in modern and extinct chondrichthyan fishes

Maisey

Denton

Burrow

et al. 2020

Journal of Fish Biology

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Tessellated calcified cartilage (TCC) is a distinctive kind of biomineralized perichondral tissue found in many modern and extinct chondrichthyans (sharks, rays, chimaeroids and their extinct allies). Customarily, this feature has been treated somewhat superficially in phylogenetic analyses, often as a single “defining” character of a chondrichthyan clade. TCC is actually a complex hard tissue with numerous distinctive attributes, but its use as a character complex for phylogenetic analysis has not yet been optimized. This study attempts to improve this situation by presenting new terminology for certain aspects of tesseral architecture, including single‐monolayered, multiple‐monolayered, polylayered and voussoir tesserae; new histological data, including thin sections of TCC in several Palaeozoic taxa, and new proposals for ways in which various characters and states (many of which are defined here for the first time) could be applied in future phylogenetic analyses of chondrichthyan fishes. It can be concluded that many, but not all, of the unique attributes of modern TCC evolved by the Early Devonian (ca. 400 before present (bp)). The globular calcified cartilage reported in Silurian sinacanthids and the so‐called subtessellated perichondral biomineralization (with irregular and ill‐defined geometries of a layer or layers of calcified cartilage blocks) of certain extinct “acanthodians” (e.g., Climatius, Ischnacanthus, Cheiracanthus) could represent evolutionary precursors of TCC, which seems to characterize only part of the chondrichthyan total group. It is hypothesized that heavily biomineralized “layer‐cake” TCC in certain Palaeozoic chondrichthyans perhaps served a dual physiological role, as a phosphate sink and in providing increased skeletal density in very large (>7 m) Devonian‐Permian marine sharks such as ctenacanths and as an adaptation to calcium‐deficient environments among Permo‐Carboniferous non‐marine sharks such as xenacanths. By contrast, the equivalent tissue in modern elasmobranchs probably serves only to reinforce regions of cartilage (mostly in the jaws) subjected to high loading. It is also noted that much of the variation observed in tesseral architecture (including localized remodelling), ultrastructure and histology in modern and extinct chondrichthyans is confined to the perichondrally facing cap zone (where Type‐1 collagen matrix predominates in modern TCC), whereas the main body of the tessera (where Type‐2 collagen matrix predominates) exhibits comparatively little evidence of remodelling and histological or structural variation.

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Section: Discussionmentioning

confidence: 99%

Architectural and ultrastructural features of tessellated calcified cartilage in modern and extinct chondrichthyan fishes

Maisey

Denton

Burrow

et al. 2020

Journal of Fish Biology

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“…2; Burrow, 2003 ; Johanson and Smith, 2003 ; Johanson and Smith, 1999 ; Young, 2003 ). In the polyodontode scales of the earliest known chondrichthyans, odontodes are often organized in parallel or radial rows by sequential addition ( Andreev et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

The developmental relationship between teeth and dermal odontodes in the most primitive bony fish Lophosteus

Chen

Blom

Sanchez

et al. 2020

eLife

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The ontogenetic trajectory of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically most basal stem osteichthyan, visualized by synchrotron microtomography, reveals a developmental relationship between teeth and dermal odontodes that is not evident 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. Stellate odontodes deposited directly on the bony plate are aligned with the alternate files of teeth, whereas new tooth positions are inserted into the files of sequential addition when a gap appears. Successive teeth and overgrowing odontodes show hybrid morphologies around the oral-dermal boundary, suggesting signal cross-communication. We propose that teeth and dermal odontodes are modifications of a single system, regulated and differentiated by the oral and dermal epithelia.

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“…However, the accuracy rates of different species of the same genus were relatively low (Fig. 9), which might be caused by the morphological similarities and the lack of histological information that is key for the intraspecific classification of fishes [17], [20], [58].…”

Section: Discussionmentioning

confidence: 99%

ADMorph: A 3D Digital Microfossil Morphology Dataset for Deep Learning

et al. 2020

Self Cite

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Microfossils, tiny fossils whose study requires the use of a microscope, have been widely applied in many fields of earth, life, and environmental sciences. The abundance and high diversity of microfossils, as well as the need for rapid identification, call for automated methods to classify microfossils. In this study, we constructed an open dataset of three-dimensional (3D) microfossils and proposed a deep learning-based approach for microfossil classification. The dataset, named 'Archives of Digital Morphology' (ADMorph), currently contains more than ten thousand 3D models from five classes of 410 million-year-old fishes. The deep learning-based method includes data preprocessing, feature extraction, and 3D microfossil model classification. To assess the method performance and dataset representability, we performed extensive experiments. Compared with multiview convolutional neural networks (MVCNN) (91.54%), PointNet (64.13%), and VoxNet (78.15%), the method proposed herein had higher accuracy (97.60%) on the experimental dataset. We also verified data preprocessing (92.36%) and feature extraction (97.10%). We combined them to obtain the macroaveraging accuracy of 97.60%, the highest accuracy of 100%, and the lowest accuracy of 88.78%. We suggest that the proposed method can be applied to other 3D fossils and biomorphological research fields. The fast-accumulating 3D fossil models might become a source of information-rich datasets for deep learning.INDEX TERMS Archives of Digital Morphology, data preprocessing, feature extraction, 3D microfossil model classification, deep learning.

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Early Silurian chondrichthyans from the Tarim Basin (Xinjiang, China)

Cited by 20 publications

References 36 publications

Architectural and ultrastructural features of tessellated calcified cartilage in modern and extinct chondrichthyan fishes

Architectural and ultrastructural features of tessellated calcified cartilage in modern and extinct chondrichthyan fishes

The developmental relationship between teeth and dermal odontodes in the most primitive bony fish Lophosteus

ADMorph: A 3D Digital Microfossil Morphology Dataset for Deep Learning

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