Phylum: Rhodophyta (Red/Brown Algae)
The taxonomy presented here follows AlgaeBase as at early August 2026. Doubtless many new species await discovery and formal description, and this may necessitate the erection of novel higher taxonomic ranks.
Subphylum: Eurhodophytina
Class: Florideophyceae
Subclass: Corallinophycidae
Order: Hapalidiales
Family: Hapalidiaceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Lithothamnion superpositum Foslie (1900) | - | Western Atlantic Ocean | Invalid [synonym] | Access |
Families: Melobesiaceae, Mesophyllumaceae
—No subordinate taxa
Orders: Corallinales, Corallinapetrales, Epiphytales, Rhodogorgonales, Sporolithales
—No subordinate taxa
Subclass: Nemaliophycidae
Order: Nemaliales
Family: Galaxauraceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Galaxaura barbata R.Chou in W.R.Taylor (1945) | - | Floreana & Santa Cruz, Galápagos Islands | Missing (1962-1963) | Access |
Families: Liagoraceae, Liagoropsidaceae, Nemaliaceae, Scinaiaceae, Yamadaellaceae
—No subordinate taxa
Orders: Acrochaetiales, Balbianiales, Balliales, Batrachospermales, Colaconematales, Corynodactylales, Entwisleiales, Ottiales, Palmariales, Rhodachlyales, Thoreales
—No subordinate taxa
Subclass: Rhodymeniophycidae
Order: Ceramiales
Family: Delesseriaceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Phycodrina elegans (Setchell & N.L.Gardner) M.J.Wynne (1985) | - | Galápagos Islands | Missing (1977) | Access |
| Vanvoorstia bennettiana (Harvey) Papenfuss (1956) | Bennett's seaweed | Port Jackson, NSW, Australia | Extinct (October 1886) | Access |
Families: Callithamniaceae, Ceramiaceae, Rhodomelaceae, Wrangeliaceae
—No subordinate taxa
Order: Gelidiales
Family: Gelidiellaceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Gelidiella ramellosa (Kützing) Feldmann & Hamel (1934) | - | near Two Rocks, WA, Australia | Rediscovered | Access |
Families: Gelidiaceae, Orthogonacladiaceae, Pterocladiaceae
—No subordinate taxa
Order: Gigartinales
Family: Gigartinaceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Gigartina australis J.Agardh (1899) | Turkish towel algae | Sydney Harbour, NSW, Australia | Extinct (1892) | Access |
Family: Sphaerococcaceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Sphaerococcites crispiformis Sternb. (1833) | - | Sokolov, Czech Republic | Extinct (Holocene) | Access |
Families: Acrotylaceae, Areschougiaceae, Blinksiaceae, Calosiphoniaceae, Caulacanthaceae, Chondriellaceae, Chondrymeniaceae, Clavicloniaceae, Corynocystaceae, Cruoriaceae, Cubiculosporaceae, Cystocloniaceae, Dicranemataceae, Dumontiaceae, Endocladiaceae, Etheliaceae, Furcellariaceae, Gainiaceae, Gloiosiphoniaceae, Haemeschariaceae, Kallymeniaceae, Mychodeaceae, Mychodeophyllaceae, Nizymeniaceae, Peltastaceae, Phacelocarpaceae, Phyllophoraceae, Placentophoraceae, Polyidaceae, Ptilocladiopsidaceae, Rhizophyllidaceae, Rissoellaceae, Schmitziellaceae, Solieriaceae, Tichocarpaceae, Tylotaceae
—No subordinate taxa
Order: Gracilariales
Family: Gracilariaceae
| Scientific Name & Authority | Common Name/s | Distribution (Habitat) | Status (Last Record) | Taxon Profile |
| Gracilaria skottsbergii W.R.Taylor (1945) | - | Galápagos Islands | Missing (27 January 1934) | Access |
Families: Pterocladiophilaceae
—No subordinate taxa
Orders: Acrosymphytales, Atractophorales, Bonnemaisoniales, Catenellopsidales, Halymeniales, Inkyuleeales, Nemastomatales, Peyssonneliales, Plocamiales, Rhodymeniales, Sebdeniales
—No subordinate taxa
Subclasses: Ahnfeltiophycidae, Hildenbrandiophycidae
—No subordinate taxa
Class: Bangiophyceae
—No subordinate taxa
Subphylum: Cyanidiophytina
Class: Cyanidiophyceae
—No subordinate taxa
Subphylum: Proteorhodophytina
Classes: Compsopogonophyceae, Glaucosphaerophyceae, Porphyridiophyceae, Rhodellophyceae, Stylonematophyceae
—No subordinate taxa
Statistics
| Conservation status | Number of taxa (in percentage) |
| Extinct | 3 (42.85%) |
| Missing | 3 (42.85%) |
| Extinct in the Wild | 0 |
| Possibly Extinct in the Wild | 0 |
| Globally Rediscovered | 1 (14.3%) |
| Rediscovered in the Wild | 0 |
| Reintroduced | 0 |
| Uncertain status | 0 |
| Hypothetical | 0 |
| Total | 7 (100%) |
| Erroneously listed | 0 |
| Invalid | 1 |
| Grand total | 8 (114.28%) |