Dentist specialties are recognized in those areas where advanced knowledge and skills are essential to maintain or restore oral health. The list of recognized dental specialties differs from country to country.
In contrast, radially symmetrical animals like jellyfish have a topside and a downside, but no identifiable front or back. The bilateria are a major group of animals, including the majority of phyla but not sponges, cnidarians, placozoans and ctenophores. For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm, and ectoderm.
The phylum Echinodermata includes about 7,000 living species. Members of Echinodermata are often called echinoderms. They are invertebrate animals that have radial symmetry, which means they have similar structures in several directions around a central point. In most starfish, this radial symmetry is consistent in five directions.