Cosmine resorption structures on three osteolepid jaws and their biological significance

Borgen, Ulf J.

doi:10.1111/j.1502-3931.1989.tb01444.x

Cited by 11 publications

(7 citation statements)

References 9 publications

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“…Previous studies on cosmine aimed to analyse its developmental process and functions of the pore-canal system (Ørvig, 1969;Thomson, 1975Thomson, , 1977Meinke, 1984;Borgen, 1989Borgen, , 1992Bemis & Northcutt, 1992). Our understanding of the origin of cosmine made little progress because of the lack of an identifiable pre-cosmine condition in the fossil record (Rosen et al, 1981), until the discovery of several primitive sarcopterygians in China (Zhu et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

The origin of novel features by changes in developmental mechanisms: ontogeny and three‐dimensional microanatomy of polyodontode scales of two early osteichthyans

Sanchez

Zhu

et al. 2016

Biological Reviews

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Recent advances in synchrotron imaging allow us to study the three-dimensional (3D) histology of vertebrate fossils, including microfossils (e.g. teeth and scales) of early jawed vertebrates. These microfossils can often be scanned at submicron resolution (<1 µm) because of their small size. The resulting voxel (3D pixel) stacks can be processed into virtual thin sections revealing almost every internal detail of the samples, comparable to traditional thin sections. In addition, 3D models of the internal microanatomical structures, such as embedded odontodes and vasculature, can be assembled and examined in situ. Scales of two early osteichthyans, Psarolepis romeri from the Early Devonian of China and Andreolepis hedei from the Late Silurian of Sweden, were scanned using propagation phase-contrast synchrotron X-ray microtomography (PPC-SRµCT), and 3D models of internal canal systems and buried odontodes were created from the scans. Based on these new data, we review the evolutionary origin of cosmine and its associated pore-canal system, which has been long recognized as a synapomorphy of sarcopterygians. The first odontode that appeared during growth shows almost identical morphology in the two scales, but the second odontode of the Psarolepis scale shows a distinctive morphology with several pores on the surface. It is suggested that a shift from ridge-like odontode to pore-bearing odontode was the key step in the origin of cosmine, which was then elaborated further in more-derived sarcopterygians. We perform a detailed comparison between the two scales and propose a primary homology framework to generate microanatomical characters, which can be used in the phylogenetic analysis of early osteichthyans when more 3D data become available. Our results highlight the importance of 3D data for the study of histology and ontogeny of the dermal skeleton of early jawed vertebrates, especially scales of the polyodontode type. The traditional microvertebrate collection is not only useful for biostratigraphic studies, but also preserves invaluable biological information about the growth of vertebrate hard tissues. Today, we are only beginning to understand the biological meaning of the new 3D data. The increasing availability of such data will enable, and indeed require, a complete revision of traditional palaeohistological studies on early vertebrates.

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Section: Discussionmentioning

confidence: 99%

The origin of novel features by changes in developmental mechanisms: ontogeny and three‐dimensional microanatomy of polyodontode scales of two early osteichthyans

Sanchez

Zhu

et al. 2016

Biological Reviews

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“…3). Borgen (1989) showed reabsorbed grooves on osteolepidid jaws, which look like postmortem or even post-fossilization etchings and have nothing to do with the growth process of these fishes. Zhu et al (2010) placed Meemannia together with Andreolepis and actinopterygians as a group without resorption at the base of their cladogram.…”

Section: Histologymentioning

confidence: 96%

Scales, Enamel, Cosmine, Ganoine, and Early Osteichthyans

Schultze

2016

Comptes Rendus Palevol

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a b s t r a c tGanoine is a different enamel from "true" enamel. The crystallites end in the middle of the projection of epidermal cell onto the ganoine surface. In contrast, "true" enamel shows the borders of the hexagonal epidermal cells. Cosmine is a combination of tissues ("true" enamel and dentine) and a structure (the pore-canal system). The pore-canal system opens in regular arranged pores on the scale surface and has a network of horizontal canals (mesh canals). Cosmine is limited to sarcopterygians possibly above actinistians and onychodonts, ganoine to actinopterygians. -Actinopterygian scales possess a narrow peg, an anterodorsal extended corner and ganoine either as overlapping or as multilayered enamel, whereas sarcopterygian scales have a broad based peg, no extended anterodorsal corner with two exceptions, but sometimes an anteroventral extension and cosmine. -The genera Andreolepis, Dialipina, Naxilepis, Terenolepis, Ligulalepis and Orvikuina are actinopterygians based on their scale characters. Additionally, Guiyu, Meemannia, Achoania and Psarolepis possess actinopterygian features. According to its scale characters Lophosteus is a stem osteichthyan.

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“…Plesiomorphically, the integumentary skeleton of sarcopterygians is characterized by the tissue complex known as cosmine (Ørvig, 1969; Thomson, 1975, 1977; Meinke, 1984, 1986; Borgen, 1989; Bemis & Northcutt, 1992). Overall, the histology of cosmoid scales closely resembles that of the polypteroid scales: a shiny superficial tissue similar to enamel or enameloid, overlying orthodentine and vascular, lamellar bone (Goodrich, 1907; Meinke, 1982, 1984).…”

Section: Origin Evolution and Diversity Of The Integumentary Skeletonmentioning

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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Cosmine resorption structures on three osteolepid jaws and their biological significance

Cited by 11 publications

References 9 publications

The origin of novel features by changes in developmental mechanisms: ontogeny and three‐dimensional microanatomy of polyodontode scales of two early osteichthyans

The origin of novel features by changes in developmental mechanisms: ontogeny and three‐dimensional microanatomy of polyodontode scales of two early osteichthyans

Scales, Enamel, Cosmine, Ganoine, and Early Osteichthyans

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

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