Barinophyton spp. (early vascular plants)
Fertile stem of Barinophyton obscurum with five strobili
(aggregations of sporangia or spore-bearing organs). (Photo courtesy
of Ted
Daeschler, ANS.)Enigmatic Early Plants
Two species of Barinophyton (B. obscurum and B. sibericum) were collected in the floodplain pond facies of Red Hill. The fossils of both species were rare.
Barinophyton belongs to a group of enigmatic early plants known as the Barinophytales. Although they have a wide geographic distribution and ranged from the late Early Devonian into the Early Carboniferous, they’re essentially known only from their strobili (clusters of sporangia or spore-producing organs); presumed individual microphylls have also been found in some strobili fossils. The strobili have two rows of sporangia which are arranged both laterally and terminally in Barinophyton and terminally in Protobarinophyton. Pectinophyton, which has only a single sporangial row, may also be a barinophyte.
The relationship of barinophytes to other plants has been the subject of some debate. Some authorities place them within the Zosterophyllophyta, an extinct group of small Devonian plants that may have given rise to the lycopsids. In any case, barinophytes, zosterophylls and lycopsids belong to the Lycophytina. As such, they belong to one of the two great lineages of vascular plants; the other lineage, the euphyllophytes, include the trimerophytes, ferns, progymnosperms and seed plants.
The longest barinophyte fragment ever collected was 29 cm long, which suggest that these plants could become moderately long. However, these plants depended on G-type water-conducting cells for support, so they were probably never tall. It’s also not clear whether barinophytes were aquatic, semi-aquatic or terrestrial. Whatever the growth habit, they’re unlikely to have occurred far from the water’s edge.
One remarkable aspect of barinophytes is their heterosporus reproduction. Heterospory is the possession of both microspores which develop into sperm-producing gametophytes (sexually reproducing plants) and megaspores which develop into egg-producing gametopytes. Heterospory is also present in several groups of lycopsids, ferns, and progymnosperms. However, barinophytes differ from these other heterosporous plants in how the spores are arranged. They contain both microspores and megaspores within the same sporangium (spore-bearing organs), whereas the virtually all other heterosporus plants contain them in separate, specialized sporangium.
- Web:
- Arizona State University's web page on heterospory:
lsvl.la.asu.edu/plb407/kpigg/plantrepro.htm - U.C. Museum of Paleontology's web page on Zosterophylls:
www.ucmp.berkeley.edu/plants/lycophyta/zostero.html - U.C. Museum of Paleontology Virtual Paleontology Lab's web page featuring Zosterophylls:
www.ucmp.berkeley.edu/IB181/VPL/Lyco/Lyco1.html#early-dev - Books:
- Niklas, K. J. 1997. The Evolutionary Biology of Plants. Chicago: Univ. Chicago Press.
- Scientific Papers:
- Berry, C.M. and M Fairon-Demaret. 2001. "The Middle Devonian Flora Revisited. pp 120-139." In: P.G. Gensel and D. Edwards (eds.). Plants Invade the Land: Evolutionary and Environmental Approaches. New York: Columbia Univ. Press.
- Brauer, D.F. 1980. "Barinophyton citrulliforme from the Upper Devonian of Pennsylvania." American J. Botany 67(8): 1186-1206.
- Cressler, W.L., 1999. "Site–analysis and floristics of the Late Devonian Red Hill locality, Pennsylvania, an Archaeopteris-dominated plant community and early tetrapod site." Unpublished Ph.D. Dissertation, Univ. Pennyslvania, Philadelphia, 156 p.
- Image Credits:
- Unless otherwise noted, all images are copyrighted, © Dennis C. Murphy, 2005. (See Terms of Use.)