Pallaviciniaceae is a widely distributed

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

of liverworts in the order

Pallaviciniales Pallaviciniales is an order of liverworts. Taxonomy * Pallaviciniineae Schuster 1984 ** Hymenophytaceae Schuster 1963 *** ''Hymenophyton'' Dumortier 1835 Umbraculum'' Gottsche 1861 non Schumacher 1817 non Kuntze 1891] ** Moerckiaceae Stotler ...

. All species are thallose, typically organized as a thick central

costa Costa may refer to: Biology * Rib (Latin: ''costa''), in vertebrate anatomy * Costa (botany), the central strand of a plant leaf or thallus * Costa (coral), a stony rib, part of the skeleton of a coral * Costa (entomology), the leading edge of th ...

(midvein), each side with a broad wing of tissue one cell in thickness. All species are

dioicous Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis ra ...

. The greatest diversity is in

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...

, with some species

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to that region, though species belonging to the family may be found on every continent except Antarctica.

Species

As accepted by

GBIF The Global Biodiversity Information Facility (GBIF) is an international organisation that focuses on making scientific data on biodiversity available via the Internet using web services. The data are provided by many institutions from around the ...

;

Evolutionary history

One of the oldest known

bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in s ...

s is '' Pallaviciniites'' of the Devonian, discovered in New York. It bears strong similarities to extant

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms ...

liverwort The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of ...

genus ''Pallavicinia'', hence the name.

References

Liverwort families Pallaviciniales {{Bryophyte-stub