Acanthocephala (Greek ἄκανθος, akanthos, thorn + κεφαλή, kephale, head) is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host.
An arthropod (/ ˈ ɑːr θ r ə p ɒ d /, from Greek ἄρθρον arthron, "joint" and πούς pous, "foot") is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans.
Brachiopod fossils show great diversity in the morphology of the shells and lophophore, while the modern genera show less diversity but provide soft-bodied characteristics. Both fossils and extant species have limitations that make it difficult to produce a comprehensive classification of brachiopods based on morphology.
Cnidaria (/ n aɪ ˈ d ɛər i ə /) is a phylum containing over 10,000 species of animals found exclusively in aquatic (freshwater and marine) environments: they are predominantly marine species. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey.
Ctenophora (/ t ɪ ˈ n ɒ f ər ə /; singular ctenophore, / ˈ t ɛ n ə f ɔːr / or / ˈ t iː n ə f ɔːr /; from the Greek κτείς kteis 'comb' and φέρω pherō 'to carry'; commonly known as comb jellies) is a phylum of invertebrate animals that live in marine waters worldwide.
The flatworms, flat worms, Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates.
Characteristics of Gastrotricha:-1)Bilaterally symmetrical, and vermiform. 2)Body has more than two cell layers, tissues and organs. 3)Body contains no internal cavity. 4)Body possesses a through gut with a subterminal anus. 5)Body covered in a cuticle bearing numerous scales, spines or hooks. 6)Has a nervous system with ganglia.
Jellyfish is the informal common name given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are not mobile, being anchored to the seabed by stalks.
Mollusca is a large phylum of invertebrate animals whose members are known as molluscs or mollusks (/ ˈ m ɒ l ə s k /). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species.
Onychophora (from Ancient Greek, onyches, "claws"; and pherein, "to carry"), commonly known as velvet worms (due to their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, Peripatus), is a phylum of elongate, soft-bodied, many-legged panarthropods.
Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms". Alternative names for the phylum have included Nemertini, Nemertinea and Rhynchocoela. Although most are less than 20 centimetres (7.9 in) long, one specimen has been estimated at 54 metres (177 ft).
The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a group containing 144–320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms. Sipuncula signifies "little tube or siphon". Traditionally considered a phylum, they might be a subgroup of phylum Annelida based on recent molecular work.
Sponges were traditionally distributed in three classes: calcareous sponges (Calcarea), glass sponges (Hexactinellida) and demosponges (Demospongiae). However, studies have shown that the Homoscleromorpha, a group thought to belong to the Demospongiae, is actually phylogenetically well separated.
About 1,150 known species form the phylum Tardigrada, a part of the superphylum Ecdysozoa. The group includes fossils dating from 530 million years ago, in the Cambrian period. Usually, tardigrades are about 0.5 mm (0.02 in) long when they are fully grown.