List of four important fossil bryophytes:- 1. Fossil Hepatophyta 2. Fossil Anthocerotophyta 3. Fossil Bryophyta 4. Problematic Fossil Bryophytes.
1. Fossil Hepatophyta (Marchantiophyta):
The earliest record of vegetative fossil bryophyte remains is the liverwort from the Upper Devonian of New York which has been assigned to the form-genus Pallavicinites, (= Hepaticites) devonicus (Fig. 6.60A).
The reproductive structures are not found with any of the species of Pallavicinites. The vegetative features suggested that the species of Pallavicinites may be more closely related to the anacrogynous Jungermanniales.
Various species of Pallavicinites have been described from the Carboniferous to the Pleistocene deposits (Fig. 6.60B) and can easily be compared with living bryophyte genera like Pallavicinia, Metzgeria, Treuba and Fossombronia.
Diettertia, an interesting hepatic, has been identified from Cretaceous era which may be more closely compared with the Jungermanniales.
The best known bryophyte fossil is Naiadita lanceolata that has been described by Harris (1938) from the Rhaetic (Upper Triassic) of England (Fig. 6.61 A-D). The spores of Naiadita show the closest resemblance to the member of the Marchantiales and Sphaerocarpales.
The type of spores, unicellular rhizoids, the nature of archegonia and capsules suggested that Naiadita represents a liverwort similar to the living genus Riella of Sphaerocarpales. However, Schuster (1966) argued that the vegetative features of Naiadita showing closer proximity to the Calobryales.
A fossil bryophyte, Marchantiolites, has been described from the Lower Cretaceous rock of central Montana. M. porosus has been identified from the Jurassic deposit of Sweden. Marchantiolites has been placed in the Marchantiales due to the similarity in the airpores.
A thalloid bryophyte identified from the Upper Triassic of South America has been placed in the genus Marchantites. Ricciopsis, a rosette- shaped bryophytic thallus has been identified from the Jurassic of Sweden.
The similar rosette-shaped thallus has been identified from Deccan Intertrappean beds of India and has been placed in the modern genus Riccia.
2. Fossil Anthocerotophyta (Hornworts):
There are no reports of fossil Anthocerotophyta thalli, although some reliable reports of hornwort spores are available from the Cretaceous (Maastrichtian) rocks of North America. The spores are trilete, circular and possess a distinct cingulum with variable ornamentations which are comparable with the modern hornwort genus Phaeoceros.
3. Fossil Bryophyta (Mosses):
The fossil record of the mosses is much less complete as compared to the fossil hepatics, though they are recorded as early as the Permian. An impression of a leafy shoot of Muscites plumatus has been described from the rocks of Lower Carboniferous age.
This plant shows an axis, covered with helically arranged leaves. Sex organs, sporophyte capsules or rhizoids were not associated with the gametophytic plant. Several species of Muscites have been reported from the Upper Carboniferous of France and the Triassic of Africa.
An extensive moss flora has been identified by Neuberg (1960) from the Permian rocks of Siberia, of which six identified genera (Intia, Salairia, Uskatia, Polyssaiuria, Bajdaieira and Buchtia) were placed under the Bryales and three (Protosphagnum, Vorentannularia and Jungajia) to a new order, the Protosphagnales.
The genus Protosphagnum has leaves comparable to the modern genus Sphagnum, except for the presence of a midrib.
Ignatov (1990) described a diverse flora of well-preserved gametophytes of mosses from the Upper Permian of the Russian platform which are comparable to the modern forms like Dicranales, Pottiales, Funariales, Leucodontales and Hypnales.
The permineralised well-preserved moss, Mercerea augustica, has been described by Smoot and Taylor (1986) from the Permian of Antarctica. The plant has a delicate axis to which are attached helically arranged leaves containing a midrib and rhizoids. Reproductive organs or sporophytes are not found associated with the plants. The external morphology and anatomy of the axes suggest its affinity with the Bryidae.
Several compression fossils of true mosses have been described from the Mesozoic, of which Tricostium and Yorekiella from the Jurassic of the Bureja Basin, Russia and Aulacomnium heterostichoides from deep water varved clays (Eocene) of a fresh water lake in British Columbia.
The well-preserved Aulacomnium heterostichoides has been extensively studied which is very closely related to the present day living species, Aulacomnium heterostichum found in eastern North America and eastern Asia.
4. Problematic Fossil Bryophytes:
The Lower Devonian compression fossil Sporogonites is one of the oldest plants that resembles a bryophyte. The plant consists of many parallel-oriented sporangial stalks that terminate in elongate capsules, developed from a common thallus.
The sporangium is multilayered and possibly contains a central columella. Numerous trilete spores are present in the sporangium. Sporogonites has been considered to be an early hornwort or gametophyte-bearing sporophyte of a moss.
A Precambrian bryophytic fossil, Longfengshania, has been described from China which shows striking similarity with Sporogonites. This unusual fossil of Precambrian age makes it doubtful about the validity of its systematic position. Tortilicaulis is an early Devonian fossil described from South Wales that shares a few morphological features common with the modern liver-worth Pellia.