Charales

Charales is an order of freshwater green algae in the division Charophyta, class Charophyceae, commonly known as stoneworts. Depending on the treatment of the genus Nitellopsis, living species are placed into either one family or two. Further families are used for fossil members of the order. Linnaeus established the genus Chara in 1753.

Taxonomy

The higher level classification of green algae was unsettled as of 2022. AlgaeBase places Charales within the class Charophyceae and its circumscription of the division Charophyta.

Families

The number of families and their division into genera varies., AlgaeBase accepts two families containing some extant species and four families containing only fossil species:

Characeae S.F.Gray
Feistiellaceae Schudack
†Aclistocharaceae X.G.Zhou
†Atopocharaceae R.E.Peck
†Clavatoraceae Pia
†Porocharaceae Grambast

AlgaeBase places the genus Nitellopsis, which has both extant and extinct species, in the family Feistiellaceae. Other sources place Nitellopsis in the family Characeae, with Feistiellaceae containing only fossil species, so that all extant species are in the family Characeae. The Interim Register of Marine and Nonmarine Genera accepts a further three extinct families:

†Eocharaceae Grambast
†Palaeocharaceae Pia
†Raskyellaceae Grambast

Fossil record

Body fossils of representatives of the order Charales do exist, but are rare. The fossil record of the Charales consists mostly of gyrogonites, that is, calcified fructifications or, more exactly, calcified spiral cells surrounding the oospores. It may be noted that the gyrogonites are studied by palaeontologists, but not often destroyed during neontological research to liberate the oospores.
The oldest known representative of the Charales is Eochara wickendenii Choquette from the Middle Devonian. The family Characeae starts dominating the fossil assemblages in the Paleogene or perhaps already in the Late Cretaceous.