Dermal Skeleton

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Dermal Skeleton


a system of bony formations that develops in the connective-tissue layer of skin, or derma, of vertebrates.

The dermal skeleton performs protective and supportive functions. It is most highly developed in fish and loricate Agnatha. The original type of dermal skeleton was the placoid scale (dermal denticles), which covered the head and body of the animal evenly (fossil telodonts and Euselachii). The dermal denticles could fuse into more or less large plates, forming a shell. In the evolution of fish, the dermal skeleton differentiated into a cephalic section, consisting of large ossifications forming a dermatocranium, and a truncal section, consisting of rows of scales (cosmoid and ganoid). Vertebrate phylogeny has shown a gradual sinking of the elements of the dermal skeleton beneath the skin, bringing the dermatocranial ossifications into closer contact with the cranium and gradually reducing the shell of truncal scales (well developed in many fossil vertebrates). In extant terrestrial vertebrates the rudiments of the primitive dermal skeleton are preserved in the form of bony scales in apodal amphibians and ventral ribs in tuataras and crocodiles. In certain vertebrate forms, such as turtles and armadillos, a heavy dermal skeleton developed secondarily. The skeletal formation in certain invertebrates is sometimes called a dermal skeleton, but such formations differ from the dermal skeleton of vertebrates in content (for example, calcareous plates and the spines of echinoderms).


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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Pharyngeal dentic1es (placoid scales) of sharks, with notes on the dermal skeleton of vertebrates.
Protective and hydrodynamic function of the dermal skeleton of elasmobranchs.
However, the fish that belonged to these groups presented a delay in the dermal skeleton regenerative process (lepidotrichia and actinotrichia) of the tail fins (Figure 3b, Figure 4b, Figure 5b and Figure 6b).
Although there was a delay of approximately 4 days in the regeneration of the tail fin dermal skeleton of the fish treated with doses of 20 and 30 mg.[L.sup.-1] of indomethacin, the morphometric analysis of the regenerating areas done in the control group fish as well as the treated fish with 3 different doses of indomethacin on days 4, 6 and 8 after amputation (days chosen due to their representability in the total process of regeneration of tail fins) when compared did not indicate any significant alteration (p > 0.05) (Table 1).
Although the doses here used delayed the regeneration of the dermal skeleton of the tail fin, they did not interfere with the migration of the epidermal cells and consequently with the formation of the epidermal cap.
This is the first evidence showing that in the dermal skeleton of Andreolepis (A.
It also seems to be true that in these two taxa the lateral line canals are situated differently in the dermal skeleton. Andreolepis does not show any dermal element with any open lateral line canal (Janvier 1978, p.
A model of morphogenetic processes in the dermal skeleton of elasmobranchs.