Animals are multicellular, heterotrophic organisms (must eat organic material) that develop from embryos and show a wide range of body forms, behaviours, and ecological roles. The animal kingdom includes everything from simple sponges to complex vertebrates such as birds, mammals, reptiles, amphibians, and fishes.

Historically, animals were often divided into “vertebrates” and “invertebrates”, but modern taxonomy recognises many distinct phyla. Different authorities vary in how they group these phyla, and some use additional levels such as subkingdoms or superphyla.

Subdivision of the Kingdom

For consistency across this site, the list below follows the structure used by iNaturalist, which recognises 33 phyla within Kingdom Animalia. The phyla most familiar to naturalists appear first, followed by the remaining phyla in the order used by iNaturalist.

Phyla within Kingdom Animalia

Commonly recognised phyla

1. Phylum Arthropoda — joint‑legged invertebrates including insects, spiders, crustaceans.
2. Phylum Chordata — animals with a notochord at some stage (vertebrates and relatives).
3. Phylum Mollusca — soft‑bodied animals such as snails, slugs, clams, octopuses.
4. Phylum Annelida — segmented worms such as earthworms and leeches.
5. Phylum Nematoda — roundworms found in soil, water, and as parasites.
6. Phylum Platyhelminthes — flatworms including planarians and tapeworms.
7. Phylum Cnidaria — jellyfish, corals, sea anemones with stinging cells.
8. Phylum Porifera — sponges, simple filter‑feeding animals.
9. Phylum Echinodermata — starfish, sea urchins, sea cucumbers.
10. Phylum Tardigrada — water bears, tiny animals known for extreme resilience.

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Other phyla recognised by iNaturalist

The remaining phyla are less commonly encountered but are included here for completeness.

Expand to show remainder of phyla

11. Phylum Bryozoa — colonial filter‑feeding animals forming encrusting mats.
12. Phylum Brachiopoda — marine animals with two shells, superficially like clams.
13. Phylum Nemertea — ribbon worms with a long eversible proboscis.
14. Phylum Gastrotricha — tiny aquatic animals with bristled bodies.
15. Phylum Entoprocta — small sessile filter‑feeders with tentacle crowns.
16. Phylum Hemichordata — acorn worms and relatives, sharing features with chordates.
17. Phylum Onychophora — velvet worms, soft‑bodied predators with stubby legs.
18. Phylum Xenacoelomorpha — simple worm‑like animals, basal bilaterians.
19. Phylum Placozoa — extremely simple, flat, multicellular animals.
20. Phylum Acanthocephala — parasitic thorny‑headed worms.
21. Phylum Nematomorpha — horsehair worms, parasites of arthropods.
22. Phylum Sipuncula — peanut worms, unsegmented marine burrowers.
23. Phylum Phoronida — horseshoe worms, tube‑dwelling marine filter‑feeders.
24. Phylum Ctenophora — comb jellies with rows of ciliary plates.
25. Phylum Cycliophora — tiny symbionts living on lobster mouthparts.
26. Phylum Loricifera — minute marine animals living in sediment grains.
27. Phylum Kinorhyncha — mud dragons, tiny segmented marine animals.
28. Phylum Priapulida — priapulid worms, burrowing marine predators.
29. Phylum Chaetognatha — arrow worms, planktonic predators.
30. Phylum Gnathostomulida — jaw worms, tiny marine interstitial animals.
31. Phylum Micrognathozoa — microscopic animals with complex jaw structures.
32. Phylum Orthonectida — simple parasitic animals with reduced bodies.
33. Phylum Rotifera — microscopic aquatic animals with a rotating ciliated “crown”.

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Major Animal Phyla Documented on This Site

Most observations currently fall within these two phyla. Each contains multiple classes, which are explored in the sections linked below. Additional phyla will be added as more groups are documented.

• Phylum Chordata (Chordates) — Birds, mammals, reptiles, amphibians and fishes.
• Phylum Arthropoda (Arthropods) — Insects (including butterflies, moths, dragonflies, damselflies, beetles and more), spiders and other arthropods.

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Notes

iNaturalist recognises 33 phyla within Kingdom Animalia. Other taxonomic authorities (NBN Atlas, Catalogue of Life, BOLD, ITIS) list additional small or molecularly defined phyla. These organisations are linked through shared data flows:

• iNaturalist contributes Research Grade observations to GBIF.
• NBN Atlas is the UK node for GBIF.
• Catalogue of Life provides the GBIF taxonomic backbone.
• BOLD contributes barcode‑based species records.

This page therefore reflects a practical, observation‑focused overview aligned with the taxonomy used throughout this site.

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Sources

1. NBN — UK biodiversity database linked with many conservation organisations; also the UK node for GBIF.
2. iNaturalist — worldwide citizen‑science platform; Research Grade observations feed into GBIF.
3. Catalogue of Life (CoL) — global species database used as the GBIF taxonomic backbone; part of the Species 2000 system.
4. BOLD — Barcode of Life Data System, listing species with DNA barcodes.
5. GBIF — Global Biodiversity Information Facility, funded by governments and wildlife organisations worldwide.
6. ITIS — Integrated Taxonomic Information System, associated with CoL and GBIF.

Although these organisations are separate entities, they are linked through shared data flows and collaborative structures.

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