Fossil Record of Bryophytes

The fossil record of bryophytes is poor compared to that of vascular plants, and the Australian record is particularly sparse. Bryophytes are probably rarely fossilised because they lack the resistant structures typically found in fossil vascular plants: thick cuticles and lignified vascular tissues. Fossil bryophytes may also have been ignored because of their size, or be destroyed by many of the common methods of extracting vascular plant fossils from sediments.

There are some clear biases in the fossil record of bryophytes. Some high order taxa are undoubtedly preserved more often than others (e.g. mosses are mostly more robust than liverworts: see Schuster 1981). Some taxa (e.g. some thallose hepatics) may have been ignored because of a lack of obvious distinctive characters. Fossil spores of some groups, particularly some hepatics, anthocerotes and Sphagnum are recognised relatively frequently because these taxa have large, distinctive and resistant spores. Preserved spores of other bryophytes may well occur in sediments but may be missed, either through loss in processing, through a lack of obvious distinctive features or due to the generally poor knowledge of bryophyte spore morphology, particularly among palynologists.

There are more records of fossil bryophytes from high latitudes (e.g. Ovenden 1993) than from low latitudes (e.g. Frahm 1993), partly because of the greater relative abundance of mosses in cool climate floras, and also probably because of more rapid weathering of sediments at low latitudes oxidising the fossils. Similarly there are better records from glacial periods than interglacial periods during the Pleistocene (Miller 1984). There are more records from younger sediments than older sediments, presumably because of the relative lack of resistant structures, but perhaps also because global cooling during the Cainozoic has favoured bryophytes.

In spite of all this, there is a long, informative fossil record of bryophytes, including records from many groups.