Phylum Hemichordate – An Outline of Phylum Hemichordate



The word “hemichord” (or “hemlock”) comes from the Greek words here (, present tense) and ord (class). In medicine, hemichordata is used to describe the tissue of some internal organs in animals. The word came from an old Latin word that meant “feathery cord”. In most cases, the tissue from the inner ear is called a hematoma. When it extends outside of the ear it is called a corpus cerosa.

Classification of hemichordata

The most complete classification of hemichordata is based on the appearance of the external parts of the body. It is a highly complex area with no well-known large areas for research. As far as I know however there is only one major taxonomic group for this tissue and that is the order Planktonic fungi.


The most complete taxonomy for the phylum hemichordata consists of four orders, each with its own pterobranchial type. The first three orders are referred to as Planktonic, which includes pterobranchians such as the climate and the starfish. The two others are known as infective or non-infective. In order to obtain a taxonomic analysis of this group all living organisms must be studied, even if they are not closely related. This includes both land and freshwater systems and all known terrestrial pests and pathogens.


The classification of hemichordates is largely based on their relationship to the other known phylum of animals, the vertebrates. The most detailed study of this group, however, still has not been completely finished. All known invertebrate animals are placed in the invertebrate phylum, but this is due primarily to lack of specific criteria for classifying them. The research community, including some renowned paleontologists, consider any living thing that has a nervous system to be a hemichordate. In most cases, the definition of a vertebrate is also combined with the definition of an invertebrate.


Based on a few specific examples, the classification of hemichordates is quite accurate. For example, climate and starfish are placed in the order Prototheria, based solely on the similarities in shape between their external appearance (shapely protrusions) and the internal structure (functional cytoplasm). Ciliates are likely to be placed in the phylum hemichordata, based on a few specific examples. These include a pair of claw-like fishes, the phalaenoptera, which belong to the phylum climate, and the spiny-bodied hemichordate, which belong to the phylum hemichordata. The spiny-bodied hemichordate is likely to be placed in the phylum hemichordata, based on its external look, when examined from the rear.

Diverse species

There are a number of diverse species that are placed in the phylum hemichordata, including the common pterobranchia, anemone fish, and even the common collar shark. Most pterobranchs are found in salt water, although there are a few living freshwater species. They typically have swim bladders, although the Acorn Worm (Lamnia aravensis) is the only pterobranch species to have an egg sack. All other pterobranchs have both a mouth and a swimming bladder.


Pterobranchs have a complete digestive system, including a very robust oesophagus which, in some species, has evolved into a tube that can engulf the entire oesophagus. This allows the pterobranch to suck food from both the bottom and the surface of the oceanic waters. In addition to sucking, they also excrete waste products through their anal glands, and some secrete feces as well, although they generally only excrete feces from the anal gland.

Type of marine animal

One other interesting type of marine animal belongs to the phylum hemichordata, and this is the tornaria larva. It is a type of worm that is peculiar to certain families and is not related to any other known phylum in the aquarium. It normally has bright red skin with spiny antennae and is often seen living near corals in the wild. Its relationship to the phylum of hemichordata may perhaps be that these animals share some of its features, namely the fact that both these organisms have a way of fertilising an external ovary through a process of copulation, but tornaria latimensis differs in that it has no fertilised eggs to release.

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