Nematoida is a grouping of animals, including the roundworms and horsehair worms.

At its origin, the "Nematoidea" included both roundworms and horsehair worms.

They are sometimes called Gordiacea, and are also known as Horsehair worms.

Nematomorpha, the horsehair worms are parasitoids not truly parasites.

Horsehair worms can be discovered in damp areas such as watering troughs, streams, puddles, and cisterns.

Mermithidae are confusable with the horsehair worms of the phylum Nematomorpha that have a similar life history and appearance.

Nematomorpha (horsehair worms)

(ecdysozoans, such as nematodes, horsehair worms, and molting bilaterians / panarthropods))

Smaller phyla related to them are the Nematomorpha or horsehair worms, and the Kinorhyncha, Priapulida, and Loricifera.

The taxon Nematoidea, including the family Gordiidae (horsehair worms), was then promoted to the rank of phylum by Ray Lankester (1877).

The first differentiation of roundworms from horsehair worms, though erroneous, is due to von Siebold (1843) with orders Nematoidea and Gordiacei (Gordiacea).

Morphological characters and molecular phylogenies agree with placement of the roundworms as a sister taxon to the parasitic horsehair worms (Nematomorpha); together they make up the Nematoida.

This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, tardigrades, and Cephalorhyncha.

Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms or Gordian worms) are a phylum of parasitoid animals superficially morphologically similar to nematode worms, hence the name.

When a series of dead bodies are found floating in the Han River, the public is shocked to discover that the deaths are related to a fatal outbreak of virus-infected mutant parasitic horsehair worms, called Yeongasi, that can control the human brain.

Some specimens preserved in alcohol made their way to the Academy of Natural Sciences, including a few gordian worms.

Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms or Gordian worms) are a phylum of parasitoid animals superficially morphologically similar to nematode worms, hence the name.

However, mounting molecular evidence indicates a closer relationship with the nematomorpha.

This relates to the fact that nematomorpha often tie themselves in knots.

Mermithidae are confusable with the horsehair worms of the phylum Nematomorpha that have a similar life history and appearance.

Nematomorpha Biodiversity Project website.

The Nematomorpha are a phylum (or group) of parasitic animals that look similar to nematode worms and live in similar environments.

Its monophyly is supported on morphological grounds, although recent molecular studies indicate that the Loricifera may be more closely related to the Nematomorpha.

They are considered to be a clade within the cycloneuralia, although their position within this group is unresolved; they may lie with the priapulids or nematomorpha.

Their closest relatives are thought to be the Panarthropoda, Nematoda and Nematomorpha; they are thus placed in the group Ecdysozoa.

The Ecdysozoa include the following phyla: Arthropoda, Onychophora, Tardigrada, Kinorhyncha, Priapulida, Loricifera, Nematoda and Nematomorpha.

Other phyla represented are Brachiopoda, Chaetognatha, Cnidaria, Ctenophora, Echinodermata, Hyolitha, Nematomorpha, Phoronida, Protista, and Chordata.