Discover every kind of animal that has ever existed. Some are familiar, but others are profoundly strange

Every animal on Earth belongs to one of about 35 groups called “phyla”. Some are familiar, but others are profoundly strange.

The number of species per phylum is always changing, as more animals are discovered. In 2014 alone, over 1,400 new marine species were discovered, and the largely unexplored deep sea surely holds many more surprises. Also, seemingly separate phyla sometimes turn out to be the same.

As a result, this list of phyla is not definitive. But it is our best attempt to sum up the vast diversity of Earth’s animal life.

1. Acanthocephala

Acanthocephala, or spiny headed worms, are parasitic creatures. Adults live in the digestive tracts of vertebrates like fish. They are usually about 20cm long but some are known to be larger than 60cm.

Their spines are not just for show. The worms use them to literally anchor themselves onto their hosts. Some species also have a hook for even firmer attachment.

2. Acoelomorpha

The worms pictured are acoel flatworms. Like all others in the Acoelomorpha phylum they do not have a gut or anus. They are remarkably resistant and can reportedly regrow from cells after being pressed through a sieve. It’s not clear whether Acoelomorpha are distinct enough to be a true phylum.

3. Annelida

This beautiful dragon-shaped ragworm belongs to the annelid phylum. Each of the segments you can see has small appendages, which help it move along. They also act like gills, usually in marine environments, though also sometimes freshwater and terrestrial.

The worm in the photo is one of 17,590 annelid species: others include earthworms, lugworms and leeches. Annelids have long been thought to be a sister group of arthropods, as they both have segmented bodies, says Philipp Schiffer, an evolutionary biologist at the University of Cologne in Germany. They are now grouped with molluscs.

4. Arthropoda

The image shows a garden spider feeding on a common wasp caught in its web. These animals are both arthropods.

The arthropod phylum includes all insects, spiders and millipedes, as well as crustaceans and sea spiders. The long-extinct trilobites were also arthropods. Arthropoda is currently the largest phylum, with well over a million species.

5. Brachiopoda

Brachiopoda, also known as lamp shells, live in the ocean in very cold water. They were once much more diverse than they are today: there are many thousands of fossil species, but less than 450 living ones.

They look a bit like shelled molluscs like oysters or mussels. But whereas molluscs have their shells on their left and right sides, brachiopods have theirs on their upper and lower surfaces. They are closely related to bryozoans and phoronids.

6. Bryozoa

Bryozoa are also known as sea mats, and look a bit like corals. They live on the sea floor, mostly on stones or algae, although a few are free-living. The tiny individuals in the colonies use their fine tentacles to filter particles of food from the water.

New individuals, called zooids, are budded from the body wall of an existing zooid or from a larva. All species have hermaphroditic colonies, but several also have male and female zooids, says Claus Nielsen of the Natural History Museum of Denmark in Copenhagen.

Some hermit crabs use bryozoans as a disguise: they let the bryozoans grow on their snail-shell house forming sturdy outgrowths, which gives some protection from predators. There are almost 6,000 living species and many more only known from fossils.

7. Chaetognatha

Chaetognaths are marine predators. They have an impressive set of grasping spines and jaws with which to capture their victims, which they then immobilise with neurotoxins. They are called “arrow worms” because of the hooked spines on each side of their heads.

Arrow worms are among the main constituents of plankton, making them very important in marine food webs.  They are found throughout the ocean but there are only just over 100 species. It is not clear how they relate to each other.

8. Chordata

All the animals pictured here are chordates. It is probably the most well-known phylum. It includes all animals with backbones, or “vertebrates”, which includes birds, reptiles, fishes, amphibians and mammals.

There are over 64,000 living species, and many more known fossil chordates. The largest chordates are also the largest animals known to have existed: blue whales.

9. Cnidaria

This lion’s mane is the largest known jellyfish and belongs to the Cnidaria phylum. Most are marine predators, although some also live in freshwater. Their stinging tentacles, which shoot out specialized harpoon-like cells called cnidocytes, help them ensnare prey.

As well as jellyfish, this phylum also includes sea anemones.

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