Rhynia

Rhynia
Temporal range: Early Devonian
Reconstruction of Rhynia gwynne-vaughanii, redrawn after[1]
Scientific classification
Kingdom: Plantae
Subkingdom: Embryophyta
clade: Polysporangiophyta
Division: Tracheophyta
Class: †Rhyniopsida
Genus: †Rhynia
Kidston & Lang (1917)
Species
  • R. gwynne-vaughanii Kidston & Lang (1917)

Rhynia gwynne-vaughanii was the sporophyte[2] generation of a vascular, axial, free-sporing diplohaplontic embryophytic land plant of the Lower Devonian that had anatomical features more advanced than those of the bryophytes, and was basal to modern vascular plants or eutracheophytes.

Contents

Description

R. gwynne-vaughanii was first described as a new species by Kidston and Lang in 1917.[3] The species is known only from the Rhynie chert in Aberdeenshire, Scotland, where it grew in the vicinity of a silica-rich hot spring. Rhynia was a vascular plant, and grew in association with other vascular plants such as Asteroxylon mackei, a probable ancestor of modern clubmosses (Lycopsida), and with pre-vascular plants such as Aglaophyton major, which is interpreted as basal to true vascular plants.[4]

Rhynia is thought to have had deciduous lateral branches, which it used to disperse laterally over the substrate[5][6] and stands of the plant may therefore have been clonal populations.

Evidence of the gametophyte generation of Rhynia has been described in the form of crowded tufts of diminutive stems only a few mm in height, with the form genus name Remyophyton delicatum.[7] Like those of Aglaophyton major,[8][9] Horneophyton lignieri[10] and Nothia aphylla[11] the gametophytes of Rhynia are dioicous, bearing male and female gametangia (antheridia and archegonia) on different axes. A significant finding is that the axes were vascular, unlike almost all of the gametophytes of modern pteridophytes except for that of Psilotum.[12]

Taxonomy

Two species of Rhynia were initially described by Kidston and Lang from the Rhynie chert bed: R. gwynne-vaughnii in 1917,[3] and R. major in 1920.[13] R. major was transferred to a new genus as Aglaophyton major by D.S. Edwards in 1986, leaving R. gwynne-vaughnii as the only species.[14] Rhynia is the type genus for the rhyniophytes, established as the subdivision Rhyniophytina by Banks,[15] but since treated at various ranks.

Phylogeny

In 2004, Crane et al. published a cladogram for the polysporangiophytes, in which Rynia and the other Rhyniaceae are placed as basal vascular plants (tracheophyes).[16]

polysporangiophytes

† Horneophytopsida (Caia, Horneophyton, Tortilicaulis)



† Aglaophyton

tracheophytes

† Rhyniaceae (Huvenia, Rhynia, Stockmansella)



† basal groups (Aberlemnia caledonica [=Cooksonia caledonica], Cooksonia pertoni)


lycophytes and their stem groups


euphyllophytes





References

  1. ^ P. Kenrick, P.R. Crane (1997) The origin and early diversification of land plants. A cladistic study. Smithsonian Institution Press, Washington & London, ISBN 1-56098-729-4. Fig. 4.8, p. 101.
  2. ^ Edwards, DS (1980) Evidence for the sporophytic status of the Lower Devonian plant Rhynia gwynne-vaughanii Kidston and Lang. Review of Palaeobotany and Palynology, 29, 177-188
  3. ^ a b R. Kidston and W.H. Lang (1917) On Old Red Sandstone plants showing structure from the Rhynie chert bed, Aberdeenshire. Part I. Rhynia gwynne-vaughanii, Kidston and Lang. Transactions of the Royal Society of Edinburgh, 5, 761-784.
  4. ^ Edwards, D.S. (1986), "Aglaophyton major, a non-vascular land-plant from the Devonian Rhynie chert", Botanical Journal of the Linnean Society 93 (2): 173–204, doi:10.1111/j.1095-8339.1986.tb01020.x 
  5. ^ Bateman, R.M.; Crane, P.R.; Dimichele, W.A.; Kenrick, P.R.; Rowe, N.P.; Speck, T.; Stein, W.E. (1998), "EARLY EVOLUTION OF LAND PLANTS: Phylogeny, Physiology, and Ecology of the Primary Terrestrial Radiation", Annual Reviews in Ecology and Systematics 29 (1): 263–292, doi:10.1146/annurev.ecolsys.29.1.263. 
  6. ^ Edwards DS (1980), "Evidence for the sporophyte status of the Lower Devonian plant Rhynia gwynne-vaughnii Kidston and Lang", Rev. Palaeobot. Palynol 29: 177–188, doi:10.1016/0034-6667(80)90057-3. 
  7. ^ H. Kerp, N.H. Trewin and H. Hass (2004) New gametophytes from the Early Devonian Rhynie chert. Transactions of the Royal Society of Edinburgh, Earth Sciences, 94, 411–428
  8. ^ Remy, W. & Hass, H. 1996. New information on gametophytes and sporophytes of Aglaophyton major and inferences about possible environmental adaptations. Review of Palaeobotany and Palynology 90, 175–93.
  9. ^ Remy, W. & Remy, R. 1980. Lyonophyton rhyniensis n. gen. et nov. spec., ein Gametophyt aus dem Chert von Rhynie (Unterdevon,Schottland). Argumenta Palaeobotanica 6, 37–72.
  10. ^ Remy, W. & Hass, H. 1991a. Langiophyton mackiei nov. gen., nov. spec., ein Gametophyt mit Archegoniophoren aus dem Chert von Rhynie (Unterdevon Schottland). Argumenta Palaeobotanica 8, 69–117.
  11. ^ Remy, W. & Hass, H. 1991b. Kidstonophyton discoides nov. gen. nov. spec., ein Gametophyt aus dem Chert von Rhynie (Unterdevon, Schottland). Argumenta Palaeobotanica 8, 29–45
  12. ^ Holloway, J.E. (1939), "The gametophyte, embryo and young rhizome of Psilotum triquetrum Schwarz", Annals of Botany 3: 313–336. 
  13. ^ Kidston, R. & Lang, W.H. (1920), "On Old Red Sandstone plants showing structure, from the Rhynie Chert Bed, Aberdeenshire. Part II. Additional notes on Rhynia gwynne-vaughani, Kidston and Lang; with descriptions of Rhynia major, n.sp. and Hornea lignieri, n.g., n.sp", Transactions of the Royal Society of Edinburgh 52: 603–627 
  14. ^ Edwards, David S. (1986), "Aglaophyton major, a non-vascular land-plant from the Devonian Rhynie Chert", Botanical Journal of the Linnean Society 93 (2): 173–204, doi:10.1111/j.1095-8339.1986.tb01020.x 
  15. ^ Banks, H.P. (1975), "Reclassification of Psilophyta", Taxon 24 (4): 401–413, doi:10.2307/1219491 , cited in Banks, H.P. (1980), "The role of Psilophyton in the evolution of vascular plants", Review of Palaeobotany and Palynology 29: 165–176, doi:10.1016/0034-6667(80)90056-1 
  16. ^ Crane, P.R.; Herendeen, P. & Friis, E.M. (2004), "Fossils and plant phylogeny", American Journal of Botany 91 (10): 1683–99, doi:10.3732/ajb.91.10.1683, PMID 21652317, http://www.amjbot.org/cgi/content/full/91/10/1683, retrieved 2011-01-27