Devonian charophyte whorls of branches
deutsche Version
charophyte whorlsThe vain search for gyrogonites of Palaeonitella has puzzled some palaeobotanists for decades [1]. Unexpectedly, new finds gave rise to the suspicion that Palaeonitella did not grow the typical individual gyrogonites at all but oogonia by the dozen on slender stalks: Rhynie Chert News 73. The problem of missing gyrogonites had been there because the smooth-walled oogonia had not been noticed or not been recognized as such. Judging from own experience, they may be easily mistaken for something else: Rhynie Chert News 138.

The images Fig.1-5 have been taken from one chert layer fragment where all these charophyte specimens had grown essentially upright so that a few of them are well seen on vertical cut faces of the sample as impressive sections with stem and branches. What is seen here as stem and branches at first sight is only the interior cavity filled with water after the cell content had decayed. Apparently the cuticle delayed the diffusional influx of silica so that there was no quick formation of silica gel and chalcedony inside. The walls got covered with slowly grown glittering quartz crystals within.

Later the water vanished. Remarkably, some of the plants remained hollow up to now. (Same scale for Figs.1-9.)

Figs.1-5: Charophyte (stonewort alga) in Rhynie chert, known as Palaeonitella, with whorls of few branches.

Fig.1 (right): Charophyte, hollow, with parts of hollow stem and branches cut off. Image height 4mm.

Fig.2 (below left): Charophyte, partially hollow and filled with quartz grains; small specimen below right:
        end of a stem with branches protecting the top. Image width 2.5mm.

Fig.3: Charophyte, hollow, with quartz on the walls. Image width 1.5mm.

Fig.4: Charophyte with asymmetrically grown whorls, hollow, with quartz inside on the walls. Image width 1.5mm.

Fig.5: Charophyte, hollow, with quartz on the inside of the walls. Image width 2.5mm. Photograph by H. Sahm.

charophyte whorlscharophyte whorlscharophyte whorlscharophyte

Even with branches and whorls cut off, Fig.1 makes a perfect three-dimensional illusion so that it can be stated that there were probably no more than 4 or 5 branches per whorl. This seems to be confirmed by Figs.2-5 but there are a few whorls with more branches hidden in this sample. Other samples have provided conspicuous whorl cross-sections with up to 11 branches (Figs. 6-9). Probably of no biological relevance is the fact that stems and branches in Figs.1-5 are mostly hollow but those in Figs.6-9 are not.
Figs.6-9 have been taken from specimens distinguished by the presence of smooth-walled oogonia (discovered in 2015, Rhynie Chert News 139) which implies the absence of gyrogonites.
charophyte whorl cross-sectioncharophyte whorl cross-sectioncharophyte whorl cross-sectioncharophyte  Figs.6-8: Charophyte whorl cross-sections with up to 10 branches. Width 1mm.

  Fig.9: Uppermost charophyte whorl cross-section with 11 amber-coloured
            upright branches and 12 (?) smooth-walled oogonia . Width 1mm.

The problem is stated but not solved here: Do the specimens with smooth-walled oogonia represent the assumedly well known Palaeonitella with female organs not noticed before 2015, or do they indicate the presence of a new charophyte species ? Anyway, the discovery of multiple oogonia at the uppermost whorl is highly relevant for the charophyte Tree-of-Life possibly leading to the land plants.

Samples: Figs.1-5: Rh5/3 (0.6kg), found by S. Weiss near Milton of Noth in 2001.  
            Fig.6: Rh9/86 (0.28kg), found in 2003.  Figs.7,8: Rh9/93 (0.6kg), found by S.W. in 2011.  Fig.9: Rh10/42 (0.16kg),
found by S.W. in 2011.

H.-J. Weiss    2021  

[1]  R. Kelman, M. Feist, N.H. Trewin, H. Hass  : Charophyte algae from the Rhynie chert,
     Trans. Roy. Soc. Edinburgh, Earth Sciences 94(2004 for 2003), 445-455.
Site map
Rhynie Chert News
Lower Plants
Rhynie chert