Squamation and scale microstructure evolution in the Porolepiformes (Sarcopterygii, Dipnomorpha) based on<i>Heimenia ensis</i>from the Devonian of Spitsbergen

Mondéjar‐Fernández, Jorge; Clément, Gérard

doi:10.1080/02724634.2012.646836

Cited by 18 publications

(25 citation statements)

References 46 publications

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“…The histological organization of the scale base in the porolepiform sarcopterygian Heimenia [43] is also different from that in Psarolepis . The scale keel ([43]: ‘internal bone layer’) in Heimenia does not show any plywood-like structure.…”

Section: Discussionmentioning

confidence: 82%

“…Dentine has been recrystallized in many parts (green under transmitted light), presumably indicating original locations of different cavities and canals (Figures 5B–D and 6A). Unlike the typical cosmine in crown sarcopterygians such as porolepiforms and lungfishes where only a single generation of enamel and odontodes are present [13], [27], [43], the cosmine-like tissue in referred scales is composed of multiple generations of enamel and odontodes, a condition that is similar to the dermal skeleton of Meemannia , Styloichthys , Psarolepis and primitive actinopterygians. This arrangement is considered primitive relative to cosmine found in some early crown sarcopterygians.…”

Section: Resultsmentioning

confidence: 99%

“…The scale keel ([43]: ‘internal bone layer’) in Heimenia does not show any plywood-like structure. However, the rest of the scale base ([43]: ‘basal layer’) is composed of lamellar bone showing a plywood-like structure. In addition, both the keel and the rest of the base are penetrated by Sharpey's fibers.…”

Section: Discussionmentioning

confidence: 99%

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Scales and Dermal Skeletal Histology of an Early Bony Fish Psarolepis romeri and Their Bearing on the Evolution of Rhombic Scales and Hard Tissues

Zhu

Wang

2013

PLoS ONE

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Recent discoveries of early bony fishes from the Silurian and earliest Devonian of South China (e.g. Psarolepis, Achoania, Meemannia, Styloichthys and Guiyu) have been crucial in understanding the origin and early diversification of the osteichthyans (bony fishes and tetrapods). All these early fishes, except Guiyu, have their dermal skeletal surface punctured by relatively large pore openings. However, among these early fishes little is known about scale morphology and dermal skeletal histology. Here we report new data about the scales and dermal skeletal histology of Psarolepis romeri, a taxon with important implications for studying the phylogeny of early gnathostomes and early osteichthyans. Seven subtypes of rhombic scales with similar histological composition and surface sculpture are referred to Psarolepis romeri. They are generally thick and show a faint antero-dorsal process and a broad peg-and-socket structure. In contrast to previously reported rhombic scales of osteichthyans, these scales bear a neck between crown and base as in acanthodian scales. Histologically, the crown is composed of several generations of odontodes and an irregular canal system connecting cylindrical pore cavities. Younger odontodes are deposited on older ones both superpositionally and areally. The bony tissues forming the keel of the scale are shown to be lamellar bone with plywood-like structure, whereas the other parts of the base are composed of pseudo-lamellar bone with parallel collagen fibers. The unique tissue combination in the keel (i.e., extrinsic Sharpey's fibers orthogonal to the intrinsic orthogonal sets of collagen fibers) has rarely been reported in the keel of other rhombic scales. The new data provide insights into the early evolution of rhombic (ganoid and cosmoid) scales in osteichthyans, and add to our knowledge of hard tissues of early vertebrates.

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Section: Discussionmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

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Scales and Dermal Skeletal Histology of an Early Bony Fish Psarolepis romeri and Their Bearing on the Evolution of Rhombic Scales and Hard Tissues

Zhu

Wang

2013

PLoS ONE

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“…A prediction of their hypothesis is the occurrence of a distinct elasmodine layer above the osteogenic tissues in the osteichthyan common ancestor and all of the cosmoid and rhomboid taxa bridging the phylogenetic gap between extant actinopterygians and sarcopterygians, however, they acknowledge that fossil evidence does not confirm this prediction (Sire & Huysseune, ). The mineralised isopedin of extinct sarcopterygians (Gross, ; Mondéjar‐Fernández & Clement, ; Qu, Zhu, & Wang, ) has a similar structure to the poorly mineralised elasmodine in extant sarcopterygian scales (e.g., Kemp, Heaslop, & Carr, ; Smith, Hobdell, & Miller, ) and could therefore be osteogenic and nonhomologous to teleost elasmodine. This negates the assumption of a distinct elasmodine layer in basal osteichthyans.…”

Section: Discussionmentioning

confidence: 99%

The dermal skeleton of the jawless vertebrateTremataspis mammillata(Osteostraci, stem‐Gnathostomata)

O'Shea

Keating

Donoghue

2019

Journal of Morphology

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Osteostracans are the closest jawless relatives of jawed vertebrates, informing the gradual assembly of the vertebrate mineralised skeleton. Conflicting interpretations of their dermal skeletal histology arise from failure to account for topological variation, obscuring their significance in elucidating vertebrate skeletal evolution. To resolve this, we characterize the cranial and trunk dermal skeleton of a single individual of Tremataspis mammillata (Osteostraci, Thyestiida) at submicron resolution using synchrotron‐ and computed‐ tomography. Our results show that the architecture of the Tremataspis dermal skeleton is, for the most part, conserved over the skeleton and is broadly consistent with previous histological hypotheses based on 2D thin section study. We resolve debate over the homology of the basal layer, identifying it as osteogenic acellular isopedin rather than odontogenic elasmodine or metaplastic ossification of the stratum compactum of the dermis. We find topological variation between all dermal skeletal elements studied, and particularly between the cranial and postcranial dermal skeleton. This variation can be largely explained by reduction in differentiation due to geometric constraints imposed within smaller skeletal elements, such as scales. Our description of the dermal skeleton of Tremataspis mammillata provides a foundation for interpreting data from cursory topological samples of dermal skeletal diversity obtained in other osteostracans. This reveals general aspects of histological structure that must be ancestral for osteostracans and, likely, ancestral jawed vertebrates. Finally, we draw the distinction between hypotheses and descriptions in palaeohistology.

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“…The paleoenvironment of Heimenia from the Klerf Beds of the Eifel, Rhenish Slate Massif of Germany is not entirely clear, but a recent study indicates that the area in the Early Devonian included marine, brackish, and terrestrial settings (Wehrmann et al 2005). Porolepidid porolepiforms are considered as fully marine or near shore inhabitants (Clément 2001a;Mondéjar-Fernández and Clément 2012). The fish-bearing sequences in the Alken quarry are interpreted as representing a nearshore marine environment.…”

Section: Paleoenvironmentmentioning

confidence: 99%

A new Early Devonian (Emsian) arthrodire from the Northwest Territories, Canada, and its significance for paleogeographic reconstruction

Schultze

Cumbaa

2017

Can. J. Earth Sci.

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An heterostiid arthrodire, Herasmius dayi sp. nov., is described from upper Lower Devonian marine deposits of the Bear Rock Formation along the Anderson River, Northwest Territories, Canada. New elements described for the genus for the first time include the suborbital, submarginal (also new for the family Heterostiidae), the lateral shoulder girdle with posterior lateral, anterior dorso-lateral, and posterior dorso-lateral plates and possible infragnathal plate. We present a new reconstruction of the cranial region of Herasmius, previously known only from supposedly freshwater – shallow marine deposits of roughly the same age in the Wood Bay Group of Spitsbergen. The late Early Devonian fishes that are common to the Arctic region of northwestern Canada and the island of Spitsbergen in the Svalbard archipelago of Norway, the porolepiform Heimenia and the arthrodire Herasmius described here, demonstrate the existence of a barrier-free paleogeographic connection between those continental blocks by the late Early Devonian. Comparison of the entire Anderson River vertebrate fauna with other boreal faunas of similar age indicates additional paleogeographic connections north of and around the Old Red Sandstone Continent to the Baltic region, central Europe, and even to the New Siberian Islands and South China, in contrast to most current published paleogeographical reconstructions.

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Squamation and scale microstructure evolution in the Porolepiformes (Sarcopterygii, Dipnomorpha) based onHeimenia ensisfrom the Devonian of Spitsbergen

Cited by 18 publications

References 46 publications

Scales and Dermal Skeletal Histology of an Early Bony Fish Psarolepis romeri and Their Bearing on the Evolution of Rhombic Scales and Hard Tissues

Scales and Dermal Skeletal Histology of an Early Bony Fish Psarolepis romeri and Their Bearing on the Evolution of Rhombic Scales and Hard Tissues

The dermal skeleton of the jawless vertebrateTremataspis mammillata(Osteostraci, stem‐Gnathostomata)

A new Early Devonian (Emsian) arthrodire from the Northwest Territories, Canada, and its significance for paleogeographic reconstruction

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