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.
1 It includes animals with jointed limbs and an exoskeleton made of chitin. 2  There are many opinions about its classification. 3  An arrangement found in several texts is: Superphylum Arthropoda: Phyla Chelicerata, Crustacea, Uniramia (Insects + Myriapoda). It includes animals with jointed limbs and an exoskeleton made of chitin. 2  There are many opinions about its classification. 3  An arrangement found in several texts is: Superphylum Arthropoda: Phyla Chelicerata, Crustacea, Uniramia (Insects + Myriapoda).