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.
Examples of organisms with radial symmetry are starfish and sea urchins. Bilateral symmetry is often seen in animals that are motile. The symmetry helps the body be streamlined, allowing the organism to move. Two organisms that have bilateral symmetry other than the roundworm are butterflies and crabs.