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.
Additionally, two groups of cnidarians, corals and sea anemones, exhibit six-or eight-fold symmetry. These types of symmetry are referred to as hexamerism and octamerism, respectively. It should be noted that cnidarians are not the only animals to exhibit radial symmetry. The echinoderms also display radial symmetry.