منابع مشابه
Sox2+ 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 کاملBiometric analysis of the teeth of fossil and Recent hexanchid sharks and its taxonomic implications
A biometric analysis of the lower teeth of Recent cow sharks (Hexanchidae) investigates the ontogenetic and phylogen− etic aspects of the dental characters employed by many ichthyologists and palaeontologists. The dental characters cur− rently used to separate two extant species of sixgill sharks (Hexanchus griseus and H. nakamurai) are analysed and the fossil record of their relatives reviewed...
متن کاملSharks in danger.
Many shark populations are in danger of extinction as a direct result of man's activities. A change in attitude and a greater understanding of species' requirements are needed to prevent further destruction and replenish numbers, thus sustaining trade, fisheries and sport activity.
متن کاملFreshwater sharks and rays
with an animal that is cognitively so capable, but has a brain anatomy that is so vastly different from us mammals, you start asking questions about our core concepts on the relationship between brain structure and function. So, I came to realize that very different kinds of brains can generate very similar kinds of mental operations. And when you realize this, you start asking yourself how exa...
متن کاملCatching Fish and Avoiding Sharks
Although researchers agree that the first 5 years of life are critical for children’s developing executive functions (EFs), further advances are hindered by a lack of consensus on the design and selection of developmentally appropriate EF tasks for young children. Given this debate, well-established adult measures of EF routinely have been adapted for young children. Given young children’s comp...
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ژورنال
عنوان ژورنال: Nature
سال: 1879
ISSN: 0028-0836,1476-4687
DOI: 10.1038/020456f0