''Trithuria'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of small aquatic

herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...

, which represent the only members of the family

Hydatellaceae Hydatellaceae are a family of small, aquatic flowering plants. The family consists of tiny, relatively simple plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges (order Poales), but has b ...

found in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

.Kew World Checklist of Selected Plant Families
/ref> Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with the exception of ''T. inconspicua'' and ''T. konkanensis'', which are found in New Zealand and India, respectively.Dmitry D. Sokoloff, Margarita V. Remizowa, Terry D. Macfarlane, and Paula J. Rudall. 2008. "Classification of the early-divergent angiosperm family Hydatellaceae: one genus instead of two, four new species and sexual dimorphism in dioecious taxa". ''Taxon'' 57(1):179-200.Yadav SR, Janarthanam MK. 1995 Trithuria konkanensis (Hydatellaceae), eine neue Art aus Indien. ''Aqua Planta'' 20. (3): 91-97 (1995). Until genetic testing proved otherwise, these plants were believed to be Monocots related to the grasses (Poaceae). They are unique in being the only plants besides Lacandonia schizmatica and L. braziliana in which the stamens are in the center of the flower while the pistels are circled in a ring around them. These diminutive, moss-like, aquatic plants are the closest living relatives of the two closely related families

Nymphaeaceae Nymphaeaceae () is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate and tropical climates around the world. The family contains nine genera with about 70 known species. Water li ...

(water-lilies) and

Cabombaceae The Cabombaceae are a family of aquatic, herbaceous flowering plants. A common name for its species is water shield. The family is recognised as distinct in the Angiosperm Phylogeny Group IV system (2016). The family consists of two genera of ...

. Together, these three families compose the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Nymphaeales The Nymphaeales are an order (biology), order of flowering plants, consisting of three Family (biology), families of aquatic plants, the Hydatellaceae, the Cabombaceae, and the Nymphaeaceae (water lilies). It is one of the three orders of basal a ...

in the

APG III system The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a fur ...

of flowering plant classification. ''Trithuria'' (Hydatellaceae) diverged from the rest of Nymphaeales soon after Nymphaeales diverged from its

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

, which comprises all of the flowering plants except the two orders Nymphaeales and

Amborellales ''Amborella'' is a monotypic genus of understory shrubs or small trees endemic to the main island, Grande Terre, of New Caledonia in the southwest Pacific Ocean. The genus is the only member of the family Amborellaceae and the order Amborella ...

Taxonomy

The genus ''Hydatella'' was recently subsumed into ''Trithuria'' based on the following morphological

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

: * lack of a vascular cambium, * lack of pericyclic sclerenchyma, * anomocytic stomata, * truncate anther connective, * boat-shaped pollen, * inner integument with two cell layers, * palisade exotesta, * seed operculum formed by cell enlargement in the inner integument, * perisperm and *

hypogeal germination Hypogeal germination (from Ancient Greek [] 'below ground', from [] 'below' and [] 'earth, ground') is a botanical term indicating that the germination of a plant takes place below the ground. An example of a plant with hypogeal germination is t ...

Species and distribution

# ''

Trithuria austinensis ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with ...

'' D.D.Sokoloff - Western Australia # '' Trithuria australis'' (Diels) D.D.Sokoloff - Western Australia # '' Trithuria bibracteata'' Stapf ex D.A.Cooke - Western Australia # '' Trithuria cookeana'' D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Northern Territory of Australia # '' Trithuria cowieana'' D.D.Sokoloff - Northern Territory # '' Trithuria filamentosa'' Rodway - Tasmania # '' Trithuria fitzgeraldii'' D.D.Sokoloff, I.Marques, T.D.Macfarl., Rudall & S.W.Graham - Western Australia # '' Trithuria inconspicua'' Cheeseman - North Island of New Zealand # ''

Trithuria konkanensis ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with t ...

'' S.R.Yadav & Janarth. - Maharashtra # ''

Trithuria lanterna ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with t ...

'' D.A.Cooke - Northern Territory, Western Australia, Queensland # ''

Trithuria occidentalis ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with t ...

'' Benth. - Western Australia # ''

Trithuria polybracteata ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with t ...

'' D.A.Cooke ex D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Western Australia # ''

Trithuria submersa ''Trithuria'' is a genus of small Aquatic plant, aquatic Herbaceous plant, herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria' ...

'' Hook.f. - Western Australia, South Australia, Victoria, New South Wales, Tasmania

References

{{Taxonbar, from=Q7844293 Nymphaeales genera Aquatic plants Nymphaeales