منابع مشابه
Denticles . A literature review
_________________________________________________________________________________________ Denticles are pulp degenerations in the form of calcified deposits of mineral salts, usually found in molars and lower incisors, as well as in impacted teeth and deciduous molars. Denticles may come in various sizes, from microscopic particles to larger mass that almost obliterate the pulp chamber and are ...
متن کاملSquamation and ecology of thelodonts
Thelodonts are an enigmatic group of Paleozoic jawless vertebrates that have been well studied from taxonomical, biostratigraphic and paleogeographic points of view, although our knowledge of their ecology and mode of life is still scant. Their bodies were covered by micrometric scales whose morphology, histology and the developmental process are extremely similar to those of extant sharks. Bas...
متن کاملDermal denticles as a tool to reconstruct shark communities
The last 50 yr of fisheries catch statistics and ecological surveys have reported sig nificant decreases in shark populations, which have largely been attributed to human activities. However, sharks are challenging to census, and this decline likely pre-dated even the longest fishery-dependent time series. Here we present the first use of dermal denticles preserved in reef sediments as a novel ...
متن کاملSox2+ progenitors in sharks link taste development with the evolution of regenerative teeth from denticles.
Teeth and denticles belong to a specialized class of mineralizing epithelial appendages called odontodes. Although homology of oral teeth in jawed vertebrates is well supported, the evolutionary origin of teeth and their relationship with other odontode types is less clear. We compared the cellular and molecular mechanisms directing development of teeth and skin denticles in sharks, where both ...
متن کاملSexual Dimorphisms in the Dermal Denticles of the Lesser-Spotted Catshark, Scyliorhinus canicula (Linnaeus, 1758)
The dermal layers of several elasmobranch species have been shown to be sexually dimorphic. Generally, when this occurs the females have thicker dermal layers compared to those of males. This sexual dimorphism has been suggested to occur as a response to male biting during mating. Although male biting as a copulatory behaviour in Scyliorhinus canicula has been widely speculated to occur, only r...
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ژورنال
عنوان ژورنال: Nature
سال: 1993
ISSN: 0028-0836,1476-4687
DOI: 10.1038/364107a0