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The IUCN estimates that 66,178 extant vertebrate species have been described, [11] which means that over 95% of the described animal species in the world are invertebrates. Characteristics The trait that is common to all invertebrates is the absence of a vertebral column (backbone): this creates a distinction between invertebrates and vertebrates.
Invertebrate paleontology - the study of fossil invertebrates These divisions are sometimes further divided into more specific specialties. For example, within arachnology, acarology is the study of mites and ticks ; within entomology, lepidoptery is the study of butterflies and moths , myrmecology is the study of ants and so on.
Research on invertebrates is the foundation for current understanding of the genetics of animal development. C. elegans is especially valuable as the precise lineage of all the organism's 959 somatic cells is known, giving a complete picture of how this organism goes from a single cell in a fertilized egg, to an adult animal. [3]
Most animals called "worms" are invertebrates, but the term is also used for the amphibian caecilians and the slowworm Anguis, a legless burrowing lizard. Invertebrate animals commonly called "worms" include annelids , nematodes , flatworms , nemerteans , chaetognaths , priapulids , and insect larvae such as grubs and maggots .
Arthropods are invertebrate animals having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages.
A plate from William Smith's 1815 work Strata by Organized Fossils. Soon thereafter, Buffon's colleague Chevalier de Lamarck – a founder of invertebrate systematics and invertebrate paleontology – published still-more shell fossils in his Systematics of Animals Without Backbones, (1801) and his Natural History of Animals Without Backbones (1815 to 1822), so as to illustrate global changes ...
Marine invertebrates are invertebrate animals that live in marine habitats, and make up most of the macroscopic life in the oceans. It is a polyphyletic blanket term that contains all marine animals except the marine vertebrates , including the non- vertebrate members of the phylum Chordata such as lancelets , sea squirts and salps .
Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are a part of the subphylum Crustacea (/ k r ə ˈ s t eɪ ʃ ə /), a large, diverse group of mainly aquatic arthropods including decapods (shrimps, prawns, crabs, lobsters and crayfish), seed shrimp, branchiopods, fish lice, krill, remipedes, isopods ...