The “bryophytes” are non-vascular seedless plants that have an alternation of generations between the independent gametophyte generation, which produces the sex organs and the sperm and eggs, and the dependent sporophyte generation, which produces the spores (Encyclopaedia Britannica). They comprise the mosses, liverworts and hornworts.
There has been much debate about phylogenetic relationships within the bryophytes (see discussion in Morris et al, 2018). The main issue is whether the mosses, liverworts and hornworts form a monophyletic group. This debate has led to confusion in nomenclature; the term “Bryophyta” has been used as a synonym for mosses as well as a name for the mosses, liverworts and hornworts taken together (as in Morris et al, 2018). Here we follow recent research (e.g. de Sousa et al, 2019; Harris et al, 2020) that presents evidence for bryophyte monophyly, as shown in the following phylogenetic time tree:
There has been much debate about phylogenetic relationships within the bryophytes (see discussion in Morris et al, 2018). The main issue is whether the mosses, liverworts and hornworts form a monophyletic group. This debate has led to confusion in nomenclature; the term “Bryophyta” has been used as a synonym for mosses as well as a name for the mosses, liverworts and hornworts taken together (as in Morris et al, 2018). Here we follow recent research (e.g. de Sousa et al, 2019; Harris et al, 2020) that presents evidence for bryophyte monophyly, as shown in the following phylogenetic time tree:
Figure 1. Phylogenetic time tree showing first appearance of total-group clades within the bryophytes
As usual, the node of the crown group is represented by a black dot.
Given that the term Bryophyta is established as a phylum name for the mosses (Ruggiero et al, 2015), the term “Bryophytes” should be considered as a clade name. The bryophytes comprise a sister group to the vascular plants, or Tracheophyta, as shown in Figure 1 above.
Research carried out for this website has not identified any member of the bryophyte stem group. Edwards et al (2022) do suggest the possibility that eophytes and the cryptospores that they contain (see Land plants page for illustration of these organisms) might belong to the bryophyte stem group, but they also state that there is no compelling evidence that would allow confident recognition of stem-group bryophytes.
The oldest known member of the bryophyte crown group is the liverwort Metzgeriothallus sharonae, described from the Middle Devonian (Middle Givetian) Plattekill Formation at the Cairo Highway Department quarry, just south of New York State Route 145, near Cairo, Greene County, New York, USA (Hernick et al, 2008; Harris et al, 2022). Unfortunately, no image is available in the public domain.
We will now briefly consider the three members of the bryophyte clade: the hornworts, liverworts and mosses.
Given that the term Bryophyta is established as a phylum name for the mosses (Ruggiero et al, 2015), the term “Bryophytes” should be considered as a clade name. The bryophytes comprise a sister group to the vascular plants, or Tracheophyta, as shown in Figure 1 above.
Research carried out for this website has not identified any member of the bryophyte stem group. Edwards et al (2022) do suggest the possibility that eophytes and the cryptospores that they contain (see Land plants page for illustration of these organisms) might belong to the bryophyte stem group, but they also state that there is no compelling evidence that would allow confident recognition of stem-group bryophytes.
The oldest known member of the bryophyte crown group is the liverwort Metzgeriothallus sharonae, described from the Middle Devonian (Middle Givetian) Plattekill Formation at the Cairo Highway Department quarry, just south of New York State Route 145, near Cairo, Greene County, New York, USA (Hernick et al, 2008; Harris et al, 2022). Unfortunately, no image is available in the public domain.
We will now briefly consider the three members of the bryophyte clade: the hornworts, liverworts and mosses.
Hornworts
The hornworts (Phylum Anthocerotophyta in superphylum Embryophyta) are flowerless, spore-producing plants whose spores are typically produced in a tapering, horn-like or needle-like capsule which develops from a flattish, green sheet (Australian National Botanic Gardens website). The number of extant hornwort species is estimated to be between 200 and 250 (Villarreal et al, 2014). The phylogeny of the extant hornworts is illustrated below:
Figure 2. Summarized phylogenetic tree of the extant hornworts
The fossil record of the hornworts is extremely sparse (Villarreal et al, 2014), and many of the terminal clades shown above are not known as fossils. Furthermore, there is no consensus on the identity of any stem-group hornworts; as Harris et al (2022) state, “…the fossil record of hornworts remains particularly sparse, and no fossils unambiguously calibrate the deepest branches within the clade."
The oldest known member of the crown hornwort is a fossil spore of the extant genus Anthoceros (in the crown-Anthocerotales), Antheros sp. (spore type A), found in the Early Cretaceous (Late Aptian) Anfiteatro de Ticó Formation in the province of Santa Cruz in southern Argentina (Harris et al, 2022). Again, no public-domain image is available.
This first known appearance of hornworts is much later than the earliest known appearance of the Setaphyta, the clade that comprises the liverworts and mosses, in the Middle Devonian (see Figure 1 above). This difference represents a long ghost lineage on the hornwort stem line, a period of at least 265 million years during which stem hornworts must have existed (if the phylogeny shown in Figure 1 is correct) but have not yet been found.
The oldest known member of the crown hornwort is a fossil spore of the extant genus Anthoceros (in the crown-Anthocerotales), Antheros sp. (spore type A), found in the Early Cretaceous (Late Aptian) Anfiteatro de Ticó Formation in the province of Santa Cruz in southern Argentina (Harris et al, 2022). Again, no public-domain image is available.
This first known appearance of hornworts is much later than the earliest known appearance of the Setaphyta, the clade that comprises the liverworts and mosses, in the Middle Devonian (see Figure 1 above). This difference represents a long ghost lineage on the hornwort stem line, a period of at least 265 million years during which stem hornworts must have existed (if the phylogeny shown in Figure 1 is correct) but have not yet been found.
Liverworts
Liverworts (Phylum Marchantiophyta in superphylum Embryophyta) are small non-vascular plants that, like all bryophytes, have a life cycle comprising gametophyte and sporophyte stages. Around 7,500 species of liverworts are known in the world today (von Konrat et al, 2014). A summarized version of the phylogeny of the extant liverworts is illustrated below:
Figure 3. Summarized phylogenetic tree of the extant liverworts
While not as limited as that of the hornworts, the fossil record of liverworts is too sparse to “permit assessments of possible morphological changes through time" (Heinrichs et al, 2014). Furthermore, no documentation of stem liverworts has been found by the research carried out for this website.
The oldest known member of the liverwort crown group is Metzgeriothallus sharonae, described from the Middle Devonian (Middle Givetian) Plattekill Formation at the Cairo Highway Department quarry, just south of New York State Route 145, near Cairo, Greene County, New York, USA (Hernick et al, 2008; Harris et al, 2022). No image is available in the public domain.
Well preserved three-dimensional remains of liverworts are not found until the mid-Cretaceous, when the appearance of amber deposits allowed excellent preservation (Feldberg et al, 2021). A couple of examples of these crown-group liverworts are illustrated below (for a larger view, click on image):
The oldest known member of the liverwort crown group is Metzgeriothallus sharonae, described from the Middle Devonian (Middle Givetian) Plattekill Formation at the Cairo Highway Department quarry, just south of New York State Route 145, near Cairo, Greene County, New York, USA (Hernick et al, 2008; Harris et al, 2022). No image is available in the public domain.
Well preserved three-dimensional remains of liverworts are not found until the mid-Cretaceous, when the appearance of amber deposits allowed excellent preservation (Feldberg et al, 2021). A couple of examples of these crown-group liverworts are illustrated below (for a larger view, click on image):
Figure 4. Examples of crown liverwort fossils, preserved in amber
Mosses
Mosses (Phylum Bryophyta in superphylum Embryophyta) are small non-vascular land plants that are commonly found in damp and shady locations. More than 12,000 species exist (Shaw et al, 2005). A recent phylogenetic tree of the extant mosses is summarized below:
Figure 5. Summarized phylogenetic tree of the extant mosses
The comment by Kenrick (2000) that stem group mosses are absent from the fossil record has not been invalidated since then, according to the research carried out for this website.
The oldest known member of the moss crown group is a fossil example of the extant order Sphagnales, found in the upper part of the Early Carboniferous (Visean) Ortelsdorf Formation in a roadcut of the A4 motorway near Chemnitz-Glösa, Saxony, Germany (Hübers and Kerp, 2012). No images of that fossil are available in the public domain, but identical characteristics are seen in the Protosphagnales of the Permian in Russia (Morris et al, 2018). Some examples of these crown-group mosses (actually members of the Sphagnophytina total group) are shown below:
The oldest known member of the moss crown group is a fossil example of the extant order Sphagnales, found in the upper part of the Early Carboniferous (Visean) Ortelsdorf Formation in a roadcut of the A4 motorway near Chemnitz-Glösa, Saxony, Germany (Hübers and Kerp, 2012). No images of that fossil are available in the public domain, but identical characteristics are seen in the Protosphagnales of the Permian in Russia (Morris et al, 2018). Some examples of these crown-group mosses (actually members of the Sphagnophytina total group) are shown below:
Figure 6. Examples of crown group moss fossils, from the Permian of Russia
References
de Sousa, F., Foster, P. G., Donoghue, P. C., Schneider, H., & Cox, C. J. (2019). Nuclear protein phylogenies support the monophyly of the three bryophyte groups (Bryophyta Schimp.). New Phytologist, 222(1), 565-575.
Edwards, D., Morris, J. L., Axe, L., Duckett, J. G., Pressel, S., & Kenrick, P. (2022). Piecing together the eophytes–a new group of ancient plants containing cryptospores. New Phytologist, 233(3), 1440-1455.
Feldberg, K., Schaefer-Verwimp, A., Renner, M. A., von Konrat, M., Bechteler, J., Mueller, P., ... & Schmidt, A. R. (2021). Liverworts from Cretaceous amber. Cretaceous Research, 128, 104987.
Harris, B. J., Harrison, C. J., Hetherington, A. M., & Williams, T. A. (2020). Phylogenomic evidence for the monophyly of bryophytes and the reductive evolution of stomata. Current Biology, 30(11), 2001-2012.
Harris, B. J., Clark, J. W., Schrempf, D., Szöllősi, G. J., Donoghue, P. C., Hetherington, A. M., & Williams, T. A. (2022). Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants. Nature Ecology & Evolution, 6(11), 1634-1643.
Heinrichs, J., Schäfer-Verwimp, A., Feldberg, K., & Schmidt, A. R. (2014). The extant liverwort Gackstroemia (Lepidolaenaceae, Porellales) in Cretaceous amber from Myanmar. Review of Palaeobotany and Palynology, 203, 48-52.
Hernick, L. V., Landing, E., & Bartowski, K. E. (2008). Earth's oldest liverworts—Metzgeriothallus sharonae sp. nov. from the Middle Devonian (Givetian) of eastern New York, USA. Review of Palaeobotany and Palynology, 148(2-4), 154-162.
Hübers, M., & Kerp, H. (2012). Oldest known mosses discovered in Mississippian (late Visean) strata of Germany. Geology, 40(8), 755-758.
Kenrick, P. (2000). The relationships of vascular plants. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 355(1398), 847-855.
Morris, J. L., Puttick, M. N., Clark, J. W., Edwards, D., Kenrick, P., Pressel, S., ... & Donoghue, P. C. (2018). The timescale of early land plant evolution. Proceedings of the National Academy of Sciences, 115(10), E2274-E2283.
Ruggiero, M. A., Gordon, D. P., Orrell, T. M., Bailly, N., Bourgoin, T., Brusca, R. C., ... & Kirk, P. M. (2015). A higher level classification of all living organisms. PloS one, 10(4), e0119248.
Shaw, A. J., Cox, C. J., & Goffinet, B. (2005). Global patterns of moss diversity: taxonomic and molecular inferences. Taxon, 54(2), 337-352.
Villarreal, J. C., Cargill, D. C., Hagborg, A., Soderstrom, L., & Renzaglia, K. S. (2014). A synthesis of hornwort diversity: Patterns, causes and future work. Phytotaxa, 9(1), 150-166.
Von Konrat, M., Soderstrom, L., Renner, M. A., Hagborg, A., Briscoe, L., & Engel, J. J. (2014). Early land plants today (ELPT): how many liverwort species are there?. Phytotaxa, 9(1), 22-40.
Edwards, D., Morris, J. L., Axe, L., Duckett, J. G., Pressel, S., & Kenrick, P. (2022). Piecing together the eophytes–a new group of ancient plants containing cryptospores. New Phytologist, 233(3), 1440-1455.
Feldberg, K., Schaefer-Verwimp, A., Renner, M. A., von Konrat, M., Bechteler, J., Mueller, P., ... & Schmidt, A. R. (2021). Liverworts from Cretaceous amber. Cretaceous Research, 128, 104987.
Harris, B. J., Harrison, C. J., Hetherington, A. M., & Williams, T. A. (2020). Phylogenomic evidence for the monophyly of bryophytes and the reductive evolution of stomata. Current Biology, 30(11), 2001-2012.
Harris, B. J., Clark, J. W., Schrempf, D., Szöllősi, G. J., Donoghue, P. C., Hetherington, A. M., & Williams, T. A. (2022). Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants. Nature Ecology & Evolution, 6(11), 1634-1643.
Heinrichs, J., Schäfer-Verwimp, A., Feldberg, K., & Schmidt, A. R. (2014). The extant liverwort Gackstroemia (Lepidolaenaceae, Porellales) in Cretaceous amber from Myanmar. Review of Palaeobotany and Palynology, 203, 48-52.
Hernick, L. V., Landing, E., & Bartowski, K. E. (2008). Earth's oldest liverworts—Metzgeriothallus sharonae sp. nov. from the Middle Devonian (Givetian) of eastern New York, USA. Review of Palaeobotany and Palynology, 148(2-4), 154-162.
Hübers, M., & Kerp, H. (2012). Oldest known mosses discovered in Mississippian (late Visean) strata of Germany. Geology, 40(8), 755-758.
Kenrick, P. (2000). The relationships of vascular plants. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 355(1398), 847-855.
Morris, J. L., Puttick, M. N., Clark, J. W., Edwards, D., Kenrick, P., Pressel, S., ... & Donoghue, P. C. (2018). The timescale of early land plant evolution. Proceedings of the National Academy of Sciences, 115(10), E2274-E2283.
Ruggiero, M. A., Gordon, D. P., Orrell, T. M., Bailly, N., Bourgoin, T., Brusca, R. C., ... & Kirk, P. M. (2015). A higher level classification of all living organisms. PloS one, 10(4), e0119248.
Shaw, A. J., Cox, C. J., & Goffinet, B. (2005). Global patterns of moss diversity: taxonomic and molecular inferences. Taxon, 54(2), 337-352.
Villarreal, J. C., Cargill, D. C., Hagborg, A., Soderstrom, L., & Renzaglia, K. S. (2014). A synthesis of hornwort diversity: Patterns, causes and future work. Phytotaxa, 9(1), 150-166.
Von Konrat, M., Soderstrom, L., Renner, M. A., Hagborg, A., Briscoe, L., & Engel, J. J. (2014). Early land plants today (ELPT): how many liverwort species are there?. Phytotaxa, 9(1), 22-40.
Image credits – Bryophytes
- Header:
- Hornwort: Jason Hollinger, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
- Liverwort: Katja Schulz from Washington, D. C., USA, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
- Moss: Futurilla (on Flickr), Attribution 2.0 Generic (CC BY 2.0)
- Figure 4 (Frullania cretacea): Open Access article FELDBERG, K., GRADSTEIN, S. R., GRÖHN, C., HEINRICHS, J., VON KONRAT, M. A. T. T., MAMONTOV, Y. S., ... & SCHMIDT, A. R. (2021). Checklist of fossil liverworts suitable for calibrating phylogenetic reconstructions. Bryophyte Diversity and Evolution, 43(1), 14-71.
- Figure 4 (Radula cretacea): ): Open Access article FELDBERG, K., GRADSTEIN, S. R., GRÖHN, C., HEINRICHS, J., VON KONRAT, M. A. T. T., MAMONTOV, Y. S., ... & SCHMIDT, A. R. (2021). Checklist of fossil liverworts suitable for calibrating phylogenetic reconstructions. Bryophyte Diversity and Evolution, 43(1), 14-71.
- Figure 6 (Protosphagnalean mosses): Open Access article IGNATOV, M. S., & MASLOVA, E. V. (2021). Fossil mosses: what do they tell us about moss evolution?. Bryophyte Diversity and Evolution, 43(1), 72-97.